The giant freshwater prawn Macrobrachium rosenbergii alters background colour preference after metamorphosis from larvae to postlarvae: In association with nature of phototaxis

The giant freshwater prawn Macrobrachium rosenbergii larvae have apposition eyes and are positively phototactic, whereas the postlarvae (PL) have superposition eyes and are negatively phototactic. M. rosenbergii has colour vision as early as larval stage. We discovered that M. rosenbergii alters background colour preference after metamorphosis from larvae to PL in association with nature of phototaxis. The test circular glass aquaria covered with a pair of two‐colour papers contained with a group of 100 larvae or 20 Pl, and the number of individuals in each colour background was recorded five times for each colour pair. The background colours tested were light blue, green, yellow, red, white and black. The numbers of larvae or PL in each colour background of different pairs were analysed by the Thurstone's law of comparative judgment. In the larvae, significant bias towards yellow was evident. In the PL, of the four pairings of black with other colours, all biased to black. The mean z‐scores were highest for yellow in the larvae, and for black in the PL. To determine the possible background brightness preference of the larvae and PL, six different colour backgrounds were presented in pairs. The larvae significantly preferred light blue over dark blue, white over yellow and white over black. The PL exhibited reversed preference. The relationship between z‐scores and light reflectance levels of five colour papers was significantly positive in the larvae and negative in the PL. The observed background colour preference was probably due to relative brightness rather than chromaticity difference.     

Effects of tank color on the growth,stress responses,and skin color of snakeskin gourami (<Emphasis Type="Italic">Trichogaster pectoralis</Emphasis>)

The effects of tank color on the growth, stress responses, and skin color of snakeskin gourami (Trichogaster pectoralis) were investigated in this study. Fish with initial body weights of 5.03±0.00 g were reared in five experimental tank colors (white, red, green, blue, and black) for 8 weeks. Each tank color was tested in triplicate with an initial stocking density of 15 fish per tank. Fish were fed with commercial sinking pellets at 4% of the average body weight per day. Growth performance, feed utilization efficiency, stress indicators (hematocrit, blood glucose, plasma cortisol levels), and skin color parameters were investigated. The fish reared in blue tanks had a significantly higher average final body weight (9.73?±?0.14 g) and significantly lower average feed conversion ratio (3.42?±?0.12) than the fish reared in black tanks (P?<?0.05). The fish reared in black tanks exhibited higher average hematocrit (36.63?±?1.11%), blood glucose (48.33?±?1.45 mg dL^?1), and plasma cortisol (9.00?±?0.56 μg dL^?1) levels than those reared in the other tank colors. However, the blood glucose levels in only the fish reared in black tanks were significantly higher than those in the fish reared in the other tank colors. The fish skin color ranged from very pale (high skin lightness) in the white tanks to very dark (low skin lightness) in the black tanks, and 80% of the variation in skin lightness were explained by the tank lightness. The use of a blue tank resulted in normal skin color; hence, blue tanks will not affect the customer acceptance of the fish. Our study revealed that blue is the most appropriate tank color for culturing snakeskin gourami.     

Limit of colour vision in dim light in larvae of the giant freshwater prawn <Emphasis Type="Italic">Macrobrachium rosenbergii</Emphasis>

Colour vision depends on sufficient ambient light and becomes ineffective at a particular low light intensity. It is not known how decapod crustaceans see colour in dim light. In the present study we investigated the colour vision threshold in larvae of the giant freshwater prawn Macrobrachium rosenbergii in a tank under natural illumination. Plastic beads of different colours (blue, red, yellow and white) in various combinations were suspended in the tank. The larvae swam straight toward the beads and gathered around them. The number of larvae was highest on the blue and white beads. The luminance in the tank was then gradually decreased by covering it with different numbers of layers of black cloth, and the response of the larvae to the beads was video-recorded under infrared illumination. The preference for blue and white beads remained manifest as the luminance was reduced from 418 to 0.07 cd/m², but not at 0.02 cd/m², indicating a colour vision threshold between 0.07 and 0.02 cd/m². The larvae have apposition compound eyes with large optical parameters, comparable to those of apposition eyes of nocturnal insects, which presumably capture more light and show enhanced sensitivity, enabling the larvae to see colour in dim light.     

