A Study of the Morphological and Histological Structure of the Caudal Fin of the Female Swordtail Fish Xiphophorus helleri and the Effect of Hydrocortisone on it

Abstract

The caudal fin is one of the most important types of fins used in the movement of fish and is important in studying the effect of various factors on bone, especially medicines and drugs. The females of the Xiphophorus helleri were obtained from aquarium fish shops. The mature females were divided into two groups, each containing 14 fish, placed in 60 liter glass aquarium, the first group treated as control group, while the second group was treated with Hydrocortisone Sodium Succinate (Roxcortisone) with a concentration of 2.5 mg/1. After a month of experimentation, the samples were fixed by a Formalin 10% in order to prepare them for the whole-mount loading method and the normal tissue sections. The results of the phenotypic study of the caudal fins of female X. helleri showed that they consist of three types of fin rays, which are unsegmented and unbranched, segmented and unbranched,  and segmented and branched. These three types differ in terms of shape and structure , as histological structures showed that the first type rays, i.e.  unsegmented and unbranched, and the first ray of the second type, i.e. segmented and unbranched, have pear shaped. The cavity between the two halves of rays is filled with connective and neural tissue, while the other rays of second type have a heart shape and  filled with  muscle tissue. The shape of the  third type, i.e. segmented and branched, varies depending on their location in the fin. The results of the study of  morphological of the caudal fin of females treated with hydrocortisone showed that there was an irregularity in the fin rays in general, which led to a difference in the branching positions of the branched rays compared to the control group. It was also noticed that there was a fusion in the rays composing the fin and another fusion of internodes composing the one fin in comparison to control group.

Keywords: Xiphophorus helleri, caudal fin ,fin rays ,hydrocortisone hormone

DOI: 10.7176/JNSR/9-4-06