Mozambique Tilapia Oreochromis Mossambicus Research Articles

Consumption of periphyton and bioseston by Mozambique tilapia in aqua dams with three different substrates

Periphyton-based aquaculture can reduce feed input costs. Here we characterised the periphyton and bioseston formation in aqua dams stocked with net, plastic, and stone substrates. The consumption of periphyton and bioseston from the net substrate by Mozambique tilapia Oreochromis mossambicus fingerlings was evaluated. Three experiments were conducted. In the first experiment, net, stone, and plastic were deployed in triplicates in aqua dams. The net substrate registered the highest (7.74 ± 1.45 g m-2, ±SE) periphyton biomass. Network analysis showed connectedness between the substrates. The degree centrality showed that the net substrate had the highest score, indicating that there were more groups of species with similar functions growing on the net substrate. The net substrate was subsequently used in the second experiment to determine the consumption of periphyton and bioseston by tilapia fingerlings in aqua dams. Three treatments were assigned: N100 (fish fed 100% commercial diet); N50 (fish fed 50% commercial diet); and N33 (fish fed 33% commercial diet). Growth performance did not differ significantly among the treatments, although N50 showed a trend for a higher growth. This suggests that periphyton may be capable of nutritionally compensating for the partial withdrawal of commercial feed. A third experiment was conducted in fibreglass tanks to determine the preference of tilapia between periphyton and bioseston. The prominent values showed that tilapia preferred to feed on bioseston. The best growth performance was achieved in a periphyton-based aquaculture system, and deployment of the net substrate is recommended in tilapia ponds.

Chronic Starvation-Induced Alterations in Biochemical Parameters and Hypothalamic-Pituitary-Testicular Axis in the Mozambique Tilapia Oreochromis mossambicus (Cichlidae)

Although fish are often exposed to food restrictions in natural or aquafarming conditions, the relationship between altered energy status and the reproduction is not well understood. The aim of the present investigation was to elucidate the effect of chronic food-deprivation on energy status and reproductive axis in male Mozambique tilapia Oreochromis mossambicus. The controls received food ad libitum, whereas the fish in the starvation group were deprived of food for 21 days. The liver showed significantly higher levels of gluconeogenesis and triglycerides, whereas the levels of blood glucose and total protein content in the liver were significantly lower in starved fish compared to controls. Furthermore, the mean numbers of different spermatogenic cells, such as spermatogonia-A, primary spermatocytes, secondary spermatocytes, early spermatids, and late spermatids were significantly lower, but the number of spermatogonia-B did not show a significant difference compared to controls. In starved fish, there was a significant increase in germ cell apoptosis at different stages of development concomitant with faintly immunoreactive androgen receptors in the Sertoli cells of the testis compared with controls. In addition, the percent areas of gonadotropin-releasing hormone—immunoreactive fibres and luteinizing hormone—immunoreactive content—in the proximal pars distalis part of the pituitary gland were significantly lower in starved fish compared with controls. Collectively, these results suggest that decreased energy status negatively affects the gonadotropin-releasing hormone—luteinizing hormone – testicular axis, leading to inhibition of spermatogenesis before entry of germ cells into meiosis through increased apoptosis and decreased expression of androgen receptors in the testis of the Mozambique tilapia.

DNA metabarcoding reveals the diet of the invasive fish Oreochromis mossambicus in mangroves of São Tomé Island (Gulf of Guinea)

AbstractInvasive species can trigger profound effects on recipient ecosystems, namely through the food web. Despite being recognized as one of the worst invasive species, little is known about the feeding ecology of the Mozambique tilapia Oreochromis mossambicus. To understand how this invasive species might impact food webs, we applied metabarcoding to analyze its diet’s composition in two African mangroves, in the Obô Natural Park in the oceanic island of São Tomé. Given the particular importance of mangroves as fish nurseries, we specifically aimed to determine if this invader might predate on other fish species. However, we found that tilapia were mostly phytoplanktivorous and indication on predation of other fish was very limited. Instead, due to their local high densities, tilapia may impact basal trophic levels and nutrient availability with the potential to cascade through the food web by means of bottom-up disruption. In addition, we recorded important changes in the taxonomic composition of the diet, linked to locations and life stages, suggesting that its opportunistic feeding associated with its aggressive territorial behavior may result in resource competition with native species with which it has overlapping dietary niches.

