Morphological revision of Ichthyborus besse besse and Ichthyborus besse congolensis (Pisces: Distichodontidae)

Document Type: Primary Research paper

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Abstract

Morphological revision was made on thirty specimens of Ichthyborus besse besse, and thirty specimens of Ichthyborus besse congolensis,taken from the collection of the Royal Museum for Central Africa in Belgium. The aim of this study is to verify the taxonomic status of the two subspecies and determine the morphological characters that characterize the ecological populations of I. besse besse from Cameron, Central Africa, and Congo and Schad basins, in their natural range. Variations of 23 morphometric measurements and 10 meristic counts were examined and compared. Principal component analysis along with discriminate analysis indicated that the most important morphometric characters that distinguish I. besse besse from I. besse congolensis are the snout length (SNL), body depth (BD), the origin of the pelvic (PRPV), anal (PRAN) and pectoral (PRP) fins, caudal peduncle length, in addition the number of: teeth in the upper jaw (TUJ) and the lower  jaw (TLJ), scales around the caudal peduncle (CPS), number of scales in the lateral line (LLS). Cluster analysis of morphometric measurements produced a hierarchical cluster separating all individuals of I. besse besse from individuals of I. besse congolensis. Discriminate analysis of the ecological populations of I. besse besse revealed that the caudal fin length (CFL) and body depth (BD) have the bigger loads in separating the ecological populations followed by the inter-orbital width (IOW), eye diameter (ED), dorsal-to-adipose distance (DAD) and snout length (SNL), in addition to the number of teeth in lower jaw (TLJ) and upper jaw (TUJ). Cluster analysis of meristic counts gave better separation of the ecological population of I. besse besse than the morphometric measurements. A detailed description of I. besse besse and I. besse congolensis according to this study is given.

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