Combined influence of water temperature, salinity and body size on energy budget in the sea cucumber Apostichopus japonicus Selenka

The worldwide demand for sea cucumber is outpacing the sustainable harvest capabilities of fisheries. Sea cucumber ranches and farms are striving to supplement wild harvest, but variable temperature and salinity conditions in pond culture systems make sea cucumber production challenging. In this study, we evaluated how water temperature, salinity and body size affected the energy budget of pond-cultured sea cucumber Apostichopus japonicus Selenka. An orthogonal design was used to identify the most suitable conditions for energy consumption and scope for growth (SFG). After the 42-day experimental period, we found that water temperature, salinity and body size significantly influenced energy consumption, while salinity and body size were the main influencing factors on SFG. Based on these results, we suggest that a water temperature of 16 °C and a salinity of 30 g L^?1 are optimal conditions for stocking sea cucumber A. japonicus with a body size of 37.34 ± 4.63 g. As such, the optimum stocking seasons for sea cucumber A. japonicus may be April in the spring and October in the autumn.     

Growth performance,oxidative stress,and non-specific immune responses in juvenile sablefish, <Emphasis Type="Italic">Anoplopoma fimbria</Emphasis>, by changes of water temperature and salinity

Juvenile sablefish, Anoplopoma fimbria (mean length 15.5 ± 1.9 cm, mean weight 68.5 ± 4.8 g), were used to evaluate the effects on growth, oxidative stress, and non-specific immune responses by changes of water temperature (8, 10, 12, 14, 16, 18, and 20 °C) and salinity (100 (35.0), 90 (31.5), 80 (28.0), 70 (24.5), 60 (21.0), 50 (17.5), and 40% (14.0) (‰)) for 4 months. The growth performance was significantly increased at the temperature of 12 and 14 °C, and the feed efficiency was notably decreased at the temperature of 18 °C. The growth performance and feed efficiency were also significantly decreased at low salinity. The antioxidant responses such as superoxide dismutase and catalase were significantly increased by the high temperature and decreased by the low salinity. The immune responses such as lysozyme and phagocytosis were elevated by the temperature of 18 °C and decreased by the salinity of 50%. The results of this study indicate that the growth performance of juvenile sablefish, A. fimbria, is influenced by the temperature and salinity, and the excessive temperature and salinity levels can affect the antioxidant and immune responses.     

Effects of rearing temperature on growth,metabolism and thermal tolerance of juvenile sea cucumber,Apostichopus japonicus Selenka: critical thermal maximum (CTmax) and hsps gene expression

Effects of different rearing temperatures (16, 21 and 26°C) on growth, metabolic performance and thermal tolerance of juvenile sea cucumber Apostichopus japonicus (initial body weight 7.72 ± 0.96 g, mean ±SD) were investigated in this study. During the 40‐day experiment, growth, metabolic performance, food intake and energy budget at different reared temperatures were determined. Sea cucumbers rearing at 16°C obtained better growth (final body weight 11.96 ± 0.35 g) than those reared at 21 (10.33 ± 0.41 g) and 26°C (8.31 ± 0.19 g) (P < 0.05), and more energy was allocated for growth at 16°C (162.73 ±11.85 J g^?1 d^?1) than those at 21(79.61 ± 6.76 J g^?1 d^?1) and 26°C (27.07 ± 4.30 J g^?1 d^?1) (P < 0.05). Critical thermal maxima (CTmax) values of juvenile sea cucumbers reared at 16, 21 and 26°C were 33.1, 34.1 and 36.6°C, respectively, and the upregulation of hsps in sea cucumbers reared at 26°C was higher than those acclimated at lower temperatures (16 and 21°C), indicating that temperature acclimation could change the thermal tolerance of the sea cucumber, and CTmax and hsps were sensitive indicators of the sea cucumber's thermal tolerance.     

Optimization of culture conditions for larval GIFT tilapia Oreochromis niloticus using response surface methodology and effects of HAMP-1 and c-type lysozyme mRNA expression in liver

Response surface methodology (RSM) in concert with central composite experimental design was firstly applied to optimize the culture condition for larval Genetically Improved Farmed Tilapia (GIFT) tilapia. Larvae were reared at different water temperature (16–37 °C) and salinity (0–20 ‰) for 35 days. Results showed that the linear and quadratic effects of temperature and salinity on specific growth rate (SGR), survival and hepatic HAMP-1 mRNA levels were statistically significant (P < 0.05). The interacting effects of temperature and salinity on SGR and survival were significant (P < 0.05), but the interaction on the levels of hepatic HAMP-1 and c-type lysozyme mRNA was not significant (P > 0.05). A significant increase in the levels of c-type lysozyme mRNA was observed as salinity increases; the quadratic effects of salinity were insignificant (P > 0.05). The regression equations of SGR, survival, the levels of hepatic HAMP-1 and c-type lysozyme mRNA toward the two factors of interest were established using multiple regression analysis, with the coefficients of determination being 0.980, 0.982, 0.968, and 0.949, respectively (P < 0.01). Based on RSM, the optimal temperature/salinity combination was obtained at 28.2 °C/6.8 ‰ of which the greatest SGR (10.08 % day^?1) and survival (91.34 %) were simultaneously attained. Adequately increasing salinity would improve growth, survival, and innate immune function in larval GIFT tilapia.     