Effects of tank colour and feed colour on growth and feed utilization of thinlip mullet (Liza ramada) larvae

The effects of aquarium background colour and feed colour on survival, growth rates and feed utilization efficiency of thinlip mullet (Liza ramada) larvae (0.035 g) were investigated in two experiments. In the aquarium background colour trial, 50 larvae were stocked in duplicates in 120 L glass aquaria filled with dechlorinated tap water. The outside walls and bottoms of each pair of the aquaria were covered with coloured paper sheets to achieve one of six colours (white, black, red, green, yellow and blue), while noncoloured aquaria served as a control. The fish were fed an experimental diet (35% crude protein) at a daily rate of 5% of their body weight (BW), twice a day for 8 weeks. The best growth rates, feed efficiency and survival were achieved in larvae reared in light‐coloured aquaria (white, noncoloured and yellow). Fish performance was significantly retarded in larvae reared in dark‐coloured aquaria (red, green, black and blue). Body composition was not significantly affected by aquarium colour. In a feed colour trial, duplicate groups of larvae (0.035 g) were stocked at 50 fish per 120 L aquarium and fed a test diet (35% crude protein) with six different colours [dark blue, red, yellow, light brown (control), light green and dark brown] at a daily rate of 5% BW, twice a day for 8 weeks. The best performance and survival were achieved in fish fed on dark‐coloured diets (red, dark blue and dark brown). Light‐coloured diets (yellow, light green and light brown) resulted in inferior performance. Body composition was not significantly affected by feed colour. These results suggest that light‐coloured tanks should be used for rearing thinlip mullet, L. ramada larvae, while dark‐coloured diets are more preferable to light‐coloured diets.     

Microbial community in a multi-trophic aquaculture system of <Emphasis Type="Italic">Apostichopus japonicus</Emphasis>, <Emphasis Type="Italic">Styela clava</Emphasis> and microalgae

An integrated multi-trophic aquaculture (IMTA) system consisting of the ascidian Styela clava and the sea cucumber Apostichopus japonicus with microalgae was grown in a seawater mesocosm. Microbial populations in the water, sediment and shelters were monitored over time. The composition of the water microbial community in the IMTA system did not differ significantly from that of the traditional culture system without ascidians. Bacterial populations in the water, sediment and shelters were low in the traditional A. japonicus aquaculture system, and lower in the IMTA system. The number of Vibrios in the water, sediment and shelters in the IMTA system was significantly lower than in the traditional culture (p < 0.05), while the quantity of Bacillus was higher in the sediment and shelters. All of these results indicate that the IMTA system effectively inhibited the growth of harmful bacteria, an important positive function in the health of the culture. The bacterial diversity index in the water in the IMTA system was between those of the baited and non-baited traditional aquacultures and was slightly reduced in the shelters. Over time, the bacterial diversity index in the sediment gradually dropped, especially in summer and autumn, when it was significantly lower than in the traditional culture. In winter, the diversity index increased to some extent, approaching that of the traditional culture.     

Combined diet of yeast,fermented soybean meal,and microparticulate as larval feed in extensive rearing systems for seed production of the oriental river prawn <Emphasis Type="Italic">Macrobrachium nipponense</Emphasis>

The present study aims to evaluate the effects of several types of larval feed on seed production of the oriental river prawn Macrobrachium nipponense and water quality in extensive rearing systems. Healthy M. nipponense were distributed into fifteen 15-m² pond outdoors, and each pond was stocked with 90 prawns including 41 egg-bearing (berried) female prawns, 37 not bearing female prawns, and 12 male prawns for larval production. The experimental design was completely randomized, with four diet groups (diet A: soybean homogenate, diet B: yeast, diet C: yeast?+?fermented soybean meal, and diet D: yeast?+?fermented soybean meal?+?microparticulate diet) and one no feeding control and three replications. There are equal levels of the total protein content in diets A–D. Higher larvae and postlarvae number was obtained for diet C and diet D. Furthermore, the increase of M. nipponense larvae and postlarvae in diets B–D can result in the decrease of zooplankton and increase of phytoplankton in the pond during some periods, simultaneously improving the water quality. The Spearman correlation coefficient (r_M,N) between the amounts of larvae and postlarvae of M. nipponense per pond and zooplankton per pond during the entire experiment period was ??0.56. The highest juvenile M. nipponense production was obtained in the diet D group (3140.00?±?461.63), which was slightly higher than that in the diet C group (2940.33?±?382.60). The juvenile M. nipponense production in diet B (2303.00?±?449.23) was also significantly higher compared to diet A (1106.33?±?176.64) and the control group (1039.67?±?212.85). There were no significant differences in the amounts of juvenile M. nipponense between the control and diet A groups, which indicated that the soybean homogenate could not increase the amount of M. nipponense juveniles. Our results clearly showed that diet D significantly raised per unit yield of prawn seed comparing with no feeding and other diet group in extensive rearing systems and that the cost of producing prawn seed with diet D is low, which provide an important foundation for the expansion of oriental river prawn culture.     

