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Introduction
Morphologically, the structure barbel is used to describe tentacular sensory podia-like organs in some vertebrates like the fishes, amphibians and reptiles (Winokur, 1982; LeClair and Topczewski, 2010; In-Seok et al., 2012). In most teleosts, barbels are skin appendages used for gustation and mechanoreception (Griswold, 1972). The number and shape of Barbel are highly inconsistent, with some species having up to 10 paired or unpaired barbels on various areas of the jaws, lips and head (Eakin et al., 2001; Park et al., 2005). Intra species barbel sexually dimorphism or polymorphism amongst fish of either sex has been reported (Eakin et al., 2006). From reported morphological descriptions, the teleost barbel contains an outer epithelium, dermal connective tissue, blood vessels, and extensions of the facial nerves that innervate numerous taste buds (Dimmick, 1988; McCormick and Shand, 1992; Sakata et al., 2001; Kiyohara et al., 2002). Variable features include a central rod of connective tissue or cartilage, and intrinsic and/or extrinsic muscle groups that allow the barbel some range of motion. Although once used as a taxonomic character to unite all "fish with whiskers", barbels are now believed to be phylogenetically undependable having been gained or lost frequently in many genera (Broilay et al., 1998; Arai and Kato, 2003).
The morphology of the barbell has been documented in some fish like striped sea catfish Plotosus lineatus (Park et al., 2005); an Hawaiian goatfish (Holland, 1976); Callichrous bimaculatus, Heteropneustes fossilis, Clarias batrachus and Rita rita (Sato and Kapoor, 1957; Srivastava and Sinha, 1961; Singh and Kapoor, 1967); Channel catfish Ictalurus punctatus (Joyce and Chapman, 1978); the ability of the barbel to regenerate is also in literature like the Parasilurus asotus, silurid fish Corydora aeneus, and Chinese Longsnout Catfish Leiocassis longirostris, (Sato and Katagiri, 1966; Shiba et al., 1982; In-Seok et al., 2012), but there is dearth of information from available literature on the barbel histology from the farmed African catfish. Hence, the aim of this work is to study its micro-morphology, fill the knowledge gap, and possibly correlate morphology to organ function especially adaptive features.
Materials and Methods
Seven adult African catfish sourced from a commercial fish farm- Yuep in Umuahia area of Eastern Nigeria were used for the study. Their mean weight and length were 30.76 ± 3.30...