Revealing the hidden diversity of Brazilian caecilians (Lissamphibia: Gymnophiona) through integrative taxonomy

• Grant number: 25/14778-0
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• Start date: May 01, 2026
• End date: April 30, 2028
• Field of knowledge: Biological Sciences - Zoology - Taxonomy of Recent Groups
• Principal Investigator: Miguel Trefaut Urbano Rodrigues
• Grantee: Rodolfo Otávio dos Santos
• Host Institution: Instituto de Biociências (IB). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

Caecilians or blind-snakes (clade Gymnophiona) form the least speciose group of living amphibians, comprising approximately 220 species that occur primarily in tropical regions. Caecilians have a peculiar morphology, featuring well-ossified skulls, reduced or absent eyes, elongated bodies, and no traces of an appendicular skeleton-characteristics commonly interpreted as adaptations to a predominantly fossorial lifestyle. 44 species are present in Brazil, representing approximately 20% of global diversity. Among these are some species of great scientific relevance, such as Atretochoana eiselti, the largest known lungless tetrapod, and Siphonops annulatus, known for its ability to secrete a nutritious fluid through its cloaca for feeding its young and for injecting venom through its bite. However, studies on caecilian systematics must address the intrinsic difficulties of collecting fossorial animals, most of which inhabit regions difficult to access. This results in a limited number of specimens available for study in museum collections. Furthermore, caecilians exhibit a conserved external morphology, thus limiting the number of morphological characters useful for taxonomy. Regarding internal anatomy (i.e., osteology), detailed descriptions are available for only a few species, generally those most readily found in herpetological collections, although previous work has demonstrated the taxonomic potential of osteological data in Gymnophiona systematics. It is worth noting that the lack of molecular data (not yet reported for more than half of Brazilian species) also hinders advances in taxonomic research. In this context, this project proposes an integrative taxonomic approach, aiming not only to acquire new genomic data, especially from previously unsampled taxa, but also to reanalyze specimens already deposited in collections, this time including aspects of their internal anatomy, using non-destructive techniques (i.e., computed tomography). Together, these analyses will provide access to a portion of the biodiversity of Brazilian caecilians that has remained hidden, thus enabling a better characterization of their biodiversity. (AU)