Today's parasite is a schistosome blood fluke which has been described from the Australian freshwater crocodile (Crocodylus johnstoni). While most schistosomes are known from mammalian and avian hosts, Griphobilharzia amoena is found in a reptilian host. Like other schistosome (as opposed to most digenean flukes), G. amoena is dioecous (they have males [left] and females [right]). This fluke occupies an important position in terms of research into the evolution history of schistosomes; it has been hypothesised that the evolution of dioecy in these blood flukes was accompanied by the evolution of endothermy ("warm-bloodedness") in their hosts. With G. amoena being found infecting a crocodilian, it seems to suggest that the origin of dioecy dates back before the evolution of endothermy. However, in another twist, it has also been suggested that the ancestors of modern crocodiles were originally endotherms which had reevolved ectothermy ("cold-bloodness"). Appropriately, "Gripho" - which forms a part of this parasite's name, actually means "a riddle".
Description for Griphobilharzia amoena:
Platt, T. R., Blair, D., Purdie, J. and Melville, L. (1991) Journal of Parasitology 77:65-68.
The paper which suggest crocodiles reevolved ectothermy:
Seymour, R. S., Bennett-Stamper, C. L., Johnston, S. D., Carrier, D. R. and Grigg, G. C. (2004) Physiological and Biochemical Zoology 77:1051-1067.
Contributed by Tommy Leung.