Pseudorhabdosynochus species (Monogenoidea, Diplectanidae) parasitizing groupers (Serranidae, Epinephelinae, Epinephelini) in the western Atlantic Ocean and adjacent waters, with descriptions of 13 new species

Seventeen of twenty-three species of groupers collected from the western Atlantic Ocean and adjacent waters were infected with 19 identified species (13 new) of Pseudorhabdosynochus Yamaguti, 1958 (Dactylogyridea, Diplectanidae); specimens of the Spanish flag Gonioplectrus hispanus, coney Cephalopholis fulva, marbled grouper Dermatolepis inermis, mutton hamlet Alphestes afer, and misty grouper Hyporthodus mystacinus were not infected; the yellowmouth grouper Mycteroperca interstitialis and yellowfin grouper Mycteroperca venenosa were infected with unidentified species of Pseudorhabdosynochus; the Atlantic creolefish Paranthias furcifer was infected with an unidentified species of Diplectanidae that could not be accommodated in Pseudorhabdosynochus. The following species of Pseudorhabdosynochus are described or redescribed based entirely or in part on new collections: Pseudorhabdosynochus americanus (Price, 1937) Kritsky & Beverley-Burton, 1986 from Atlantic goliath grouper Epinephelus itajara; Pseudorhabdosynochus yucatanensis Vidal-Martínez, Aguirre-Macedo & Mendoza-Franco, 1997 and Pseudorhabdosynochus justinella n. sp. from red grouper Epinephelus morio; Pseudorhabdosynochus kritskyi Dyer, Williams & Bunkley-Williams, 1995 from gag Mycteroperca microlepis; Pseudorhabdosynochus capurroi Vidal-Martínez & Mendoza-Franco, 1998 from black grouper Mycteroperca bonaci; Pseudorhabdosynochus hyphessometochus n. sp. from Mycteroperca interstitialis; Pseudorhabdosynochus sulamericanus Santos, Buchmann & Gibson, 2000 from snowy grouper Hyporthodus niveatus and Warsaw grouper Hyporthodus nigritus (new host record); Pseudorhabdosynochus firmicoleatus n. sp. from yellowedge grouper Hyporthodus flavolimbatus and snowy grouper H. niveatus; Pseudorhabdosynochus mcmichaeli n. sp., Pseudorhabdosynochus contubernalis n. sp., and Pseudorhabdosynochus vascellum n. sp. from scamp Mycteroperca phenax; Pseudorhabdosynochus meganmarieae n. sp. from graysby Cephalopholis cruentata; Pseudorhabdosynochus beverleyburtonae (Oliver, 1984) Kritsky & Beverley-Burton, 1986 from dusky grouper Mycteroperca marginata; Pseudorhabdosynochus mizellei n. sp. from red hind Epinephelus guttatus; Pseudorhabdosynochus williamsi n. sp. from rock hind Epinephelus adscensionis; Pseudorhabdosynochus bunkleywilliamsae n. sp. from Nassau grouper Epinephelus striatus; Pseudorhabdosynochus mycteropercae n. sp. from tiger grouper Mycteroperca tigris; and Pseudorhabdosynochus tumeovagina n. sp. from speckled hind Epinephelus drummondhayi. Pseudorhabdosynochus woodi n. sp. from red hind Epinephelus guttatus is described based on specimens from the US National Parasite Collection (USNPC). Drawings of the haptoral and copulatory sclerites of the type specimens in the USNPC of Pseudorhabdosynochus monaensis Dyer, Williams & Bunkley-Williams, 1994 from rock hind Epinephelus adscensionis are presented. Finally, a note confirming Pseudorhabdosynochus epinepheli Yamaguti, 1958 rather than its senior synonym Pseudorhabdosynochus epinepheli (Yamaguti, 1938) Kritsky & Beverley-Burton, 1986 as the type species of Pseudorhabdosynochus is provided.


Introduction
Pseudorhabdosynochus Yamaguti, 1958 (Monogenoidea: Dactylogyridea: Diplectanidae) was proposed, with the new species Pseudorhabdosynochus epinepheli Yamaguti, 1958 collected from the gills of Hong Kong grouper Epinephelus akaara (Temminck & Schlegel) from the Inland Sea of Japan, assigned as its type species by Yamaguti [57]. The genus was characterized in part by species (P. epinepheli) having unarmed squamodiscs and an intercecal germarium. Twenty years earlier, Yamaguti [55] had described Diplectanum epinepheli Yamaguti, 1938 from E. akaara; this species was based partly on the presence of armed haptoral squamodiscs and an intercecal germarium. The two species were subsequently placed in synonymy by Kritsky & Beverley-Burton [25], who, upon examination of the type specimens, found that the germarium looped the right intestinal cecum dorsoventrally in both nominal species; they also stated that absence of an armed squamodisc in P. epinepheli was not sufficient to exclude it from the complex of species with armed squamodiscs because the rodlets of the squamodiscs are easily lost if fixation is not done shortly after death of the diplectanid. Finally, Kritsky & Beverley-Burton [25] transferred 13 species of Cycloplectanum  to Pseudorhabdosynochus after determining that Cycloplectanum was its junior synonym.

