See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/281785514 MORPHOLOGICAL REVISION OF THE NILE CATFISH BAGRUS BAYAD (FORSSKAL, 1775) AND BAGRUS DOCMAC (FORSSKAL, 1775) (PISCES : BAGRIDAE) Article · January 2013 READS 16 2 authors, including: Elagba Mohamed University of Khartoum 40 PUBLICATIONS 23 CITATIONS SEE PROFILE All in-text references underlined in blue are linked to publications on ResearchGate, Available from: Elagba Mohamed letting you access and read them immediately. Retrieved on: 02 May 2016 Journal of Aquatic Biology & Fisheries Journal of Aquatic Biology & Fisheries, Vol. 2(1) 2014: 105-114 © Department of Aquatic Biology & Fisheries, University of Kerala. MORPHOLOGICAL REVISION OF THE NILE CATFISH BAGRUS BAYAD (FORSSKAL, 1775) AND BAGRUS DOCMAC (FORSSKAL, 1775) (PISCES : BAGRIDAE) Elagba H.A. Mohamed* and Eithar A.G. Awad Elseed Natural History Museum, Faculty of Science, University of Khartoum, Sudan. *Corresponding auther: [email protected] Received on: 14.10.2013, accepted on: 22.12.2013 Abstract: The present study was designed to revise and compare the morphological characteristics of the sympatric catfishes: Bagrus bayad (Forskal, 1775) and B. docmac (Forskal, 1775) in Nile waters of Sudan, and to determine the morphological characteristics that contribute mostly to the variation in the two species. In this study, analysis based on measurement of 28 morphological characters (24 morphometeric and 4 meristic) was done using the PAST software. Fifteen morphometric characters were significantly different between the two species. The number of pectoral fin rays and dorsal fin rays also separated B. bayad from B. docmac. The length-weight relationship of each species and type of growth determined was Log10W = 0.29349 + 1.7603 1.7603 log10SL corresponding to W = 0.29349L for B. bayad; Log10W = 0.54647 + 1.0197 log10SL, corresponding to W = 0.54647 L1.0197for B. docmac. The values (b = 1.7605) for B. bayad and (b = 1.0197) for B. docmac indicated allometric growth of both species.The results indicated that morphological characters can separate B. bayad from B. docmac. In addition, both lobes of caudal fin in B. bayad, and only upper lobe in B. docmac extend into long filaments. Given that morphological and molecular data are only complementary this outcome of morphological phylogeny analysis should be compared, contrasted and combined with the molecular phylogenetics for the populations of both species to more clearly define the taxonomical status of B. bayad and B. docmac in the Nile waters from different regions in Sudan. Key words: Allometric growth, Bagrus bayad, B. docmac, Length-weight relationship, morphology, cat fish. INTRODUCTION The genus Bagrus belongs to the family Bagridae The distribution ofboth species in Sudan was (bagrid catfishes) and known to comprise seven reported by Boulenger (1909), Stubbs (1949), species; three species Bagrus bayad (Forsskal Sandon (1950), Risch (1986) and Baily (1994). 1775), B. docmac (Forsskal 1775) and B. degeni The habitats and habits of Bagrus fish are fairly occur in Africa (Boulenger, 1907). These species similar to those of the Nile perch. Both species are observed to have a wide range of natural are predacious, feeding on small fish, insects, distribution in all principal river-systems of crustaceans, molluscs and fish, some debris and Africa. They were reported in the Nile River, Lakes vegetable matter may also be ingested (Baily, Albert and Turkana, Lake Chad, Niger and 1994). Bagrus bayad lives and feeds on or near Senegal Rivers and also found in Setit in Eritrea the bottom, while B. docmac is a benthopelagic and the Tekeze basins in Ethiopia (Risch, 1986; species, widespread in both shallow and deep Paugy et al., 2003). Bagrus bayad and B. docmac water (Olaosebikan and Raji, 1998). Both species are common throughout the Nile waters in Sudan. are common in Khartoum at any time except 105 Morphological revision of the Bagrus bayad and B. docmac November to December, and can attain a length MATERIAL AND METHODS of 600 mm or more. Bagrus is an important food Collection of fish specimens fish in Sudan. It is considered by consumers and Fresh specimens of each of Bagrus bayad and of fishermen as (grade I) fish with the Nile perch. B. docmac were purchased from the Central Fish The flesh of the fish is good for eating and of Market in Khartoum, Sudan. Fish was washed economic importance commonly sold at high and weighed. Twenty-four morphometric prices. measurements were taken for each specimen by Environmental changes in the habitats of the fish a fine dial caliper to (0.00) mm, according to due to human activities and continuous Teugels and Audenaerde (1990). All constructions along the Nile, as well as the measurements were usually made on the left side pollution of the aquatic environment by of the specimens, unless this side was damaged, fertilizers and pesticides, are expected to cause the right side was used. The length of fish barbells some morphological changes within these and four meristic counts were also taken for each species. As stated