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| Nemacheilus pullus Kottelat, 2023 |
Abstract
Nemacheilus pullus, new species, is described from the Nam Ngiep and Nam Xan watersheds, Mekong drainage, in central Laos. It was earlier misidentified as N. platiceps. It is distinguished from congeners in having an incomplete lateral line, with 23–57 pores, reaching between verticals of pelvic-fin origin and of anus; anterior nare at tip of a short tube; body plain yellowish grey in life in adults; a conspicuous suborbital flap in males; small tubercles on anterior pectoral-fin rays and on flank. It was found in habitats with moderate flow, usually small streams, on mud to stone bottoms. An informal platiceps group is recognised, including N. platiceps, N. cacao and N. pullus.
Key words. Mekong, Nam Ngiep, Nam Xan
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| Nemacheilus pullus, Laos: Mekong drainage: Nam Ngiep watershed; before fixation; a, CMK 27566, paratype, female, 51.9 mm SL; b, CMK 27552, female, 54.6 mm SL. |
Nemacheilus pullus, new species
Diagnosis. Nemacheilus pullus is distinguished from all other
species of the genus except N. platiceps and N. cacao in
having an incomplete lateral line reaching between verticals
of pelvic-fin origin and of anus, with 23–57 pores (vs.
complete). Nemacheilus pullus is most easily distinguished
from N. platiceps (Fig. 3) and N. cacao (Fig. 4) by its colour
pattern, with a plain grey body when preserved (yellowish
grey in life), but small specimens (less than about 45 mm
SL) may have numerous faint, narrow and very irregular
bars, darker along dorsal midline where they appear as
small darker saddles. The patterning on the caudal peduncle
and the dark saddles may remain, including in some of the
largest specimens, especially females. In contrast, N. platiceps
has 12–16 narrow bars on the flank, clearly distinct at all
sizes; quite regular in juveniles (Fig. 3a), about as wide as
interspaces; with increasing size they become wider and
less regular, the median area becomes paler and in some
specimens the bars even appear as two bars (Fig. 3d). In
N. cacao adult males have a uniform dark brown body;
in females, most bars are split and become fainter with
increasing size, resulting in a pattern of numerous narrow
grey bars along body and broader dorsal saddles.
...
Distribution and habitat. Nemacheilus pullus is presently known only from central Laos, in the Nam Ngiep and Nam Xan watersheds (Fig. 10). It was observed in a variety of habitats, from small forest streams to larger streams, in stretches with slow to moderate current, on substrate from mud to stones (Fig. 11). In larger rivers it was rarely observed, along shores, in shallow (less than 50 cm), sheltered areas close to shore vegetation, with little flow; it has not been collected in deeper waters and rapids. It was also present in open areas without canopy, and with signs of eutrophication and siltation.
Etymology. From the Latin pullus, meaning dark yellow to blackish. An adjective, -us, -a, -um.
Maurice Kottelat. 2023. Nemacheilus pullus, A New Species of Loach from central Laos (Teleostei: Nemacheilidae). RAFFLES BULLETIN OF ZOOLOGY. 71; 106–115.
