TRICHOSTRONGYLINA, NEMATODE PARASITES OF AMPHIBIANS AND REPTILES - TAXONOMIC, PHYLOGENETIC AND BIOGEOGRAPHIC PROBLEMS

Except for four species of the Mertensinematinae (Molineoidea) not con sidered in this work, the Trichostrongylina parasitic in amphibians an d reptiles, comprising 15 genera and 105 species, are reviewed. The mo rphological characteristics of each species are analysed. The most imp ortant characteristics are provided by the disposition of the caudal b ursal rays, the morphology of the synlophe (at the oesophago-intestina l junction and mid-body level) and by the anatomy of the spicules. The species are classified into seven groups: Group 1: ''relict'' species with six lips and well-developed buccal capsule (six genera and 16 sp ecies). Group 2: ''ancient'' species with one or two primitive charact ers (eight genera and 15 species). Seventy-four species, without primi tive characters, comprise the genus Oswaldocruzia which is subdivided into five groups. Group 3: Oriento-Ethiopian species with non-''idiomo rphic'' spicules with two to three tips (10 species). Group 4: Neo-Eth iopian species with non-''idiomorphic'' spicules with numerous tips (1 1 species). Group 5: Holarctic species with ''idiomorphic'' spicules w ith the spicular fork divided above the distal third of the spicule le ngth (24 species). Group 6: Continental Neotropical species with ''idi omorphic'' spicules and spicular fork divided within the distal third of the spicule length (21 species).Group 7: Caribbean Neotropical spec ies with modified ''idiomorphic'' spicules, the three main branches of which are each divided into numerous tips (eight species). The geogra phical distribution of the species appears to be of greater significan ce than the host spectrum and suggests the following biogeographical h ypotheses: Group I, entirely Gondwanan, diversified during the Cretace ous era prior to the separation of the southern continents. The expans ion of Group 2, which is represented by Gondwanan and Oriental species mainly from India, Malaysia and Indochina, could have occurred throug hout South-East Asia at the end of the Cretaceous era when India colli ded with Eurasia. Group 3 could be interpreted either as a migration f rom Asia to Africa during the upper Eocene, or more likely during the Miocene, or, by a dispersion due to the migrations of Bufo melanostict us. Group 4 may result from the expansion of the former group in the E thiopian region. Group 5 could be interpreted as a colonisation of wes tern Europe and the Nearctic from Asia during the Tertiary. Group 6 co uld have arisen after the migration of the Neartic species to the Neot ropical region during the Pliocene period and Group 7 by the expansion of the former group in the Caribbean. Amongst the Trichostrongylina, the ''relict'' and ''ancient'' genera parasitic in amphibians and rept iles can only be compared with the genera parasitic in birds and mamma ls, probably dating from the Palaeocene period (mainly marsupials and primitive insectivores). On the other hand, the genus Oswaldocruzia ca n be compared with other members of the Molineoidea parasitic in fissi peds, Pholidota and Chiroptera dating from a later period (Eocene) (se e Durette-Desset, 1971). Thus, the Trichostrongylina of amphibians and reptiles are distinguished by the persistence of very old species, th e evolution and the geographical distribution of which was arrested fo r millions of years, and by the existence (in some regions) of groups undergoing full evolutionary expansion. The new taxa proposed in the p aper are: Bakeria (Moravec & Sey, 1986) status emend. (= Bakeria Morav ec & Sey sub. g.), Ragenema n. g., Ragenema robustum (Baker, 1982) n. comb. (= Oswaldocruzia robusta), Typhlopsia quentini (Durette-Desset, 1980) n. comb. (= Trichoskrjabinia quentini), T. secundus (Pinnell & S chmidt, 1977) n. comb. (= Trichoskrjabinia secundus), T. gansi (Crusz & Ching, 1975) n. comb. (= Oswaldocruzia gansi), T. limnodynastes (Joh nston Bi Simpson, 1942) n, comb. (= Oswaldocruzia limnodynastes), T. l egendrei (Chabaud & Brygoo, 1962) n. comb. (= Oswaldocruzia legendrei) .