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Differences in meristic counts of the genus Clarias35between 58 and 60. Teugels and Thys Van DenAudenaerde (1981) reported vertebrae ranges of59 to 62 in C ebriensis and 59 to 64 vertebrae inC. dahomeyensis. The VC in the present studyfalls within the 50 – 68 distribution of vertebrae inthe genus Clarias (Sydenham, 1978).Teugels and Thys Van Den Audenaerde(1981), while comparing the original description oftwo nominal species, C . ebriensis and C.dahomeyensis, observed that only the number ofthe dorsal and the anal fin rays can be indicated asbeing strikingly different. C . ebriensis had 70 - 73dorsal and 53 - 62 anal fin rays, while they were80 - 87 and 62 - 75 respectively in C.dahomeyensis. Teugels (1980) had alreadydemonstrated that the systematic value of thesecounts was doubtful because of their widevariation. It is worthy to observe that therejection of AFRC by Teugels (1980) based onwide variation may be invalid reasoning becauseall meristic counts examined by Teugels (1980) aswell as those examined in the present studyexhibited heterogeneous variance within stipulatedranges. Furthermore, species classification usingmorphological features is not based on one keycharacter but on a wide range of key characters.In C. angolensis, Sydenham (1978) recorded 70anal fin rays. Other numbers recorded for AFRCwere 46 - 53 in C. liberiensis = C. buettikoferi, 64 -66 in C. submarginatus = C. albopunctatus, 70 inC. laeviceps, 57 in C. walkeri = C. camerunensisand 63 – 71 in C. longior (Sydenham, 1978), 66 –73 in C. agboyiensis, 51 – 60 in C. isheriensis = C.agboyiensis and 59 to 62 in C. aboinenesis(Sydenham and Olawoye, 1981). The observedrange of the AFRC in all the species falls within theestablished range of 46 – 73 for the genus Clarias.Other authors have strongly supported thesystematic values of both AFRC and VC.Considering the use of meristic counts indifferentiating other fish species, the AFRC was amajor character in discriminating among Oryziasspecies (Uwa and Parenti, 1988). Similarly,Ferguson and Liskauskas (1995) employed bothAFRC and VC in discriminating among populationsof the brook charr (Salvelinus fontinalis). Thus, thepresent study further justifies the taxonomicimportance of AFRC and VC in differentiatingbetween clariids.REFERENCESEYO, J. E. (1997). Morphometric and cytogeneticvariations among Clarias species(Clariidae) in Anambra River, Nigeria.Ph.D. thesis, University of Nigeria,Nsukka. 267 pp.EYO, J. E. (2002a). Congeneric discrimination ofmorphometric characters among membersof the Pisces Genus Clarias (Clariidae) inAnambra River, Nigeria. The Zoologist ,Vol. 1 (1): (In Press).EYO, J. E. (2002b). Conspecific discriminationin ratio morphometric characters amongMembers of the Pisces Genus: ClariasScopoli, 1777. The Zoologist, Vol. 1 (1):(in Press).EZENWAJI, H. M. G. (1989). Aspects of thebiology of some “small” Clarias species inAnambra river basin, Nigeria. Ph.D.thesis. University of Nigeria, Nsukka. 224pp.FERGUSON, M. M. and LISKAUSKAS, A. P. (1995).Heritability and evolution of meristicvariation in a naturalized population ofbrook char (Salvelinus fontinalis). NordicJournal of Freshwater Research, 71: 217 –228.LOWE-MCCONNELL, R. H. (1972). FreshwaterFishes of the Volta and Kainji lakes.Ghana University Press, Accra.SYDENHAM, D. H. J. (1978). Redescriptions of thetype specimen of six Clariid species(Pisces) from Western Africa. ZoologicalJournal o f Linnean Society, 64: 347 - 371.SYDENHAM, D. H. J. (1980). New species ofClarias from West Africa. (Pisces,Clariidae). Revue Zoologica africana,94(3 ): 659 - 677.SYDENHAM, D. H. J. 1983. A key to the genusClarias in Nigeria. Mimeograph of theDepartment of Zoology, University ofIbadan, Nigeria. 2 pp.SYDENHAM, D. H. J. and OLAWOYE, O. F. (1981).A new species of Clarias from Nigeria(Pisces, Clariidae). Revue Zoologicaafricana, 95(1): 234 - 241.TEUGELS, G. G. (1980). Notes on the status andthe synonyms of Clarias pachynemaBoulenger 1903 (Pisces, Clariidae). RevueZoologica africana, 94(3): 678 - 692.TEUGELS, G. G. (1982). Preliminary data of asystematic outline of the African speciesof the genus Clarias (Pisces, Clariidae).Revue Zoologica africana, 96(1): 731 -748.TEUGELS, G. G. and THYS VAN DENAUDENAERDE, D. F. E. (1981). On thesynonym of the West African speciesClarias ebriensis and Clariasdahomeyensis (Pisces, Clariidae). RevueZoologica africana, 95(1): 11 - 28.UWA, H. and PARENTI, L. R. (1988).Morphometric and meristic variation inrice fishes, genus Oryzias: a comparisonwith cytogenetic data. Japan Journal ofIchthyology, 35(2): 159 – 166.