by Mohamed (1990), Goncalves specimen. The institutional abbreviations et al. (1996), Froese and Pauly (1998), Mwanja et followed Daget and Grosse (1984) al. (2011), morphological change and divergence Data analysis within species are expected to take place when fishes are exposed to new developmental and All morphometric measurements taken were evolutionary forces that determine their body expressed as a percentage of standard length (% forms. A change could take place, either through SL), in order to standardize the data. The natural hybridization or the effect of the measurements of head structures were expressed environmental factors that operate in early stages as percentage of head length (% HL). of development (Nei, 1987; Currens et al., 1989; Principal component analysis (PCA) was used to Mohamed, 2010). extract principal components from the The present study was, therefore, designed to morphometric and meristic characters. Using revise and compare the morphological (PAST 2005), the recorded morphological (24) characteristics of two sympatric catfishes: Bagrus and meristic (4) characters were subjected to bayad (Forsskal, 1775) and B. docmac (Forsskal, multivariate analysis. To ensure normality and 1775) by using a combination of both homogenous variances, and to correct for length morphometric and meristic characters. The study differences all morphometric measurements (not attempted to taxonomically characterize the meristic counts) were log10 – transformed before populations of these catfishes in the Nile waters statistical analyses were performed. of Sudan, and to determine the morphological The significant components that contributed characteristics that contribute mostly to the most to the variation between the two species variation of the two species. In this study, analysis were then used in determining the morphological based on measurement of 28 morphological phylogenetic relationships of B bayad and B. characters (24 morphometeric and 4 meristic) docmac in the Nile waters. The loadings of these was done using the software package variables were done to determine their Paleontology Statistical programme (PAST) importance on the variability explained. (Hammer et al., 2001). It is a tool highly Component one was not considered for recommended for determining the relationships discrimination in case of morphometric between species and populations of a species measurements, because it is affected by the length (Thorpe, 1987). The study also considered the of the f ish: the longest specimens usually shift length – weight relationships and the type of to the right, so component 2 and 3 were taken to growth for each species. determine the loading of each character. Cluster analysis of morphometric and meristic characters was performed separately to identify 106 Journal of Aquatic Biology & Fisheries the similarity of individuals of each subspecies. exponent (slope) and a = proportionality A hierarchical clustering was established in constant (intercept). The ‘a’ and ‘b’ values were dendrograms for the individuals of the two obtained from a linear regression of length and species B. bayad and B. docmac by using the weight of fish: Log W = log a+ b log L. The value statistical program (Past, 2005). of the coefficient “b”was used to determine the The length – weight relationships and type of type of growth in each species according to growth of pooled data for each species were (Bagenal, 1978).The correlation or degree of 2 estimated by the equation W = aLb, where W = association (r ) between length and weight was weight of fish in grams, L = SL in cm, b = length calculated from linear regression analysis. Fig. 1a. A photograph of the Nile catfish Bagrus bayad Fig. 1b. A photograph of the Nile catfish Bagrus docmac RESULTS presence of a large adipose fin, originated slightly Morphological description behind the rayed dorsal, well developed spines To a trained eye the two species are easily of the pectoral f in and well-developed four pairs distinguished by the dimensions of the head, of un-branched barbells, of which the maxillary where, B. bayadhas relatively narrower head pair extends well beyond the spine of the dorsal compared toB. docmac (Fig.1a&b). All specimens fin; a dorsal fin with branched rays and one spine; of both fish are moderately elongated freshwater a well developed pelvic fin with 1-2 spines, a fishes, with compressed body and naked skin medium-sized anal fin, also with branched rays; without scales. They are characterized by the and a forked caudal fin. The colour of the fish is 107 Morphological revision of the Bagrus bayad and B. docmac grey (B. bayad) or grayish blue to dark olive (B. DFR, which accounted for 36.1% of the total docmac), darker above and white beneath, and variability, and the third component of variation the fins are colourless. accounted for 10.3% of the total variability, and Eight out of nineteen morphometric characters that was the number of rays in pectoral fin (Table expressed as percentage of standard length, % 5).
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