Etude morpho-anatomique et génétique de deux nouveaux Proteocephalus Weinland, 1858 (Cestoda: Proteocephalidae) parasites de Platydoras costatus (L.), poisson siluriforme du Paraguay
The cat-fish Platydoras costatus (L.) is abundantly parasitised by the cestode genus Proteocephalus in Paraguay, previously unrecorded from this host. Morpho-metrical studies suggest the presence of two species, Proteocephalus soniae n. sp. and P. renaudi n. sp. They differ in the scolex, the distribution of the testes, the mean number of testes and uterine diverticula, the presence or absence of a vaginal sphincter, and the shape of the eggs and their envelopes. A single specimen, representing a possible third taxon, is morphologically similar to P. renaudi. Data from protein electrophoresis on amidon gel confirm the morpho-metrical conclusions. Of the 13 enzymes investigated, ACP, AAT, GPI and MDH have alleles of different electrophoretic mobilities in the three taxa. Only two alleles are distinguishable on locus HK. There is no evidence of heterozygotes in the tested systems. The specific status of the examined taxa is therefore confirmed. More material of the third species is required for establishing a species definition. P. renaudi has following unique anatomical features: the egg bears an enormous external envelope and an elongate embryophore with a unilateral appendix; the vitelline glands are paramuscular; and the eggs, laid in packets, are evacuated in an unusual way. The establishment of species based on protein electrophoresis allows a critical examination of the validity of anatomical characters usually used for taxonomic purpose. Good specific characters are the presence or absence of an apical organ and a vaginal sphincter and the relatively constant ratio between ovary width and the width of mature proglottids. The number of testes and uterine diverticula, both frequently used in species diagnoses, show variations which are often considerable and are, therefore, less unequivocal. The coefficients of variation observed calculating the mean numbers of testes can be high and reach up to 28%. This variation is itself a specific character in our opinion.
- 1 - sciences appliquees, technologies et medecines
- 2 - sciences biologiques et medicales
- 3 - sciences biologiques fondamentales et appliquees. psychologie
- 4 - genetique des eucaryotes. evolution biologique et moleculaire