Growth enhancement and protective potential of feed-based outer membrane proteins against vibriosis in <Emphasis Type="Italic">Macrobrachium rosenbergii</Emphasis>

The use of antibiotics to curtail vibriosis, which is a major infectious disease, plaguing shrimp and prawn is rather becoming less effective and the need for a better alternative is expedient. The outer membrane proteins (OMPs) of V. alginolyticus were extracted, mixed with powdered commercial feed and fed to the prawns to evaluate its effect on growth performance and protective potential. Sixty prawns were divided into groups A, B and C of 10 prawns each, with two replicates in six (150 L) glass aquaria. Groups A, B and C were fed with OMPs mixed diet, with OMPs-Freund’s incomplete adjuvant mixed diet and OMPs or adjuvant free diet (control diet) respectively. All the prawns were weighed weekly, and haemolymph was collected to determine the total haemocyte count (THC) and phenoloxidase (PO) activity. At the end of the feeding trial, prawns were intramuscularly challenged with 50 μL of 10⁷ CFU V. alginolyticus. The treated groups were significantly higher in growth performance and THC than the control group, but no significant difference between the groups in terms of PO activity and mortality rate. The study, however, submitted that oral administration of OMPs with or without adjuvant is a good growth promoter and has the potential for protection against vibriosis in giant freshwater prawn (Macrobrachium rosenbergii).     

Effect of biofilm on water quality and growth of <Emphasis Type="Italic">Etroplus suratensis</Emphasis> (Bloch, 1790)

An experiment was conducted to compare the efficiency of biofilm production in natural and artificial substrates and to study their effect on water quality and growth of Etroplus suratensis. Four different substrates were used for biofilm formation: paddy straw (T1), sugarcane bagasse (T2), polyvinylchloride (PVC) pipe (T3) and plastic sheet (T4). The experiment was carried out in mud-bottomed fibre-reinforced plastic tanks (300 L) in triplicates. About 3000 cm² surface area (600 g) of each substrate was suspended in water supplemented with fertilizers. Only cow dung and urea were applied in control tanks. The tanks were stocked with 25 fishes with average weight of 9.1 ± 0.22 g. The overall mean value of heterotrophic bacteria in substrate was found higher in straw followed by bagasse, plastic and PVC. The dominant genera of bacteria in the substrate were Bacillus, Pseudomonas and Micrococcus in that order of preponderance. The mean phytoplankton and zooplankton density on the substrates were higher in bagasse followed by straw, plastic and PVC. The biofilm developed on the substrate significantly reduced the ammonia nitrogen and nitrite-nitrogen content of water. The growth of fishes was significantly (P < 0.05) higher in substrate-based treatments than that in the control with better results in bagasse followed by straw, plastic and PVC. The conclusions of the present study are that biofilm produced on natural substrates, especially on bagasse, enhanced growth of E. suratensis and reduced the necessity of water exchange during the culture, which certainly decreases the cost of Etroplus production.     

Effect of stocking density on growth performance,serum biochemical parameters,and muscle texture properties of genetically improved farm tilapia, <Emphasis Type="Italic">Oreochromis niloticus</Emphasis>