Materials and methods
Groupers were collected by fish trap, hook and line, or longline from marine waters off Florida, Alabama, Mississippi, Puerto Rico, and southern Brazil. In the case of the protected Atlantic goliath grouper, we opportunistically evaluated moribund or freshly dead specimens suspected to have been killed by red tide, a geographically widespread and highly concentrated bloom of the toxin-producing dinoflagellate Karenia brevis (Davis) [28]. Groupers were identified by collectors using various resources available at the respective sites. For US collections, most fish specimens were identified morphologically in the field by fisheries biologists familiar with the local fauna; some specimens of questionable identity were returned to the laboratory for further morphological examination and comparison of 16s and 18s rRNA sequences with those published for groupers in GenBank. Morphological identifications of specimens of dusky grouper collected in Brazil were verified by molecular barcoding comparison with sequences available through BOLDsystems (http://www. boldsystems.org). The classification and scientific names of the groupers follow Craig & Hastings [4]; common names of the fishes are those provided in FishBase [11] and verified in Eschmeyer & Fong [8].
When fresh material was available, the host's gill basket was removed shortly after capture and placed in hot (65-70°C) 4% phosphate-buffered formalin to relax and fix the parasites. Additional parasite specimens were evaluated from other authors' collections that had been deposited in the US National Parasite Collection (USNPC). To check for specimens of Pseudorhabdosynochus spp. infecting host species not represented in our collections and to supplement those available from the USNPC, we isolated monogenoids that had been incidentally fixed with their hosts and deposited in the Florida Fish and Wildlife Conservation Commission's Fish and Wildlife Research Institute's (FWC/FWRI, formerly Florida State Board of Conservation Marine Laboratory) ichthyological specimen collection (FSBC) in St. Petersburg, Florida. To avoid damaging FSBC fish specimens, the gills were not excised but rinsed in situ with a jet of tap water to dislodge the parasites. The rinsate was then evaluated under a dissecting scope to isolate the worms. Fishes from the FSBC collection had been fixed or preserved inconsistently and may have spent some time at ambient temperature in solutions of 50% isopropyl alcohol or 10% buffered formalin; at the time of processing, the fishes and their helminth specimens were stored in 70% ethanol; helminths collected from the rinsate were transferred to 5% phosphate-buffered formalin. As would be expected for specimens fixed with these non-ideal methods, there was substantial intra-and inter-host variance in the physical integrity of monogenoid specimens. Whether collected fresh or isolated from FSBC hosts, materials from each host were placed individually in labeled vials or plastic bags with fixative and shipped to Idaho State University for study. There, a small probe and dissecting microscope were used to isolate diplectanids from the gills or sediment. Some specimens were mounted unstained in Gray and Wess medium for a study of sclerotized structures; other specimens were stained with Gomori's trichrome [18,26] and mounted in Canada balsam from beechwood creosote for observation of internal anatomy.
The latter method, during which the stained specimens were mounted in Canada balsam, frequently resulted in the collapse of the proximal two chambers of the male copulatory organ (MCO). In order to minimize collapse of the two chambers, some unstained specimens were carried through a graded ethanol series, cleared in xylene, and then placed in a small watch glass containing a weak solution of Canada balsam in xylene. The xylene was allowed to slowly evaporate over a period of 10-14 days by slightly offsetting the watch glass cover. When the consistency of Canada balsam reached a suitable level, the unstained specimens were individually mounted on a microscope slide under a coverslip. D.C. Kritsky et al.: Parasite 2015, 22, 24 Illustrations were prepared with the aid of a camera lucida or microprojector. Measurements, all in micrometers, represent straight-line distances between extreme points and are expressed as the mean followed in parentheses by the range and number (n) of structures measured; body length included that of the haptor; length of the MCO was represented by a straight-line distance from the distal tip of the cone to the farthest point on the wall of the proximal chamber of the MCO; length of the ventral anchor was obtained from the tip of the superficial root to the distal point on the curve of the anchor shaft and point (use of the tip of the deep root as a point in the measurement was not considered useful because it seldom occurred in the same plane of view as the point and shaft). All measurements were obtained from structures lying within the plane of view under microscopy; structures with portions lying outside the plane of view or those damaged during fixation and mounting were not measured. Terminology of the MCO was in part that suggested by Justine [19]. Terminology of the vagina was adjusted from that of Hinsinger & Justine [17] to include a vaginal vestibule, vaginal sclerite, and vaginal canal; Hinsinger & Justine [17] represented the vagina as only the two former structures. Numbering of haptoral-hook pairs follows the system of Mizelle [32,33]. Minimum prevalence [23] was provided only when the number of infected and uninfected hosts was known.
Type and voucher specimens collected during the present study were deposited in the US National Museum, Smithsonian Institution, Suitland, Maryland (USNM), the FWC/FWRI's Invertebrate Specimen Collection, St. Petersburg, Florida (FSBC-I), and the helminth collections of the Natural History Museum, London, UK (NHMUK) and the Muséum National d'Histoire Naturelle, Paris, France (MNHN) as indicated in the respective species accounts. Available specimens of diplectanids from western Atlantic groupers previously accessioned into the USNPC were also examined.
Unconfirmed and erroneous host and locality records: Stereolepis gigas Ayres (Polyprionidae): Salina Cruz, Oaxaca, Mexico (as Diplectanum americanum) [3]; D. americanum of Caballero & Bravo Hollis [3] renamed Cycloplectanum caballeroi Oliver, 1984 by Oliver [38] [now Pseudorhabdosynochus caballeroi  Body flattened dorsoventrally. Tegumental scales with rounded anterior margins extending from peduncle anteriorly into posterior trunk. Cephalic region broad, with two terminal and two bilateral poorly developed cephalic lobes, three bilateral pairs of head organs, pair of bilateral groups of cephalic-gland cells at level of pharynx. Posterior pair of eyespots lacking lenses, lying immediately anterior to pharynx (two specimens lacking one member of the pair); anterior pair usually absent, often represented by few poorly associated chromatic granules (one specimen with well-developed anterior eyespots lacking lenses); accessory chromatic granules small, irregular, usually anterior to posterior pair of eyespots. Pharynx with muscular wall; esophagus short to nonexistent; intestinal ceca blind, extending posteriorly to near anterior limit of peduncle. Peduncle broad, tapered posteriorly. Haptor with dorsal and ventral anteromedial lobes containing respective squamodiscs and lateral lobes having hook pairs 2-4, 6, 7. Dorsal and ventral squamodiscs subequal, with 19-23 (usually 21) U-shaped rows of rodlets; 1-3 (usually 2) innermost rows closed. Ventral anchor with well-developed superficial root, long deep root having lateral swelling, slightly curved shaft, and short recurved point extending to just past level of tip of superficial root. Dorsal anchor with subtriangular base, poorly developed roots, arcing shaft, recurved point extending past level of superficial tip of base. Ventral bar with slight medial constriction, tapered ends, longitudinal medioventral groove. Paired dorsal bar with spatulate medial end. Hook with elongate depressed thumb, delicate point, uniform shank; filamentous hook (FH) loop nearly shank length. Testis ovate, lying sinistroposterior to germarium; proximal vas deferens, prostatic reservoir not observed; seminal vesicle an indistinct dilation of distal vas deferens, lying just posterior to MCO; ejaculatory bulb not observed. MCO reniform, quadriloculate, with short distal cone, elongate tube with comparatively thick walls, delicate apparently retractile distal filament; walls of two distal chambers thick, walls of proximal two chambers thinner but comparatively rigid. Germarium pyriform, shaped as an inverted comma; germarial bulb lying diagonally at body midlength, with elongate dorsoventral distal loop around right intestinal cecum; ootype lying to left of body midline, with well-developed Mehlis' gland and giving rise to delicate banana-shaped uterus when empty.  [2,55,56]. Lacking information on host specificity and intraspecific limits on morphology among the diplectanid species, subsequent investigators frequently assigned specimens possessing a compartmentalized MCO and parasitizing a variety of fish hosts to D. americanum. Several of these assignments [1,3,10,49] were determined to represent other diplectanid species [25,38,39]. Other reports of D. americanum from hosts other than the Atlantic goliath grouper are probably erroneous. As a result, the present specimens likely represent the only valid record of P. americanus since its original description and the only one of the species from Atlantic goliath grouper in its natural environment.
Oliver [38]  After examination of the type specimens of Diplectanum americanum and D. hargisi, Yang et al. [58] considered the latter species a junior (subjective) synonym of D. americanum.
They based the synonymy on similarity of measurements provided by Aljoshkina [1] and by Oliver [39] and Santos et al. [46], who first suggested the synonymy. In addition, Yang et al. [58] supported their proposed synonymy by stating that ''the vaginal hard parts and other sclerotized structures of the types of both [species]'' and their measurements were ''virtually identical''. Although the vaginal sclerites of the two species appear to have some common features, the drawings of these structures by Yang et al. [58] are relatively diagrammatic and hardly diagnostic, and our examination of the types of D. americanum showed that many features of the vaginal sclerite were not clearly visible in these specimens. That the two species are doubtful synonyms is supported by their  respective geographic and host distributions, with P. hargisi known only from the white grouper Epinephelus aeneus (Geoffroy Saint-Hilaire) in the eastern Mediterranean Sea and P. americanus unequivocally from the Atlantic goliath grouper in the western Atlantic region. As a result, the synonymy of the two species is herein rejected, while recognizing that P. hargisi requires redescription that should be based on new collections from its type host from or near the type locality.
Examination of the holotype and four paratypes (USNPC 35703) confirmed that present specimens from the Atlantic goliath grouper were conspecific with D. americanum. Although the type specimens are in poor condition, their visible haptoral sclerites and MCO (the latter often damaged) were basically identical to those of current specimens. The type specimens differed from specimens collected during the present study in that they possessed three or four eyespots (one anterior eyespot dissociated or absent in two specimens); most specimens of the current collection possessed only the posterior pair of eyespots.
Pseudorhabdosynochus americanus is easily distinguished from its congeners that infect groupers in the western Atlantic region by its unique vaginal sclerite consisting of a distal funnel and two comparatively large juxtaposed thick-walled chambers. The Atlantic goliath grouper, the largest grouper species occurring in the region (up to 2.5 m total length) [11], is likely the only natural host for P. americanus.  Gibson (2005, unpublished) suggested that the three paratypes probably represented P. sulamericanus Santos, Buchmann & Gibson, 2000].  Body elongate ovate, flattened dorsoventrally, with slight constriction at level of MCO. Numerous tegumental scales with rounded anterior margins extending from posterior ends of intestinal ceca into peduncle. Cephalic region broad, with rounded terminal and two poorly developed bilateral lobes; three bilateral pairs of head organs; pair of bilateral groups of cephalic-gland cells at level of pharynx. Four eyespots lacking lenses immediately anterior to pharynx; members of posterior pair larger, equidistant or slightly closer together than those of anterior pair; accessory chromatic granules small, irregular in outline, uncommon or absent in cephalic region. Pharynx ovate, muscular; esophagus short to nonexistent; intestinal ceca blind, extending posteriorly to level of peduncle. Peduncle broad, tapering posteriorly. Haptor subtrapezoidal, with dorsal and ventral anteromedial lobes containing respective squamodiscs and lateral lobes having hook pairs 2-4, 6, 7. Squamodiscs similar, each with 11 or 12 (usually 12) U-shaped rows of rodlets; innermost row closed. Ventral anchor with elongate superficial root, shorter deep root having lateral swelling, curved shaft, and moderately long recurved point extending to level of tip of superficial root. Dorsal anchor with subtriangular base, superficial root short to lacking, knoblike deep root, curved shaft, recurved point extending past level of tip of superficial root. Ventral bar with slight medial constriction, tapered ends, longitudinal medioventral groove. Paired dorsal bar with slightly spatulate medial end. Hook with elongate slightly depressed thumb, delicate point, uniform shank; FH loop nearly shank length. Testis subspherical, lying immediately posterior to germarium; proximal vas deferens not observed; seminal vesicle a simple dilation of distal vas deferens, lying just posterior to MCO; ejaculatory bulb apparently absent; large vesicle (prostatic reservoir?) with translucent contents lying dorsal to common genital pore. MCO reniform, quadriloculate, with moderately long cylindrical distal cone; distal tube with delicate wall; terminal filament delicate, variable in length; walls of three distal chambers comparatively thick; proximal chamber with delicate wall, frequently collapsing during mounting of specimen on slide. Germarium pyriform; germarial bulb lying slightly to right of body midline, with elongate dorsoventral distal loop around right intestinal cecum; ootype lying slightly to left of body midline, with well-developed Mehlis' gland and giving rise to delicate banana-shaped uterus when empty. Common genital pore ventral, dextral to distal chamber of MCO. Vaginal pore sinistroventral at or slightly anterior to level of seminal vesicle; vagina with distal vestibule, small vaginal sclerite having two small tandem chambers; vaginal canal unsclerotized, extending diagonally within body to seminal receptacle. Seminal receptacle lying on body midline immediately anterior to ootype. Bilateral and common vitelline ducts not observed; vitellarium absent in regions of other reproductive organs, otherwise extending from level of MCO to anterior limit of peduncle.

