Desaturase Delta-6 mRNA Expressions In Highly Unsaturated Fatty Acids Biosynthesis Pathway During Follicle Maturation In Female Zebrafish (Danio rerio)

Sangat sedikit yang diketahui tentang sintesis asid lemak tidak tepu seperti asid eikosapentanoik (EPA, C20:5n-3), asid dokosaheksaenoik acid (DHA, C22:6n- 3) dan asid arakidonik (ARA, C20:4n-6), atau secara berkumpulan lebih dikenali sebagai asid lemak sangat tidak tepu (HUF A), di dalam ovari ikan walaupun ia memainkan peranan yang sangat penting dalam pembiakan vertebrata ini. Ikan zebrafish (Dania rerio) mempamerkan keupayaan untuk mensintesis ketiga-tiga HUF A ini melalui kitaran yang melibatkan desaturasi dan elongasi dua prekursor iaitu asid linoleik (LA, Cl8:2n-6) dan asid linolenik (LNA, Cl8:3n-3). Bagi lebih memahami kepentingan serta pengawalaturan sintesis HUF A dalam ovari, kaj ian ini menunjukkan corak ekspresi mRNA untuk desaturase (jadsd6), iaitu satu enzim perlu yang terlibat dalam kitaran biosintesis HUF A dalam lima peringkat folikel ovari zebrafish yang berbeza iaitu pre-vitelogenik, vitelogenik awal, vitelogenik akhir, kematangan dan ovulasi. Aras mRNA bagi fadsd6 dalam peringkat-peringkat folikel ovari yang berbeza ini ditentukan oleh kaedah esei RT-PCR. Very little is known about the synthesis of unsaturated fatty acids such as eicosapentaenoic acid (EPA, C20:5n-3), docosahexaenoic acid (DHA, C22:6n-3) and arachidonic acid (ARA, C20:4n-6), or collectively known as the highly unsaturated fatty acids (HUF A), in the fish ovary although they play pivotal roles in this vertebrate reproduction. The zebrafish (Dania rerio) display capability to synthesize all three HUF A via pathways involving desaturation and elongation of two precursors, the linoleic acid (LA, C18:2n-6) and linolenic acid (LNA, Cl8:3n-3). In order to gain understanding on the importance and regulation of ovarian HUF A synthesis, this study shows the mRNA expression pattern of desaturase (jadsd6), an essential enzyme involved in HUF A biosynthesis pathway, in five different zebrafish ovarian follicle stages; pre-vitellogenic, early vitellogenic, late vitellogenic, maturation and ovulation stages. The mRNA levels of fadsd6 in different ovarian follicle stages were determined by semi-quantitative RT-PCR assays

Zebrafish (Danio rerio) ecotoxicological ABCB4, ABCC1 and ABCG2a gene promoters depict spatiotemporal xenobiotic multidrug resistance properties against environmental pollutants

Marine organisms are naturally equipped with multixenobiotic resistance mechanisms that are often governed by ATP-binding cassette (ABC) transporter family members. Previous studies focused on the target genes of ABC but little is known about the functionality of their promoter regions. Due to the importance of promoters in ABC transporter gene regulation, we functionally characterized three major xenobiotic transporter promoters of zebrafish, namely ABCB4, ABCC1 and ABCG2a via in silico transcription factor binding analysis and in vivo spatiotemporal expression analysis. The former revealed the major functional contributors (such as AP-1, C/EBP beta, HNF-1 and NF-1 TFBSs) towards promoter activity enhancement across four different tissues (liver, muscle, cell cycle and immune cells) where majority of them discovered were liver-specific whereas the latter unearthed the localization of these promoters at liver and intestinal tracts during late embryogenesis (48, 72 and 96 hpf). This study contributes towards future xenobiotic transporter ecotoxicology studies in zebrafi

Effects of different temperature profiles and corn-sago starch ratios on physical properties of extruded tilapia diets

