Browsing by Author "Samwel Mchele Limbu"
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Item Adverse effects of chronic ammonia stress on juvenile oriental river prawn (Macrobrachium nipponense) and alteration of glucose and ammonia metabolism(Wiley, 2023-03) Shanshan Wei; Jin Zhang; Wanxin Chen; Anfu Shen; Dongsheng Zhou; Jinxian Zheng; Habib Thiam; Zhili Ding; Samwel Mchele Limbu; Youqin KongAmmonia is one of the common stress factors in aquaculture. However, the effect of chronic ammonia exposure in juvenile oriental river prawn (Macrobrachium nipponense) is currently unexplored. This study explored the effects of chronic ammonia on juvenile healthy oriental river prawns. Fifty prawns (0.123 ± 0.003 g) were exposed to 0, 5, and 15 mg/L total ammonia nitrogen (TAN) in triplicates for 28 days. The effects of chronic ammonia challenge were evaluated on growth, antioxidant capacity, hepatopancreas and gill morphology, and glucose and ammonia metabolism. The results showed that, the chronic ammonia exposure reduced significantly survival rate and weight gain of prawns. The prawns exposed to 15 mg/L ammonia had induced oxidative stress. However, the prawn exposed to 15 mg/L ammonia had significantly lower aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, and acid phosphatase activities in the serum. Furthermore, exposure of prawns to 15 mg/L ammonia increased the activities of hexokinase, pyruvate kinase, pyruvate and lactic acid content, and glutamine synthase activity. However, the prawns exposed to 15 mg/L ammonia, reduced succinic dehydrogenase, 6-phosphogluconic dehydrogenase, phosphoenolpyruvate carboxykinase, glutamate synthase, and glutamate dehydrogenase activities but increased ammonia content in serum. The exposure of ammonia deformed lumen, damaged basement membrane and decreased secretory cells in the hepatopancreas, disordered gill epithelial and pillar cells, and caused gill filament base vacuolation. Our study indicates that chronic ammonia stress impairs growth performance, tissue morphology, induces oxidative stress, and alters glucose and ammonia metabolism in juvenile oriental river prawns.Item Aflatoxin B1 variations in animal feeds along the supply chain in Tanzania and its possible reduction by heat treatment(Taylor & Francis, 2022-03-04) Anjelina W. Mwakosya; Samwel Mchele Limbu; Nuria Majaliwa; Xiaobo Zou; Jiyong Shi; Oscar KibazohiThis study evaluated the presence of aflatoxin B1 in five different animal feeds collected from manufacturers, suppliers and consumers and its possible reduction by heating at 100°C for 180 min. A total of 160 animal feed samples were collected and analyzed by using lateral flow immunoassay method. The results revealed that all animal feeds analyzed were positive for aflatoxin B1 with 91% samples containing high concentrations ranging from 24.00 to 76.23 ng/g above the international allowable standard for animal feeds (20 ng/g). Maize bran (76 ng/g) and sunflower cake (63 ng/g) had higher aflatoxin B1 concentrations, correlating with higher moisture content. Upon heating the feeds, aflatoxin B1 was reduced to a concentration ranging from 2.24 to 9.78 ng/g (<20 ng/g). Our study suggests high potential health problems to animals and humans from aflatoxins requiring proper heating and frequent monitoring of the animal feeds for aflatoxin B1.Item Antibiotics Use in African Aquaculture: Their Potential Risks on Fish and Human Health. In: Abia A. and Lanza G. (Eds) Current Microbiological Research in Africa. Springer, Cham, pp. 203-221.(Springer, 2020-02) Samwel Mchele LimbuAntibiotics are used abusively in humans and agriculture, including aquaculture, making them omnipresent in the environment, posing health risks to aquatic animals and humans. However, how antibiotics affect the anatomy and physiology of fish, including the presence of antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs) in fish in Africa are currently poorly understood. This chapter synthesized the available literature on the potential risks of antibiotics on cultured fish and human health from Africa. The limited available studies indicate that few antibiotics improve fish growth but do not affect their survival rate. Antibiotics application on fish cause body malformation and damage, which induce hepatotoxicity, nephrotoxicity, leukocytosis, hematopoiesis, and lymphocytosis, suggesting sustained toxic effects. Antibiotics use in fish and other foods like shrimps and vegetables together with antibiotics residues in the aquatic environment have led to an increase in the prevalence of ARB and ARGs, posing a human health risk in various African countries. Limited studies indicate higher residues of antibiotics in cultured fish, which exceed the maximum limits set by the Codex Alimentarius Commission and the World Health Organization. Thus, policies and mechanisms for limiting the use of antibiotics in food animals to protect human health in Africa are urgently needed.Item Aquaculture and Fisheries Extension. In: Mgaya, Y.D. and Mahongo, S.B. (Editors), Lake Victoria Fisheries Resources: Research and Management in Tanzania.