ABSTRACThe present investigation aims to illustrate the histological and ultrastructural differences of the liver and pancreas of a carnivorous fish, Schilbe mystus, and a herbivorous fish, Labeo niloticus. The histological examination of the liver of both studied species revealed that the liver is mainly composed of a continuous compact field of the hepatocytes. The hepatocyte-sinusoidal structure of the liver of Schilbe mystus consists of the solid form and tubular one, while that of Labeo niloticus consists of the tubular form and cord-like one.The ultrastructural examination of the liver of both studied species revealed that it is composed mainly of hepatocytes, Kupffer (macrophages) and to (fat-storing) cells. The hepatocytes of Schilbe mystus are characterized by the presence of numerous glycogen rosettes, numerous lipid droplets and a rough endoplasmic reticulum, while those of Labeo niloticus are characterized by the presence of numerous glycogen rosettes, a few lipid droplets and a rough endoplasmic reticulum. The hepatocytes of both studied species possess numerous microvilli, which extend into the space of Disse or into the bile canaliculi lumina.In both studied species, there is a prominent perisinusoidal space between the hepatocytes and blood sinusoids, the space of Disse. This space usually contains the Ito cells, which are stellate in shape and are characterized by the presence of lipid droplets.The bile canaliculi of Schilbe mystus are of the intercellular type, while those of Labeo niloticus are of both the intercellular and intracellular types.The histological investigation of the pancreas of both studied species revealed that there are three types: the compact, disseminated and intrahepatic types. This pancreas showed that it consists of a highly lobulated gland of the compound acinar type. The acinar (pancreatic) cells are pyramidal in shape; they possess a basophilic cytoplasm and eosinophilic zymogenous secretory granules.The ultrastructural investigation of the acinar cells of both studied species revealed two cell types: the dark and light acinar cells. These cells are characterized by the presence of numerous zymogenous secretory granules and a well-developed rough endoplasmic reticulum.

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The reproductive biology of the small-scaled terapon, Terapon puta (Cuvier, 1829), from Lake Timsah, Ismailia Governorate, Egypt, has been studied during the period from June 2011 to May 2014. The results 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 one to three years. 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 indicated that the females T. puta were dominant throughout all the seasons of the year. The average values of the gonadosomatic index of T. puta were small in winter (the pre-spawning season) for both sexes, while they gradually increased in spring and summer to reach highest values in summer. The values of GSI then decreased gradually to reach minimal values in autumn (the postspawning season) for both sexes. The aforementioned data indicates that T. puta has a long spawning season that starts in early spring and ends in late summer. Moreover, the study of the fecundity of T. puta revealed that 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 (r 2 =0.999), consequently, the total body weight was the best indicator of the fecundity of T. puta. The recommendation of the present study is to prevent fishing of T. puta in Lake Timsah during the spawning season, which extends from April to August, or use nets with wider meshes in order to protect the spawning biomass of T. puta resources.

The age, growth and reproductive biology of the Liza carinata from the Suez Bay were studied. Age determination was based on otolith readings and validated by the decomposition of the seasonal length frequency distributions collected during the period from January 2009 to January 2011. The estimated von Bertalanffy growth equation was L t = 21.279 (1 -e -0.463 (t + 0.325) ). The fish grows allometrically (b = 2.8692; 95% CI: 3.1687-3.370) and relatively rapid, achieved more than 50% of the growth during the first year of life. Seasonal distribution of gonado-somatic index (GSI) values showed that the main peak of GSI was in autumn. The seasonal development of maturity stages indicated that the spawning activity occurs during autumn. The size at which 50% of fishes are mature was 13.3 cm for males and 13.5 cm for females, which indicates that all individuals over two years of age were sexually mature. The absolute fecundity of the present species ranged from 60732.3 to 98549.3 eggs for fishes in the size ranging from 13.6 to 18.4 cm in total length. This study recommends altering the closer season in Suez Bay to be during autumn in order to protect the spawning biomass of Liza carinata resources in the Bay.

Morphological and histological studies on the ovaries of the small-scaled terapon, Terapon puta, from Lake Timsah, Ismailia governorate, Egypt ABSTRACT:Morphological and histological studies were carried out on the ovaries of the small-scaled terapon, Terapon puta, 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 to May 2014. The morphological studies of T. puta indicate that the maturity stages of the ovaries could be divided into three stages, namely: the prespawning, the spawning and the post-spawning stages. 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 oogonia, chromatin nucleolar, early and late perinucleolar are found all over the year, however they are predominant in the pre-spawning and post-spawning seasons, but they are rarely encountered in the spawning season. In addition, the vesicular oocytes are usually abundant in the prespawning and spawning seasons and entirely absent in the post-spawning season. In addition, the vitellogenic stage is of common occurrence in the ovaries during the spawning season; however, it is rarely encountered during the post-spawning season and entirely absent in the pre-spawning season.