Animal Research International (2004) 1(1): 36 – 41 36MAYR’S COEFFICIENT OF DIFFERENCE AND TAXONOMY OF CLARIAS(CLARIIDAE – SCOPOLI, 1777)EYO, Joseph Effiong and INYANG, Nicholas MathiasDepartment of Zoology, University of Nigeria, Nsukka. Enugu State, Nigeria.Corresponding author: EYO, Joseph Effiong, Department of Zoology, University of Nigeria, Nsukka.Enugu State, Nigeria. Email: divinelovejoe@yahoo.comABSTRACTCoefficient of difference in 54 morphometric characters was studied using 258 Clariasspecies from Anambra river, Nigeria. There were no differences between C. ebriensis andC. albopunctatus for all the 54 characters studied. The coefficient of difference inmorphometric 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 34morphometric characters. Thirty seven differentiating morphometric characters occurredbetween C. ebriensis and C. anguillaris. Considering the discriminating charactersbetween C. albopunctatus and C. gariepinus, 90 % of C. albopunctatus differed from 90% of C. gariepinus in about 32 characters. Furthermore, about 90 % of C. albopunctatusdiffered from 90 % of C. anguillaris in about 35 characters. Differentiating of C.gariepinus from C. anguillaris based on the coefficient of difference was impossible for allthe 54 characters studied. The coefficients of difference among all clariids studied werealmost identical in 10 characters namely: maximum body depth, pectoral spine height,anal fin base length, inner mandibular barbe l 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 “keycharacters” for differentiating between the “small” and “large” clariids.Key words: Mayr’s Coefficient of Difference, Clarias, Clariidae, TaxonomyINTRODUCTIONDifferences in fifty-four morphometriccharacters among four Clarias species Scopoli,1777 of Anambra river, Nigeria, using F-LSDhave been reported (Eyo, 2002 a, b). In thereport, Clarias albopunctatus and C. ebriensis aswell as C. anguillaris and C. gariepinus wereshown to have overlapping morphometriccharacter ranges. Differences among thestudied Clarias species occurred in 2 raw(pectoral fin base length (PFBL) and frontalfontanel width (FFW)), 9 ratio (pelvic fin baselength (PeFBL), pectoral spine height (PSH),dorsal fin height (DFH), maxillary teeth bandwidth (MTBW), premaxillary teeth band depth(PmTBD), frontal fontenelle length (FFL),internasal space (INS), pelvic fin – anal finspace (PeAS) and prenasal barbel length(PNBL)) and not easily established in 6 residual(Total length (TOL), prepectoral length (PPL),pectoral fin base length (PFBL), Dorsal fin baselength (DFBL), outer mandibular barbel space(OMBS) and eye diameter (EDIA))morphometric characters. The 2 raw and 9ratio characters were recommended asimportant generic and specific key characters inclariid systematics and their ecological andtaxonomic implications were reassessed (Eyo,2002 a).Similarly, sex differentiatingmorphometric characters between male andfemale clariids inhabiting the Anambra riversystems employing studentized t -test occurredin 7, 11, 20 and 26 morphometric characters forClarias ebriensis, C. albopuncatus, C . gariepinusand C. anguillaris respectively.Furthermore, specific differences in thedistribution of meristic character among theclariids of Anambra river, Nigeria, utilizing F-LSD, indicated that both the anal fin ray andvertebrae counts were of taxonomic importance.There was a close numerical relationshipbetween the number of anal fin rays andnumber of vertebrae (Eyo, 2004).Another univariate statistical toolcapable of discriminating 90 % population ofspecies A from 90 % population of species B isMayr’s coefficient of difference (CD) (Mayr,1969). Thus in the present study, Mayr’s
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