(Springer, 2017-11-29) Shoko, A.P.; Mgaya, Y.D.; Samwel Mchele Limbu; Hoza, R.The dwindling catch from Lake Victoria has caused an insufficient fish supply to the population of the Lake Victoria basin, Tanzania. The decrease in catch rates and demand for fish has created room for fish farming practices at both small and commercial scales in the Lake Basin. This chapter provides a result-oriented status of aquaculture research and development efforts made by the government and Non-Governmental Organizations (NGOs) in the Lake Basin from the colonial era to the present. The chapter also highlights strengths, weaknesses, opportunities and challenges (SWOCs) to aquaculture development in the basin. Results show that the basin has a high potential for fish farming development due to suitable characteristics for fish farming. Fishponds are the common culture system used in fish farming in the basin. The ponds are stocked with either Nile tilapia Oreochromis niloticus or African sharptooth catfish, Clarias gariepinus, reared in monoculture or polyculture. A system of integrated aquaculture-agriculture (IAA) farming is also practised in some areas of the basin. The yield from the lake basin has increased with time due to improved pond management techniques. However, more room is available for further increase pending the adoption of technology and improved extension services. Fish farming could help to reduce fishing pressure on capture fisheries in the main lake and contribute significantly to the conservation of the lake’s biodiversity. Ultimately, fish farming will generate income for the people, which is in line with the government’s efforts to alleviate poverty in the country.Item Are Fiddler Crabs Potentially Useful Ecosystem Engineers in Mangrove Wastewater Wetlands? Mari Poll Bull(Elsevier, 2009) Penha-Lopes, Gil P.; Bartolini, Fabrizio; Samwel Mchele Limbu; Cannicci, Stefano; Kristensen, Erik; Paula, JoséThe effect of different organic-rich sewage concentration (0%, 20% and 60% diluted in seawater) and absence or presence of mangrove trees on the survival, bioturbation activities and burrow morphology of fiddler crabs species was assessed. After 6 months, males of both species always showed higher survival (80%) when compared to females (20%). Crabs inhabiting pristine conditions achieved higher survival (67–87%) than those living in sewage-exposed mesocosms (40–71%). At 60% sewage loading, fiddler crabs processed less sediment (34–46%) during feeding and excavated slightly more sediment (45– 80%) than at pristine conditions. While percent volume of the burrow chambers increased (13–66%) at contaminated mesocosms for both vegetation conditions, burrows were shallower (33%) in bare cells loaded with sewage. The results show that fiddler crabs presented moderate mortality levels in these artificial mangrove wetlands, but mainly in sewage impacted cells. However, they still function as ecosystem engineers through bioturbation activities and burrow construction.Item Arginine supplementation in plant-rich diets affects growth, feed utilization, body composition, blood biochemical indices and gene expressions of the TOR signaling pathway in juvenile Asian red-tailed catfish (Hemibagrus wyckoiides)(Wiley, 2022-02) Dahai Gu; Jingying Zhao; Samwel Mchele Limbu; Yunan Liang; Junming Deng; Baoliang Bi; Lingfu Kong; Hui Yan; Xiaowen Wang; Qing Hu; Yu Gao; Dan Jia; Hua RongArginine (Arg) is an important essential amino acid required for optimum fish growth. However, its role in plant-rich diets on growth and the required level in juvenile Hemibagrus wyckioides are currently unknown. This study evaluated the effects of Arg supplementation in plant-rich diets on growth, feed utilization, whole body composition, blood biochemical indicators and gene expressions of the target of rapamycin (TOR) signaling pathway in juvenile H. wyckioides. A total of 450 fish (6.40 ± 0.06 g) were randomized into six equal groups and fed on diets with graded Arg levels: 0 (control), 3, 6, 9, 12 and 15 g/kg of dry feed for eight weeks. The results revealed that specific growth rate (SGR) and feed conversion ratio of juvenile H. wyckioides were significantly improved and reduced, respectively in fish fed on 9 g/kg of Arg supplementation (p < .05). The optimum amount of dietary Arg content in plant-rich diets for H. wyckioides was 63.77 g/kg diet based on SGR. Feeding fish with dietary Arg supplementation ranging from 9 to 12 g/kg improved significantly (p < .05) whole body protein contents and decreased lipid deposition. The mRNA levels of TOR, eukaryotic translation initiation factor 4E (4EBP) and ribosomal protein S6 kinase 1 (S6K1) in muscle and liver were significantly affected by increasing dietary Arg levels. Meanwhile, the mRNA relative expression levels of TOR and S6K1 in the liver and muscle increased significantly as Arg supplementation increased. On the other hand, the mRNA relative expression levels of 4EBP was significantly higher in fish fed on the 9 g/kg Arg diet compared to those fed on the control and 15 g/kg Arg diets. In conclusion, our current results indicate that dietary Arg supplementation in plant-rich diets, might activate the TOR signaling pathway, which promotes protein synthesis and reduces lipid accumulation of H. wyckioides, resulting in improved growth.Item Arginine supplementation in plant-rich diets affects growth, feed utilization, body composition, blood biochemical indices and gene expressions of the TOR signaling pathway in juvenile Asian red-tailed catfish (Hemibagrus wyckoiides), Journal of the World Aquaculture Society, 1–18. .