Larval Anatomy of Andean Toads of the Rhinella spinulosa Group (Anura: Bufonidae)

Abstract

The Rhinella spinulosa group is a clade of toads that inhabit the Andes mountains from northern Ecuador to Patagonia. Its taxonomy was recently revised, and in its new arrangement comprises nine species, including Rhinella gallardoi, traditionally placed in a different intrageneric group. In this work we studied the larval external and internal morphology in this group, by describing for the first time tadpoles of R. achalensis, R. gallardoi, and R. vellardi, and then summarizing morphological data for R. altiperuviana, R. limensis, R. papillosa, R. spinulosa, and R. trifolium. Although we found no diagnostic larval features for the whole clade, two distinct morphs were identified. Most tadpoles were highly pigmented and slender, and their oral discs showed a long gap in the second labial tooth row; conversely, tadpoles of R. limensis and R. vellardi shared a globose body and a very short gap. Buccal and musculoskeletal features were highly conserved within the group and regarding other Rhinella, and included four lingual papillae, nonkeratinized spurs, tripartite suprarostral cartilages, quadrato-orbital commissure, and in musculature, m. subarcualis rectus II–IV invading the branchial septum III and laryngeal muscles reduced or absent.