Properties and Characteristics of Multi-Layered Films from Tilapia Skin Gelatin and Poly(Lactic Acid)

Multi-layered films based on tilapia skin gelatin and poly(lactic acid) (PLA) were characterized, in comparison with the control gelatin and PLA films. Three different layers of multi-layered films (PLA/Gelatin/PLA) were visualized by scanning electron microscopic (SEM) analysis. The synergetic effect of lamination was evidenced by the increased mechanical properties (P < 0.05). Multi-layered films had higher water vapor barrier property and water resistance, compared to control gelatin film (P < 0.05). Gelatin films showed increased lightness (L*) with coincidental decrease in total color difference (?E*) in the presence of PLA layers (P < 0.05). Transparency and solubility of films decreased with increasing ratio of PLA (P < 0.05). In addition, multi-layered films showed the enhanced hydrophobicity and thermal stability as evidenced by increased water contact angle and degradation temperature, respectively. Thus, PLA/Gelatin/PLA multi-layered film with improved water vapour barrier property could serve as bio-degradable packaging material for wider applications.     

Physical Stability and Interfacial Properties of Oil in Water Emulsion Stabilized with Pea Protein and Fish Skin Gelatin

Food Biophysics - This study aimed to investigate the physical stability and interfacial properties of oil-in-water (O/W) emulsions stabilized with fish skin gelatin (FG) and pea protein (PP) at...     

Continuous Exposure to Light Suppresses the Testicular Activity in Mozambique Tilapia Oreochromis mossambicus (Cichlidae)

Journal of Ichthyology - Although photoperiod plays a critical role in seasonally breeding fish, effect of altered photoperiod on reproduction of continuously breeding fish is not well understood....     

Immunolocalization of Vacuolar-Type H(+)-ATPase in the Yolk-Sac Membrane of Tilapia (Oreochromis mossambicus) Larvae

To investigate the involvement of the yolk-sac membrane in ion absorption, developmental changes in whole-body cation contents, cellular localization of vacuolar-type H(+)-ATPase (V-ATPase), and size and density of pavement and chloride cells in the yolk-sac membrane were examined in tilapia (Oreochromis mossambicus) larvae in fresh water (FW) and those transferred to seawater (SW) at 2 days before hatching (day-2). The whole-body content of Na(+) in embryos and larvae adapted to both FW and SW increased constantly from day-2 to day 10, although they were not fed through the experiment. The yolk-sac membrane of FW larvae at days 0 and 2 showed V-ATPase immunoreactivity in pavement cells, but not in chloride cells. No positive immunoreactivity was detected in SW larvae. Whole-mount immunocytochemistry showed that some pavement cells were intensively immunoreactive, whereas others were less or not immunoreactive. Electron-microscopic immunocytochemistry revealed that V-ATPase immunoreactivity was present in the apical regions of pavement cells in FW larvae, especially in their ridges. The pavement cells in FW larvae were significantly smaller in size but higher in density than those in SW. These results suggest that pavement cells are the site of active Na(+) uptake in exchange for H(+) secretion through V-ATPase in FW-adapted tilapia during early life stages.     

Detection of Clostridium botulinum type C cells in the gastrointestinal tracts of Mozambique Tilapia (Oreochromis mossambicus) by polymerase chain reaction

We established a method of directly detecting Clostridium botulinum type C cells, while minimizing spore detection, in the intestinal contents of Mozambique tilapia (Oreochromis mossambicus). This technique involved extraction of predominantly cellular DNA from tilapia intestinal tracts and used a polymerase chain reaction assay to detect presence of type C1 toxin gene. We consistently detected C. botulinum type C cells in tilapia gastrointestinal contents at a level of 7.5 x 104 cells per 0.25 g material or 1.9 x 103 cells. This technique is useful for determining prevalence of the potentially active organisms within a given population of fish and may be adapted to other types of C. botulinum and vertebrate populations as well.     

Effect of methallibure on gonad development and carotenoid content of the fins of Sarotherodon mossambicus (Tilapia mossambica)

Juvenile Sarotherodon mossambicus were exposed to a daily dose of 1 or 2 p.p.m. of the antigonadotropic drug methallibure for a period of seven weeks. The control fish all showed well-developed gonads and a considerable concentration of astaxanthin in the dorsal fins. The dominant male showed a much higher astaxanthin value than the other fishes. Methallibure completely prevented gonad development. Nevertheless, some astaxanthin deposition did occur in the drug-treated fish.     

