Subterranean Fishes of the World

6692

2024

Ichthyology and Herpetology

375-390

112(3)

A new highly troglomorphic and diminutive swamp eel inhabiting muddy subsoil in remnants of a tropical rainforest in the Caribbean versant of Costa Rica is described. Comparative anatomical and mitogenomic data support the distinctiveness of the new species and its placement in the genus Ophisternon. The new species is unique among Neotropical congeners in having: 1) a greatly elevated number of precaudal vertebrae, 2) proportionally longer and larger premaxillary, dentary, palatine, and ectopterygoid teeth, 3) palatine and ectopterygoid teeth in a single row, and 4) a small, narrow, and crescent-shaped gill membrane opening. A novel phylogenetic hypothesis of synbranchid relationships proposed herein, derived from comparative mitogenomic data, adds to a body of evidence demonstrating that Ophisternon is not monophyletic (with respect to Synbranchus). This phylogeny, however, strongly supports the monophyly of Neotropical Ophisternon, with the new species resolved as sister to a clade consisting of Ophisternon infernale 1 Ophisternon aenigmaticum. A pattern of northwestern lineage dispersal and cladogenesis within the Neotropical clade of Ophisternon after its divergence from Synbranchus is inferred from our phylogenetic results and present-day species distributions. Our findings also reinforce the notion that the classification of synbranchid fishes is in dire need of a systematic and comprehensive revision, particularly with respect to the limits and composition of the genera with presence in the Neotropics

1

Arroyave, J., Angulo, A., Mar-Silva, A.F. and Stiassny, M.L.J. (2024)