The objective of this study was to assess the effects of stocking density on growth performance, serum biochemical parameters, and muscle texture properties of genetically improved farmed tilapia (Oreochromis niloticus, GIFT). Juvenile GIFT with an average initial weight of 12.54?±?0.45 g (mean?±?SD) were randomly stocked in 16 tanks (80 L) in a recirculation aquaculture system at four densities of 10 (D1), 20 (D2), 30 (D3), and 40 (D4) fish per tank for 56 days, with quadruplicate for each density. There were no significant differences in water temperature among the four treatments (P?>?0.05). D4 had the significantly lowest dissolved oxygen content (5.52 vs 5.69–6.09 mg L^?1) (P?>?0.05) and pH (6.63 vs 6.87–7.20) (P?<?0.05). NO₂-N and NH₄-N concentrations significantly increased with increasing stocking density (P?<?0.05). Weight gain (WG) and specific growth rates (SGR) decreased with increasing stocking density. The lowest WG (617.20 vs 660.45–747.06%), SGR (3.52 vs 3.62–3.81% day^?1), and highest feed conversion ratio (1.68 vs 1.53–1.58) were observed in D4. Fish at D4 had significantly lower condition factor (3.11 vs 3.29–3.37%) and survival rate (91.25 vs 97.50%) than those from D1 and D2 (P?<?0.05). With increasing stocking density, serum total cholesterol, triglyceride, and total protein concentrations decreased (P <?0.05) and aspartate aminotransferase and alanine aminotransferase activities increased (P <?0.05). D4 fish had higher moisture content (78.80 vs 76.97%) and lower crude protein content (18.14 vs 19.39%) in muscle than D1 fish (P?<?0.05). Compared to D1 and D2, D3 and D4 had lower muscle hardness (1271.54–1294.07 vs 1465.12–1485.65 g), springiness (0.62–0.65 vs 0.70–0.72), gumminess (857.33–885.32 vs 1058.82–1079.28 g), and chewiness (533.04–577.09 vs 757.53–775.69 g) (P <?0.05). High stocking density resulted in growth inhibition, declines in flesh quality, and disturbance to several serum biochemical parameters.     

The effects of starvation and re-feeding on growth and swimming performance of juvenile black carp (<Emphasis Type="Italic">Mylopharyngodon piceus</Emphasis>)

We investigated the effects of starvation and re-feeding on growth and swimming performance and their relationship in juvenile black carp (Mylopharyngodon piceus). We measured the specific growth rate (SGR), resting metabolic rate (RMR) and constant acceleration test speed (U _CAT, the maximum swimming speed at exhaustion by constant acceleration test with 0.1667 cm s^?2 rate) in a treatment group (21 days of starvation then 21 days of re-feeding) and control group (routine feeding) (n = 20). Starvation resulted in a 17 % decrease in body mass of black carp (P < 0.05). After 21 days of re-feeding, body mass was greater than that of pre-starvation but still less than that of the control group at 42 days. During the re-feeding phase, the SGR of the treatment group was higher than that of the control group (P < 0.05). Starvation resulted in a significant decrease in the RMR and U _CAT. After 21 days of re-feeding, both the RMR and U _CAT recovered to the pre-starvation levels. In the control group, individual juvenile black carp displayed strong repeatability of the RMR and U _CAT across the measurement periods (P ≤ 0.002). In the treatment group, RMR showed significant repeatability between pre-starvation and re-feeding (P = 0.007), but not between pre-starvation and starvation or between starvation and re-feeding. U _CAT showed significant repeatability between pre-starvation and starvation (P = 0.006) and between pre-starvation and re-feeding (P = 0.001), but not between starvation and re-feeding. No correlation or only a weak correlation was found between any two variables of RMR, U _CAT and SGR, whereas the increment of the U _CAT (ΔU _CAT) was negatively correlated with that of SGR during the starvation phase (r = ?0.581, n = 20, P = 0.007) and re-feeding phase (r = ?0.568, n = 20, P = 0.009). This suggested that within individual black carp, there is a trade-off between growth and maintenance (or development) of swimming performance under food-limited conditions.     

Microalga <Emphasis Type="Italic">Isochrysis galbana</Emphasis> in feed for <Emphasis Type="Italic">Trachinotus ovatus</Emphasis>: effect on growth performance and fatty acid composition of fish fillet and liver

Seeking alternatives to the depleting fish oil are crucial for marine fish aquaculture, which is currently dependent on fish oil as the primary source of n-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFAs). Five isonitrogenous (46% crude protein) and isolipidic (16% crude lipid) feed diets (FO, ISO2.9, ISO4.8, ISO6.7, ISO8.6) were formulated by partially replacing fish oil with microalgae Isochrysis galbana. These diets were fed to triplicate tanks of Trachinotus ovatus (mean initial weight 1.92 g) for 80 days. This work demonstrates that a moderate inclusion (around 4.5–5.0 wt%, equivalent to the replacement of 24–26 wt% fish oil) of I. galbana biomass in fish diet improves fish growth performance, lipid deposition and enhances total n-3 fatty acids, DHA, and EPA contents in neutral and polar lipids (PLs) of fish muscle and liver of T. ovatus. The results disclosed in this study suggest that I. galbana microalgae represents a potential high-quality substitute for fish-based ingredients in aquaculture feeds, which can be a promising sustainable solution to resolve the depleting fish oil resource in a cost-effective manner.     

