Description of the external morphology and buccopharyngeal cavity of the tadpole of Odontophrynus reigi (Anura: Odontophrynidae)

Abstract

The first mention of a tadpole belonging to frogs of the genus Odontophrynus was made by Berg (1896) when describing Ceratophrys occidentalis, now considered a junior synonym of Odontophrynus americanus (Duméril & Bibron), a species widely distributed in the arid and semiarid regions of central and western Argentina (see Rosset et al. 2022; and bibliography cited therein). Later, Fernández & Fernández (1921), Scott-Birabén & Fernández-Marcinowski (1921), and Gallardo (1963) described some morphological characters based on tadpoles that, according to their geographical origin (e.g., Buenos Aires and Córdoba, Argentina), would belong to O. americanus and the currently recognized Odontophrynus asper (Philippi). More detailed descriptions, taking into account developmental stages, were carried out by Savage & Cei (1965), Caramaschi (1979), and Cei (1980, 1987; see bibliography cited therein) for tadpoles of O. americanus (referred to as O. occidentalis as well as O. achalensis di Tada et al. and O. barrioi Cei et al.), O. asper (referred to as O. americanus), O. carvalhoi Savage & Cei, and O. cultripes Reinhardt & Lütken. Nowadays, the genus Odontophrynus is composed of 11 species that, except for O. americanus, are arranged in the O. asper and O. cultripes groups (Rosset et al. 2022 and references therein). The external morphology of the tadpoles of almost all the species is known and generally well documented (e.g., González et al. 2014; Menegucci et al. 2016; Santos et al. 2017; Pezzuti et al. 2021 for tadpoles ofO. americanus and species of the O. cultripes group), but other characters, such as those of the buccopharyngeal cavity, were described only for a few species (Wassersug & Heyer 1988; Fabrezi & Vera 1997; Nascimento et al. 2013). This note aims to describe the external and buccopharyngeal morphology of the tadpole of Odontophrynus reigi Rosset et al., a species belonging to the O. asper group that occurs mainly in the grassland of the subtropical regions of Argentina, Brazil, and Paraguay. Recently, Schvezov et al. (2023) compared growth and development in tadpoles of O. reigi exposed to different soils in Corpus, Misiones, Argentina, and Vicente-Ferreira et al. (2024) included them in an identification key of tadpoles from Foz do Iguaçu, Paraná State, Brazil. However, the tadpole of this species has not yet been fully described. Additionally, we provide a comparison of the tadpole of O. reigi, focusing on the species of the O. asper group, based onthe data available in the literature and from direct observations.