Tuesday, July 1, 2025

[Ichthyology • 2025] Sewellia pudens • A New Species of loach (Cypriniformes: Gastromyzontidae) from Dakchung Plateau, southern Laos


Sewellia pudens  
Kottelat, 2025
 
 Raffles Bulletin of Zoology. 73

Abstract
 Sewellia pudens, new species, is described from the Xe Kaman watershed on Dakchung Plateau, Sekong Province, southern Laos. It is distinguished from other species of the genus in having a yellowish brown body; no markings on the fins; in males, a patch of tubercles on the snout divided longitudinally by a deep groove; no modified pelvic-fin rays with dorsal bone extension. The mouth of Sewellia and the tubercles and ornamentation on the fins of several species are described; the ‘pelvic valve’ is figured. 

Key words. Cobitoidei, loach, pectoral fin, pelvic fin, tubercles, bony extensions

Sewellia pudens, MHNG 2799.022, holotype, 49.2 mm SL, male; Laos: Xe Kaman watershed, Dakchung Plateau. Tip of axillary pelvic lobe on left side damaged.

Sewellia pudens, new species
 
Diagnosis. Sewellia pudens is distinguished from all species of Sewellia by the poorly developed patterning of the body and fins. On the body, black pigments are present in a vague midlateral stripe and 3–8 small saddles on the back, especially on caudal peduncle. Some irregular markings are also present on the body of some specimens, but not forming a clear pattern. The fins of most specimens have no colour marks, except for thin black lining along rays in the dorsal, anal and caudal fins, and, rarely, 1 or 2 faint blotches along lower edge of the caudal fin. The pectoral and pelvic fins ...

Etymology. The Latin adjective ‘pudens’ means modest, humble, reserved, discreet. It refers to the absence of conspicuous pattern on the body and fins (compared to most other species of the genus) and the absence of ostentatious modification on pectoral- and pelvic-fin rays. Pudens is indeclinable.


MAURICE KOTTELAT. 2025. Sewellia pudens, A New Species of loach from Dakchung Plateau, southern Laos (Teleostei: Gastromyzontidae). Raffles Bulletin of Zoology. 73; 304–317.