Osmoregulation and differential penetration of two grey mullets, Chelon labrosus (Risso) and Liza ramada (Risso) in estuarine fish ponds

Grey mullet ponds situated in Arcachon Bay on the western Atlantic coast of France, display contrasting mixohaline habitats.The pattern of osmoregulation of Chelon labrosus and Liza ramada exhibiting differential penetration of fish ponds has been investigated. Key variables of salinity and temperature have been considered. The tolerances to low salinities and to fresh water have been determined. The dynamics of variation in plasma osmotic pressure and major plasma electrolytes (Na⁺, Cl^?, K⁺) were studied in terms of: (1) gradual adaptation to a decreasing salinity gradient; (2) effects of a long-term adaptation in fresh water; (3) effects of low temperatures on sea water adapted fish.Both species can adapt to a wide range of salinities; however, while L. ramada show a good hypoosmotic regulation, with no alteration in plasma concentration over a wide range of salinity and after a long stay (5 months) in fresh water, C. labrosus cannot live for long periods of time in a wholly fresh water habitat. Both field samples obtained from thick-lipped grey mullets forced to stay in a freshwater pond and experimentally adapted fish showed, after 3 months, an unequivoqual decrease in plasma sodium and chloride, and plasma osmolality decreased to the same extent; this pattern of no compensation is bound, sooner or later, to end in death. The inability of C. labrosus to develop a long-term hypoosmoregulation in fresh water is referred to salinity preferences which probably limit the upstream penetration of this species.Plasma osmolality and major electrolytes (sodium and chloride) increased in cold (4 °C) sea water. This response might be due to a reduced ability of grey mullets to osmoregulate in cold waters. In the poly-mesohaline ponds, Winter drop in temperature (4–6 °C) causes grey mullets to migrate to the meso-oligohaline ponds where the mean temperature is more elevated (8 °C) and temperature changes less rapid (6–9 °C).     

Release size and stocking density for grow-out of <Emphasis Type="Italic">Apostichopus japonicus</Emphasis> in the sea with raft-cultured macroalgae

Sea cucumber, Apostichopus japonicus, is the main cultured species in China. The main culture style for this species is the sea ranching model. Field trials were conducted in bottom-cages to preliminary reveal optimal releasing size, as well as maximum density of A. japonicus in an integrated multi-trophic aquaculture sea ranching area. Different sizes (4–30 g ind^?1) and densities (336–1342 g m^?2) of sea cucumbers were cultured for 13 months in Rongcheng Bay, Shandong Province, China. The size experiment showed that sea cucumber of all sizes grew throughout the experimental period. Sea cucumbers <15 g had high mortality in summer and low SGR in winter, while larger individual (>20 g ind^?1) had no advantage of growth. Sea cucumber sizes of 15–20 g may be suitable for release, considering their higher survival rate and SGR. The density experiment showed that the high biomass group had a low SGR and that the maximum release biomass was 793 g m^?2 based on a regression analysis. The optimal practical release season for sea cucumber was spring based on the results of two field experiments.     

Salinity and temperature tolerance of brown-marbled grouper Epinephelus fuscoguttatus

Grouper have to face varied environmental stressors as a result of drastic changes to water conditions during the storm season. We aimed to test the response of brown-marbled grouper to drastic and gradual changes in temperature and salinity to understand the grouper’s basic stress response. The results can improve the culture of grouper. Brown-marbled grouper, Epinephelus fuscoguttatus (6.2 ± 0.8 g) were examined for temperature and salinity tolerances at nine different environmental regimes (10, 20, and 33 ‰ combined with 20, 26 and 32 °C), in which the fish were subjected to both gradual and sudden changes in temperature and salinity. The critical thermal maximum (50 % CT_MAX) and the upper incipient lethal temperature (UILT) were in the ranges of 35.9–38.3 and 32.7–36.5 °C, respectively. The critical thermal minimum (50 % CT_MIN) and the lower incipient lethal temperature (LILT) were in the ranges of 9.8–12.2 and 14.9–22.3 °C, respectively. The critical salinity maximum (50 % CS_MAX) and the upper incipient lethal salinity (UILS) were in the ranges of 67.0–75.5 and 54.2–64.8 ‰, respectively. Fish at temperature of 20 °C and a salinity of 33 ‰ tolerated temperatures as low as 10 °C when the temperature was gradually decreased. Fish acclimated at salinities of 10–33 ‰ and a temperature of 32 °C tolerated salinities of as high as 75–79 ‰. All fish survived from accumulating salinity after acute transfer to 20, 10, 5, and 3 ‰. But all fish died while transferred to 0 ‰. Relationships among the UILT, LILT, 50 % CT_MAX, 50 % CT_MIN, UILS, 50 % CS_MAX, salinity, and temperature were examined. The grouper’s temperature and salinity tolerance elevated by increasing acclimation temperature and salinity. On the contrary, the grouper’s temperature and salinity tolerance degraded by decreasing acclimation temperature and salinity. The tolerance of temperature and salinity on grouper in gradual changes were higher than in drastic changes.     

