Segama basin

This species is variable in terms of colour. Large adults may be bright green, orange or barred but are apparently capable of changing from barred to plain in just a few seconds. These different forms have been recorded in the same natural habitats, and some individuals also possess prominent nuptial tubercules covering much of the body.

This species can be most easily distinguished from other members of the genus by its colour pattern which consists of a blackish midlateral stripe extending from the tip of the gill opening to the middle of the caudal-fin base, which is separated from the dark brown dorsum by a pale yellowish brown stripe. This differs from the pattern seen in other Crossocheilus species with a black midlateral stripe in which the the dorsum is olive brown and much paler than the midlateral stripe, there is no yellow stripe between the dorsum and the black stripe, and the black stripe extends to the tip of the snout.

Predominantly a riverine fish preferring clear, well-oxygenated, running waters with substrates of sand, gravel, rock or mud, and apparently displays a preference for deeper, slower-moving stretches. In Sabah such habitats typically flow through tropical forest, although in recent years freshwater habitats throughout much of the state have been extensively modified by human activity such as conversion to palm or rubber plantations.

The five species which currently comprise Luciosoma can be distinguished by elements of colour pattern. Popta described the colour pattern of L. pellegrinii as follows: body colour olive dorsally, with dark-edged scales, yellow ventrally; a lateral series of dark spots on the flank forming a midlateral band which extends onto the opercle but not the head; 4-8 blackish-brown, distinctly-separate spots on the lateral line; fins yellow; dorsal and anal fins with a blackish-brown band; anterior half of some pectoral-fin rays blackish-brown...

It looks particularly similar to N. alestes with both species possessing a colour pattern comprising a dark lateral stripe on the body, but can be distinguished immediately by possessing barbels longer than the head (vs. shorter than the head in N. alestes).

Nematabramis species are found a variety of habitat-types, from swiftly-flowing affluent streams to pools, lakes, and degraded swamps. Based on the available collection records juveniles and subadults of N. everetti display a preference for fast-moving water whereas adults are found in deeper, slower stretches of minor tributaries.