Remarks
Examination of the holotype, three paratypes, and voucher specimens from red grouper off Florida and Mississippi indicated that the original description of P. yucatanensis [50] was based on specimens representing two distinct species of Pseudorhabdosynochus. Figures 1A and 1C in the original description show the distal parts of the vagina to comprise a weakly sclerotized vaginal vestibule and a large vaginal sclerite having an elongate sigmoid tube originating from a comparatively large thick-walled chamber, while the vaginal sclerites of the holotype and three paratypes were noticeably smaller, each possessing a short distal tube and two small tandem chambers (Fig. 10). The collections from Florida and Mississippi included many specimens representing the two forms.
The comparative morphology of the vaginal sclerite is one of the primary features defining species of Pseudorhabdosynochus. Figures 1A and 1C in the original description of P. yucatanensis would suggest that the species is defined by the larger vaginal sclerite having a single thick-walled chamber. However, a species is not unequivocally defined by the original description but rather by the holotype, which in this case possessed the smaller sclerite. As a result, P. justinella n. sp. is proposed and described below for the form having the larger sclerite as depicted in Figure 1C by Vidal-Martínez et al. [50], and P. yucatanensis (s. s.) is redescribed and assigned to specimens with the smaller sclerite (Fig. 10).
Vidal-Martínez et al. [50] stated that tegumental scales were absent, and their Figure 1I suggests that comparatively few rodlets occur in the respective rows of the squamodiscs of P. yucatanensis. Tegumental scales, however, are clearly visible, and the concentric rows in the squamodiscs have as many as five or six more rodlets per row in specimens of both P. yucatanensis (s. s.) and P. justinella n. sp. from Florida. In addition, a few tegumental scales were observed along the margins of the peduncle in one of the paratypes of P. yucatanensis deposited in the USNPC. These differences may be a result of fixation procedures used for the type specimens, as tegumental scales and the rodlets of the squamodiscs are frequently lost if fixation does not occur immediately after the death of the helminth.
Several other differences between present specimens and the original account of P. yucatanensis are in part a result of the original description being based on two distinct species. Figures 1A (whole mount), 1B (MCO), and 1H (ventral bar) of Vidal-Martínez et al. [50] are undoubtedly from specimens of P. justinella (compare with Figs. 17,19,23). The original figures show the whole mount to have a vaginal sclerite with a single large chamber, the comparatively large MCO with delicate chamber walls and a tapered cone, and the ventral bar being short and robust, all features of P. justinella. In P. yucatanensis (s. s.), the vaginal sclerite is comparatively small with two chambers (Fig. 10), the smaller MCO has a cylindrical cone and robust chamber walls (Fig. 11), and the ventral bar is slender and elongate (Fig. 16).
Finally, the original description of P. yucatanensis includes several erroneous statements and depictions. The whole-mount figure shows the germarium looping the right intestinal cecum ventrodorsally (germarium loops the right cecum dorsoventrally in all species of Pseudorhabdosynochus); the description and whole-mount drawing (Fig. 1A) suggest that only four pairs of hooks are present (the species possesses a full complement of seven pairs of hooks having the usual distribution in the haptor [32,33]); and although eggs were not observed in the specimens of P. yucatanensis (s. s.) from Florida, the original measurements of the egg (22 long · 12 wide) are hardly large enough as all eggs observed in the species of Pseudorhabdosynochus collected during the present study are in the order of 100 lm in length.
Pseudorhabdosynochus yucatanensis (s. s.) most closely resembles P. meganmarieae n. sp. in the comparative morphology of their vaginal sclerites. In both species, the sclerite possesses two small chambers and a distal funnel-shaped tube, but in P. yucatanensis, the sclerite is smaller and more delicate than in P. meganmarieae. The MCO of P. yucatanensis has a cylindrical cone and thick walls of the distal three chambers, while the cone is tapered and the walls of distal chambers are comparatively thin in P. meganmarieae. Finally, the shafts of the dorsal and ventral anchors of P. yucatanensis are comparatively short and arcing, but in P. meganmarieae, they are noticeably longer and minimally arced. Etymology: The specific name is in honor of our friend and colleague Dr. Jean-Lou Justine, Muséum National d'Histoire Naturelle, Paris, France, in recognition of his extensive work on the species of Pseudorhabdosynochus occurring in the western Pacific Ocean and for his support of the present study by providing type specimens from the MNHN.

Description (Figs. 17-24)
Body fusiform, dorsoventrally flattened, with a slight constriction at level of MCO; peduncle with small tegumental scales having rounded anterior margins. Cephalic region broad, with two terminal and two bilateral poorly developed lobes, three bilateral pairs of head organs, two bilateral groups of cephalic-gland cells at level of pharynx. Four eyespots lacking lenses immediately anterior to pharynx; members of posterior pair larger, slightly closer together than those of anterior pair; accessory chromatic granules small, irregular in outline, uncommon in cephalic region. Pharynx ovate to subspherical, muscular; esophagus short to nonexistent; intestinal Bilateral and common vitelline ducts not observed; vitellarium dense, absent in regions of other reproductive organs, otherwise extending in bilateral fields of trunk from level of MCO to anterior limit of peduncle; bilateral fields confluent posterior to testis. Egg ovate (often collapsed due to staining and mounting procedures), lacking filaments.

Remarks
Pseudorhabdosynochus justinella n. sp. is most similar to P. woodi n. sp. based on the comparative morphology of the vaginal sclerite, the ventral bar, and the ventral and dorsal anchors. In both species, the vaginal sclerite possesses an elongate sigmoid distal tube attached to the distal end of the chamber, the ventral bar is short and robust, the deep root of the ventral anchor is shorter than the superficial root, and the dorsal anchors of the two species are morphologically indistinguishable. Pseudohaliotrema justinella differs from P. woodi by having a vaginal sclerite with a larger (~20 lm in diameter) subspherical chamber (vaginal sclerite with a small [~10 lm in length] ovate chamber in P. woodi).
Pseudorhabdosynochus justinella, P. woodi, and P. bunkleywilliamsae spp. n., from three western Atlantic species of groupers making up the terminal clade (E. guttatus (E. morio, E. striatus)) within Epinephelus [4], appear to form a complex of morphologically similar species characterized by having a vaginal sclerite with a distal sigmoid tube arising from the distal end of the chamber. Although phylogenetic analyses of the helminths are wanting, occurrence of these parasites on closely related congeneric groupers suggests that some level of coevolution occurred between the parasites and their respective hosts. Similar relationships between species of Pseudorhabdosynochus species and their grouper hosts assigned to Mycteroperca may have also been recognized (see Remarks for P. kritskyi), indicating that the Pseudorhabdosynochus species and their hosts may provide useful models for investigating coevolutionary relationships.
The original description of P. yucatanensis [50] was based on a series of 14 specimens that included members of both P. yucatanensis (s. s.) and P. justinella (see Remarks for P. yucatanensis). Pseudorhabdosynochus yucatanensis has been subsequently reported only by Vidal-Martínez and coworkers from regions near its type locality (see References listed above in ''Previous records''). Because Vidal-Martínez and coworkers apparently did not differentiate between the two species, the latter records probably also included specimens of P. justinella. Nonetheless, those records published subsequent to the original description of P. yucatanensis require confirmation for the presence of both P. yucatanensis and P. justinella. bilateral poorly developed lobes, three bilateral pairs of head organs, pair of bilateral groups of cephalic-gland cells at level of pharynx. Four eyespots immediately anterior to pharynx, lacking lenses; members of posterior pair slightly larger, closer together than those of anterior pair; accessory chromatic granules small, irregular in outline, usually absent in cephalic region. Pharynx ovate, muscular; esophagus short to nonexistent; intestinal ceca blind, extending posteriorly to peduncle, diverging posterior to testis. Peduncle broad. Haptor subtriangular, with dorsal and ventral anteromedial lobes containing respective squamodiscs and lateral lobes having hook pairs 2-4, 6, 7. Squamodiscs subequal, with 14 or 15 U-shaped rows of rodlets; three or four innermost rows oval, closed. Ventral anchor with elongate superficial root, long deep root having lateral swelling, slightly curved shaft, and short recurved point extending just short of level of tip of superficial root.

