Pituitary cytology of the teleost fish Tilapia mossambica (Peters)

In the pituitary of Tilapia mossambica, eight cell types were identified on the basis of their staining reactions. the RPD consists of erythrosinophils and PbH positive cells. PbH cells border the NH and give amphipilic reaction to tri- and tetrachrome dyes and Halmi's stain. Erythrosinophils are also stained with acid fuchsin and orange G. The PPD is made up of acidophils and cyanophils. The acidophils are stained with orange G, acid fuchsin and erythrosin. These cells form a palisade zone between the neurohypophysis and the cyanophils. The cyanophils are AB, AF, ATh, PAS and aniline blue positive. They include both thyrotrophs and gonadotrophs and cannot be differentiated. The gonadotrophs may be those which are degranulated and vacuolated in the breeding season. The PI is formed of PAS- and PbH positive cells which lack any definite pattern of arrangement. Apart from the chromophils, scattered chromophobes were seen throughout the adenohypophysis. Occasionally, cells resembling the cyanophils of PPD were noticed in the RPD and PI also.     

Morphology of lymphoid organs in a cichlid teleost, Tilapia mossambica (Peters).

In Tilapia mossambica organized lymphoid tissues are present in the thymus, head-kidney and spleen, whereas they are lacking in pericardial tissue, liver, mesonephros, intestine and rectum. No lymphoid tissue was observed in the chondrocranium and cartilaginous viscerocranium of young adults. The thymus in Tilapia is encapsulated by thin strands of collagen fibers and consists of outer, middle and inner zones. While middle and inner zones are comparable to the thymic cortex and medulla of higher vertebrates, the homology of the outer zone is not clear. At the anterior end of the thymus, a loose aggregation of lymphocytes without a definite boundary has been observed. The head-kidney is characterized by the presence of lymphoid follicles, a subcapsular sinus, a hilus-like area and lymphatic vessels. The spleen is grossly divisible into white pulp and red pulp; the white pulp contains only a reticular area without definite lymphoid centers and the latter contains predominantly erythrocytes. Morphological changes in the lymphoid organs associated with immune response have been discussed.     

Sensitivity of brain cholinesterase to cypermethrin toxicity in freshwater teleost Tilapia mossambica

Cypermethrin at sublethal concentrations induced significant changes in acetylcholinesterase (AChE) activity and acetylcholine (ACh) content in the brain tissue of both juvenile and adult-fish. Maximum inhibition of AChE activity is noticed at 6h and 12h after exposure to cypermethrin in juvenile and adult fish respectively. In contrast, the ACh levels registered an elevation in both the cases. During subsequent periods the rate of recovery in AChE activity and ACh content is variable in both the groups.     

New aspects of the intrafilamental vascular system in gills of a euryhaline teleost,Tilapia mossambica

Summary The non-respiratory vascular system of T. mossambica gill filaments was studied in serial longitudinal and cross sections. Comparatively few scattered vascular communications occur between the afferent filament artery and the central venous sinus (AVA_aff). The efferent filament artery, however, is connected by regularly arranged anastomoses (AVA_eff), directly, and sometimes indirectly via nutritive vessels, to the central sinus. These AVA_eff are about as numerous as lamellae counted on one side of each filament, although they diminish slightly in number towards the filament base. The relation AVA_eff to AVA_aff was 17.6:1 in the distal and 17.8:1 in the basal filamental region, while in the tip region of 7 filaments 126 AVA_eff but only 1 AVA_aff were encountered. No direct connection between the lamellar lacunae and the central sinus was detected. According to these results, non-respiratory intrafilamental blood shunting appears unlikely. AVA_eff are assumed to be the main route for blood entering the central venous sinus which would consequently flow into the branchial veins.The authors wish to express their sincere thanks to Miss Angelika Krauß for her valuable technical assistance and to Miss Erna Finger for making the photographs. Thanks are also due to Mr. W. Zeltmann for drawing Figs. 2, 5, and 8 and to Mr. K. Herzog for Fig. 7.     

A teleost (Tilapia mossambica) gonadotropin that resembles luteinizing hormone.

A purified gonadotropin preparation was obtained from pituitaries of a teleost fish ($\text{Tilapia}$$\text{mossambica}$). This gonadotropin was found to resemble LH in that it behaved identically to mammalian and non-mammalian LHs in several chromatographic systems, and stimulated testerone production in isolated rat Leydig cells. In this assay, specific for LH, the $\text{Tilapia}$ gonadotropin was less potent than mammalian LHs but significantly more active than avian, reptilian or amphibian LHs. The $\text{Tilapia}$ gonadotropin was found to be a glycoprotein; preliminary amino acid composition data show resemblances to both mammalian and non-mammalian LHs.     

Scanning microscopy of pharyngeal and oral teeth of the teleost Tilapia mossambica (Peters)

The pharyngeal and oral teeth of the fish Tilapia mossambica (Peters) were examined with a scanning microscope. It appeared that the dorsal pharyngeal teeth form a peculiar hooklike extension at the tip, whereas the ventral pharyngeal teeth tend to curve in a posterior direction. The two lateral flanges at the tip of the ventral teeth are probably the areas of contact with the dorsal teeth when the latter are pressed down during sound production or feeding. However, the oral teeth develop along a different line. A part from villiform teeth the upper and lower jaws also develop tricuspid and bicuspid oral teeth, with the bicuspids concentrated mainly along the outer edge of the jaw.     