Long-term fluctuations in mollusk populations before and after the appearance of the alien predator <Emphasis Type="Italic">Euspira fortunei</Emphasis> on the Tona coast,Miyagi Prefecture,northern Japan

The impact of Euspira fortunei as an alien predator on fluctuations in population densities of prey mollusks between 2001 and 2010 on the Tona coast, northern Japan, was investigated. This species increased dramatically from 2002 to 2004. In contrast, prey species such as Ruditapes philippinarum and Macoma incongrua decreased rapidly from 2001 to 2004, whereas Pillucina pisidium and Batillaria cumingii did not show a significant decrease during this period. Using a laboratory experiment, we were able to show that these decreases in the population densities of some species of mollusks but not other species were the result of species-selective predation by E. fortunei, as the experiment revealed that E. fortunei preferred to attack R. philippinarum and M. incongrua rather than P. pisidium, although the predator did expand its diet to include P. pisidium after it had consumed 16 of the 20 preferred prey available (i.e., R. philippinarum and M. incongrua). This case study suggests that invasive naticid predators have the potential to affect the population density and community structure of prey mollusks in recipient coastal ecosystems through predation.     

Gene structure and expression analyses of multiple vitellogenesis-inhibiting hormones in the whiteleg shrimp <Emphasis Type="Italic">Litopenaeus vannamei</Emphasis>

In the whiteleg shrimp Litopenaeus vannamei, the existence of six sinus gland peptides (SGPs) possessing vitellogenesis-inhibiting hormone (VIH) function has been previously demonstrated. Genomic and cDNA sequence information for two of these is already known. Here, we cloned cDNAs for the remaining three, i.e., those encoding Liv-SGP-A, -B, and -F. The deduced amino acid sequences were comprised of a signal peptide, a CHH precursor-related peptide, a mature peptide, and a C-terminal amidation signal. The genomic DNA for Liv-SGP-A, -B, -C, -F, and -G, was found to be organized as three exons and two introns. The insertion of the two introns were conserved in all VIH genes, with intron I being inserted six residues following the signal peptide, and intron II after the 40th residue of the mature peptide. We also quantified the relative simultaneous expression of Liv-SGP-A, -B, -C, -F, and -G in relation to molting and unilateral eyestalk ablation. The expression levels of each gene in the eyestalks of adults did not change significantly during molting or following unilateral eyestalk ablation. However, unilateral eyestalk ablation significantly decreased expression levels at 10 and 20 days for Liv-SGP-A and -C, and at 20 days for Liv-SGP-G in the eyestalks of subadults. This study has therefore clarified the genomic structure of the five major subtype I VIHs in L. vannamei, and elucidated their expression levels in the eyestalks in relation to molting and unilateral eyestalk ablation.     

The effect of tank colouration on survival, metamorphosis rate, growth and time to metamorphosis freshwater prawn (Macrobrachium rosenbergii) rearing

Seedstock‐costs of the freshwater prawn Macrobrachium rosenbergii can represent >50% of the total production costs. The purpose of this study was to evaluate the effect of culture tank colouration on survival, metamorphosis rate, weight and time required to reach the postlarval (PL) stage. Newly hatched prawn larvae were stocked into eighteen 16‐L plastic culture tanks at a density of 30 L^?1. Tank colours evaluated were red, black, white, blue, green and yellow. Larval prawns were fed brine shrimp (Artemia franciscana) nauplii and a supplemental diet. Data indicated that larval tank colour had no significant impact (P>0.05) on the final PL size or days required to reach PL stage. However, total survival was significantly higher (P<0.05) in red and green tanks (84% and 78% respectively) than in white and blue tanks (56% and 44% respectively). Survival in the yellow and black tanks (71% in both) was not significantly different (P>0.05) from the red, green or white treatments, but was significantly higher (P<0.05) than the blue treatment. This could have a significant financial impact on commercial hatchery, and growout production, as most larval tanks currently in use are blue or black.     