Remarks
Groupers assigned to Mycteroperca are parasitized by a complex of similar species of Pseudorhabdosynochus that differ from congeners infecting other western Atlantic serranids primarily in the comparative morphology of the vaginal sclerite. The complex includes P. kritskyi from M. microlepis, Pseudorhabdosynochus hyphessometochus n. sp. from M. interstitialis, P. capurroi from M. bonaci, Pseudorhabdosynochus vascellum n. sp., and Pseudorhabdosynochus contubernalis n. sp. from M. phenax and Pseudorhabdosynochus mycteropercae n. sp. from M. tigris. In these species, the vaginal sclerite has a single subspherical to ovate chamber and a distal tube that is strongly recurved near its articulation with the vaginal vestibule (Fig. 26).
Pseudorhabdosynochus kritskyi differs from P. vascellum and P. hyphessometochus by having a large cavity within the chamber of the vaginal sclerite (cavity comparatively small in P. vascellum and P. hyphessometochus) and from P. vascellum and P. contubernalis by having a short heavy cone of the MCO (cone delicate in latter two species). It is distinguished from P. mycteropercae by having comparatively short dorsal and ventral anchor shafts and a dorsal bar with an enlarged medial end (medial end of dorsal bar spatulate in P. mycteropercae). It differs further from these species by having more rows of rodlets in the haptoral squamodiscs (14 or 15 rows in P. kritskyi, 11 or 12 in P. vascellum, 12-14 in P. contubernalis, and 12 or 13 in P. mycteropercae and P. hyphessometochus). Finally, the tegument is smooth and lacking scales in P. kritskyi, P. capurroi, P. vascellum, P. hyphessometochus, and P. mycteropercae (tegument scaled in posterior trunk and peduncle in P. contubernalis).
In view of the similarity of species infecting groupers assigned to Mycteroperca, the records of P. kritskyi from M. bonaci, M. tigris, M. venenosa, E. guttatus, and C. fulva in Puerto Rico [44] require confirmation. Unfortunately, Rios [44] apparently did not deposit voucher specimens of the helminths from Puerto Rican groupers, and his material was not available for study.  Examination of a black grouper housed in the FSBC and collected by FWC/FWRI personnel in 1967 provided the 10 specimens identified herein as P. capurroi. Although of sufficient quality to determine their specific identity, the latter specimens had severely contracted which precluded determination of many characters associated with their reproductive systems and the possibility of providing a redescription and a wholemount figure of the species. Nonetheless, the species is easily differentiated from all congeners by the morphology of its dorsal bars, which Vidal-Martínez & Mendoza-Franco [52] described as being ''twisted''. The morphology of the anchors, ventral bar, hooks, and vaginal sclerite is nearly identical to that of P. kritskyi, which differs most significantly from P. capurroi by possessing dorsal bars with enlarged bilobed medial ends and lacking the twisted nature of those of P. capurroi.

Pseudorhabdosynochus capurroi
Espínola-Novelo et al. [9] indicated that two species of Pseudorhabdosynochus occurred on M. bonaci off the Yucatan Peninsula, Mexico, near the type locality of P. capurroi. While no evidence is available that would suggest that the original description [52] was based on specimens representing two distinct species as occurred in the original description of P. yucatanensis, confirmation of the identity of P. capurroi may depend on examination of its holotype if another species of Pseudorhabdosynochus is verified from M. bonaci in the region (see Remarks for P. yucatanensis and P. justinella).
Pseudorhabdosynochus hyphessometochus n. sp.  Etymology: The specific name (a noun) is from Greek (hyphesson = somewhat smaller + metochos = a companion) and refers to the species being a member of the group of similar species of Pseudorhabdosynochus parasitizing groupers assigned to Mycteroperca and having a comparatively small cavity within the chamber of the vaginal sclerite.
Description (Figs. [40][41][42][43][44][45][46][47][48] Body flattened dorsoventrally, with broad cephalic region, trunk with nearly parallel lateral margins, and moderately long peduncle tapering posteriorly. Tegumental scales absent. Cephalic region with terminal and two bilateral poorly developed lobes; three pairs of head organs; pair of bilateral groups of cephalic-gland cells at level of pharynx. Two pairs of eyespots anterior to pharynx lacking lenses; chromatic granules small, irregular in outline; accessory granules usually absent in cephalic region. Pharynx subspherical; esophagus short to nonexistent; intestinal ceca blind, extending posteriorly into anterior portion of peduncle. Haptor with dorsal and ventral anteromedial lobes containing respective squamodiscs and lateral lobes having hook pairs 2-4, 6, 7. Squamodiscs subequal, with 12 or 13 concentric U-shaped rows of rodlets; innermost rows of ventral squamodisc (three) and dorsal squamodisc (two) closed, forming ovals. Ventral anchor with short superficial root, deep root with small lateral swelling, slightly curved to straight shaft, and recurved point extending to level of tip of superficial root. Dorsal anchor with subtriangular base, short roots, curved shaft, and recurved point extending past level of tip of superficial root. Ventral

Remarks
Pseudorhabdosynochus hyphessometochus n. sp. is a member of the apparently closely related group of Pseudorhabdosynochus species infecting most Mycteroperca species occurring in the western Atlantic region (see Remarks for P. kritskyi for a list of species). It most closely resembles P. mycteropercae n. sp. in the basic morphology of the MCO and haptoral sclerites but is distinguished from the latter species by having a vaginal sclerite with a smaller thick-walled chamber with a reduced cavity and a distal tube with a single recurve before its attachment to the vaginal vestibule (vaginal sclerite with a comparatively thinner wall and larger cavity of the chamber and a double recurve of the distal tube in P. mycteropercae). Body dorsoventrally flattened. Tegumental scales with rounded anterior margins extending from peduncle anteriorly into posterior trunk. Cephalic region broad, with terminal and two bilateral poorly developed lobes, three bilateral pairs of head organs, pair of bilateral groups of cephalic-gland cells at level of pharynx. Two pairs of eyespots lacking lenses immediately anterior to pharynx; one to all eyespots poorly defined, apparently replaced by dissociated chromatic granules; accessory chromatic granules small, irregular in outline, usually present in cephalic region. Pharynx subspherical to subovate; esophagus short to nonexistent; intestinal ceca blind, extending posteriorly to near peduncle. Peduncle broad. Haptor with dorsal and ventral anteromedial lobes containing respective squamodiscs and lateral lobes having hook pairs 2-4, 6, 7. Squamodiscs subequal, with 14-17 (usually 15) U-shaped rows of rodlets; innermost row teardrop shaped, closed. Ventral anchor with short superficial root, longer deep root having lateral swelling, slightly curved shaft, and recurved point extending just past level of tip of superficial root. Dorsal anchor with subtriangular base, superficial root short to lacking, short deep root, slightly arcing shaft, recurved point extending past level of tip of superficial root. Ventral bar with medial constriction, tapered ends, longitudinal medioventral groove.

Remarks
The original description of P. sulamericanus [46] was based on 11 of 22 specimens they observed parasitizing a single snowy grouper from southern Brazil. The helminths collected from snowy and Warsaw groupers off Florida during the present study generally correspond to the original description, except that Santos et al. [46] reported that the ''vas deferens enters the basal part of the cirrus-bulb [MCO], forming a large, round reservoir of the male accessory glands, which give an appearance of being an additional [5th] chamber of the proximal cirrus-bulb'' (articles and brackets ours). Their statement is somewhat confusing because they implied that their so-termed reservoir is formed from the vas deferens but apparently serves as storage for product from the male accessory glands (prostate glands?).
Examination of the larger collection of P. sulamericanus from the hosts off Florida revealed that this ''round reservoir of the male accessory glands'' is actually a large portal in the dorsal wall of the proximal chamber of the MCO through which the distal ducts of the male reproductive system enter the organ. Santos et al. [46] apparently mistook the rim of the portal for walls of the reservoir of the male accessory glands. The portal is not unique to P. sulamericanus. It has been observed on all species described herein for which full descriptions or redescriptions are presented. The portal is usually not visible in individual specimens in which the wall of the proximal chamber of the MCO has collapsed.
Pseudorhabdosynochus sulamericanus is most similar to P. firmicoleatus n. sp. based on comparative morphology of the vaginal sclerite, MCO, and haptoral elements. The vaginal sclerite of both species has a comparatively small basal chamber and a small secondary bulge of the tube that flares at its union with the vaginal vestibule. The sclerite of P. sulamericanus, however, differs from that of P. firmicoleatus by having a slightly larger chamber and irregular sclerites associated with the distal tube. Etymology: The specific name (an adjective) is from Latin (firm/i = firm + cole/o = sheath +-atus = marked by having) and refers to the heavy thick-walled chambers of the MCO.