(Wiley, 2020-10-12) Dahai Gu; Jingying Zhao; Samwel Mchele Limbu; Yunan Liang; Junming Deng; Baoliang Bi; Lingfu Kong; Hui Yan; Xiaowen Wang; Qing Hu; Yu Gao; Dan Jia; Hua RongArginine (Arg) is an important essential amino acid required for optimum fish growth. However, its role in plant‐rich diets on growth and the required level in juvenile Hemibagrus wyckioides are currently unknown. This study evaluated the effects of Arg supplementation in plant‐rich diets on growth, feed utilization, whole body composition, blood biochemical indicators and gene expressions of the target of rapamycin (TOR) signaling pathway in juvenile H. wyckioides. A total of 450 fish (6.40 ± 0.06 g) were randomized into six equal groups and fed on diets with graded Arg levels: 0 (control), 3, 6, 9, 12 and 15 g/kg of dry feed for eight weeks. The results revealed that specific growth rate (SGR) and feed conversion ratio of juvenile H. wyckioides were significantly improved and reduced, respectively in fish fed on 9 g/kg of Arg supplementation (p < .05). The optimum amount of dietary Arg content in plant‐rich diets for H. wyckioides was 63.77 g/kg diet based on SGR. Feeding fish with dietary Arg supplementation ranging from 9 to 12 g/kg improved significantly (p < .05) whole body protein contents and decreased lipid deposition. The mRNA levels of TOR, eukaryotic translation initiation factor 4E (4EBP) and ribosomal protein S6 kinase 1 (S6K1) in muscle and liver were significantly affected by increasing dietary Arg levels. Meanwhile, the mRNA relative expression levels of TOR and S6K1 in the liver and muscle increased significantly as Arg supplementation increased. On the other hand, the mRNA relative expression levels of 4EBP was significantly higher in fish fed on the 9 g/kg Arg diet compared to those fed on the control and 15 g/kg Arg diets. In conclusion, our current results indicate that dietary Arg supplementation in plant‐rich diets, might activate the TOR signaling pathway, which promotes protein synthesis and reduces lipid accumulation of H. wyckioides, resulting in improved growth.Item Aspilia mossambicensis and Azadirachta indica medicinal leaf powders modulate physiological parameters of Nile tilapia (Oreochromis niloticus).(Taylor & Francis, 2018-05-03) Imani Benedict, Kapinga; Samwel Mchele Limbu; Nazael Amos, Madalla; Wahabu Hamisi, Kimaro; Rashid Adam, TamahtamahGrowing mixed-sex Nile tilapia, Oreochromis niloticus in earthen ponds to table size is a major challenge due to its early maturity and prolific breeding. This study determined the effects of two medicinal plants; Aspilia plant, Aspilia mossambicensis and Neem tree, Azadirachta indica on hatchlings production, growth performance, feed utilization, survival and haematology of O. niloticus. Experimental diets were prepared by adding 1.0, 2.0, 4.0 and 8.0 g of either A. mossambicensis or A. indica leaf powders into a kg of the control diet subsequently administered daily to twenty triplicates of O. niloticus for three months. Both A. mossambicensis and A. indica leaf powder at the used doses, reduced significantly hatchlings production of O. niloticus when compared to the control (P < .05). The lowest value of hatchlings count was found in A. indica dose 8.0 g kg−1 (P < .05). The use of A. mossambicensis leaf powder at a dose of 4.0 g kg−1 improved significantly growth performance and feed utilization (P < .05). In contrast, survival rate was not affected significantly by the two plants (P > .05). Both plants differentially increased significantly haematological parameters such as Hb concentration, packed cell volume (PCV), mean corpuscular haemoglobin (MCH), mean corpuscular haemoglobin concentration (MCHC), white blood cells (WBC), monocyte and lymphocytes while reduced significantly neutrophils and eosinophils (P < .05). In conclusion, A. mossambicensis and A. indica leaf powders control prolific breeding of O. niloticus, modulate its growth performance and feed utilization. The two plants also modulate haematological parameters of O. niloticus indicating immunological response towards stress or intoxication, however, the values obtained were not beyond the recommended range for healthy fish.Item Atorvastatin remodels lipid distribution between liver and adipose tissues through blocking lipoprotein efflux in fish(American Physiological Society, 2023-03-01) Rui-Xin Li; Ling-Yun Chen; Samwel Mchele Limbu; Bing Yao; Yi-Fan Qian; Wen-Hao Zhou; Li-Qiao Chen; Fang Qiao; Mei-Ling Zhang; Zhen-Yu Du; Yuan LuoThe regulation of cholesterol metabolism in fish is still unclear. Statins play important roles in promoting cholesterol metabolism development in mammals. However, studies on the role of statins in cholesterol metabolism