Sago starch is a locally grown and produced starch resource in Malaysia. In this study, corn starch to sago starch ratios (CS:SS) of 0:20, 5:15, 10:10, 15:5 and 20:0 were included in feed mixture to contain 20% starch and produce five isonitrogenous and isocaloric (30% crude protein and 16.7 kJ/g, respectively) tilapia Oreochromis sp. diets. Diets were preconditioned to contain 40% moisture and extruded using a single-screw extruder at screw speed of 120 rpm using three different temperature profiles (I 60-100-140-180˚C; II 60-100-120-160˚C; and III 60-120-120-180˚C). Effects of these factors were evaluated on physical properties of extrudates including expansion ratio, bulk density, water stability, floatability, sinking velocity and durability. From the results, different temperature profiles and CS:SS had significant effects (p<0.05) on expansion ratio and floatability. Sago starch performed as a good binder as it gave higher percentage of water stability and pellet durability. The mixture with 10:10 of corn to sago starch extruded using temperature profile II (60-100-120-160˚C) produced the best extrudates with desirable physical properties

Effects of varying dietary carbohydrate levels on growth performance, body composition and liver histology of Malaysian mahseer fingerlings (Tor tambroides)

We investigated the effects of four iso-nitrogenous (40% crude protein) and iso-caloric (17.6 kJ g(-1)) diets with different dietary carbohydrate levels (15%, 20%, 25% and 30%) on the growth performance, feed utilization efficiency, body composition and liver histology of Malaysian mahseer (Tor tambroides) fingerlings in a 10-week feeding trial. Fish (initial weight of 0.8?0.1 g; initial total length 4.2?0.1 cm) were fed twice daily at 4% body mass. Dietary carbohydrate level had significant effects (P<0.05) on weight gain, SGR (specific growth rate), FCR (feed conversion rate), PER (protein efficiency rate), survival percentage and all nutrient retention values (PRV, LRV, CRV, ERV). Protein, carbohydrate and gross energy composition of the fish body were also significantly differed (P<0.05) among treatments. Liver histology showed mild hepatic steatosis and hypertrophy for fishes receiving a higher dietary carbohydrate inclusion. In general, treatments with 20% and 25% dietary carbohydrate levels produced better growth results compared to the rest of the treatments. Using a second-order polynomial regression analysis model, the optimal dietary carbohydrate level of 23.4% was estimated for mahseer fingerlings

A Review on the Emerging Asian Aquaculture Fish, the MalaysianMahseer (Tor tambroides): Current Status and the Way Forward

The Malaysian mahseer (Tor tambroides)is a sport, ornamental and food all-in-one treasured aquaculture fish member of the Cyprinidae family. However, this freshwater riverine species is currently under the threats of habitat degradation and overfishing, apart from its poorly documented taxonomy. Despite its socio-economic significance, taxonomy confusion and conservation inadequacy, the knowledge gaps in some fields like the genomic landscape and biology are yet to be filled. In this comprehensive review, we presented an overview of all the past and current T. tambroides related research fields, namely morphology, population genetics, growth environment, reproduction, diet and nutrition, metagenome, mitogenome as well as conservation. Furthermore, we have included some future perspectives and recommendations for the advancement of the respective fields. It is anticipated that this review would be of great benefit to those planning to consolidate resources and work in tandem to pace the conservation and fish farming industry improvement endeavours

Dietary carbohydrate utilization by the Malaysian Mahseer, Tor tambroides (Bleeker, 1854)

