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
Highlights
Fins are one of the extensions of the lateral structural system, and their shape and composition vary according to the types of fish, in addition to their differences in number and location
Due to the lack of morphological studies of the fins of Xiphophorus helleri in general and the importance of caudal fin in the study of the action or effect of medicines and drugs on bone, the present study aimed to examine the morphological structure of the caudal fin of X. helleri and the effect of hydrocortisone on it
The Morphological Structure of the Caudal Fin The results of the morphological study of the caudal fins of X. helleri's showed that these fins were homocercal, almost rounded (Picture 1), asymmetrical, 31-29 of the Lepidotrichia fin ray
Summary
Fins are one of the extensions of the lateral structural system, and their shape and composition vary according to the types of fish, in addition to their differences in number and location. Fins are either paired which include pectoral and pelvic, or unpaired, which are the dorsal, anal and the caudal, as well as the adipose fin, which is found in the fish of the family Salmonidae and Ictaluridae (Spurny, 1998; Baruš and Oliva , 1995). Fins in bony fish are generally epidermis structures consisting of bone rays called Lepidotrichia and a thin collagen membrane that binds rays to each other (Lauder, 2006). Each bony ray consists of a pair of long convex in two halves or parts, each member of this pair is called Hemitrichia, they appear connected to each other at the base of the fin only. Extending from the far end of each bony ray to the outer edge of the fins are a group of small, thin spindle called Actinotrichia which in turn support the membrane tip of the fin (Krukenberg, 1985; Becerra et al, 1983)
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