Comparative study of vitellogenesis in the anuran amphibians Ceratophrys cranwelli (Leptodactilidae) and Bufo arenarum (Bufonidae).

The present study analyses, by transmission electron microscopy, vitellogenesis in two anuran amphibian families: Leptodactilidae (Ceratophrys cranwelli) and Bufonidae (Bufo arenarum). These differ in the type of stimulus that sets off their reproductive period, pluvial changes being the trigger in C. cranwelli and temperature increase in B. arenarum. We found that vitellogenesis follows an endocytic pathway that involves membranous structures (coated pits, coated vesicles, endosomes and multivesicular bodies). This process results in a fully grown yolk platelet of similar structure in both species. Despite the above similarity, a distinctive feature in B. arenarum was that the multivesicular bodies exhibited condensed proteins together with lipid droplets, the latter remaining as such even in the primordial yolk platelet. In C. cranwelli, however, lipids droplets were only found attached to the primordial yolk platelet. The coexistence of lipid droplets together with proteins in the nascent precursor yolk platelets observed in B. arenarum is similar to that found in B. marinus. This fact might constitute a characteristic feature of the Bufonidae family.