in fish are currently limited. The present study evaluated the effects of statins on cholesterol metabolism in fish. Nile tilapia (Oreochromis niloticus) were fed on control diets supplemented with three atorvastatin levels (0, 12, and 24 mg/kg diet, ATV0, ATV12, and ATV24, respectively) for 4 wk. Intriguingly, the results showed that both atorvastatin treatments increased hepatic cholesterol and triglyceride contents mainly through inhibiting bile acid synthesis and efflux, and compensatorily enhancing cholesterol synthesis in fish liver (P < 0.05). Moreover, atorvastatin treatment significantly inhibited hepatic very-low-density lipoprotein (VLDL) assembly and thus decreased serum VLDL content (P < 0.05). However, fish treated with atorvastatin significantly reduced cholesterol and triglycerides contents in adipose tissue (P < 0.05). Further molecular analysis showed that atorvastatin treatment promoted cholesterol synthesis and lipogenesis pathways, but inhibited lipid catabolism and low-density lipoprotein (LDL) uptake in the adipose tissue of fish (P < 0.05). In general, atorvastatin induced the remodeling of lipid distribution between liver and adipose tissues through blocking VLDL efflux from the liver to adipose tissue of fish. Our results provide a novel regulatory pattern of cholesterol metabolism response caused by atorvastatin in fish, which is distinct from mammals: cholesterol inhibition by atorvastatin activates hepatic cholesterol synthesis and inhibits its efflux to maintain cholesterol homeostasis, consequently reduces cholesterol storage in fish adipose tissue.Item Behavioural Responses of the Mangrove Fiddler Crabs (Uca Annulipes and U. Inversa) To Urban Sewage Loadings: Results of a Mesocosm Approach(Elsevier, 2009) Bartolini, Fabrizio; Penha-Lopes, Gil P.; Samwel Mchele Limbu; Paula, José; Cannicci, StefanoThe study aimed at investigating the effects of sewage loadings on the behaviour of two fiddler crabs species maintained in a system of experimental mesocosms, built in a mangrove area in Tanzania and inundated with different seawater/sewage mixtures. Our results show that sewage loads led to a modification of the overall activity budget of the crab community as a result of increased hypertrophic conditions (high COD, increased chlorophyll-a concentrations). During their activity period, crabs inside contaminated mesocosms seemed to satisfy their feeding demand faster than those of the control cells, spending a significant longer time in other activities like courtship and territorial defence. Apart from being a good biological indication of ecosystem eutrophication, such a reduced foraging activity by fiddler crabs also depresses their sediment bioturbation activity, important factor for the health of mangrove systems, suggesting practical implications regarding the efficiency of mangrove-based wetlands for treatment of domestic sewage.Item Biodiversity Indicators: Plankton and Macroinvertebrates in Lake Victoria, Selected Satellite Lakes and Rivers. In: Mgaya, Y.D. and Mahongo, S.B. (Editors), Lake Victoria Fisheries Resources: Research and Management in Tanzania.(Springer, 2017-11-29) Mgaya, Y.D.; Samwel Mchele Limbu; Lugomela, C.V.; Kayanda, R. J.; Ngupula, G.W.Plankton and macroinvertebrates are used as biodiversity indicators on account of their sensitivity to changes in aquatic ecosystems. This chapter assesses the changes in the diversity, abundance and distribution of plankton and macroinvertebrates in the inshore and offshore areas of Lake Victoria, selected satellite lakes and rivers within the lake basin. Samples for both plankton and macroinvertebrates were collected during dry and wet seasons between 2000 and 2006. The results indicated that cyanobacteria were most diverse in both seasons. Microcystis spp., Planktolyngbya spp. and Anabaena spp. were the most dominant cyanophyte species at the sampled sites. The dominant phytoplankton (cyanobacteria) are less digestible and provide poor quality food for the fish; that may have contributed to the reduction or loss of planktivorous haplochromines and tilapiines that once flourished in Lake Victoria. Zooplankton community composition in the lake is dominated by rotifers and cyclopoid copepods, in both inshore and offshore areas. The dominance of cyclopoid copepods is important in the production and sustainability of small fishes and larvae that utilize these organisms as a food base. Macroinvertebrate abundance has shifted from an oligochaete and insect dominated community in 1984 to a community dominated by molluscs. The occurrence of a relatively high abundance of low-oxygen tolerant macroinvertebrate taxa at inshore and offshore stations is an indication of deteriorating water quality water quality conditions due to eutrophication and pollution processes. There is a need for a reduction in nutrient loads and pollutant inputs into the lake in order to ensure the ecosystem health.Item Black soldier fly (Hermetia illucens, L.) larvae improves growth performance, feed efficiency and economic returns of Nile tilapia (Oreochromis niloticus, L.) fry(Wiley, 2022-05-23) Samwel Mchele Limbu; Amon Paul