Abstract
Hampala siamensis, new species, is described from the Lower Tennasserim basin in Peninsular Thailand. This new species can be distinguished from its congeners by a saddle-like bar or inverted triangular marking on the body beneath the dorsal fin, rarely reaching the lateral-line scale row, by measurements of the head and body and scale counts. It is the fourth species of Hampala recorded from Thailand.
Key words. aquatic biodiversity, Southeast Asia, freshwater fish, taxonomy, Cypriniformes
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| Underwater photographs of Hampala siamensis documenting ontogenetic differences in colour pattern, all from Lam Ru Yai River. From top to bottom: individual below 30 mm SL; individual below 50 mm SL; larger juvenile ca. 100 mm SL. Not collected (all photographs by N. Panitvong). |
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| Underwater photograph of Hampala siamensis (center) in a mixed school with Barbodes lateristriga (left) and B. binotatus (right); Lam Ru Yai River. Underwater photograph of Hampala siamensis in close association with Mastacembelus favus; Lam Ru Yai River. (photograph by N. Panitvong). Not collected. |
Hampala siamensis, new species
Diagnosis. Hampala siamensis, new species, can be
distinguished from its congeners by the combination of the
following characters: lateral line scales 26–27; in adults: bar
1 saddle or inverted triangle shape, 5½–6 scales wide by
2½–3 scales deep, barely visible in preserved specimen; a
faint horizontal stripe along lateral side of body, 1½–2 scales
wide, visible in life only when stressed; upper and lower
edges of caudal fin with a gray to black marginal band; all
fins pale orange in life; head pointed, wedge-shaped, large
(length 32.3–35.0 % SL).
Etymology: Named for Siam, historical name of Thailand
and of the website “siamensis.org”, run by a group of
Thailand-based conservationists.
Proposed English name:
black-backed hampala,
Thai name: ปลากระสูบหลังดำ.
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| Species of Hampala showing live colouration. From top to bottom: H. siamensis (ca. 100–120 mm SL); H. ampalong (ca. 150 mm SL); H. dispar (ca. 150 mm SL); H. macrolepidota (ca. 150 mm SL); H. sabana (ca. 120 mm SL); H. salweenensis. Not collected. Photographs by N. Panitvong. |
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