Effect of dietary carbohydrate levels on growth performance,non‐specific immune enzymes and acute response to low salinity and high temperature of juvenile sea cucumber Apostichopus japonicus

This study was performed to determine the optimum dietary carbohydrate (CHO) levels of sea cucumber, based on the parameters of growth, digestive enzymes, digestibility, non‐specific immune enzymes and acute low‐salinity (20 g/L) stress and high‐temperature (30°C) stress tolerance. Diets with eight different CHO (dextrin) levels (32.9, 107.6, 192.5, 257.2, 316.8, 428.0, 482.4 and 572.8 g/kg) were fed to sea cucumber juveniles (0.49 ± 0.01 g) for 60 days. Significant higher amylase activity was observed in sea cucumbers fed diet with CHO ranging between 32.9 and 192.5 g/kg than that of other treatments (p < .05). The sea cucumbers fed with 192.5 g/kg CHO showed significantly higher acid phosphatase activity than the treatments of 482.4 and 572.8 g/kg CHO (p < .05), and significantly higher alkaline phosphatase activity than other treatments (p < .05, except 257.2 g/kg). The treatments of 428.0–572.8 g/kg were found significantly lower values than other treatments in apparent digestibility coefficients for dry matter and crude protein (p < .05). The sea cucumbers fed with 192.5, 257.2 and 316.8 g/kg CHO showed better tolerance to high‐temperature (30°C) and low‐salinity (20 g/L) stress than other treatments. In brief, the optimal dietary CHO level for the growth of juvenile sea cucumber is 177.96 g/kg. However, excessive CHO will inhibit amylase enzyme activity and decrease digestibility, resulting in low growth of sea cucumber.     

Large‐scale mortality and limited expression of heat shock proteins of aestivating sea cucumbers Apostichopus japonicus after acute salinity decrease

This study deals with the mortality and related physiological responses of aestivating sea cucumber Apostichopus japonicus to acute salinity decrease. Aestivating and active sea cucumbers were exposed to a decrease in salinity (from 30 to 20 psu) at a rate of 2.5 psu every 6 h, and then maintained at 20 psu for 96 h. The mortality of aestivating sea cucumbers was ~30%, which was significantly higher than that of active sea cucumbers (~10%). This result indicated that sea cucumbers in aestivation were more susceptible to hypo‐salinity stress. To elucidate the underlying physiological mechanisms, the osmotic pressure in coelomic fluid and the levels of hsp70 and hsp90 mRNA in aestivating and active sea cucumbers were measured. No significant difference in osmoregulation was observed between the two groups. The osmotic pressure of coelomic fluid in both groups changed with decrease in ambient salinity. There were significant differences in the time course and magnitude of hsp70 and hsp90 expression between the two groups. After exposure to decreased salinity, aestivating sea cucumbers showed a delayed up‐regulation of hsp70 and hsp90 expression compared with animals in active state, and these levels decreased rapidly to control values. The expression of hsp70 and hsp90 in aestivating sea cucumbers were significantly lower than those in active sea cucumbers after salinity change. The differences in hsp70 and hsp90 expression between the states may partly explain the higher mortality of sea cucumbers in aestivation when exposed to low salinity.     

Phylogenetic analysis of bacterial communities in the shrimp and sea cucumber aquaculture environment in northern China by culturing and PCR–DGGE

In this study, we investigated the bacterial communities in the shrimp and sea cucumber culture environment, including shrimp ponds (SP), sea cucumber ponds (SCP), mixed-culture ponds (MCP) and the effluent channel (EC) in Qingdao, China. Bacteria cultivation showed that the counts of heterotrophic, nitrate-reducing and sulfate-reducing bacteria in the sediment of SP were higher than that in the sediment of SCP and MCP, varying between 8.7 × 10⁴ and 1.86 × 10⁶, 2.1 × 10⁴ and 1.1 × 10⁵, and 9.3 × 10¹ and 1.1 × 10⁴ CFU g^?1, respectively. In contrast, the counts of ammonium-oxidizing and nitrifying bacteria in the sediment of SP was lower than that in the sediment of SCP and MCP. Denaturing gradient gel electrophoresis (DGGE) of 16S rDNA gene and dendrogram analyses showed that bacterial diversity in the mixed-culture environment was higher than that in the monocultures. The similarity of bacterial community between EC and SCP or MCP was higher than that between EC and SP. These results indicated that sea cucumber culture played a significant role in influencing the environmental bacterial communities that were composed mainly of Flavobacteriaceae (64.3%), Bacteriodetes (21%) and delta proteobacteria (14.7%), including the genera of Croceimarina, Lutibacter, Psychroserpens and so on. The results explained the benefit of sea cucumber culture in shrimp ponds at the level of microbial ecology.