Dr. Murai Éva szerk.: Parasitologia Hungarica 21. (Budapest, 1988)
Examination of the scope of the definitive hosts of the amphistomes having plesiomorphic characters shows that they successfully colonized each class grade of vertebrates. If we visualize the process of amphistome parasitism as it is accepted in general, viz. parasite evolution has been accomplished parallel with the development of their definitive hosts, it means in the time perspective that the sequence of the vertebrate hosts represented newer and newer areas for colonization. This process included series of adaptation, thereafter adaptive radiation with diversification and specialization of parasites to their colonized hosts. Hence, each vertebrate grade has its own special group of amphistomes and it can be said that the host or hos^agroups are so characteristic of parasites as parasites are of their hosts. Nevertheless, there is no direct connection between the taxonomic level of the amphistomes and their hosts. The tempo of the higher level differentiation of amphistomes seems to be slower than that of their definitive hosts. Namely, the amphistomes of the lower vertebrates and those of some of the mammals, have fundamentally the same general plan of structure, indicating that the amphistomes have their own phylogeny. Hence, the groups of hosts and their sequence reveal rather the evolutionary trends of the amphistomes than those of their developmental level. Bearing the phylogenetic value of the structure of the reproductive organ system in mind, the proposed systematics of the family Cladorchiidae necessitates the designation of some new subfamilies (Travassosiniinae - monotypic, characterized by the extracaecal position of uterus; Colocladorchiinae - monotypic, characterized by the position of testes and the compact vitellaria; Megalodiscinae - with two genera (Megalodiscus , Opisthodiscus) , characterized by two testes and by accessory sucker or muscular plug in the acetabulum; Caballerodiscinae - with two genera (Caballerodiscus gen.n.* for species Schizamphistomoides resu- pinatus and S. tabascensis, characterized by more or less horizontal testes, and Elseya- trema) ; Chiorchiinae - with three genera (Chiorchis, Chiostichorchis , Paraibatrema) , characterized by the tandem position of testes. At the same time, several previously described subfamilies disappeared and the systematics of all the subfamilies, now regarded to be valid, should be rearranged with a few excreptions. Splitting of the family Cladorchiidae in several subfamilies is in connection with the ancestry of this taxon and thus there is no solid morphological ground to elevate the subfamilies series to family level. In the analysis of the phylogenetic relationships among the subfamilies, the position of the testes was considered as the main guiding principles in establishing the transformation series: anterior tandem » horizontal »posterior tandem. Accordingly, the Cladorchiidae were divided into 20 subfamilies. Their phylogenetic relationship is depicted by the cladogram (Fig. 2) and a key to the subfamilies is given below. 1. One or both testes caecal or extracaecal, vitellaria follicular or compact 2 - Testes and uterus intercaecal, vitellaria follicular 4 - Testes intercaecal, uterus mainly extracaecal, vitellaria follicular Travassosiniinae 2. Testes caecal, horizontal , 3 - Anterior testis either caecal or extracaecal Sandoniinae - Testes extracaecal, uterus partly extracaecal Osteochilotrematinae 3. Ovary intertesticular, vitellaria compact Colocladorchiinae - Ovary post-testicular, vitellaria follicular, testes caecal Pseudocladorchiinae 4. Acetabulum simple 5 - Acetabulum with accessory sucker or with prominence Megalodiscinae m Description of Caballerodiscus gen.n. DIAGNOSIS. Caballerodiscinae. Body elongate oval. Pharynx terminal with extramural appendages, oesophagus short, caeca convoluted, sinuous. Testes tandem or slightly diagonal, in middle part of body, lobate of irregulat in outline. Ovary submedian spherical, in front of acetabulum. Uterine coils post-testicular. Vitelline follicules along posterior part of caeca. Acetabulum ventroterminal. Intestinal parasites of freshwater turtles. Type species: Caballerodiscus tabascensis (Caballero et Sokoloff, 19 34) n. comb.
