Bryconops rheoruber
From Wikipedia, the free encyclopedia
| Bryconops rheoruber | |
|---|---|
Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Actinopterygii |
| Order: | Characiformes |
| Family: | Iguanodectidae |
| Genus: | Bryconops |
| Species: | B. rheoruber |
| Binomial name | |
| Bryconops rheoruber | |
Bryconops rheoruber is a species of freshwater ray-finned fish belonging to the family Iguanodectidae. This species is found in Brazil. Its back scales are tan-to-cream, and its belly is silvery; the divide between the two colors is marked by a broad iridescent-silver stripe. Its fins are a mixture of pale, clear, and reddish, which contributed to its specific name. "Rheo" means "flow" or "current" in Greek, and "ruber" means "red" in Latin.
It was first described from the rapids of the Rio Xingu (hence "rheo" in its scientific name), and its range is known to extend into the Rio Iriri, the largest tributary therein. Like many other species of Bryconops, it prefers fast-flowing waters over a rocky or sandy substrate.
Sexual dimorphism
Bryconops rheoruber ranges from 4.61 to 5.49 cm in standard length.[1] This makes it smaller than most Bryconops, members of which are largely between 6 and 8 cm long.[2] It is deep-chested, with its deepest body section just before the dorsal fin, and it has 8–9 pre-dorsal scales; the latter is a feature it only shares with B. marabaixo and B. chernoffi.[3][4] Unlike several other species of Bryconops, B. rheoruber lacks a humeral spot (a mark near either pectoral fin). Many fish in Bryconops have either one humeral spot or two.[5]
Bryconops rheoruber has a broad, iridescent-silver lateral stripe that turns lead-gray when a deceased specimen is preserved in alcohol. The scales themselves are tan-to-cream dorsally and silver ventrally in life, with all scales turning pale-yellow upon preservation. Some specimens may have an isolated blotch of pigment upon the distal portion of the caudal fin's dorsal lobe; this is superficially similar to coloration seen in congener B. florenceae, though in B. florenceae the pigmentation is limited to the base of the dorsal lobe and the distal regions are left pale.[6]
The other fins are somewhat varied in coloration. The dorsal fin may have a diffuse, red crescent arching backwards from the center of the base to the outer fin-rays, which leaves a half-oval patch of hyaline dorsal fin near the base, and the tip is whitish. The adipose fin is red. The dorsal half of the caudal fin has a diffuse red ocellus (eyespot) near the base, terminating about midway down the lobe, and the tip of both lobes therein is dusky, sometimes with a darkly-pigmented dorsal tip. The anal, pelvic, and pectoral fins are mostly hyaline (clear).[3]
Mature males of B. rheoruber sport bony hooks on the rays of the anal and pelvic fins. These hooks are pointed back towards the body.[3] Many members of Bryconops display similar hooks or spines, though appearance varies based on species.[7]