Remarks
This species most closely resembles P. sulamericanus in the general morphology of the vaginal sclerite. The structure in both species possesses a delicate distal funnel at its attachment to the vaginal vestibule, a proximal bulge of the distal tube, and a small chamber. In P. firmicoleatus, however, the vaginal sclerite is delicate and lacks the irregular sclerites along the distal tube typical of P. sulamericanus. It further differs from P. sulamericanus in that the deep root of the ventral anchor has its proximal end directed dorsally (deep root of ventral anchor of P. sulamericanus straight). Finally, tegumental scales are lacking and the squamodiscs of P. firmicoleatus have 11-13 (usually 12) rows of rodlets (tegumental scales present and 14-17 rows, usually 15, in the squamodics of P. sulamericanus).
No significant differences were observed between specimens of P. firmicoleatus collected from yellowedge and snowy groupers (compare Figs. 58-72). The differences in the cone of the MCO depicted in Figures 59 and 65 were not specific to specimens from the respective hosts, but occurred among specimens from both hosts. Body flattened dorsoventrally. Tegumental scales small, with rounded anterior margins, extending from peduncle anteriorly into posterior trunk. Cephalic region broad, with terminal and two bilateral poorly developed lobes, three bilateral pairs of head organs, pair of bilateral groups of cephalic-gland cells at level of pharynx. Four eyespots lacking lenses anterior to pharynx; members of posterior pair larger and slightly closer together than those of anterior pair; accessory chromatic granules small, irregular in outline, infrequent or absent in cephalic region. Pharynx subovate, muscular; esophagus short to nonexistent; intestinal ceca blind, extending posteriorly to peduncle. Peduncle broad, tapered posteriorly. Haptor subtriangular, with dorsal and ventral anteromedial lobes containing respective squamodiscs and lateral lobes having hook pairs 2-4, 6, 7. Squamodiscs subequal, with 11-13 (usually 12) concentric U-shaped rows of rodlets; innermost two rows usually closed, teardrop shaped. Ventral anchor with comparatively short superficial root, elongate deep root having lateral swelling, slightly curved shaft and short recurved point extending to just

Remarks
Pseudorhabdosynochus mcmichaeli n. sp. is easily distinguished from all congeners from western Atlantic waters by its unique vaginal sclerite. Within the region, it is probably most similar to the congeners infecting other Mycteroperca species. In P. mcmichaeli, however, the vaginal sclerite has two tandem chambers, each with comparatively thin walls, while all other species infecting Mycteroperca species, including P. kritskyi, P. capurroi, P. vascellum n. sp., P. hyphessometochus, P. contubernalis n. sp., and P. mycteropercae n. sp., possess a vaginal sclerite with a single comparatively thickwalled chamber.
Based on the similarities of the respective vaginal sclerites, P. mcmichaeli most closely resembles the recently described Etymology: This species is named for Megan-Marie (Duckworth) Bakenhaster, who helped to make this study possible by spending weeks and innumerable late nights isolated from adult company while caring for a young, singular child possessed of strong opinions on the limits of parental authority. Her patience and perseverance facilitated our collections of specimens of this and other species of Pseudorhabdosynochus reported herein.

Description (Figs. 81-88)
Body elongate ovate, flattened dorsoventrally. Tegument smooth, lacking tegumental scales. Cephalic region broad, with terminal and two bilateral poorly developed lobes, three bilateral pairs of head organs, pair of bilateral groups of cephalic-gland cells at level of pharynx. Four eyespots lacking lenses, lying anterior to pharynx; members of posterior pair larger, closer together than those of anterior pair; accessory chromatic granules small, irregular in outline, uncommon or absent in cephalic region. Pharynx subovate; esophagus short to nonexistent; intestinal ceca blind, extending posterior to anterior limit of peduncle. Peduncle broad, tapered posteriorly. Haptor subtriangular, with dorsal and ventral anteromedial lobes containing respective squamodiscs and lateral lobes having hook pairs 2-4, 6, 7; squamodiscs subequal, with 11-13 (usually 12) U-shaped rows of rodlets; 2-3 innermost rows circular, closed. Ventral anchor with subequal comparatively short superficial and deep roots; deep root with slight lateral swelling; shaft long straight; short recurved point extending to level of tip of superficial root. Dorsal anchor with subtriangular base, superficial root short to lacking, deep root knoblike, comparatively long shaft forming gentle arc, recurved point extending past level of tip of superficial root. Ventral bar with deep medial constriction, elongate tapered ends, longitudinal medioventral groove. Paired dorsal bar with spatulate medial end. Hook with long slightly depressed thumb, delicate point, uniform shank; FH loop nearly shank length. Testis subspherical, lying dorsoposterior to germarium; proximal vas deferens not observed; seminal vesicle an indistinct dilation of distal vas deferens, lying just posterior to MCO; ejaculatory bulb and duct not observed: large vesicle (prostatic reservoir?) with lightly staining reticulate contents dextral of distal chamber of MCO. MCO reniform, quadriloculate, with long tapered cone, moderately long distal tube, and variable retractile filament often not observed; chamber walls of MCO comparatively thin, delicate, often collapsed. Germarium pyriform; germarial bulb lying diagonally at midlength of trunk, with elongate distal loop dorsoventrally around right intestinal cecum; ootype lying on or near body midline, with well-

Remarks
Pseudorhabdosynochus meganmarieae n. sp. is easily distinguished from all other known congeners from the western Atlantic region by having ventral anchors with short roots (superficial root slightly longer than deep root) and an elongate straight shaft. Based on the presence of two small chambers and a distal funnel-shaped tube in the vaginal sclerites, P. meganmarieae most closely resembles P. yucatanensis, but the vaginal sclerite in P. meganmarieae is more robust and its distal end has a more pronounced funnel shape than that of P. yucatanensis. It differs further from P. yucatanensis by lacking tegumental scales (scales present in P. yucatanensis) and by having a comparatively deep medial constriction in the ventral bar (medial constriction of the ventral bar minimal in P. yucatanensis) and a tapered cone and thinner walls of the chambers of the MCO (cone cylindrical and walls of the three distal chambers noticeably thicker in P. yucatanensis).

Remarks
Pseudorhabdosynochus vascellum n. sp. belongs to the group of congeners parasitizing groupers assigned to Mycteroperca and characterized by having a distally reflexed tube and a single chamber in the vaginal sclerite. The group includes P. kritskyi, P. capurroi, P. vascellum, P. contubernalis n. sp., P. hyphessometochus n. sp., and P. mycteropercae n. sp. Except for P. hyphessometochus, P. vascellum is easily distinguished from the these species by its small thick-walled chamber of the vaginal sclerite having a meager cavity (chamber of the remaining species comparatively large and with a large cavity). Pseudorhabdosynochus hyphessometochus also possesses a vaginal sclerite with a thick wall of the chamber, but the cavity of the chamber in this species is comparatively large. The new species is probably closest morphologically to P. contubernalis by possessing a delicate, almost nonexistent cone of the MCO. Etymology: The specific name (a noun) is from Latin (contubernalis = a companion or comrade) and refers to its co-occurrence with P. vascellum n. sp. on M. phenax.  Body flattened dorsoventrally, with nearly parallel lateral margins along trunk. Tegument with numerous scales on peduncle; scales small, with rounded anterior margins. Cephalic region broad, with terminal and two bilateral poorly developed lobes, three bilateral pairs of head organs, three pairs of bilateral groups of cephalic-gland cells prepharyngeal (two pairs) and at level of pharynx. Four eyespots lacking lenses anterior to pharynx; members of posterior pair larger, closer together than those of anterior pair; accessory chromatic granules small, irregular in outline, infrequent in cephalic region. Pharynx subspherical, muscular; esophagus short to nonexistent; intestinal ceca blind, extending posteriorly to peduncle.

Remarks
This species most closely resembles P. vascellum n. sp. It differs from P. vascellum by its larger overall size (body length about 700 lm vs. 500 lm) and length of the MCO (about 60 lm vs. 40 lm). In addition, the proximal two chambers of the MCO of P. contubernalis n. sp. have comparatively thin walls which frequently have collapsed or are absent (walls of proximal chambers sturdy and seldom collapsed in P. vascellum). Pseudorhabdosynochus contubernalis is a member of the group of Pseudorhabdosynochus species (P. kritskyi, P. capurroi, P. mycteropercae n. sp., P. contubernalis, P. hyphessometochus n. sp., and P. vascellum) infecting species assigned to Mycteroperca by having a prominent chamber and a distally recurved tube of the vaginal sclerite. It differs from all of these species by having a scaled tegument on the peduncle (tegumental scales absent in all other members of the group); in addition, it is differentiated from P. kritskyi, P. capurroi, P. hyphessometochus, and P. vascellum by having a doubly recurved distal tube of the vaginal sclerite (distal tube simply recurved in all of the latter species). The distal tube of the vaginal sclerite of P. mycteropercae is doubly recurved.

