Gross and Histological Structure of the Caudal Fin of Adult Mosquitofish , Gambusia Affinis , (Baird & Girard)

Abstract

The  present  study  showed  that  the  caudal  fin  of  adult mosquitofish  (Gambusia  affinis)  is  homocercal  and  rounded . It  consists  of  22-24 fin rays (Lepidotrichia) . Each fin ray  consists  of  many  segments . Some of these rays are short and  unbranched  whereas  others long and branched dichotomously. Pigment cells are shown to be dispersed on the fin and they are condensened at the edges of the fin rays and at the regions of their dichotomy .        Histologically the transverse section of the fin is surrounded by a fin membrane (composed of epidermis and dermis) and each fin ray consists of two semilunar hemisegments (bone –like or acellular bone) , surrounding  an intrasegmental region of loose connective tissue, containing blood vessel and two bundles of nerve fibers.  The transverse sections near the base of the caudal fin showed bundles of skeletal muscle fibers in company with the fin  rays