Sound production in the cichlid Tilapia mossambica Peters

Aquarium-bred adult and juvenile Tilapia mossambica Peters can produce sounds ofvarying frequency, duration and intensity. However, minor environmental disturbancesmay cause the fish to fall silent for long periods. The sounds produced by excited feedingfishes are different from those produced by territorial males and from those emitted by fryswimming in school formation. The frequency of the sounds recorded varied from about1–16 kHz; no data are available on frequencies lower than 1 kHz. The sound producingmechanism consists of a single ventral and two dorsal pharyngeals located in the buccalcavity and provided with numerous small teeth. These teeth have a specially modifieddistal surface area which is already evident in younger fish. Young Tilapia , including3-week old fry, are able to emit sounds as soon as a sufficient number of teeth havedeveloped in the pharyngeal region.     

Cypermethrin induced changes in nitrogen metabolism of fish, Tilapia mossambica

At sublethal concentrations, cypermethrin caused a decrease in total proteins and an increase in free amino acids, protease, alanine aminotransferase and aspartate aminotransferase in liver, brain and gill tissues of Tilapia mossambica. Nitrogen metabolic profiles like ammonia, urea and glutamine were also elevated in all the tissues as a consequence of cypermethrin toxicity. Glutamate dehydrogenase, AMP deaminase and adenosine deaminase activity was also increased in the present study.     

Perturbations in carbohydrate metabolism during cypermethrin toxicity in fish, Tilapia mossambica

Sublethal concentrations (0.04 ppm) of cypermethrin induced significant metabolic changes in brain, liver and gill tissues of fish, T. mossambica. While cypermethrin caused depletion in glycogen and pyruvate levels lactate content was elevated in all the tissues. While phosphorylase 'a' and aldolase activity increased, phosphorylase 'b' activity registered a decrease in the present study. A decrease in lactate dehydrogenase activity with increase in lactate levels suggests reduced mobilization of pyruvate into citric acid cycle. Glucose-6-phosphate dehydrogenase activity was also elevated indicating enhanced oxidation through HMP pathway during cypermethrin toxicity. Inhibition of succinate, malate and isocitrate dehydrogenases and cytochrome c oxidase activity indicates impaired oxidation of carbohydrates through citric acid cycle.     

Effect of malathion exposure on some physical parameters of whole body and on tissue cations of teleost,Tilapia mossambica (Peters)

Exposure of fish to a sublethal (2 mg/litre/48h) concentration of malathion showed no significant changes in any of the physical parameters investigated like, body weight and body water content, while the oxygen consumption of the fish showed a consistent increase upto 24 h and later declined to 8% suggesting the reduction of oxidative metabolism at the end of 48 h. The sodium, potassium and calcium ions showed a remarkable decrease in all the tissues of malathion-exposed fish, suggesting the loss of ions from the body of these fish. The results suggested that the regulation of osmotic balance may occur by an effective operation of the salt pump rather than the water pump.     

Studies on Manganese uptake in Tilapia mossambica and Salmo gairdnerii

Tilapia mossambica fingerlings, 5 weeks of age, were reared in simulated fresh water medium which was either free of manganese or supplied with manganese at a concentration of 2.5 µg/l. They were fed synthetic diets which were either deficient (2.8 mg Mn/kg dry diet) or supplied with manganese (35.5 mg Mn/kg dry diet). The feeding tests were carried for 10 weeks. Best growth was obtained when the element was supplied in both food and water. When manganese was absent or was supplied only in water or food, the following symptoms were noted: (1) Poor growth, (2) reduced food consumption, (3) loss of equilibrium, and (4) increased mortality. From the results, the daily requirement for manganese by Tilapia for growth and development was calculated to be 1.7 mg/kg live fish.This paper is based on a part of a thesis submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Graduate College of University of Washington, Seattle, Washington.     

Aminopeptidase from the skeletal muscle of fresh water fish Tilapia mossambica

An aminopeptidase from the skeletal muscle of fish, Tilapia mossambica, was partially purified to 96-fold using salt precipitation, ion-exchange chromatography and molecular sieve chromatography. The enzyme showed optimum activity between pH 6.5-7.5 at 43 degrees C and Vmax and Km of 14.36 units/mg and 0.059 mM respectively with alanine beta-naphthylamide as the substrate. The aminopeptidase having a molecular weight of 305 kDa was activated by sulphydryl compounds and Co2+ and inhibited by bestatin, puromycin and metal chelators. Inhibition caused by metal chelators could be reversed by the addition of Co2+. Inclusion of L-amino acids, particularly isoleucine and leucine, in the assay medium caused inhibition of the enzyme activity. Substrate specificity together with inhibition and activation pattern indicated that the enzyme is alanine aminopeptidase.     

Ultrastructural study of arterio-venous anastomoses in gill filaments of Tilapia mossambica

Cell and Tissue Research - Arterio-venous anastomoses (AVA) in gill filaments of Tilapia mossambica exhibit a distinct polarity. Two different types of highly specialized endothelial cells, both of...