Remarks
This species was not collected during the present study, and the three type specimens available in the USNPC were insufficient for a complete redescription of the species. Nonetheless, P. monaensis is easily distinguished from its congeners of the western Atlantic Ocean by its unique vaginal sclerite (Fig. 107). Other features defining the species include the elongate ventral bar with a minimal medial constriction (Fig. 111) and an MCO having a comparatively long cone (Fig. 106).
Dyer et al. [6] did not indicate how many specimens were used to develop the original description of this species but stated that six specimens were used to obtain measurements and that ''specimens'' had been deposited in the USNPC. USNPC records showed that the collection only holds three specimens of P. monaensis (the holotype and two paratypes). Whereas Dyer et al. [6]  Body flattened dorsoventrally, elongate ovate in dorsoventral view. Tegument smooth. Cephalic region broad, with terminal and two bilateral poorly developed lobes; head organs, cephalic-gland cells not observed. Four eyespots anterior to pharynx lacking lenses; members of posterior pair larger, closer together than those of anterior pair; chromatic granules small, irregular in outline; accessory granules infrequent or absent in cephalic region. Pharynx subspherical; gut not observed. Peduncle broad. Squamodiscs subequal, with 11-13 concentric rows of rodlets; ventral squamodisc with two or three innermost rows closed; dorsal squamodisc with two innermost rows closed. Shape of haptor indistinct. Ventral anchor with short superficial and deep roots; deep root with lateral swelling; shaft slightly arced, recurved point extending to level of tip of superficial root. Dorsal anchor with subtriangular base, inconspicuous superficial root, knoblike deep root, minimally arced shaft, and slightly recurved point extending past level of tip of superficial root. Ventral bar with conspicuous medial constriction, tapered ends, longitudinal ventral groove. Paired dorsal bar with spatulate medial end. Hook with elongate slightly depressed thumb, delicate point, uniform shank; FH loop nearly shank length. Gonads indistinct; soft reproductive ducts not observed. MCO reniform, quadriloculate, with short cone and elongate distal tube (based on voucher specimens); retractile filament not observed.

Remarks
The description of P. mycteropercae n. sp. is based on three type specimens collected from the tiger grouper in Bermuda by John D. Mizelle and Raymond M. Wood, who deposited them in the USNPC as Diplectanum mycteropercae (nomen nudum), and supplemented by 23 voucher specimens from a tiger grouper in the ichthyology collection of the Florida Fish and Wildlife Conservation Commission in St. Petersburg, Florida (FSBC 11990). Although the type and voucher specimens were of sufficient quality to determine that they represented the new species, many features of the reproductive systems could not be discerned and a drawing of a whole mount was not possible.
The species differs from other members of the group of species infecting Mycteroperca spp. by having an open chamber of the vaginal sclerite (chamber of P. kritskyi, P. capurroi, P. vascellum n. sp., and P. contubernalis n. sp. is closed; in P. hyphessometochus n. sp., the closed anterior wall of the chamber is formed by the two overlapping ends of the chamber wall). In addition, the cavity of the chamber in P. vascellum is small (large in P. mycteropercae); the wall of the chamber in P. contubernalis has external projections (absent in P. mycteropercae); the distal portion of the distal tube of the vaginal sclerite is simply recurved in P. kritskyi, P. capurroi, and P. hyphessometochus (distal tube doubly recurved in P. mycteropercae). Other differences include a comparatively small spatulate medial end of the dorsal bars in P. mycteropercae (medial ends large in P. kritskyi and P. capurroi and subtriangular in P. contubernalis) and a ventral anchor having a deep root shorter than the superficial root in P. mycteropercae (deep roots subequal or longer than the superficial roots in P. kritskyi, P. capurroi, P. hyphessometochus, and P. vascellum). Museum specimen examined: Paratype of P. monaensis, USNPC 82790 (MT26-25B) (redetermined as P. williamsi).
Etymology: This species is named for Dr. Ernest (Bert) H. Williams, Jr., professor (retired), University of Puerto Rico, Lajas, Puerto Rico, in recognition of his extensive research on the parasites of fishes in the Caribbean region. Dr. Williams was one of the investigators who collected the voucher specimen (a paratype of P. monaensis) of this species from rock hind in Puerto Rico.

Description (Figs. 120-128)
Body flattened dorsoventrally, subovate in dorsoventral view. Tegumental scales scattered on peduncle. Cephalic region broad, with terminal and two bilateral poorly developed lobes; three pairs of head organs; pair of bilateral groups of cephalic-gland cells lateral to pharynx. Four eyespots anterior to pharynx lacking lenses; members of posterior pair larger, closer together than those of anterior pair; chromatic granules small, irregular in outline; few accessory granules near eyespots or absent in cephalic region. Pharynx subspherical; esophagus short to nonexistent; intestinal ceca blind, extending to level of anterior limit of peduncle. Peduncle broad.

Remarks
This species was first thought to be distinct upon examination of the type specimens of P. monaensis deposited in the USNPC, when one of the specimens [USNPC 82790 (MT26-25B)] was found to lack the distinctive vaginal sclerite of P. monaensis. Confirmation of the validity of the specimen representing an undescribed species was obtained when numerous specimens of the species were found infecting two rock hinds off Florida. In that species, herein named P. williamsi n. sp., the vaginal sclerite is comparatively small with a small subspherical chamber [vaginal sclerite much larger and with an ovate chamber in P. monaensis (compare Figs. 107 and 123)]. Pseudorhabdosynochus williamsi differs further from P. monaensis by possessing a small MCO (about 51 lm in P. williamsi vs. 121 lm in P. monaensis), and dorsal bars with a minimally expanded medial end (medial end of dorsal bar about twice as wide as the proximal end in P. monaensis). The new species most closely resembles P. justinella n. sp. and P. meganmarieae n. sp. based on the comparative morphology of the respective vaginal sclerites. It differs from P. justinella by having a delicate cone of the MCO (cone robust in P. justinella) and a ventral bar with a moderately constricted medial region (constriction minimal in P. justinella). It differs from P. meganmarieae by the minimally expanded medial end of the dorsal bars (medial end of dorsal bar about twice as wide as the distal end in P. meganmarieae) and by having the shaft of the ventral anchor forming a gentle arc (shaft comparatively straight in P. meganmarieae). Finally, the morphology of the MCO varied significantly among specimens of P. williamsi.
In what appeared to be fully mature specimens, the walls of the respective chambers were noticeably thicker than those of putatively younger specimens (compare Figs. 121 and 122).
Pseudorhabdosynochus bocquetae (Oliver & Paperna, 1984) Kritsky & Beverley-Burton, 1986 was described from a fish identified as Epinephelus adscensionis and collected from the Gulf of Aqaba [40]. This species possesses a relatively non-descript vaginal sclerite similar to that of P. williamsi. Pseudorhabdosynochus williamsi, however, is easily distinguished from P. bocquetae by having 19 open concentric rows of rodlets in the squamodisc (8-10 rows with the innermost three rows closed in P. bocquetae).
The recording of P. bocquetae on E. adscensionis in the Gulf of Aqaba is clearly erroneous. The fish host reported by Oliver & Paperna [40] for P. bocquetae apparently does not occur within these waters. According to Heemstra & Randall [16], rock hind are known from Ascension and St. Helena islands and the western Atlantic from Massachusetts into the Gulf of Mexico and Caribbean Sea, and south to southern Brazil. It is highly unlikely, therefore, that Oliver & Paperna [40]  Body flattened dorsoventrally, elongate-ovate in dorsoventral view. Tegument with numerous small scales in posterior trunk and peduncle; scales indistinct or appearing absent in poorly fixed specimens. Cephalic region narrow when body relaxed, with terminal and two bilateral poorly to moderately developed lobes; head organs large, usually poorly defined; pair of bilateral groups of cephalic-gland cells lateral or posterolateral to pharynx. Four eyespots prepharyngeal, equidistant, lacking lenses; members of posterior pair larger than those of anterior pair; chromatic granules small, irregular in outline; accessory granules absent. Pharynx subspherical; esophagus short; intestinal ceca blind, extending to level of anterior limit of peduncle. Peduncle broad, tapered posteriorly. Haptor with dorsal and ventral anteromedial lobes containing respective squamodiscs and lateral lobes having hook pairs 2-4, 6, 7. Squamodiscs subequal; each with 11-12 (usually 11) concentric U-shaped rows of rodlets; innermost row closed, subcircular. Ventral anchor with deep root shorter than superficial root, slightly curved shaft, point extending to level of tip of superficial root. Dorsal anchor with subtriangular base, short upright superficial root, knoblike deep root, arced shaft, and recurved point extending past level of tip of superficial root. Ventral bar with slight medial constriction, tapered ends, longitudinal ventral groove. Paired dorsal bar with slightly expanded medial end. Hook with slightly depressed thumb, delicate point, uniform shank; FH loop approaching shank length. Testis subspherical; distal soft tissue organs of male reproductive system not observed. MCO reniform, quadriloculate, with elongate cone, short distal tube, variable retractile filament. Remarks Pseudorhabdosynochus mizellei n. sp. most closely resembles P. williamsi n. sp. in the basic morphology of the vaginal sclerite and MCO. In both species, the sclerite has small chambers and the cone of the MCO is elongate. The new species is easily differentiated from P. williamsi by the deep root of the ventral anchor being shorter than the superficial root and the shaft of the dorsal anchor forming a gentle curve (dorsalanchor shaft comparatively straight in P. williamsi). In addition, the ventral and dorsal bars of P. mizellei are noticeably shorter than those of P. williamsi.
Although P. mizellei occurs concurrently with P. woodi n. sp. on red hind in Bermuda (based on specimens collected by Mizelle and Wood, unpublished, and deposited in the USNM), the latter species was not recovered from red hind collected off Florida during the present study. Pseudorhabdosynochus mizellei differs from P. woodi by having a comparatively small vaginal sclerite with two small chambers. The vaginal sclerite of P. woodi has a larger single ovate chamber (compare Figs. 130 and 156).

