Indostomus spinosus
| Indostomus spinosus | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Systematics | ||||||||||||
|
||||||||||||
| Scientific name | ||||||||||||
| Indostomus spinosus | ||||||||||||
| Britz & Kottelat , 1999 |
Indostomus spinosus ( lat. Spinosus - thorny) is one of two species of the previously monotypical fish genus Indostomus that were newly described in the 1990s. The specific epithet alludes to the jagged bulges on the skull of the animals, which give them a somewhat bizarre, prickly appearance.
distribution and habitat
The holotype was caught in Laos , Bolikhamsai province at the confluence of the Nam Leuk and Nam Ngang rivers. In addition, some of the paratypes come from the Thai province of Nong Khai . All specimens were found in slow-flowing to stagnant water between the roots of bank vegetation and thick layers of fallen leaves. Indostomus spinosus lives in rivers and lakes as well as swamps.
Appearance
The species is small and reaches a maximum standard length of only about 3 centimeters. The body is covered by bone plates with a series of 20 to 21 plates lying on the back and 21 to 22 shields protecting the abdomen and sides. Each of the back plates corresponds to one of the lateroventral plates, with the exception of the second dorsal plate, which corresponds to two of the side shields. Serrated ridges run across the bone plates all along the body. The skull and shoulder girdle are covered by strongly toothed bone ridges, which are particularly pronounced in male animals. At the rear edge of the gill cover there are five to six spines arranged one above the other, which increase in size from bottom to top. Each of the upper four to five spines forms the end of a jagged ridge that runs over the gill cover. In the male fish, the outer rays of the pectoral fins are curved and longer than the almost straight rays of the females. In front of the soft-radiated dorsal fin, there are usually five, more rarely but also three or four spines.
Indostomus spinosus distinguishes itself from its close relatives by its characteristic bone ridges on the skull, which in I. crocodilus are only slightly toothed and in I. paradoxus either slightly or not at all. External differences can also be found in the coloring, while the underside of I. spinosus is dark brown and the throat is dotted brown, the other two species have a light brown underside and only rarely have a few points on the throat. Adult males also have black stripes on their dorsal and anal fins, which the male I. paradoxus either completely lack or are only weakly pronounced.
Fin formula : dorsal (III–) V / 6, anal 6, pectoral 22–23, ventral 4