Channa stewartii belongs to that group of Channa sp. which has 4-5 scales between orbit and angle of preopercle and 12-13 scales before the dorsal fin. It conies very close to Channa orientalis (Bl. Schn) , 1 but could be distinguished from the latter by 39-40 rays in the dorsal (VS 32-37), 26-27 rays in the anal (VS 21-23) and ventral 1/3 of the pectoral (VS 2/5). 2
While working out a collection of C. stewartii and C. orientalis from Khasi Hills, we observed that all the specimens of C. stewartii have considerably lesser number of rays in the dorsal (35-37). There was also a greater range of variation in the number of anal rays (23-28) and ventral was mostly 1 (rarely 1/3) of the pectoral. Colour pattern and other characters were so distinctive that there is no difficulty in distinguishing it from C. orientalis . These variations, being unrecorded so far, entail a redefinition of C. stewartii and the key character of the species shall therefore be as under 35-40 rays in the dorsal, 23-28 rays in the anal and ventral from 1/2 to 1/3 of the pectoral.
Channa stewartii occurs in Chindwin, Brahmaputra. and Kosi drainages of the Himalayas 3 . In the Khasi Hills, both C. stewartii and C. orientalis coexist in streams living along the edges having overhanging vegetation.
While examining the material of C. stewartii we also came across two abnormal specimens, one ( A ) having its dorsal fin divided into two owing to, a gap caused by the absence of rays after 6th ray to nearly opposite the origin of the anal fin and the other ( B ) having a similar gap after the 8th dorsal ray to nearly opposite the 8th anal ray. In specimen A the total number of dorsal rays is 33, whereas in specimen B it is only 31. The specimen B also lacked the pelvic fin and the pelvic girdle of the left side. The examination of the alizarin preparation of these specimens shows that the pterygiophores are also absent in the region of the gap. Though occasional absence of both pelvic fins is on record in the genus Channa 4 there is no earlier record of such abnormalities, as, we have observed.
We are thankful to Dr. R. S. Pillai for encouragement and going through the manuscript. We are also thankful to Dr. A. G. K. Menon for useful suggestions.
1 In fact, this is not Channa orientalis (Bloch & Schneider, 1801) but Channa gachua (Hamilton, 1822) because Channa orientalis is an endemic species of Sri Lanka. The synomization of these two admittedly closely resembling species is very common in Indian ichthyology. In the following we keep the Channa orientalis but the name is realized as hyperlink to Channa gachua (Hamilton, 1822). [snakeheads.org] Back
2 Day, The Fauna of British India including Ceylon and Burma Fishes . London, 2, 360-364, 1889. G.E. Shaw and E. O. Shebbeare, The fishes of Northern Bengal . J. Roy. Asiatic Soc., Bengal (Science), 3, 119-123. 1937. Back
3 A.G.K. Menon, A distributional list of fishes of the Himalayas. J. Zool. Soc. India , Calcutta, 14, 23-32, 1962. Back
4 Hora, S. L., 1921. Notes on the occasional absence of the paired fins in fresh-water fishes, with some observations on the two apodal genera Channa Gronow and Apua Blyth . Rec. Ind. Mus., 22: 27-32. Back
This text was originally published 1971 with the above title in: Science and Culture vol. 37 No. 12, pages 580-581.
|© 2001 - 2008 snakeheads.org||HOME of this page|