Pseudorhabdosynochus beverleyburtonae (Oliver, 1984) Kritsky & Beverley-Burton, 1986
Syns Diplectanum americanum of Euzet & Oliver (1965), nec Price [42]; Cycloplectanum americanum (Price, 1937)  Body dorsoventrally flattened, with nearly parallel lateral margins. Tegument smooth, lacking scales. Cephalic region broad, with terminal and two bilateral poorly developed lobes, three bilateral pairs of head organs, pair of bilateral groups of cephalic-gland cells at level of pharynx. Two pairs of prepharyngeal eyespots lacking lenses; members of posterior pair larger, closer together than those of anterior pair; chromatic granules small, irregular in outline; accessory granules generally absent in cephalic region. Pharynx subspherical to subovate, muscular; esophagus short; intestinal ceca blind, extending posteriorly to level of anterior limit of peduncle. Peduncle broad, tapered posteriorly. Haptor with dorsal and ventral anteromedial lobes containing respective squamodiscs and lateral lobes having hook pairs 2-4, 6, 7. Squamodiscs subequal, with 10-12 (usually 12) concentric U-shaped rows of rodlets; innermost two or three rows closed, circular. Ventral anchor with short superficial and deep roots; deep root with small lateral swelling; shaft curved; short recurved point extending to level of tip of superficial root. Dorsal anchor with subtriangular base, superficial root short to lacking, deep root knoblike, arcing shaft, short recurved point extending slightly past level of tip of superficial root. Ventral bar with conspicuous medial constriction, tapered ends, longitudinal medioventral groove. Paired dorsal bar with spatulate irregular medial end, bilobed lateral end. Hook with depressed thumb, delicate point, uniform shank; FH loop nearly shank length. Testis subspherical, lying sinistroposterior to germarium along body midline; proximal vas deferens not observed; seminal vesicle a simple dilation of vas deferens; distal vas deferens forming a sigmoid curve before entering lacriform ejaculatory bulb; ejaculatory duct entering dorsal portal of proximal chamber of MCO; vesicle with reticulate contents (prostatic reservoir?) dextral to MCO. MCO quadriloculate, with thick walls, long tapered cone, elongate distal tube, and long protruding filament. Germarium pyriform; germarial bulb lying to right of body midline and slightly overlapping testis, with distal loop dorsoventrally around right intestinal cecum; ootype lying on body midline, with poorly developed Mehlis' gland; uterus delicate, banana shaped when empty.

Remarks
This species was first recorded by Euzet & Oliver [10] as Diplectanum americanum from dusky grouper collected from the Mediterranean Sea and later by Ulmer & James [49] and Oliver [36,37] as Cycloplectanum americanum from the Mediterranean Sea. That the helminth from dusky grouper in the Mediterranean Sea represented a species distinct from C. americanum (now P. americanum) was later recognized by Oliver [38], who described it as Cycloplectanum beverleyburtonae. Kritsky & Beverley-Burton [25] transferred the species to Pseudorhabdosynochus when it was determined that C. americanum (sensu Price [42]), type species of Cycloplectanum , was a member of the senior Pseudorhabdosynochus Yamaguti, 1958. Although the synonymy of the two genera is broadly accepted, Oliver [39] continued to consider them distinct and C. beverleyburtonae as the valid name of this helminth.
The dusky grouper is one of only four epinephelin groupers with a trans-Atlantic distribution. In addition to M. marginata, the trans-Atlantic species include the rock hind, E. adscensionis, the Atlantic goliath grouper, E. itajara, and the Atlantic creolefish, Paranthias furcifer (Valenciennes). Dusky groupers are known from western Europe and the Mediterranean Sea to south around the southern tip of Africa; in the Americas, they have been reported from the coastal areas of southern Brazil [16]. It is the only trans-Atlantic grouper known to harbor a species of Pseudorhabdosynochus (P. beverleyburtonae) throughout its geographic range. Comparison of the type specimens of P. beverleyburtonae (USNPC 77469; MNHN 249H-TC 167, 249H-TC 167 bis) with the voucher specimen of Santos et al. [46] (NHMUK 1999.1.6.4-6) and those of the present study from M. marginata off southern Brazil, did not reveal any morphological features that distinguished eastern Atlantic from western Atlantic specimens. Thus, the Mediterranean and western Atlantic populations are considered conspecific as first proposed by Santos et al. [46]. Body flattened dorsoventrally, elongate ovate in dorsoventral view. Tegument smooth. Cephalic region broad, with terminal and two bilateral poorly developed lobes, three bilateral pairs of head organs, pairs of bilateral groups of cephalicgland cells prepharyngeal and at level of pharynx. Four eyespots lacking lenses anterior to pharynx; members of posterior pair larger, equidistant, or slightly closer together than those of anterior pair; chromatic granules small, subovate; accessory granules absent in cephalic region. Pharynx subspherical, muscular; esophagus short; intestinal ceca blind, extending posteriorly to anterior limit of peduncle. Peduncle broad. Haptor with dorsal and ventral anteromedial lobes containing respective squamodiscs and lateral lobes having hook pairs 2-4, 6, 7. Squamodiscs subequal, wider than peduncle, with 11 or 12 concentric U-shaped rows of rodlets. Ventral anchor with moderately long superficial and deep roots; deep root with lateral swelling; shaft slightly arced; recurved point extending to level of tip of superficial root. Dorsal anchor with Body flattened dorsoventrally, ovate in dorsoventral view. Tegument smooth, lacking scales. Cephalic region broad, with terminal and two bilateral poorly developed lobes; head organs, cephalic-gland cells not observed. Four eyespots anterior to pharynx lacking lenses; members of posterior pair larger, slightly closer together than those of anterior pair; chromatic granules small, irregular in shape; accessory granules absent in cephalic region. Pharynx subspherical; gut not observed. Peduncle broad. Squamodiscs subequal, with 11 or 12 concentric rows of rodlets; ventral squamodisc with two innermost rows closed; dorsal squamodisc with innermost row closed. Haptor with dorsal and ventral anteromedial lobes containing respective squamodiscs. Ventral anchor with moderately long superficial and deep roots; deep root with lateral swelling, somewhat shorter than superficial root; shaft forming gentle arc; recurved point extending to level of tip of superficial root. Dorsal anchor with subtriangular base, short superficial root, knoblike deep root, arced shaft, and recurved point extending past level of tip of superficial root. Ventral bar robust, with medial constriction, tapered narrow ends, longitudinal ventral groove. Paired dorsal bar with spatulate medial end. Hook with slightly depressed thumb, delicate point, uniform shank; FH loop nearly shank length. Gonads indistinct; soft reproductive ducts and vesicles not observed. MCO damaged by pressure from coverslip, reniform, quadriloculate, with short cone, elongate distal tube; retractile filament not observed. Vaginal sclerite with sigmoid distal tube, small ovate chamber. Vitellarium absent in regions of other reproductive organs, otherwise dense throughout trunk.

Remarks
This species is based on specimens obtained from one of two speckled hind examined for gill parasites and held in the FSBC ichthyology collection of the Florida Fish and Wildlife Conservation Commission. The infected speckled hind was collected in 1972 and was not fixed and preserved with its external parasites in mind. As a result, the specimens of P. tumeovagina n. sp. from this fish were in generally poor shape, and many of the internal features, particularly those of the male and female reproductive systems, could not be determined. Nonetheless, the unique vaginal sclerite clearly indicated the species to be new to science.
Pseudorhabdosynochus tumeovagina n. sp. is differentiated from all previously described species of Pseudorhabdosynochus from the region by having an expanded (bulbous) distal tube and a small chamber of the vaginal sclerite. It most closely resembles P. williamsi n. sp., by possessing an MCO having an elongate and curved distal cone and comparatively thick-walled chambers. Pseudorhabdosynochus tumeovagina differs from P. williamsi in the morphology of the distal tube of the vaginal sclerite (bulbous expansion of the distal tube lacking in P. williamsi). Infection site: Gill lamellae. Minimum Prevalence: 100% (1 yellowfin grouper examined and infected).