Metazoan Parasites of Mozambique tilapia (Oreochromis mossambicus) Native to Lake Urema, Mozambique

Mozambique tilapia Oreochromis mossambicus (Peters, 1852), an important aquaculture species investigated herein, is at risk and listed as vulnerable on the IUCN Red List. During a preliminary survey conducted in 2011, 30 Mozambique tilapia from Lake Urema in Gorongosa National Park in central Mozambique, were examined for metazoan parasites. Two groups of ectoparasites were recovered consisting of two species of copepods and a monogenean. Endoparasites retrieved were in the larval stage and included one trematode and one nematode species. This study provides new parasite records for O. mossambicus in Mozambique and forms a baseline for monitoring against the presence of ichthyoparasites associated with the introduction in neighbouring systems of non-native fish such as Nile tilapia Oreochromis niloticus (Linnaeus, 1758), a fish of worldwide importance in capture fisheries and especially aquaculture.

Exopolysaccharides-Mediated ZnO Nanoparticles for the Treatment of Aquatic Diseases in Freshwater Fish Oreochromis mossambicus.

Bacterial fish disease outbreaks are a key concern for aquaculture. Complementary feed additives such as immunostimulants can serve as an ideal solution for disease prevention. Herein, we scrutinized the efficacy of exopolysaccharides (EPSs) from probiotic Bacillus licheniformis and EPS-mediated zinc oxide nanoparticles (EPS-ZnO NPs) for a diet to evaluate growth parameters, antioxidant enzyme activities, and immune stimulation together with disease resistance against Aeromonas hydrophila and Vibrio parahaemolyticus in Mozambique tilapia Oreochromis mossambicus. Fish were separated into seven groups, with six experimental groups fed with EPS and EPS-ZnO NPs at 2, 5, and 10 mg/g and a control fed a basal diet. The fish ingesting feed supplemented with EPS and EPS-ZnO NPs at 10 mg/g showed improved growth performance. Cellular and humoral-immunological parameters were tested in serum and mucus after 15 and 30 days of feeding. These parameters were substantially enriched with a 10 mg/g diet (p < 0.05) of EPS and EPS-ZnO NPs in comparison with the control. Furthermore, the EPS and EPS-ZnO NP supplemental diet actively enhanced the antioxidant response (glutathione peroxidase, superoxide dismutase, and catalase). In addition, the supplemental diet of EPS and EPS-ZnO NPs lowered the death rate and improved the disease resistance of O. mossambicus following assessment with A. hydrophila and V. parahaemolyticus at 50 µL. Hence, the overall results suggest that the supplemental diet of EPS and EPS-ZnO NPs might be used to ensure aquaculture feed additives.

Predicting the functional morphology of lotic and lentic populations of the invasive Mozambique tilapia Oreochromis mossambicus (Peters, 1852)

A better understanding of the mechanism which connects the morphology of fishes and their ecological performance is a major goal in evolutionary studies. As accepted widely, intra-species polymorphism mostly arises from divergent selection pressures between different environments. The present study sought to understand the functional morphological variations exhibited by Mozambique tilapia Oreochromis mossambicus (Peters, 1852) inhabiting heterogeneous habitats, using functional indices derived from the body. We found that O. mossambicus exhibited clear functional responses to divergent habitats indicating trait-habitat linkages. Fishes differed in three out of fifteen indices compared, which are mainly related to swimming performances. Fishes collected from the river possess more streamlined bodies and achieve higher values in indices related to swimming efficiencies. However, there were no significant intra-species differences in the indices related to feeding between habitats, indicating that functional divergences in O. mossambicus are mainly related to swimming and locomotion. The study confirmed that the morpho-functional variations observed in this species are primarily of selection pressure caused by habitat heterogeneities. The present findings further confirm our understanding of the predictive power of the trait-environment approach and indicate that fishes tend to change their traits related to swimming and foraging with changing ecological conditions of the habitat.Keywords: Cichlids, Ecomorphology, Functional traits, Phenotypic variation, Trophic polymorphism

Energy utilization during ovarian development of the cichlid fish Oreochromis mossambicus (Peters) inhabiting a perennial lentic water body in Bangalore, India.

