Mayr\'s coefficient of difference and taxonomy of clarias (clariidae – scopoli, 1777)

Abstract

Coefficient of difference in 54 morphometric characters was studied using 258 Clarias species from Anambra river, Nigeria. There were no differences between C. ebrensis andC. albopunctatus for all the 54 characters studied. The coefficient of difference in morphometric characters of C. ebriensis vs. C.gariepinus indicated that about 90 % of C. ebriensis were significantly different from about 90 % of C. gariepinus in about 34 morphometric characters. Thirty seven differentiating morphometric characters occurred between C. ebriensis and C. anguillaris. Considering the discrimnating characters between C. albopunctatus and C. gariepinus, 90 % of C. abopunctatus differed from 90% of C. gariepinus in about 32 characters. Furthermore, about 90 % of C. albopunctatus differed from 90 % of C. anguillaris in about 35 characters. Differentiating of C. gariepinus from C. anguillaris based on the coefficient of difference was impossibe for all the 54 characters studied. The coefficients of difference among all clariids studied were almost identical in 10 characters namely: maximum body depth, pectoral spine height, anal fin base length, inner mandibular barbe length, outer mandibular barbel length, maxillary barbel length, premaxillary teeth band depth, vomerine teeth band depth, prenasal length and nasal - nasal barbel space, with exception of C. ebriensis vs. C. albopunctatus and C. gariepinus vs. C. anguillaris. These characters thus represent “key characters” for differentiating between the “small” and “large” clariids. Keywords: Mayr's Coefficient of Difference, Clarias, Clariidae, Taxonomy Animal Research International Vol. 1 (1) 2004: pp. 36-41