Shoko; Eusebia Ernest Ulotu; Siwema Amran Luvanga; Fridah Mukiri Munyi; John Obedy John; Mary Adhiambo OpiyoInsects have been proposed as potential alternative animal protein sources to replace fishmeal (FM), which is expensive and has limited availability for fish feed formulation. However, studies on the effects of replacing FM with black soldier fly (Hermetia illucens) larvae (BSF-L) on growth performance of Nile tilapia (Oreochromis niloticus) fry, water quality and economic benefits are currently limited. This study determined the effects of replacing 100% FM, 75% FM, 50% FM, 25% FM and 0% FM with cheap BSF-L meal, hereafter referred to as BSF-L0, BSF-L25, BSF-L50, BSF-L75 and BSF-L100 diets, respectively for rearing all-male Nile tilapia fry produced by YY technology. The study further determined the optimum percentage of BSF-L meal for maximum growth of Nile tilapia fry. A total of 2400 visually healthy Nile tilapia fry weighing 0.001 g were randomly stocked into 20 plastic tanks (120 fry per tank, four replicates per treatment) and fed the BSF-L diets for 12 weeks. The BSF-L75 diet increased significantly specific growth rate, total weight gain, Zihler's index of fry and nitrate in the culture water but reduced feed conversion ratio of diet and total suspended solids in the culture water (p < 0.05). Feeding the Nile tilapia fry with BSF-L50 diet increased significantly hepatosomatic index (p < 0.05). The diets with BSF-L75 and BSF-L100 reduced significantly the incidence cost by 31.97% and 28.77% (p < 0.05), and increased profit index by 3.97 and 3.44%, respectively. The optimum percentage of BSF-L inclusion required for maximum growth performance of Nile tilapia fry was estimated as 81% to 84% based on polynomial analysis. Taken together, feeding Nile tilapia fry with diets containing 81% to 84% BSF-L meal improved growth performance. The BSF-L75 diet enhanced feed efficiency and had no deleterious effect on the liver and intestines. Meanwhile, it improved nitrate concentration for increased natural productivity. Incorporating 75% BSF-L meal in diets for Nile tilapia fry reduced 30% of feed cost leading to 4% higher economic returns.Item Chronic exposure to low environmental concentrations and legal aquaculture doses of antibiotics cause systemic adverse effects in Nile tilapia (Oreochromis niloticus) and provoke differential human health risk.(Elsevier, 2018-03-28) Samwel Mchele Limbu; Li, Zhou; Sheng-Xiang, Sun; Mei-Ling, ZhangBackground Antibiotics used globally to treat human and animal diseases exist ubiquitously in the environment at low doses because of misuse, overdose and poor absorption after ingestion, coupled with their high-water solubility and degradation resistance. However, the systemic chronic effects of exposure to low environmental concentrations of antibiotics (LECAs) and legal aquaculture doses of antibiotics (LADAs) in fish and their human health risk are currently unknown. Objective To investigate the in vivo chronic effects of exposure to LECAs and LADAs using oxytetracycline (OTC) and sulfamethoxazole (SMZ) in Nile tilapia (Oreochromis niloticus) and their human health risk. Methods Twenty O. niloticus weighing 27.73 ± 0.81 g were exposed to water containing LECAs (OTC at 420 ng/L and SMZ at 260 ng/L) and diets supplemented with LADAs (OTC 80 mg/kg/day and SMZ 100 mg/kg/day) for twelve weeks. General physiological functions, metabolic activities, intestinal and hepatic health were systemically evaluated. The possible human health risks of the consumption of the experimental Nile tilapia fillets in adults and children were assessed by using risk quotient. Results After exposure, we observed retarded growth performance accompanied by reduced nutrients digestibility, feed efficiency, organ indices, and lipid body composition in treated fish. Antibiotics distorted intestinal morphological features subsequently induced microbiota dysbiosis and suppressed intestinal tight junction proteins. Exposure of fish to LECAs and LADAs induced oxidative stress, suppressed innate immunity, stimulated inflammatory and detoxification responses, concomitantly inhibited antioxidant capacity and caused lipid peroxidation in intestine and liver organs. Both LECAs and LADAs enhanced gluconeogenesis, inhibited lipogenesis and fatty acid beta oxidation in intestine and liver organs. The exposure of fish to LECAs and LADAs induced anaerobic glycolytic pathway and affected intestinal fat catabolism in intestine while halted aerobic glycolysis, increased hepatic fat catabolism, and induced DNA damage in liver. The hazard risk quotient in children for fish treated with OTCD was >1 indicating human health risk. Conclusion Overall, both LECAs and LADAs impair general physiological functions, nutritional metabolism, and compromise fish immune system. Consumption of fish fed with legal OTC provokes health risk in children. Global stringent prohibition policy for use of antibiotics in aquaculture production and strategies to limit their release into the environment are urgently required to protect human health.Item Cloning, tissue distribution and mRNA expression analysis of typeIcollagen