Mozambique tilapia Oreochromis mossambicus (Peters) is an invasive fish and a continuous breeder in inland waters of India. Present investigation highlights the distinct developmental stages of developing ovary and associated changes in the energy content. This investigation helps to understand the allocation of energy for development of eggs, prespawn and also oral brooding by the female. Although it is a continuous breeder, based on size of the ovary, number of eggs, their size and energy content, immature, early maturing, developing, prespawning and spawning stages are clearly noticed. Egg diameter during development of ovary varied between 0.31 mm (immature) and 2.21 mm (spawning). Energy content of ovary from immature to spawning stage ranged from 20.7515 kJ g-1 dry ovary to 31.1560 kJ g-1 dry ovary. Nearly 28.73% of energy content of ovary is expended for spawning. Similarly, yolk-sac fry utilized nearly 25.85% of energy of the fertilized egg for its development. Energy content of ovary of mouth-brooding female averaged 22.9528 kJ g-1 dry ovary, which is comparable to energy content of early maturing stage of ovary (24.5558 kJ g-1 dry ovary). A strong correlation between body weight and energy content of the developing ovary (P < 0.01), and between ovary weight and energy content of ovary (P < 0.01), was evident. During mouth-brooding, the fish continues to allocate energy to its developing ovary. Energy investment by the fish is the result of simultaneous processes associated with gonadal and somatic energy. As body size growth and gonadal development are interconnected, information on energy utilization by an iteroparous mouth-brooding fish could provide the pattern of energy allocation during ovarian developmental phase. Further details of energy utilization, as explained in this paper, could be used as one of the factors to predict the efficiency of fish production.

The Influence of Kappa Opioid Receptor Antagonist 5'-Guanidinonaltrindole during Reproductive Stress Response in the Mozambique Tilapia Oreochromis mossambicus (Cichlidae)

The Influence of Kappa Opioid Receptor Antagonist 5'-Guanidinonaltrindole during Reproductive Stress Response in the Mozambique Tilapia Oreochromis mossambicus (Cichlidae)

Behavioural Responses and Mortality of Mozambique Tilapia Oreochromis mossambicus to Three Commonly Used Macadamia Plantation Pesticides

The use of pesticides in agricultural systems may have deleterious effects on surrounding environments. Aquatic systems are no exception and are increasingly polluted through the leaching of pesticides from agricultural activities. However, the pesticide pollution effects on key aquatic species have not been studied in many regions. In southern Africa, increasing pesticide use associated with macadamia tree Macadamia integrifolia farming presents a growing risk to surrounding aquatic ecosystems. This study assessed behavioural responses of an important and widely-distributed freshwater fish, Mozambique tilapia Oreochromis mossambicus, following exposure to three commonly used macadamia pesticides (i.e., Karate Zeon 10 CS, Mulan 20 SP, Pyrinex 250 CS) at different concentrations (0.7–200 µL, 0.3–1000 mg, and 0.7–8750 µL, respectively) over 24 h. Behavioural responses, i.e., swimming erratically, surfacing, vertical positioning, loss of equilibrium, being motionless and mortality were observed after pesticides exposure. Lethal dose 50 (LD50) values of Karate Zeon 10 CS, Mulan 20 SP and Pyrinex 250 CS were 2.1 µL (per water litre dilution—WLD), 5.2 mg (WLD) and 21.5 µL (WLD), respectively. These concentrations are therefore expressed as a maximal threshold usage in the environment around macadamia farms and a minimum distance of the plantations to water systems should be considered. Further studies should examine effects on other fish species and aquatic invertebrates to inform on pesticide pollution threats and mitigation plans for the region.

Changes in an Exotic Fish Community Assemblage of a Thermal Spring in Central Idaho

Barney Hot Springs is a thermal spring in the headwaters of the Little Lost River drainage in central Idaho. Tropical fish have been released into Barney Hot Springs, and several species have established self-sustaining populations. The objectives of this study were to determine the current community assemblage of tropical fish in Barney Hot Springs and to assess species composition and extent of downstream distribution of tropical fish in Barney Creek. The composition in 2017 consisted of Amelanic Convict Cichlids Amatitlania nigrofasciata, Mozambique Tilapia Oreochromis mossambicus, Zebra Mbuna Maylandia zebra, and Green Swordtails Xiphophorus hellerii. Total abundance of all fish species was estimated at 12,043 fish (95% CI 9807–15,600), with Green Swordtails making up 68% of the population, Zebra Mbuna 20%, Convict Cichlids 9%, and Mozambique Tilapia 3%. In Barney Creek, fish were collected within 800 m of Barney Hot Springs. In March 2018, a rain-on-snow event occurred that resulted in a fish kill. In fall 2018 after this event, Convict Cichlids, Green Swordtails, and Goldfish Carassius auratus were collected. Overall abundance was estimated at 1972 fish (95% CI 1757–2227), with Green Swordtails and Goldfish each composing 50% of the population; no Convict Cichlids were recaptured, so abundance could not be estimated. In Barney Creek, fish were collected within 400 m of Barney Hot Springs. We documented current changes to the fish community assemblage of Barney Hot Springs and Barney Creek that were driven by colonization (i.e., introduction of aquarium fish) and by local extinction through species interactions and stochastic events. Currently, we do not know the impact that the introduced fish fauna of Barney Hot Springs may have on native species or ecosystem function.

Habitat structure differentially mitigates predation impact of juvenile largemouth bass and Florida bass

Habitat complexity plays an important role in structuring species diversity, behaviour and distribution. Furthermore, habitat complexity can mediate the strength of predator-prey interactions through the provision of prey refugia or through enhancing ambush predation. In this study, we use functional responses (FRs) to compare the effect of habitat complexity on resource utilisation between Largemouth Bass Micropterus salmoides and Florida Bass Micropterus floridanus predating upon Mozambique Tilapia Oreochromis mossambicus fry. Treatments for this study were zero and high habitat complexities, with the latter being artificially constructed using plastic strips. Both predator species exhibited a Type II FR in both habitat complexities, with Florida Bass exhibiting significantly higher FR magnitudes, compared with Largemouth Bass under both habitat complexities. Both species experienced dampening of FR magnitudes under high habitat complexity. Florida Bass had persistently lower handling parameters than Largemouth Bass regardless of habitat complexity. While higher habitat complexity may offer prey refugia from Florida Bass, changes in complexity had a negligible effect upon Largemouth Bass predatory efficiency. Measures to enhance natural complexity through system restoration may be a useful conservation measure for endemic fish in rivers invaded by Florida Bass, however, the same mitigation measures may not be as effective for Largemouth Bass.

Predictor complexity and feature selection affect Maxent model transferability: Evidence from global freshwater invasive species

AbstractAimEcological niche models (ENMs) are widely used to address urgent real‐world problems such as climate change effects or invasive species; however, the generality of models when projected through space and/or time, that is transferability, remains a key challenge. Here, we explored the effects of complex predictors and feature selection on ENM transferability in a widely employed algorithm, Maxent, using five globally invasive freshwater species as case studies.LocationGlobal.MethodsWe modelled the global distributions of five notorious freshwater invasive species (African sharptooth catfish Clarias gariepinus, Mozambique tilapia Oreochromis mossambicus, American bullfrog Lithobates catesbeianus, red swamp crayfish Procambarus clarkii, and Australian redclaw crayfish Cherax quadricarinatus), using three predictor datasets of varying complexities derived from two commonly used climatic data sources (WorldClim and IPCC) and three methods of model tuning that differentially incorporated feature selection. Spatially explicit transferability assessments were then conducted using a suite of evaluation metrics previously used to quantify Maxent model performance.ResultsWe show that in the absence of detailed biological knowledge of focal species, simpler predictor datasets produce models that are more accurate than those calibrated using comprehensive “bioclimatic” datasets. Additionally, we find that tuning models for both optimal regularization parameters as well as feature‐class combinations led to the greatest increases in transferability and geographic niche conservatism. Results indicate a tenuous link between model transferability and Akaike's information criterion corrected for small sample sizes (AICc), suggesting that the indiscriminate use of AICc as an estimate of model parsimony may lead to erratic model performance.Main conclusionsOur findings demonstrate that methodological considerations can drastically affect the reliability of spatial and possibly temporal projections, which has severe implications when ENMs are used to infer species’ niches, and quantify ecological or evolutionary change across impacted landscapes.

Assessment of interspecific interactions between the invasive red-claw crayfish (Cherax quadricarinatus) and the Mozambique tilapia (Oreochromis mossambicus).