Growth and fatty acid composition of <Emphasis Type="Italic">Octopus vulgaris</Emphasis> paralarvae fed with enriched <Emphasis Type="Italic">Artemia</Emphasis> or co-fed with an inert diet

The rearing of Octopus vulgaris paralarvae during its planktonic life stage is a major challenge, as mortality is currently very high and unpredictable. In this study, we examined the survival and growth rates, as well as the fatty acid composition, of O. vulgaris paralarvae fed on three different dietary treatments: group ArDHA was offered juvenile Artemia enriched with a lipid emulsion (Easy DHA-Selco^®); group ArMA was fed with juvenile Artemia enriched with a mixture of microalgae (Rhodomonas lens and Isochrysis galbana); and group ArMA+ID received the same Artemia as group ArMA complemented with an inert diet. Dietary treatments were tested in triplicate with homogenous groups of paralarvae (25 individuals l^?1) established in 50-l tanks, and the experiment was conducted for 15 days. The survival rate of 15-day post-hatch (-dph) paralarvae from groups ArMA (20 ± 8%) and ArMA+ID (17 ± 4%) tended to be higher than in group ArDHA (13 ± 5%), though these differences were not statistically different. The dry weight (DW) of 15-dph paralarvae increased by almost 60% in groups ArMA and ArMA+ID, and nearly 40% in group ArDHA, with respect to hatchlings. The fatty acid (FA) composition of paralarvae revealed a remarkable drop of docosahexaenoic acid (22:6n-3, DHA) from hatchlings to 15-dph paralarvae of all groups (P < 0.05). However, paralarvae from group ArDHA contained higher levels of DHA than those from ArMA and ArMA+ID (P < 0.05). Despite Artemia enriched with DHA-Selco^® contained three-times more DHA than Artemia enriched with microalgae, no beneficial effects of this dietary treatment were observed on the performance of paralarvae.     

Influence of different microalgal diets on gonadal development of the carpet shell clam <Emphasis Type="Italic">Ruditapes decussatus</Emphasis> broodstock

Studies considering broodstock conditioning of Ruditapes decussatus mostly used flagellates and diatoms for feeding, mainly Isochrysis galbana and Chaetoceros calcitrans, respectively. The present study evaluated the effect of different microalgal diets on gonadic maturation of R. decussatus including three microalgae species (C. calcitrans, Tetraselmis suecica, and Nannochloropsis oculata) which were used to prepare six diets: three monospecific and three bispecific mixed diets at a proportion of 1:1. Clams were daily fed at a ratio of 1% dry weight of algae/live weight of clam and unfed treatment was used as control. Results showed that clams fed C. calcitrans alone or mixed with T. suecica attained earlier full maturity with the highest response to spawning induction (after 34 conditioning days) and largest proportion in the partial spawning phase for both, followed by T. suecica alone after 48 days. In contrast, N. oculata alone or mixed diets demonstrated poor performance for gonadal maturation. Unfed treatment did not show any sign of maturation. The results indicated that T. suecica has high conditioning potential like C. calcitrans and their mixture gave the highest benefit. Therefore, T. suecica can be recommended for R. decussatus broodstock conditioning.     

Characterization and expression of <Emphasis Type="Italic">lin-28a</Emphasis> involved in <Emphasis Type="Italic">lin28/let-7</Emphasis>signal pathway during early development of <Emphasis Type="Italic">P. olivaceus</Emphasis>

Heterochronic lin-28 is a conserved RNA-binding protein that plays a key role in the timing of developmental events in organisms. As a crucial heterochronic gene, the protein controls developmental events of the second of four larval stages in Caenorhabditi elegans. Heterochronic let-7 miRNAs are often present in various species and highly conserved in sequence and biological function and are required for various biological processes. Previous studies showed that ten let-7 miRNAs were identified in the Japanese flounder (Paralichthys olivaceus) and that they were primarily expressed during metamorphosis. In this study, we clone and characterize the lin-28a gene from P. olivaceus and exhibit its dynamic expression pattern at different developmental stages and various adult tissues. The results show that the P. olivaceus lin-28a gene has high sequence similarity with other species and is highly expressed in the embryonic stage but weakly expressed in the larval stage. In addition, lin-28a overexpression causes cell proliferation and significantly promotes the levels of pre-let-7a and pre-let-7d while markedly depressing let-7a and let-7d expression in FEC (Flounder Embryonic Cell), which indicate that lin-28 possibly blocks the maturation of let-7 miRNAs. Additionally, lin-28a is identified as a target gene of let-7 miRNAs, and let-7 miRNAs directly regulate lin-28a expression by targeting its 3′ UTR. Taken together, lin-28a along with let-7 miRNA participates in a lin-28/let-7 axis pathway that regulates cell division and timing of embryonic and metamorphic events in P. olivaceus.     