Remarks
Although the single specimen collected from the yellowfin grouper was strongly contracted and unsatisfactory for species identification, it was easily assigned to Pseudorhabdosynochus and recognized as a member of the species group infecting most western Atlantic Mycteroperca spp. (see Remarks for P. kritskyi for a list of species in the group) based on the general morphology of the MCO and vaginal sclerite. The basic morphology of its dorsal bars and ventral squamodisc, the latter with 16 rows of rodlets (4 innermost rows closed), indicated that the specimen was closest morphologically to P. capurroi. However, specific details of the haptoral sclerites, the dorsal squamodisc, the vaginal sclerite, the MCO, and the internal anatomy could not be determined, precluding resolution of the specimen as new or previously described. Specimens studied: 2 voucher specimens, USNM 1273685.

Remarks
While the two specimens of Pseudorhabdosynochus sp. 2 were unsatisfactory for species identification, they appear to represent an undescribed species. The vaginal sclerite comprises a small chamber associated with a complex of structures situated externally along its proximal wall; the distal tube of the vaginal sclerite was not visible. The MCO had an elongate cone, and the ventral and dorsal squamodiscs had 12 and 10 or 11 concentric rows of rodlets, respectively (two innermost rows closed in both squamodiscs). The single observed egg was bacilliform and lacked filaments. Pseudorhabdosynochus sp. 2 appears closest morphologically to P. mcmichaeli n. sp. based on the presence of an elongate cone of the MCO and a number of concentric rows of rodlets in the squamodiscs but can be differentiated from P. mcmichaeli by the morphology of their vaginal sclerites.

Pseudorhabdosynochus sp. 3
Host and locality: Tiger grouper, Mycteroperca tigris (Valenciennes) (Serranidae: Epinephelinae: Epinephelini) (FSBC 11990):~15 km NNW of Dry Tortugas National Park, Florida (24.533°N, 82.983°W; these coordinates are in the records of the FSBC collection but are not congruent with the written collecting notes accompanying the specimens, the latter of which are considered to be more accurate in this case), April 23, 1980. Infection site: Gill lamellae. Minimum Prevalence: 100% (1 specimen from Florida examined and infected).

Remarks
Specimens of Pseudorhabdosynochus sp. 3 were in poor condition, which precluded determination of internal anatomy and specific assignment of the specimens. Pseudorhabdosynochus sp. 3 appears closest, if not identical, to P. mcmichaeli n. sp., based on the comparative morphology of the MCO, vaginal sclerite, anchors, and ventral bar. In Pseudorhabdosynochus sp. 3, the MCO is delicate and has a long depressed cone, an elongate distal tube, and conspicuous filament; the vaginal sclerite has two apparently tandem chambers from which the delicate vaginal duct arises; and the ventral bar and dorsal and ventral anchors are similar to those of P. mcmichaeli. The only possibly significant difference observed between the specimens of Pseudorhabdosynochus sp. 3 and those of P. mcmichaeli is the medial end of the dorsal bar, which in Pseudorhabdosynochus sp. 3 is somewhat more spatulate. However, morphology of the dorsal bar is generally not a good feature for species identification because its appearance often changes depending on the rotation of the bar within the plane of view under microscopy.

Discussion
Species of Pseudorhabdosynochus are parasites almost exclusively of groupers (Serranidae) assigned to the tribe Epinephelini. Of the 25 known species of groupers assigned to the tribe and occurring in western Atlantic waters [4,16], individuals of 23, including those collected during the present study, were examined for species of Pseudorhabdosynochus. Prior to the present study, only seven species of Pseudorhabdosynochus were documented from seven epinephelin species in the region. Thirteen new species are described herein, resulting in a total of 20 species of Pseudorhabdosynochus known to infect the gills of these fishes off eastern North and South America.
This number is likely an underestimate of the total diversity of Pseudorhabdosynochus species on groupers in the region given that members of the genus generally exhibit a relatively high host specificity, with most restricted to a single species [48]. Although we found no infections by Pseudorhabdosynochus species in groupers belonging to six species (the coney Cephalopholis fulva, marbled grouper Dermatolepis inermis, Spanish flag Gonioplectrus hispanus, misty grouper Hyporthodus mystacinus, Atlantic creolefish Paranthias furcifer, and mutton hamlet Alphestes afer), our sample sizes for these potential hosts were small (generally < 5 specimens per species) and all representative host specimens were drawn from the shelves of the FSBC where fixation and sampling methods could easily have led to loss of parasite specimens. An additional two species of epinephelin groupers from the region [the comb grouper Mycteroperca acutirostris (Valenciennes) and the Venezuelan grouper Mycteroperca cidi (Cervigón)] have yet to be examined. In the present study, none of the 19 identified species of Pseudorhabdosynochus crossed host generic boundaries in host preference, and only two occurred on more than one congeneric host: P. firmicoleatus on Hyporthodus flavolimbatus and H. niveatus; and P. sulamericanus on H. niveatus and H. nigritus.
Recent studies on parasites of other fishes off the eastern coasts of North and South America further demonstrate that the overall monogenoidean fauna of the region is larger than previously recorded. In what are primarily focused studies dealing with specific host groups or individual species of fish in the region, new species of Monogenoidea have frequently been described [21, 24, 27, 43, 47, among others]. The monogenoidean fauna off western North and South America is even less documented, although a few studies, in which new species of Monogenoidea are described, have recently been published [15, 29, 30, 31, 41, 60, and others].
Based on molecular data, Craig & Hastings [4] revised the Epinephelini to include 11 genera, of which representatives of seven, comprising all epinephelin genera with species in the western Atlantic region, were examined for Pseudorhabdosynochus species during the present study. While phylogenetic analyses are lacking for this group of helminths, comparative morphology and the occurrence of Pseudorhabdosynochus species on these hosts suggest that concomitant speciation among these helminths occurred at least in part with that of their hosts. For example, the six host species assigned to Mycteroperca by Craig & Hastings [4] and examined during the present study are parasitized by morphologically similar species (P. kritskyi, P. capurroi, P. vascellum, P. contubernalis, P. hyphessometochus, P. mycteropercae, and Pseudorhabdosynochus sp. 1), suggesting that coevolution is a likely component of the evolutionary histories of the respective host/parasite relationships. Similarly, species of Hyporthodus are parasitized by identical or similar species of Pseudorhabdosynochus (P. sulamericanus and P. firmicoleatus), while P. yucatanensis, P. bunkleywilliamsae, and P. woodi, all parasites of Epinephelus spp., also may share a common ancestor based on the comparative morphology of their respective vaginal sclerites.
A note on the type species of Pseudorhabdosynochus Yamaguti, 1958 Kritsky & Beverley-Burton [25] discussed the concept of the type species of a genus sensu the International Code of Zoological Nomenclature (ICZN), in regard to that of Pseudorhabdosynochus. Based on the ICZN, these authors indicated that type species was a nomenclatural concept and not one of taxonomy or biology. As a result, Kritsky & Beverley-Burton [25] stated that the type species of Pseudorhabdosynochus was P. epinepheli Yamaguti, 1958, which was a junior subjective synonym of P. epinepheli (Yamaguti, 1938) Kritsky & Beverley-Burton, 1986. According to the ICZN, the placement of P. epinepheli Yamaguti, 1958 as a junior synonym does not invalidate the nominal species as the type species of Pseudorhabdosynochus. Unfortunately, some recent publications [20,46] erroneously stated that the type species of the genus was P. epinepheli (Yamaguti, 1938) Kritsky & Beverley-Burton, 1986, apparently because it was the senior synonym of the ''taxonomic'' species. Indeed, Justine [20] included the error in the title of his paper.
Subjective synonymy of the type species of a genus is not an unusual occurrence. An example comparable to that described above for Pseudorhabdosynochus was found within the genera comprising the host group on which the present study is based. Hyporthodus Gill was recently resurrected for 14 grouper species previously assigned to other epinephelin genera [4]. Hyporthodus was originally proposed by Gill [14], who by monotypy assigned Hyporthodus flavicauda Gill, 1861 as its type species. Hyporthodus flavicauda was listed as a subjective junior synonym of Epinephelus niveatus by Heemstra & Randall [16]. Craig & Hastings [4] accepted the junior subjective synonymy of H. flavicauda with E. niveatus (now H. niveatus), while rightfully recognizing H. flavicauda as the type species when resurrecting Hyporthodus. Information on the nomenclatural and taxonomic history of Hyporthodus and its type species is available in Eschmeyer & Fong [8], who concurred with the actions of Heemstra & Randall [16] and Craig & Hastings [4].
Additional funding for field sampling in the Gulf of Mexico was provided by three NOAA grants: NA06NMF4350009 to FWC; NA11NMF4720151) to the University of South Florida (USF); and NA12NMF454008) to USF. Additional sampling was conducted on research cruises funded by the NOAA awards to FWC: NA08NMF4330403 and NA11NMF4540116. The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the opinions or policies of the US government or any of its agencies. The authors confirm that there are no conflicts of interest or competing interests in regard to the manuscript.