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| Ophisternon berlini |
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 + 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.
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| Type locality of Ophisternon berlini, new species. (A) Vantage point view of the Destierro River within the premises of Las Brisas Nature Reserve near collecting sites. (B) One of the artificial lentic bodies of water inside the reserve near collecting sites. (C, D) Photographs of the 2021 collecting site ... displaying the muddy nature of the soil at the time of collection. (E) Live specimen of Ophisternon berlini, new species, freshly dug out from the abovementioned site. |
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| Unearthing of specimens of Ophisternon berlini, new species. Photograph displaying the process of pulling out live specimens of the new species from a block of mud collected at the type locality. |
Ophisternon berlini, new species
Berlin’s Bloodworm Eel
Diagnosis.— Ophisternon berlini is assigned to the genus Ophisternon by having a pectoral girdle connected to the skull by a forked posttemporal joining the supracleithrum at the level of the third vertebra vs. posteriorly displaced to the level of the fifth vertebra with posttemporal reduced to a simple rod and disconnected from the supracleithrum in Synbranchus (Fig. 4) and a branchiostegal membrane opening slit-like vs. small pore-like in Synbranchus (Fig. 5). Ophisternon berlini is unique among its Neotropical congeners in having: 1) an elevated number of precaudal vertebrae: ∼100 vs. ...
Etymology.— The specific epithet (a noun in the genitive case) is a patronym honoring Mr. Erick Berlin, a strong supporter of conservation and scientific research of Costa Rican biodiversity, discoverer of the population of swamp eel herein formally described, and owner of La Brisas, a private nature reserve that contains the type locality of the new species.
Jairo Arroyave; Arturo Angulo; Adán Fernando Mar-Silva and Melanie L. J. Stiassny. 2024. A New Endogean, Dwarf, and Troglomorphic Species of Swamp Eel of the Genus Ophisternon (Synbranchiformes: Synbranchidae) from Costa Rica: Evidence from Comparative Mitogenomic and Anatomical Data. Ichthyology & Herpetology. 112(3); 375–390. DOI:
