Direct development or endotrophic tadpole? Morphological aspects of the early ontogeny of the plump toad Osornophryne occidentalis (Anura: Bufonidae)

ROMERO-CARVAJAL, ANDRÉS; NEGRETE, LEONARDO; SALAZAR-NICHOLLS, MARÍA J.; VIZUETE, KARLA; DEBUT, ALEXIS; DIAS, PEDRO H.; VERA CANDIOTI, FLORENCIA

JOURNAL OF MORPHOLOGY

WILEY-LISS, DIV JOHN WILEY & SONS INC

Lugar: New York; Año: 2023 vol. 284

0362-2525

Andean Toads of the genus Osornophryne are suspected to have direct developmenton the basis of clutch and egg features. In this work, we describe the morphology ofOsornophryne occidentalis embryos from a nest collected in the field. Several traitsare similar to those reported in brachycephaloid Eleutherodactylus coqui and otherdirect‐developing lineages. These include the pattern of formation of the body walland the absence of oral and buccopharyngeal structures. Other features indicate theretention of ancestral larval characters. The development of forelimbs occurs in partwithin the operculum as in species with biphasic ontogeny; this has been reported inother direct‐developing species, and is similar to what is described in Africanviviparous bufonids. This salient feature, along with the long, low‐finned tail and thelong and folded intestine early differentiated, gives these embryos a rather tadpolelikeappearance. Our data confirm that development in O. occidentalis occurs withinterrestrial eggs until advanced stages, and this would satisfy current definitions ofdirect development. At the same time, morphological differences regarding otherspecies with comparable breeding reinforce interpretations about the wideanatomical and ontogenetic variations associated with endotrophic nutrition.