Mémoire

Présence chez un Rongeur du Chili d’un Nématode Inglamidinae (sub. fam. nov.) appartenant aux Amidostomatidae, famille connue des Mammifères d’Australie

A chilean Rodent as host of a Nematode Inglamidinae (sub-fam. nov.) belonging to the Amidostomatidae previously known excluvisely from australian Mammals

¹ Laboratoire de Zoologie (Vers) associé au C.N.R.S., Muséum national d’Histoire naturelle, 43, rue Cuvier, F 75231 Paris Cedex 05, France.
² Instituto de Ecologia y Evolucion, Casilla 57-D, Universal Austral de Chile, Valdivia, Chile.

Résumé

Une nouvelle sous-famille d’Amidostomatidae est décrite chez des Cricétidés du Chili : Inglamidinae n. sous-f., représentée par le genre type et l’espèce type : Inglamidum akodon n. gen., n. sp.

La sous-famille est caractérisée, d’une part, par des éléments archaïques (structure céphalique), qui la rattachent aux autres Amidostomes, et, d’autre part, par des éléments évolués (monodelphie, synlophe, spicules), qui la rattachent aux Héligmosomes et, en particulier, à la lignée Viannaia-Viannella, parasite de Marsupiaux sud-américains.

Nous interprétons cette espèce comme un parasite de capture et nous pensons que des formes proches doivent se trouver chez d’autres Mammifères endémiques, en particulier les Marsupiaux. Du point de vue paléobiogéographique, cela permettrait de situer l’origine des Amidostomatidae de Mammifères à l’ère secondaire, au moment de l’expansion des Marsupiaux. Ces Nématodes auraient alors donné naissance aux autres Trichostrongyloidea par atrophie de la capsule buccale et aux Ancylostomatoidea par élaboration progressive des structures buccales. Contrairement à Inglis, nous préférons considérer les genres Globocephaloides et Hypodontus respectivement comme des Globocephalinae et Uncinariinae (Ancylostomatidae), et non comme des Amidostomatidae.

Abstract

The Inglamidinae n. sub-fam., a new sub-family of Amidostomatidae from chilean Cricetidae is described with Inglamidum akodon gen. et sp. n. as the type genus and species.

Out of the 23 Akodon captured in the same area, three samples of this nematode have been collected from two different species. These findings confirm that we are dealing with a well-adapted parasite and exclude the possibility of a fortuitous catch or an accidental transfer.

This family displays two significant groups of taxonomic characters, including archaic characters such as cephalic structures which unite them to the Amidostomatidae, and on the other hand some more recently elaborated characters such as monodelphism and shape of synlophe and spicules which relate them to the Heligmosoms and more significantly to the line Viannaia-Viannella parasite of South-American Marsupials.

We interpret this species as a « parasite of capture » and we assume that very similar species might occur in other endemic Mammals, mostly Marsupials.

On a paleobiogeographical point of view this interpretation would make due allowance for postulating that the Amidostomatidae from Mammals have originated during the Secondary, concurrently with the Marsupial expansion.

These ancestral Nematodes would have given birth to the other Trichostrongyloidea through reduction of buccal cavity, and to the Ancylostomatoidea by further elaboration of buccal apparatus.

Contrary to Inglis’s hypothesis we are in favour of the genera Globocephaloides and Hypodontus to be assigned to the Globocephalinae and Uncinariinae (Ancylostomatidae) respectively, rather than to the Amidostomatidae.

The occurrence of an Amidostomatidae in a South American Cricetidae is somewhat quite unexpected, mostly because this family is known to occur from australian Mammals only and alco because the parasited Mammals are the most primitive of the group (Monotremes and Marsupials).