Gastric Brooding - a New Form in a Recently Discovered Australian Frog of the Genus Rheobatrachus

Abstract

The phenomenon of gastric brooding and oral birth displayed by the Australian frog Rheobatrachus silus has not previously been observed in the Animal Kingdom. This report describes another example of gastric brooding in a recently discovered, closely related species, Rheobatrachus vitellinus. The stomach of a female R. vitellinus that had given birth to 22 froglets revealed morphologic changes which were quite different to those described in R. silus. Unlike the atrophy of the mucosa and acid-secreting oxyntic cells in the latter species, there was no evidence of major structural changes in the brooding stomach of R. vitellinus. Furthermore, no differences were observed in the light microscopic appearances of the stomach in the brooding female and that from a non-brooding female and male R. vitellinus. A striking finding not observed in the non-brooding stomachs of R. vitellinus nor in R. silus was the presence of widespread and numerous apoptotic bodies in the gastric epithelium. The apoptotic bodies were recognized as phagocytosed fragments of eosinophilic cytoplasm and pyknotic nuclear material. Ultrastructurally, well preserved organelles were observed in the phagocytosed fragments. This diffuse deletion of cells and the striking absence of major structural changes in the brooding stomach may indicate a dichotomy in the evolution of this bizarre and unique reproductive habit.