Toxicological impact of Zinc Nano Particles on tilapia fish (Oreochromis mossambicus)

In this study we investigated the acute toxicity of Zinc Nano Particles (ZnO NPs) and bulk ZnO on tilapia fish (Oreochromis mossambicus). Oreochromis mossambicus was exposed to the different concentration of ZnO NPs, ZnO and mixed solution of both ZnO NPs and ZnO (20 ppb, 20 ppb, 20 ppb) respectively for 96 h. A very high impact was recorded in hematological parameters which shows significant increased (p < 0.05) in count of white WBCs and platelets in all the experimental groups compared tocontrol group. The count of RBCs, Hb, hematocrit and MCHC were significantly decreased. The remarkable changes which were recorded during this study were histopathological lesions in the gills of exposed fish including, disorganization of gill lamella, cartilaginous core disruption, lifting of epithelium, loss of secondary gill lamellae, blood congestion, fusion of secondary gills lamellae, shortening of secondary gills lamellae, atrophy and curling. Disassembly were seen in plasma membrane of liver along with blood congestion, pyknosis, necrosis, hyperplasia and formation of vacuoles. Intestinal alterations which were observed include shortening of villi, necrosis, detachment and fusion of villi and extreme goblet cells formation. It is concluded from the present study that high level of ZnO NPs, ZnO and mixed solution has a strong tendency to alter hematological parameters, histological architecture, therefore, the indiscriminate use of ZnO NPs and ZnO can subsidize in reducing the population of Oreochromis mossambicus in natural water bodies.     

Evaluating the toxic potential of agrochemicals on the hypothalamic-pituitary-thyroid axis in tilapia (Oreochromis mossambicus)

Agrochemicals are a major cause of concern for the aquatic environment because of their toxicity, persistence, and tendency to accumulate in the organisms. The impact of these chemicals on aquatic organisms is due to their movement from various diffuse or point sources, which poses a great threat to aquatic fauna especially fishes, which constitute one of the major sources of protein-rich food for mankind. The present study is a first of its kind, where the toxic potential of two sublethal concentration (LC_1/10th and LC_1/25th) of four different classes of agrochemicals have been tested (Insecticide- Imidacloprid-0.074 ppm, 0.02 ppm, Fungicide-Curzate- 4.9 ppm, 1.96 ppm, Herbicide- Pyrazosulphuron ethyl-50 ppm, 20 ppm and Fertilizer-Micronutrient mixture 500 ppm, 200 ppm) on candidate markers of hypothalamus pituitary-thyroid axis (TSH, T₃, T₄, TSHβr) in Oreochromis mossambicus (tilapia) by validating hormonal level and mRNA expression. The results reveal that exposure to agrochemicals resulted in a broad range of alterations with maximum damage being caused by insecticide followed by herbicide and fungicide in that order on the thyroid axis. The results of the present study highlight the need for more detailed studies on the effects of agrochemicals that accumulate in organisms and propose that there should be a check on the rampant use of agrochemicals.     

Diurnal changes in the territorial behaviour of the tilapia Oreochromis mossambicus (Peters)

The numbers of black, territorial, male tilapia in large tanks undergoes a clear diurnal cyclicity, with peak numbers seen in the afternoon. It is suggested that this cyclicity is functionally related to an observed spawning cyclicity.     

Effect of hypergravity on the Ca/Sr composition of developing otoliths of larval cichlid fish (Oreochromis mossambicus)

The amounts of calcium and strontium were measured by inductively coupled plasma mass spectrometry (ICP-MS) in saccular and utricular inner ear otoliths (sagittae and lapilli, respectively) of developing cichlid fish. These fish had been maintained for 22 days at 3-g hypergravity conditions within a centrifuge. During this time-span, the animals completed their ontogenetic development from hatch to the free-swimming stage. Neither the morphogenetic development nor the timely onset and gain of performance of the swimming behaviour was impaired by the experimental conditions. Experimental and control animals also did not differ concerning their size (total length). ICP-MS revealed that the otoliths contained significantly less calcium (in microg/otolith) after hyper-g exposure compared to parallelly raised 1-g control specimens (lapilli: 0.74+/-0.21 vs. 1.16+/-0.41; sagittae: 2.09+/-0.49 vs. 2.76+/-0.47). The content of strontium (in microg/otolith: lapilli: 0.0044+/-0.0023 vs. 0.0022+/-0.0013; sagittae: 0.0094+/-0.0026 vs. 0.0081+/-0.0016) and, consequently, the Sr/Ca ratio (Sr/Cax100) was increased (lapilli: 0.607+/-0.267 vs. 0.201+/-0.12; sagittae: 0.439+/-0.093 vs. 0.301+/-0.086). Since the calcium content can be taken as a proxy for otolith weight, and because parallelly undertaken morphometric investigations revealed smaller otoliths (maximum radius and surface area) due to hyper-g exposure, the results suggest that the growth of otoliths at hyper-g is slowed down. Since the concentration of trace elements incorporated into otoliths is likely based on the composition of the respective protein matrix, our findings suggest that the protein metabolism is affected by hypergravity.     

