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| Sciadonus alphacrucis Melo, Gomes, Møller & Nielsen, 2022 |
Highlights:
• A new species of the rare genus Sciadonus is discovered from Brazilian waters.
• Highly specialized reproductive apparatus enables internal fertilization and viviparity in a deep-sea fish.
• The depletion of sunlight resulted on convergent evolution of troglomorphic traits in deep-sea fishes and cave fishes.
• Human activities of oil and natural gas exploration, fisheries and littering may be impacting rare deep-sea species.
Abstract
A new species of the rare, deep-sea genus Sciadonus Garman, 1899 (Bythitidae) is described based on two specimens obtained by the Brazilian R/V Alpha Crucis on the continental slope off São Paulo State, Southeastern Brazil, western South Atlantic. It differs from its congeners by the combination of the following characters: body pale lacking dark pigmentation except for on female claspers; a pair of dermal tissue flaps anteriorly on lower jaw; pelvic-fin rays present; precaudal vertebrae 39 or 40 and total vertebrae 74 or 75. The key to the species of Sciadonus is updated. A discussion of the presence and differentiation between troglomorphic and miniature characteristics among the species in the aphyonid clade is provided and compared with other bythitids.
Keywords: Aphyonid clade, Continental slope, Western South Atlantic, R/V Alpha Crucis
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| Sciadonus alphacrucis sp. n. ; western South Atlantic, São Paulo State, off Ilhabela, 794 m depth MZUSP 125949, holotype, female, 82.7 mm SL MZUSP 125950, paratype, male, 60.3 mm SL. |
Order Ophidiiformes Berg, 1937.
Family Bythitidae Gill, 1861.
Sciadonus alphacrucis n. sp.
Etymology: The specific name honors the Brazilian R/V Alpha Crucis. A noun in apposition.
Marcelo Roberto Souto de Melo, Amand Alves Gomes, Peter Rask Møller and Jørgen G. Nielsen. 2022. A New Species of the rare deep-sea Genus Sciadonus Garman, 1899 (Teleostei, Bythitidae) from off Brazil, with a discussion of the evolution of troglomorphism and miniaturization in the aphyonid clade. Deep Sea Research Part I: Oceanographic Research Papers. 180, 103684. DOI: 10.1016/j.dsr.2021.103684