This study was carried out to investigate the utilization of dietary carbohydrate by the Malaysian mahseer, Tor tambroides (Bleeker, 1854). Wild mahseer fingerlings were obtained from fish suppliers in Pahang and Kelantan. Different batches of fish were used in different feeding trials and they were acclimatized for three weeks before the start of these trials. The effects of different experimental diets on the growth performance, feed utilization efficiency, body nutrient composition, nutrient retention, liver and intestine morphology, and glucose-6-phosphate dehydrogenase (G6PD) gene expression were measured. This study also attempted to evaluate the physical properties of extruded diets using selected starch sources for suitability in mahseer feeding. In the first feeding trial, fish were fed four experimental diets containing four carbohydrate levels (15%, 20%, 25% and 30%) using food grade corn starch as the carbohydrate source for 10 weeks. The best growth performance was observed in fish fed 20-25% dietary carbohydrate. Using a second-order polynomial regression analysis on the fish growth, the optimal dietary carbohydrate requirement of Malaysian mahseer was determined at 23.44%. Subsequent feeding trials were then based on this optimum level. In the second study, three locally grown starch sources, sago (Metroxylon sagu), cassava (Manihot esculenta) and taro (Colocasia esculenta) were tested as replacement for imported corn starch in the production of extruded feed for mahseer. Results showed that sago starch gave good expansion ratio and floatability and thus suitable for the production of floating mahseer feed. These feeds were then fed to mahseer juveniles for 10 weeks to evaluate the suitability of these starches as dietary carbohydrate and energy source for the Malaysian mahseer. Results showed that fish fed with corn starch and taro starch performed significantly better (P<0.05) than those fed sago and cassava starch. However, fish fed corn starch had the highest body lipid, lipid retention, and intraperitoneal fat indicating high conversion of carbohydrate to lipid compared to taro starch. Therefore, taro starch seemed to be the best candidate as a full or partial replacement of corn starch for the production of extruded feed for this species. The third feeding trial was conducted for 12 weeks to determine the effects of three forms of carbohydrates (starch, disaccharide sucrose and monosaccharide glucose) on the growth performance, feed utilization efficiency, body composition, nutrient retention, and liver and intestine morphology of mahseer. Best performance was observed in fish fed starch which suggested that mahseer benefited from higher complexity of carbohydrates compared to simple carbohydrates. The final feeding trial was conducted for 10 weeks to evaluate the effect of dietary carbohydrate level and form on the regulation of G6PD gene in mahseer. Fish were fed experimental diets prepared from the first and third feeding trials. Using real time PCR assays, the mRNA expression of G6PD gene in fish liver was estimated. Results showed that G6PD gene expression was significantly elevated (P<0.05) in the liver of fish fed 20% carbohydrate and maximum G6PD expression was achieved at 22.2% carbohydrate level which was very close to the optimal dietary carbohydrate requirement obtained in the first experiment. Among fish fed different carbohydrate forms, the highest G6PD gene expression (P<0.05) was observed in fish fed glucose. Dietary carbohydrate level and form influenced blood glucose level in mahseer which directly regulated the mRNA expression of G6PD gene during carbohydrate metabolism. A 20-25% dietary carbohydrate inclusion was recommended for the Malaysian mahseer. A higher or lower inclusion would affect the fish growth. This fish preferred dietary starch with corn and taro starches giving a good growth. High G6PD gene expression indicated increased carbohydrate metabolism and blood glucose level were due to the increasing dietary carbohydrate level. In conclusion, this present study strongly indicated that the Malaysian mahseer has a moderate ability in utilizing dietary carbohydrate inclusion level with a preference for soluble polysaccharides and a limited ability in utilizing starch sources

Different starch sources affect physical characteristics of extruded feeds prepared for the Malaysian mahseer, Tor tambroides

Starches from three local crops (sago, Metroxylon sagu; cassava, Manihot esculenta; and taro, Colocasia esculenta) were tested as replacements for corn starch in the production of extruded feed for the Malaysian mahseer, Tor tambroides . Four test feeds were formulated to contain 40.00% protein and 23.44% starch, and extruded using a single-screw extruder (120 rpm speed, 2 mm diameter die head). Temperatures at the feeding, mixing, compressing, and die zones were set at 60°C, 100°C, 120°C, and 160°C, respectively. Physical properties used to evaluate the quality of the extrudates were expansion ratio, bulk density, true density, pellet durability index, water stability, floatability index, sinking velocity, and sample microstructure. Results showed that test starches produced extrudates with fairly equal quality to corn starch extrudates for expansion ratio, pellet durability index, pellet durability index, and floatability index. Cassava starch extrudates had the best external appearance observed under electron microscopy. This study shows the potential that these three starches have in aquafeed production especially in producing quality Malaysian mahseer feed

Assessing impact of stingray gill net fishery to bycatch population around Bidong Island, Malaysia

This study assessed the bycatch composition around Bidong Island, Malaysia, and factors affecting its assemblages. Bycatch samples were collected monthly from January to December 2018 with supplementary samplings in February and October 2019. A total of 648 individuals of bycatch from 15 fish species were collected, which accounted for 84.2% of the total catch. The most dominant species were Alectis indica, Rachycentron canadum and Epinephelus areolatus. The abundance of bycatch varied significantly between seasons (P0.05). The most abundant bycatch was found at a depth of 20 m in moderate rainy and rainy seasons. The non-metric multidimensional scaling ordination clearly separated the three major groups of the community structure of bycatch based on depth, but not season. It is therefore concluded that season affected bycatch abundance, and conversely, depth influenced the community structure of the bycatch from stingray gillnet