The Australian red-claw crayfish, Cherax quadricarinatus, has been introduced for aquaculture purposes worldwide and consequently colonized natural environments, where it might cause ecosystem services losses or adversely affect native species and the local environment. This species was first found in Pequenos Libombos Reservoir in Maputo Province, Southern Mozambique in the late 2009 and is linked to reduction in tilapia fisheries. This study, conducted in 2015 under controlled conditions, aimed to assess the interspecific relationships between the Mozambique tilapia (Oreochromis mossambicus) and the alien crayfish. For both species, no significant differences in growth and survival rates were found between animals reared in the presence versus the absence of heterospecifics, indicating no direct deleterious interspecific effects. Behavioural observations revealed that fish and crayfish competed for shelter and food. Both species reduced the foraging in the presence of heterospecifics during feeding period, in the daytime. Crayfish seemed to have an advantage in competition for shelter, suggesting that they may interfere with tilapia sheltering activity and make tilapia vulnerable to predators in natural habitats.

Exploring source differences on diet-tissue discrimination factors in the analysis of stable isotope mixing models

Stable isotope mixing models are regularly used to provide probabilistic estimates of source contributions to dietary mixtures. Whilst Bayesian implementations of isotope mixing models have become prominent, the use of appropriate diet-tissue discrimination factors (DTDFs) remains as the least resolved aspect. The DTDFs are critical in providing accurate inferences from these models. Using both simulated and laboratory-based experimental data, this study provides conceptual and practical applications of isotope mixing models by exploring the role of DTDFs. The experimental study used Mozambique Tilapia Oreochromis mossambicus, a freshwater fish, to explore multi-tissue variations in isotopic incorporation patterns, and to evaluate isotope mixing model outputs based on the experiment- and literature-based DTDFs. Isotope incorporation patterns were variable for both muscle and fin tissues among the consumer groups that fed diet sources with different stable isotope values. Application of literature-based DTDFs in isotope mixing models consistently underestimated the dietary proportions of all single-source consumer groups. In contrast, application of diet-specific DTDFs provided better dietary estimates for single-source consumer groups. Variations in the proportional contributions of the individual sources were, nevertheless, observed for the mixed-source consumer group, which suggests that isotope assimilation of the individual food sources may have been influenced by other underlying physiological processes. This study provides evidence that stable isotope values from different diet sources exhibit large variations as they become incorporated into consumer tissues. This suggests that the application of isotope mixing models requires consideration of several aspects such as diet type and the associated biological processes that may influence DTDFs.

Evaluation of genotoxicity, enzymatic alterations and cadmium accumulation in Mozambique tilapia Oreochromis mossambicus exposed to sub lethal concentrations of cadmium chloride

Abstract Cadmium (Cd), a heavy metal, is widely used in modern industries including in metal and mining industries as well as in the manufacture of Ni Cd batteries. Its bioaccumulation is reported to induce hazardous effects in aquatic organisms including fish. Hence, the present study was undertaken to evaluate the toxic potential of cadmium in Tilapia (Oreochromis mossambicus Peters). Fish were exposed to 3 sub-lethal concentrations of CdCl2: 7.4 μg/l (high), 3.7 μg/l (medium) and 1.85 μg/l (low) for a period of 21 days. Ten fish were used for each group and each exposure was done in triplicates. A group of 10 fish without exposure to CdCl2 was used as control. Genotoxic effects of Cd were assessed employing micronucleus assay and the comet assay. Along with these tests, alterations in the amount of the enzymes acetylcholine esterase (AChE) and catalase (CAT), as well as, the quantum of Cd accumulated in different tissues of the organism were also studied. A significant increase in DNA damage as % tail DNA and micronuclei were observed in the fish exposed to CdCl2. CdCl2 also induced a significant increase in the activity of CAT whereas a decrease in the activity of AChE was observed. A significant association was also observed between DNA damage parameters and catalase activity as well as Cd concentration in the gills. Cd may thus induce genotoxicity in O. mossambicus via oxidative stress and tissue accumulation. The combined use of these biomarkers in O. mossambicus could be used to monitor Cd contamination in the aquatic environment.

Influence of endomorphins along the pituitary-ovary axis in the Mozambique Tilapia Oreochromis mossambicus.