alpha 1 gene from Chu's croaker (Nibea coibor)(Elsevier, 2022-05-25) Hua Rong; Fan Lin; Lijun Ning; Kun Wu; Baojia Chen; Jia Zheng; Samwel Mchele Limbu; Xiaobo WenThe demand for collagen has been increasing over years due to its wide application in food, cosmetics and biomedicine industries. The synthesis of collagen protein in fish depends on instructions provided by collagen, type I, alpha 1 (COL1A1) gene. However, cloning, tissue distribution and mRNA expression of COL1A1 gene in a gel-producing Chu's croaker (Nibea coibor) is currently unknown. This study cloned the cDNA of COL1A1 gene (GenBank accession number: MK641512) from six N. coibor fish. The distribution and mRNA expression pattern of COL1A1 was analyzed in eight tissues of N. coibor. The COL1A1 cDNA had a full length of 6130 bp and contained a 4344 bp open reading frame (ORF) encoding a polypeptide of 1448 amino acids. The homology of N. coibor COL1A1 amino acid had 98% similarity with Larimichthys crocea, indicating conservatism with other members in same family (Sciaenidae). The deduced polypeptide contained the same signal peptides, C-propeptide and N-propeptide domains, and triple helix domains, which are the characteristics of type I collagen in vertebrates. The mRNA of COL1A1 gene was expressed significantly higher in the spine of N. coibor than in all other tissues (P < 0.05), followed by swim bladder, skin and scales. The swim bladder had higher collagen and hydroxyproline contents than other tissues, followed by spine >, scales > and > skin (P < 0.05). Our study successfully cloned the COL1A1 gene from N. coibor for the first time. The COL1A1 gene contained all the features of collagen pro-α1(I) chain proteins, and shared high homology with other marine teleost. COL1A1 gene in N. coibor is highly expressed in spine and swim bladder, consistent with collagen distribution. Our study contributes to better understanding on collagen biosynthesis in N. coibor tissues for various industrial uses.Item Comparative Performance of Mixed-Sex and Hormonal-Sex-Reversed Nile Tilapia Oreochromis Niloticus and Hybrids (Oreochromis Niloticus × Oreochromis Urolepis Hornorum) Cultured in Concrete Tanks(Springer Link, 2016) Mbiru, Moses; Samwel Mchele Limbu; Chenyambuga, Sebastian W.; Lamtane, Hieromin A.; Tamatamah, Rashid; Madalla, Nazael A.; Mwandya, Augustine W.Uncontrolled breeding and precocious maturity in Nile tilapia, Oreochromis niloticus can be avoided by using all-male population. This study compared the growth performance, survival rate, condition factor and final fish tank biomass (yield) of mixed-sex and hormonal-sex-reversed O. niloticus and hybrids (O. niloticus × O. urolepis hornorum) cultured in tanks. Sex-reversed males were produced by feeding newly hatched fry with a diet containing 60 mg of 17α-methyltestosterone for 28 days. Fourteen O. niloticus with initial mean weight (±standard error) of 0.50 ± 0.04, 0.48 ± 0.06 and 0.46 ± 0.01 g for mixed-sex, sex-reversed and hybrids, respectively, were separately stocked in triplicate tanks at a density of two fish m−2 and fed a 300 g kg−1 crude protein diet for 12 weeks. Results showed that hybrids had significantly higher final mean weight (31.41 ± 0.33 g) than hormonal-sex-reversed (25.82 ± 1.51 g) and mixed-sex O. niloticus (19.50 ± 1.26 g; p < 0.05). Similarly, sex-reversed O. niloticus had significantly higher final mean weight than mixed-sex (p < 0.05). The condition factor of hybrids (1.71 ± 0.05) was significantly higher than that of sex-reversed (1.46 ± 0.01; p = 0.001) and mixed-sex O. niloticus (1.43 ± 0.01; p = 0.001). Survival rate was not significantly different among treatments (p = 0.445). The final fish tank biomass was significantly higher in hybrids (535.24 ± 31.67 g tank−1) and hormonal-sex-reversed (486.52 ± 33.70 g tank−1) than mixed-sex O. niloticus (330.05 ± 17.08 g tank−1; p < 0.05). This study demonstrates that hybrids have superior growth performance and condition factor than sex-reversed and mixed-sex but have similar yields to hormonal-sex-reversed O. niloticus. These results suggest that O. niloticus farmers can improve growth rate and yield by rearing hybrids without affecting survival rate.Item A comparison of diurnal dynamics of water quality parameters in Nile tilapia (Oreochromis niloticus, Linnaeus, 1758) monoculture and polyculture with African sharp tooth catfish (Clarias gariepinus, Burchell, 1822) in earthen ponds.