الفهرس 
INTRODUCTION AND AIM OF WORKOnly 14 pages are availabe for public view
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Abstract
Biological, histological and ultrastructural studies were carried out on the gonads of the small-scaled terapon, Terapon puta (Cuvier, 1829), from the Lake Timsah, Ismailia Governorate, Egypt. The fish specimens were seasonally collected during a period of three consecutive years, that extended from June 2011 through May 2014.
The biological studies of T. puta revealed that the growth of the total body weight relative to the total body length is negative allometric (b = 2.4954). Moreover, the collected fishes were divided into three age groups from of one to three years. The mean observed body lengths of these groups were 8.71, 12.62 and 14.81 cm, respectively. The age composition of T. puta catch indicated that individuals belonging to age group two have predominated the fish population (90.53% of the total collected individuals).
The overall sex ratio indicates the preponderance of females throughout all the seasons of the year. Moreover, the ratio of females to males in the total fish sample collected during the study period was 1.3:1, respectively.
The average values of the gonadosomatic index of T. puta (GSI) were small in Winter (the pre-spawning season) for both sexes (1.389 and 0.337 for females and males, respectively). This index is gradually increased in Spring and Summer to reach highest values (5.356 for females, and 3.308 for males) in Summer. The values of GSI then are decreased gradually to reach minimal values in Autumn (the post-spawning season) for both sexes (0.974 for females and 0.291 for males). The aforementioned data indicates that T. puta has a long spawning season which starts in early Spring and ends in late Summer.
The values of the observed absolute fecundity of T. puta are proportionally increased with the total body length, and total body weight of the fish. It ranged between 20437and 45272.83 eggs for fish with the mean total body length ranging from 9.9 to 12.35cm. However, it ranged from 25190.12 to 46508 eggs for fish with the mean body weight ranging from 16.54 to 25.19 gm.
The highest significant relationship was found between the logarithmic values of both mean total body weight, and mean observed absolute fecundity, with highest correlation coefficient (r2=0.999). The total body weight was, consequently, the best indicator of the fecundity of T. puta.
The morphological studies of T. puta indicate that the maturity stages of the gonads could be divided into three stages, namely: the pre-spawning, the spawning and the post-spawning stages. Moreover, the morphological study of the ovaries during the pre-spawning season showed that they are cylindrical in shape, pale yellow in color, with little vascularization and small ova that were observed by the naked eye. They occupy more than half of the abdominal cavity. In addition, the ovaries of the spawning season showed maximum development in length and width, occupying the most of the abdominal cavity. They are opaque, yellow in color, and have a heavy network of blood vessels. Yellowish ova can be easily extruded by pressure on the walls of the belly. In the post-spawning season, the ovaries become flaccid and shrunken, occupying less than half of the abdominal cavity. They are greyish white in color with little vascularization and residual ova.
Histologically the oogenesis in T. puta is divided into six oocyte developmental stages, namely: oogonium, chromatin nucleolar, early perinucleolar, late perinucleolar, vesicular and vitellogenic stages. Moreover, the vitellogenic stage is divided into two main stages, namely: the early and the late vitellogenic stages. The scanning electron microscopical examination indicated that the outer surface of the late vitellogenic oocyte of consists of ridges and furrows, and possesses a single aperture; namely, the micropyle, through which spermatozoa pass into the mature oocyte. During the course of oogenesis, some oocytes may suddenly cease growth and become atretic follicles. After the discharge of the ovum from the follicle of the vitellogenic oocyte, the follicle undergoes remarkable structural variations which lead to the post-ovulatory structure.
The morphological studies of males T. puta showed that the testes in the pre-spawning season are whitish in color, have a smooth texture and occupy more than half of the abdominal cavity. Moreover, the testes during the spawning season are creamy in color, smooth in texture with observed vascularization. They increase sharply in length and width to occupy the entire abdominal cavity. In the post-spawning season, the testes are highly reduced in size, completely shrunken and collapsed, greyish white in color, and occupy nearly half of the abdominal cavity.
Histologically, the testes of T. puta belong to the lobular unrestricted spermatogonial type, and the spermatogenesis is of the cystic type. The spermatogenic cells are classified into six stages, namely: the spermatogonia A, spermatogonia B, primary spermatocytes, secondary spermatocytes, spermatids and spermatozoa.
The ultrastructural examination of the testes reveals that the spermatids are differentiated into three stages, namely: the early, mid and late spermatid stages. The spermatozoon of this fish belongs to type I aquasperm which consists of three main regions, namely: anacrosomal head, short middle piece and a single flagellum.