Endomorphins (EM-1 and EM-2) are the tetrapeptides involved in pain and neuroendocrine responses with a high affinity for μ-opioid receptors in vertebrates. However, their role in fish reproduction is not clear. The aim of this study was to investigate the influence of EM-1 and EM-2 on the pituitary-ovary axis in the Mozambique tilapia Oreochromis mossambicus. The experimental set-up consisted of four groups, namely, initial controls, controls, EM-1- and EM-2-treated groups (n = 10 in each group consisting of two replicates). Although the number of stage IV (vitellogenic) follicles was significantly lower (P < 0.05) in controls compared to initial controls, the stage V (preovulatory) follicles were present in controls in contrast to their absence in initial controls. Treatment of 40 μg EM-1/0.1 ml saline/fish/day for 22 days resulted in significant increase (P < 0.05) in the number of stage I follicles compared to controls. While similar treatment of EM-2 did not significantly alter the number of stage I follicles compared to controls, the number of stage II follicles was significantly lower (P < 0.05) in this group compared to those of controls and EM-1 treated fish. The number of stage III and IV follicles did not significantly differ among controls, EM-1- and EM-2-treated groups. However, a significant reduction (P < 0.05) in the mean number of stage V follicles was observed in EM-1- and EM-2-treated fish compared to controls. These changes were concomitant with significant reduction (P < 0.05) in the intensity and the percent area of immunoreactivity of luteinizing hormone (LH) secreting cells in the proximal pars distalis (PPD) of the pituitary gland and significantly higher (P < 0.05) percent occurrence of follicular atresia in EM-1- and EM-2-treated fish compared to those of controls. Taken together, these results suggest an inhibitory effect for endomorphins along the pituitary-ovary axis, for the first time in fish.

Rapid In Situ Action of Estradiol 17β on Ion Transporter Function in Brain Segments of Female Mozambique Tilapia ( Oreochromis mossambicus Peters)

Being the principal estrogen, estradiol 17I² (E 2 ) is essential for normal ovarian function in the vertebrates including fishes. Besides its primary role in reproduction, E 2 is also known for its role in many other physiological processes including water and mineral balance. However, it is uncertain, how E 2Â regulates ion-specific ATPases that drive Na + , K + , H + , Ca 2+ and Mg 2+ transport in fish brain. We, therefore, examined the short-term in situ action of E 2 on ion transporter function in the brain segments of freshwater female Mozambique tilapia Oreochromis mossambicus . Tilapia were perfused with increasing doses of E 2 (10 -9 , 10 -8 and 10 -7 M) for 20 min and sampled for determining Na + /K + -ATPase, H + -ATPase, Ca 2+ -ATPase, and Mg 2+ -ATPase activities in the prosencephalon (PC), mesencephalon (MC) and metencephalon (MeC) segments of brain. Dose-dependent increase in Na + /K + - and Ca 2+ -dependent transporter activities after E 2 perfusion were found in PC. In MC, E 2 treatment, however, produced significant increase in Mg 2+ , Ca 2+ and H + transport activities in mitochondria but decreased Na + /K + - and I½H + transporter activities. On the contrary, in MeC, E 2 administration while producing increase in Na + /K + -, mitochondrial- and I½H + -transport, lowered cytosolic and mitochondrial Ca 2+ transport. Taken together, the data indicate that E 2 has rapid and direct action on ion transporter function that corresponds to the differential activation/inactivation of neuronal clusters in the brain segments of female freshwater tilapia.

SAT-LB069 Differential Regulation of Hypothalamic and Hepatic Reproductive Signals by Leptin and Sex Steroids in the Mozambique Tilapia Oreochromis mossambicus