Hematological effects of textile mill effluent on freshwater fish Oreochromis mossambicus (Trewaves)

O. mossambicus was exposed to sublethal concentrations of a textile mill effluent to study the hematological changes as a function of feeding/starvation, aeration/non-aeration and concentration. Increase in concentration produced a dose dependent increase in RBCs (0.87 x 10(6) to 1.63 x 10(6)/mm3), WBCs (0.070 x 10(6) to 0.520 x 10(6)/mm3), hemoglobin (3.7 to 5.6%) and hematocrit (9.0 to 12.3%) and a decrease in MCV (111.8 to 88.2 microns 3), MCHC (41.05 to 31.35%) and MCH (44.2 to 33.9 pg).     

Effect of Oil Content and Composition on the Gelling Properties of Egg-SPI Proteins Stabilized Emulsion Gels

Effects of different oils on the rheological properties, textural profile, water loss (WL), oil loss (OL) and microstructure of egg-soybean protein isolate (SPI) stabilized emulsion gels were investigated at neutral pH, wherein soybean oil, olive oil and menhaden oil were used to form emulsions. The results showed that viscosity of emulsions progressively increased with the increase of oil content. Similarly, analysis of the rheological behavior of the formulated emulsion gels revealed an increase in the mechanical strength (G’) with the increase in oil concentration, indicating that oil droplets played a significant role in the formation of the gel structure. In addition, at high levels of oil, the hardness and chewiness of emulsion gels were also high, while a slight decrease in springiness and cohesiveness were observed. A linear relationship between hardness and water/oil loss was found, whereas the Pearson correlation suggested that less drainage of water may slow down the outflow of oil. The microstructural images showed a more compact network as a result of the increase of oil content in the formulation. Scarce significant differences were found among emulsion gels formulated with different oil type, suggesting oil composition played a dispensable role on the gelling properties of emulsion gels.

     

The effect of temperature and mass on routine metabolism in Sarotherodon (Tilapia)mossambicus (Peters)

A reappraisal of oxygen uptake by Sarotherodon mossambicus was undertaken using a continuous flow respirometer. Measurements were obtained over the temperature range 16°C–37°C for fish weighing between 10 g and 150 g. Oxygen uptake was converted to energy equivalents ( Q _ox) using the value 13.68 J mg O₂^–1and the routine metabolic energy expenditure can be described by the equation E =0.0086 t ^{2 0783} M ^{0 652} where E is the energy requirement for routine metabolism expressed in J h^-1, t the temperature in °C and M the mass in g.     

Postprandial changes in pH and enzyme activity from the stomach and intestines of Tilapia rendalli (Boulenger, 1897), Oreochromis mossambicus (Peters, 1852) and Clarias gariepinus (Burchell, 1822)

The ability to utilise dietary components differs among fish species. Digestive enzymes may be used to determine the efficiency of the digestive process. In this study, the activities of the digestive enzymes in Tilapia rendalli, Oreochromis mossambicus and Clarias gariepinus were explored. Protease, amylase, lipase and cellulase activities were measured in different parts of the digestive tract of the three fish species. The pH dynamics along the digestive tract were monitored. In all fish species, the presence of food led to a reduction in stomach pH, whereby pH values of 1.54, 1.58 and 2.01 were recorded 12 h after feeding in O. mossambicus, T. rendalli and C. gariepinus, respectively. Protease and amylase activities were significantly higher (P < 0.05, anova ) in the tilapias than in C. gariepinus. The tilapias may be pre‐adapted to produce more protease and amylase to digest plant material, which is more difficult to digest than animal matter. In all species amylase activity was significantly higher in the proximal intestine than in the other parts of the digestive tract (P < 0.05, anova ). The highest protease activity was recorded in the distal intestines. This is because of the alkaline pH recorded in the proximal and distal intestines, which favours amylase and protease activity, respectively. Lipase activities were significantly higher (P > 0.05) in C. gariepinus than in both tilapias. Marginal cellulase activities were recorded in all species. It is inferred here that phylogeny and not diet may be the main factor influencing enzyme activities, as all fish were fed a similar diet.     

Observations on the nesting habits of Oreochromis mossambicus (Peters) (Pisces: Cichlidae) in Sri Lankan reservoirs

The nest-building characteristics of Oreochromis mossambicus (Peters) were studied in five manmade lakes (reservoirs) Sri Lanka. The nests were always found in clusters (arenas) and were generally located in or near coves and/or bays in shallow water. The density of nests in an arena varied between arenas in a reservoir and between reservoirs. The overall mean density of nests ranged between 0.47 and 6.31 m ² in the five reservoirs. The nests ranged from 11 to 110 cm in diameter, two size groups of nests being recognizable: small, with diameter 10–50 cm, and large with diameter >50 cm. At any nesting site only one size group of nests was found.
Nest diameter ( ND ) was curvilinearly related to mean nest density ( D ) and linearly to mean distance between nests ( Dis ), the respective statistical relationships being
The diameter of nests was also related to nest depth ( Dep ) as
There was no apparent relationship between nesting characteristics and morphometric characters of the reservoirs.