Dietary supplementation of curcumin augments heat stress tolerance through upregulation of <Emphasis Type="Italic">nrf-2</Emphasis>-mediated antioxidative enzymes and <Emphasis Type="Italic">hsps</Emphasis> in <Emphasis Type="Italic">Puntius sophore</Emphasis>

Heat stress is one of the major environmental concerns in global warming regime and rising temperature has resulted in mass mortalities of animals including fishes. Therefore, strategies for high temperature stress tolerance and ameliorating the effects of heat stress are being looked for. In an earlier study, we reported that Nrf-2 (nuclear factor E2-related factor 2) mediated upregulation of antioxidative enzymes and heat shock proteins (Hsps) provide survivability to fish under heat stress. In this study, we have evaluated the ameliorative potential of dietary curcumin, a potential Nrf-2 inducer in heat stressed cyprinid Puntius sophore. Fishes were fed with diet supplemented with 0.5, 1.0, and 1.5% curcumin at the rate 2% of body weight daily in three separate groups (n = 40 in each group) for 60 days. Fishes fed with basal diet (without curcumin) served as the control (n = 40). Critical thermal maxima (CTmax) was determined for all the groups (n = 10, in duplicates) after the feeding trial. Significant increase in the CTmax was observed in the group fed with 1.5% curcumin- supplemented fishes whereas it remained similar in groups fed with 0.5%, and 1% curcumin-supplemented diet, as compared to control. To understand the molecular mechanism of elevated thermotolerance in the 1.5% curcumin supplemented group, fishes were given a sub-lethal heat shock treatment (36 °C) for 6 h and expression analysis of nrf-2, keap-1, sod, catalase, gpx, and hsp27, hsp60, hsp70, hsp90, and hsp110 was carried out using RT-PCR. In the gill, expression of nrf-2, sod, catalase, gpx, and hsp60, hsp70, hsp90, and hsp110 was found to be elevated in the 1.5% curcumin-fed heat-shocked group compared to control and the basal diet-fed, heat-shocked fishes. Similarly, in the liver, upregulation in expression of nrf-2, sod, catalase, and hsp70 and hsp110 was observed in 1.5% curcumin supplemented and heat shocked group. Thus, this study showed that supplementation of curcumin augments tolerance to high temperature stress in P. sophore that could be attributed to nrf-2-induced upregulation of antioxidative enzymes sod, catalase, gpx, and the hsps.     

Effects of starvation and feeding on blood chemistry,fatty acid composition and expression of vitellogenin and fatty acid-binding protein genes in female swimming crab <Emphasis Type="Italic">Portunus trituberculatus</Emphasis> broodstock

Portunus trituberculatus broodstock were stocked in plastic tanks to evaluate the effects of starvation and feeding on gonadal development, blood chemistry, fatty acid composition, and expression of vitellogenin (Vtg) and fatty acid-binding protein genes (FABP) in females. Two treatments (starved and fed) were randomly assigned to triplicate groups of 90 swimming crab broodstock (approximately 230 ± 45 g). In the starved treatment, crabs were starved for 30 days, whereas in the fed treatment crabs were fed once a day with clams. The gonadosomatic index decreased significantly in starved crabs (P < 0.05), as did the serum glucose and cholesterol concentrations; conversely, the total protein concentration in serum significantly increased (P < 0.05). In the ovary, there was a significant relative decline of 18:0, 16:1n-7 and 20:1n-9 fatty acids and relative increases of 20:4n-6, 22:6n-3, 18:1n-9 and 20:5n-3 in starved crabs compared to fed crabs (P < 0.05). Relative expression of Vtg in the ovary decreased significantly in starved crabs (P < 0.05), while there was no significant difference in hepatopancreas Vtg expression between starved and fed crabs (P > 0.05). Starvation suppressed gonadal development in female swimming crab broodstock.