Reproduction is a physiologically demanding process that relies on energy sufficiency, the lack of which can result in delayed puberty and suppression of reproductive function. The pleiotropic peptide hormone leptin is a key signal in energy homeostasis that relays information on peripheral energy availability to central circuits. In mammals, leptin has been found to serve as a critical permissive signal in the activation of the gonadotropic axis and onset of puberty. Although leptin effects on reproduction have been explored extensively in mammals, its actions and regulatory properties on reproduction in fishes remain unclear. The current study assesses (i) the effect of in vivo leptin treatment on hypothalamic kisspeptin (kiss2) and gonadotropin-releasing hormone (gnrh1), (ii) the effect of leptin treatment on major egg-yolk precursors, vitellogenins (vtga, vtgb, vtgc), and insulin-like growth factor (igf1) in primary tilapia hepatocytes, and (iii) the effect of sex steroid treatment on leptin (lep) and insulin-like growth factor in primary tilapia hepatocytes. Gene expression of lep in the liver, the primary source of circulating hormone, increased with gonadosomatic index and sexual maturation of male and female tilapia, suggesting the hormone may regulate reproductive function. Intraperitoneal injection and 6-hour treatment with recombinant tilapia leptin (rtLep) in adult male tilapia resulted in increased hypothalamic kiss2 and gnrh1 transcript levels versus saline control (P < 0.01). In primary hepatocyte culture, rtLep suppressed vtgb and vtgc transcript levels (P < 0.01), while it stimulated igf1 (P < 0.0001). Testosterone and estradiol reduced lep levels (P < 0.001), but disparately regulated ­igf1 whereby testosterone increased igf1 and estradiol decreased igf1 at 10 and 100 nM (P < 0.001). The non-aromatizable 11-ketotestosterone increased lep and igf1 transcript levels at 100 nM (P < 0.05). Our findings suggest that leptin expression rises with sexual maturation and the hormone exerts stimulatory effects on hypothalamic gonadotropic factors. By contrast, leptin reduces estrogen-sensitive vitellogenesis while promoting elements of the somatotropic axis (e.g., igf1), suggesting the hormone may have dual roles in regulating reproductive and somatic growth processes. We speculate that this latter effect may be associated with limiting energy partitioning to reproduction in instances of negative energy balance. Unless otherwise noted, all abstracts presented at ENDO are embargoed until the date and time of presentation. For oral presentations, the abstracts are embargoed until the session begins. s presented at a news conference are embargoed until the date and time of the news conference. The Endocrine Society reserves the right to lift the embargo on specific abstracts that are selected for promotion prior to or during ENDO.

Hormonal Profile and Reproductive Parameters of Pre-vitellogenic Mozambique tilapia (Oreochromis mossambicus) on Pawpaw (Carica papaya) Seed Meal

The use of phytochemicals to control precocious maturation and indiscriminate spawning among tilapia species is an important issue in aquaculture. This study investigated the influence of pawpaw (Carica papaya) seed meal on the reproductive performance, and the sex hormone profile of sexually immature Mozambique tilapia (Oreochromis mossambicus). Pawpaw seed meal (PSM) were included in a tilapia commercial diet (basal diet) at an inclusion level of 0 PSM, 10 PSM and 30 PSM g/kg of the basal diet (BD), respectively, and fed to immature O. mossambicus for a period of 30 and 60 days, respectively. Enzyme-linked immune-sorbent assay (ELISA) procedures were used to quantify the plasma levels of 17&amp;beta;-estradiol and 11-ketotestosterone. The inclusion of PSM did not affect the growth and survival rate of the O. mossambicus. The plasma levels of 11-ketotestosterone did not differ among the treatment groups. The 17&amp;beta;-estradiol levels of female fish that received 30 PSM g/kg BD for 60 days were significantly lower (p &amp;lt; 0.05) than the levels reported for females that were not fed the PSM. In females, the PSM reduced the gonad weight, GSI, fecundity and egg diameter of fish. The study concludes that pawpaw seed meal affected the reproductive function of the female O. mossambicus though the changes were reversible.

Food habits of three non-native cichlid fishes in the lowermost Chao Phraya River basin, Thailand

The food habits of three non-native cichlid fishes, Mayan cichlid (Mayaheros urophthalmus), Mozambique tilapia (Oreochromis mossambicus) and Nile tilapia (O. niloticus), in the lowermost Chao Phraya River basin, Thailand, was examined by stomach contents analysis. The index of preponderance, an index of the importance of prey items, was calculated from two relative metrics of prey quantity: percent frequency and percent volume. The index of niche breadth and the overlap coefficient were calculated to compare the breadth of food habits among the size classes and species groups. The M. urophthalmus mainly preyed on fish scales, detritus and aquatic invertebrates (molluscs and crustaceans). The O. mossambicus and O. niloticus fed mostly on detritus. The diets of the latter two species overlapped almost completely; however, green filamentous algae mixed with detritus was observed in the diet of the O. niloticus only. The observation that fish scales were a predominant food source in the stomach of M. urophthalmus (high importance value 45.48%) was specific to this study area.