Pathologic Lesions of the Budgett Frog (Lepidobatrachus laevis), an Emerging Laboratory Animal Model.

Lepidobatrachus laevis, commonly called the Budgett frog, is a member of the horned frog family (Ceratophryidae), which has become increasingly popular among amphibian hobbyists. L. laevis is also used in biologic research on embryonic development, providing a novel model species for the study of organogenesis, regeneration, evolution, and biologic scaling. However, little scientific literature details disease processes or histologic lesions in this species. Our objective was to describe spontaneous pathologic lesions in L. laevis to identify disease phenotypes. We performed a retrospective analysis of 14 captive L. laevis frogs (wild-caught and captive-bred), necropsied at the NC State University College of Veterinary Medicine between 2008 and 2018. The majority of frogs exhibited renal changes, including varying combinations of tubular epithelial binucleation, karyomegaly, and cytoplasmic vacuolation; polycystic kidney disease; and renal carcinoma. Many of the renal changes are reminiscent of a condition described in Japanese (Bufo japonicus) and Chinese (Bufo raddei) toad hybrids that progresses from tubular epithelial atypia and tubular dilation to polycystic kidney disease to renal carcinoma. A second common finding was variably sized, randomly distributed bile duct clusters (biliary proliferation). Other noteworthy findings included regional or generalized edema, intestinal adenocarcinoma, aspiration pneumonia, and parasitism. This retrospective analysis is the first description of histologic lesions identified in captive L. laevis populations, providing new insight into spontaneous disease processes occurring in this species for use in disease diagnosis and clinical management.

Morphogenesis of the primitive gut tube is generated by Rho/ROCK/myosin II-mediated endoderm rearrangements.

During digestive organogenesis, the primitive gut tube (PGT) undergoes dramatic elongation and forms a lumen lined by a single-layer of epithelium. In Xenopus, endoderm cells in the core of the PGT rearrange during gut elongation, but the morphogenetic mechanisms controlling their reorganization are undetermined. Here, we define the dynamic changes in endoderm cell shape, polarity, and tissue architecture that underlie Xenopus gut morphogenesis. Gut endoderm cells intercalate radially, between their anterior and posterior neighbors, transforming the nearly solid endoderm core into a single layer of epithelium while concomitantly eliciting "radially convergent" extension within the gut walls. Inhibition of Rho/ROCK/Myosin II activity prevents endoderm rearrangements and consequently perturbs both gut elongation and digestive epithelial morphogenesis. Our results suggest that the cellular and molecular events driving tissue elongation in the PGT are mechanistically analogous to those that function during gastrulation, but occur within a novel cylindrical geometry to generate an epithelial-lined tube.