Scanning microscopy of surface structures of Tilapia mossambica (Peters) scales

Scanning microscopic observations were made of the surface structures of isolated scales of Tilapia mossambica (Peters). The circuli were found to form numerous minute processes called scalar denticles, which may act to secure the position of the scale with reference to surrounding dermal tissues. The skin covering the lunula of the scale includes a number of pores which are thought to represent the terminal openings of dermal mucous cells. This part of the skin also shows peculiar epidermal surface patterns. These surface patterns may be indicative of areas subject to increased mechanical stress.     

Food utilization by Tilapia mossambica (Peters): Function of size

Experiments were done with three size groups of Tilapia mossambica (Peters) to study the rate of energy intake, absorption and conversion and absorption efficiency and conversion efficiency. Experimental animals were fed with beef ad libitum for a period of 40 days. It was found that the rates of intake, absorption and conversion of energy were inversely related to size, whereas efficiencies of absorption and conversion were directly related to size. The reason for the marked difference in the efficiency of energy conversion between small and large size groups is discussed.     

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.     

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.     

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.     

Respiratory quotient and ammonia quotient in Tilapia mossambica (Peters) with special reference to hypoxia and recovery

At oxygen concentrations below air saturation, R.Q. and A.Q. values of Tilapia mossambica increase with decrease in ambient oxygen at 30 and 35°C, indicating an increase in anaerobic metabolism and protein utilization. The recovery metabolism indicates that T. mossambica accumulates an oxygen debt at 30°C, which was not obvious at 35°C. The post-hypoxic oxygen consumption at 30°C is quite pronounced and the fish repays almost wholly the oxygen debt accumulated. At 30°C, R.Q. and A.Q. reach prehypoxic level immediately after exposure to high oxygenated water. In contrast to this, during recovery the first high R.Q. which is higher than unity and subsequent low R.Qs., almost as low as 0.5, suggest respectively that, anaerobic energy utilization persists and carbon dioxide is retained. The differences in the recovery metabolism of T. mossambica at the two temperatures may be due to changes in metabolism and pathways due to temperature. The recovery metabolism of T. mossambica suggests that energy derived anaerobically could proceed through other pathways than the conventional glycolytic way. The decrease in random activity during the hypoxic phase at 30 and 35°C may have a special significance for survival.From a thesis (M.P.M.) approved for the degree of Doctor of Philosophy, Madurai University, Madurai, India.From a thesis (M.P.M.) approved for the degree of Doctor of Philosophy, Madurai University, Madurai, India.     

The ultrastructure and calcification of the scales of Tilapia mossambica (Peters)

Summary The scales of Tilapia are surrounded by an envelope of scleroblasts responsible for the production of layers of collagen that constitute the bulk of the scale. The scleroblasts adjoining the lateral face of the oldest scale region gradually atrophy. New collagen layers are deposited against the inner face of the scale, the adjoining scleroblasts showing evidence of high metabolic activity. Calcification occurs by inotropic deposition of crystals alongside the fibres. There is no sharp demarcation between calcified and non-calcified scale regions, a calcification front gradually moving towards newly formed collagen layers. It is felt that fish scales should be considered as calcified derivatives of dermal collagen layers.     

The ability of Tilapia mossambica (Peters) to enter deep water

Juvenile Tilapia mossambica (Peters) are extremely tolerant of depth and can compensate to a depth increase of 0 to 33 m in a few minutes. As the fish grow they become less able to compensate to deep water. At a total length of 15–18.5 cm small adult male T. mossambica can compensate to 20 m whereas females can only compensate to 13 m. Large adults (20–25 cm) of both sexes compensated to 11.5 m (range 9.5–13 m). Adult fish require 4 to 7 days for maximum depth compensation at 22°C. Analysis of the oxygen content of the swimbladder indicated that this gas accounts for over half the gas in surface equilibrated fish. Oxygen secretion into the swimbladder appears to be the mechanism of equilibration at depth.     

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.     

Dominant lethal mutations in Tilapia mossambica (Peters) elicited by myleran

Tilapia mossambica (Peters) Teleostei, Cichlidae, is of commercial importance being farmed for human consumption. An effective means of sterilization would be of value since prolific breeding under farming conditions reduces growth rate. The possibility of using the antileukaemic drug myleran as a chemosterilant has been investigated previously, however the present study indicated that it can induce dominant lethal mutations in this species.     

The Ultrastructure of Erythrophores and Melanophores from the Skin of Tilapia mossambica (Peters)

Abstract The ultrastructure of erythrophores and melanophores present in the skin of adult Tilapia mossambica is described. A comparison of the two types of chromatophores indicates that both show a smooth endoplasmic reticulum, pinocytotic vesicles, microtubules and complexly branching cell processes. However, differences in the form, consistency and distribution of erythrosomes and melanosomes are noted. It is suggested that erythrophores be defined as chromatophores including carotenoid derivatives as the main pigment in their erythrosomes.     

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.     

Development of colour patterns in relation to behaviour in Tilapia mossambica (Peters)

The development of chromatophores and the formation of colour patterns in Tilapia mossambica are described. A number of colour patterns are associated with certain aspects of behaviour. Four different melanophore systems are involved in the colour pattern formation. There appear to be 14 patterns which, in various combinations, produce a series of colour patterns. Each of these may convey a different message to different species of Tilapia .     

Formation of the Micropyle in Tilapia mossambica Peters and Stigmatogobius javanicus (Blkr.)

The formation of the micropyle in Tilapia mossambica and Stigmatogobius javanicus, two fresh water teleosts is described. In T. mossambica the micropyle is formed by a single modified follicular cell, while in S. javanicus it is formed by a cellular mass derived from the follicle.     

Effects of methallibure on the external morphology,behaviour and chromatic physiology of the teleost,Tilapia Mossambica (Peters).

Morphological and behavioural alterations occurred in the fish Tilapia mossambica, following methallibure treatment. A complete loss of sexual dimorphism, absence of reproductive and agonistic behaviours and a total blanching of the body due to destruction of the melanophores were the changes recorded. Moreover, significant changes were also induced in the pars intermedia by this drug. These results are discussed in the light of available data.     

Chloride transport in red cells of the teleost,Tilapia mossambica

• 1.1. The transcellular movement of chloride was measured in the red blood cells of the fish Tilapia mossambica utilizing 36-chloride.
• 2.2. Tilapia red cells possess an efficient anion carrier which is totally blocked by SITS.
• 3.3. Although a factor in tilapia plasma inhibits the dehydration of extracellular bicarbonate by the red cells, it was without effect on the transcellular movement of chloride.
• 4.4. It is concluded that the inability of fish whole blood to dehydrate extracellular bicarbonate is not explained by a general anion impermeability as was suggested by Haswell & Randall (1976).