(Springer, 2014) Shoko, Amon P.; Samwel Mchele Limbu; Mrosso, Hillary D. J.; Mgaya, Yunus D.The overall performance of an aquaculture system is partly determined by its water quality parameters. Poor water quality stresses and adversely affects fish growth causing low production, profit and product quality. Diurnal dynamics of water quality parameters were investigated in Nile tilapia (Oreochromis niloticus) monoculture and polyculture with Clarias gariepinus in earthen ponds. Dissolved oxygen, temperature and pH were measured and monitored for 24 h. Water samples for nutrient analysis were collected from the middle of ponds in triplicate at about 30–35 cm below the water surface using a plastic bottle. Nitrite–nitrogen (NO2–N), nitrate–nitrogen (NO3–N), unionised ammonia (NH3–N), soluble reactive phosphorus and free carbon dioxide were analysed following standard methods and procedures. The results show that dissolved oxygen concentrations during the past midnight and pre-dawn hours were significantly lower than the levels in the morning and afternoon hours (ANOVA, F = 45.709, P < 0.05) which is dangerous to the life of the cultured fishes. The levels of unionised ammonia and temperature were higher and lower, respectively, than the acceptable levels for optimum growth of O. niloticus and C. gariepinus. Nitrite–nitrogen, nitrate–nitrogen, pH, soluble reactive phosphorus and free carbon dioxide were within the recommended limits for fish growth in aquaculture. Growth parameters, feed conversion ratio and survival rate were not significantly different between culture systems (P > 0.05). Fish yield was relatively higher in polyculture (45.74 ± 0.44 tons/ha) than monoculture (30.77 ± 0.54 tons/ha). During fish farming, optimum fish growth and hence economic benefits can be accrued by devoting some efforts on monitoring the fish pond water at regular intervals. This quality assurance process will ensure that fish farmers produce fish with maximum growth and yield without polluting pond water and the surrounding environment.Item The comparisons in protective mechanisms and efficiencies among dietary α-lipoic acid, β-glucan and L-carnitine on Nile tilapia infected by Aeromonas hydrophila(Elsevier, 2018-12-13) Lu, Dong-Liang; Samwel Mchele Limbu; Hong-Bo, Lv; Ma, Qiang; Chen, Li-Qiao; Zhang, Mei-Ling; Du, Zhen-YuDietary α-lipoic acid (LA), β-glucan (Gluc) and l-carnitine (L-Ca) are commonly used additives to promote fish growth and stress resistance in aquaculture production. However their mechanisms and efficiencies in helping fish to resist diseases have not been compared before. In this study, we fed Nile tilapia (Oreochromis niloticus) with diets containing appropriate doses of LA, Gluc and L-Ca for five weeks and further intraperitoneally injected the fish with Aeromonas hydrophila. After dietary treatment, none of the additives affected the fish growth, but dietary Gluc and L-Ca reduced protein and lipid body contents in fish, respectively. After A. hydrophila challenge, all fish treated with the three dietary additives showed higher survival rate, but those fed on dietary L-Ca had lower survival than those fed on LA and Gluc diets, indicating high protection efficiency of LA and Gluc. The protective mechanisms of the three feed additives were quite different under A. hydrophila infection. Dietary LA induced higher total antioxidant capacity and higher mRNA expression of anti-oxidative genes than other additives in liver and also activated partly the immune function in serum and spleen. Gluc largely increased the immune function by activating the immunity enzymes in serum, inducing inflammation in liver and increasing the expression of immune genes in spleen and head kidney. Gluc also increased partly the antioxidant capacity in serum and liver and lipid catabolism in liver. L-Ca largely increased lipid catabolism in liver while it increased partly the antioxidant capacities in serum and liver. Taken together, these results indicate that, dietary LA, Gluc and L-Ca have various protective mechanisms and differ in their efficiencies on resisting A. hydrophila infection in Nile tilapia.Item Concentration-dependent effects of 17 β-estradiol and bisphenol A on lipid metabolism, inflammation and antioxidant response in male zebrafish (Danio rerio). Chemosphere, 237: (2019) 124422.(Elsevier, 2019-12) Sheng-Xiang Sun; Yun-Ni Zhang; Dong-Liang Lu; Wei-Li Wang; Samwel Mchele Limbu; Dong-Liang Li; Li-Qiao Chen; Mei-Ling Zhang; Zhen-Yu DuEnvironmental estrogenic compounds are important pollutants, which are widely distributed in natural water bodies. They produce various adverse effects on fish, but their concentration-dependent toxicities in fish metabolism and health are not fully understood. This study investigated the effects of 17β-estradiol (E2) and bisphenol A (BPA) at low and high concentrations on lipid deposition, inflammation and antioxidant response in male zebrafish. We measured fish growth parameters, gonad development, lipid contents and the activities of inflammatory and antioxidant enzymes, as well as their mRNA expressions. All E2 and BPA concentrations used increased body weight, damaged gonad structure and induced feminization in male zebrafish. The exposure of zebrafish to E2 and BPA promoted lipid accumulation by increasing total fat, liver triglycerides and free fatty acid contents, and also upregulated lipogenic genes expression, although they decreased total cholesterol content. Notably, zebrafish exposed to low concentrations of E2 (200 ng/L) and BPA (100 μg/L) had higher lipid synthesis and deposition compared to high concentrations (2000 ng/L and 2000 μg/L, respectively). However, the high concentrations of E2 and BPA increased inflammation and antioxidant response. Furthermore, BPA caused greater damage to fish gonad development and more severe lipid peroxidation compared to E2. Overall, the results suggest that the toxic effects of E2 and BPA on zebrafish are concentration-dependent such that, the relative low concentrations used induced lipid deposition, whereas the high ones caused adverse effects on inflammation and antioxidant response.Item The Current Status of Antibiotic-Resistant Bacteria and Resistance Genes in African Aquaculture(Springer, 2023-02-28) Samwel Mchele LimbuAquaculture is currently the fastest-growing food production sector, supplying half of the fish consumed by humans globally. Nevertheless, aquaculture has been indicated as a medium for production and gateway for the transfer of antibiotic resistance bacteria (ARB) and their corresponding antibiotic resistance genes (ARGs). However, the precise sources, factors responsible, types and consequences of ARB and ARGs in African aquaculture are currently not well known. This chapter fills such as a knowledge gap by discussing the sources of ARB and ARGs in African aquaculture, the possible factors contributing to their increase, the types of ARB and ARGs found in the industry and the socioeconomic consequences to humans. The chapter found that, African aquaculture represents a hotspot reservoir of ARB and ARGs. However, the ARB and ARGs in African aquaculture are complex and not solely derived from the industry. They originate from multiple sources, including antibiotics application in aquaculture, livestock manure and integrated aquaculture systems, agriculture and human health. The ARB and ARGs also originate from wastewater treatment plants, hospitals and pharmaceutical industries. The African aquaculture sector is currently dominated by multiple ARB and their genes, resistant to antibiotics commonly used to treat human diseases. The ARB and ARGs in aquaculture are caused by overuse and misuse of antibiotics in the sector, lack of regulations, ineffective enforcement, loose rules and inadequate surveillance and monitoring systems, which increase the availability and accessibility of antibiotics. Moreover, incorrect prescription, easy affordability and prolonged use of the same antibiotics also contribute to the increased ARB and ARGs in the African aquaculture industry. The ARB and ARGs existing in aquaculture are transferred to humans via aquaculture product contamination during handling and consumption of raw or undercooked food, horizontal and vertical gene transfers and direct contact with water or drinking contaminated water. The consequences of ARB and ARGs from aquaculture include increased infections, frequency of treatment failures, severe infections, prolonged duration of illness and increased frequency of bloodstream infections and hospitalisation. These make primary healthcare redundant for previously curable diseases, thereby increasing costs to society on treating cultured species and humans, leading to animal and human deaths. The information generated in the chapter calls for a “One Health” approach to combat ARB and ARGs while formulating stringent measures, legislations and regulations for antibiotics use in aquaculture, agriculture and sick patients to safeguard human health.Item Dietary Aspilia mossambicensis and Azadirachta indica supplementation alters reproductive performance and induces gonadal histopathological effects in Nile tilapia (Oreochromis niloticus)(Wiley, 2018-12-07) Kapinga, Imani Benedict; Samwel Mchele Limbu; Madalla, Nazael Amos; Kimaro, Wahabu Hamisi; Mabiki, Faith Philemon; Lamtane, Hieromin Amon; Tamatamah, Rashid AdamThe use of medicinal plants to control reproduction in aquaculture have recently received considerable attention because they are biodegradable, safe, effective and locally available. However, information on their effects on gonadal characteristics and histological features in fish is currently limited. The present study evaluated the gonadal characteristics and histological changes of Nile tilapia, Oreochromis niloticus gonads fed on Aspilia plant, Aspilia mossambicensis and Neem tree, Azadirachta indica. Juvenile fish were fed diets supplemented with four doses (1.0, 2.0, 4.0 and 8.0 g/kg diet) of A. mossambicensis or A. indica leaf powders at 3% of their body weight daily for 90 days to examine absolute fecundity (AF), relative fecundity, gonadosomatic index (GSI) and histology of gonads. The antifertility phytocompounds in the two plants were quantified by using standard methods. Results indicated that, all doses of A. indica and A. mossambicensis used reduced significantly AF and GSI values (p < 0.05). Dose‐dependent histological alterations of gonads were noticed in both plants starting from doses of 2.0 g/kg in males and 4.0 g/kg in females. The highest percentages of total flavonoids (23.7%) and alkaloids (14.2%) were obtained from A. indica ethanol extract (p < 0.05). Taken together, dietary supplementation with A. mossambicensis and A. indica leaf powders alter gonadal characteristics of O. niloticus and histology triggered by alkaloids and flavonoids. Farmers interested in using the two plants to control prolific breeding should limit the dose inclusion to 2 g/kg to avoid severe effects on fish testis and ovaries.