Growth response of Nile tilapia fry to salinity stress in the presence of an 'internal reference' fish

Growth of three strains of Oreochromis niloticus L. fry exposed to salinity stress in the presence of an internal reference fish were compared. The Central Luzon State University (CLSU) strain was obtained from the Freshwater Aquaculture Center, CLSU, Philippines. The ISRAEL strain was acquired from the Philippine government's Bureau of Fisheries and Aquatic Resources National Freshwater Fisheries Technology Center (BFAR‐NFFTC), Munoz, Nueva Ecija. The National Inland Fisheries Institute (NIFI) strain was obtained from the NIFI, Bangkok, Thailand. Eight to nine full‐sib families (replicates) per strain were split into two groups. One group was grown in freshwater for 2 weeks, acclimated to 32 ppt and reared for 2 weeks and finally grown in freshwater for another 2 weeks. Another group was contemporaneously grown in freshwater polyethylene tanks for 6 weeks. Each replicate family included a size‐matched internal reference population of red tilapia strain. Two‐way analysis of variance (anova ) revealed no significant strain differences (P=0.081; r²=0.106). However, analysis of covariance with the internal reference strain used as a covariate showed significant (P=0.049; r²=0.638) strain effects on specific growth (based on standard length measurements). The ISRAEL strain showed consistently better growth rate in both saline and freshwater environments than the NIFI and CLSU strains. We estimated the statistical power of the two‐way anova (?=√(k′?1)(factor MS?s²)/(k′s²); Zar 1984) to be ～0.30. There was a 70% probability of a Type II error and no true difference in the growth of the three strains was detected. The use of internal reference strain as a covariate improved the r² from 0.106 to 0.638 and increased the efficiency of the test in detecting a true difference. Other strain comparison studies in our laboratory at the Southeast Asian Fisheries Development Center Aquaculture Department showed that the ISRAEL strain shows better growth than the NIFI and CLSU strains in a crowding stress tolerance experiment, when fed only with rice bran and under restrictive feeding regimes.     

Spatial correlation patterns in coastal environmental variables and survival rates of salmon in the north-east Pacific Ocean

We examined spatial correlations for three coastal variables [upwelling index, sea surface temperature (SST), and sea surface salinity (SSS)] that might affect juvenile salmon ( Oncorhynchus spp.) during their early marine life. Observed correlation patterns in environmental variables were compared with those in survival rates of pink ( O. gorbuscha ), chum ( O. keta ), and sockeye ( O. nerka ) salmon stocks to help identify appropriate variables to include in models of salmon productivity. Both the upwelling index and coastal SST were characterized by strong positive correlations at short distances, which declined slowly with distance in the winter months, but much more rapidly in the summer. The SSS had much weaker and more variable correlations at all distances throughout the year. The distance at which stations were no longer correlated (spatial decorrelation scale) was largest for the upwelling index (> 1000 km), intermediate for SST (400–800 km in summer), and shortest for SSS (< 400 km). Survival rate indices of salmon showed moderate positive correlations among adjacent stocks that decreased to zero at larger distances. Spatial decorrelation scales ranged from approximately 500 km for sockeye salmon to approximately 1000 km for chum salmon. We conclude that variability in the coastal marine environment during summer, as well as variability in salmon survival rates, are dominated by regional scale variability of several hundred to 1000 km. The correlation scale for SST in the summer most closely matched the observed correlation scales for survival rates of salmon, suggesting that regional-scale variations in coastal SST can help explain the observed regional-scale covariation in survival rates among salmon stocks.     

可口革囊星虫对温度、盐度的耐受性试验

可口革囊星虫(Phascoloma esculenta)属星虫动物门、革囊星虫纲、革囊星虫目、革囊星虫科、革囊星虫属,是我国的特有种,主要分布于广东、广西、海南岛、福建、浙江沿海,有些地方的潮间带栖息密度较大[1-2]。可口革囊星虫肉味鲜美、营养丰富,加工成品“沙虫干”是著名的海产珍品之一,深受国内外消费者欢迎;做成“土蒜冻”制品具有滋阴降火、补肾益智、泻火的功效[3-4]。目前,有关可口革囊星虫的生物学基础资料较少[5-7],笔者探讨温度和盐度变化对可口革囊星虫的影响,从而为可口革囊星虫的人工养殖和人工育苗提供理论依据。1材料与方法1.1材…     

Effect of salinity change on free amino acid content in Pacific oyster

ABSTRACT:   In order to identify free amino acids (FAA) that are importantas intracellular osmolytes in Crassostrea gigas , we investigatedthe change in FAA content in the mantle exposed to an abrupt decreaseor increase in salinity. In hypo-osmotic adaptation, most FAA showedremarkable and synchronous decreases from 2 to 8 h, suggestingthat the non-selective efflux of FAA was mainly responsible forthe decrease in FAA. Taurine that accounted for approximately 80% oftotal FAA content contributed most significantly to the hypo-osmoticadaptation. In hyper-osmotic adaptation, significant increases inglycine, alanine, β-alanine, proline, arginine and taurinewere observed. Of these, alanine showed an immediate increase thatis important to short-term adaptation to hyper-osmolality, whiletaurine showed a slower and substantial increase that contributesto a long-term adaptation to hyper-osmolality.     

Phenoloxidase and peroxidase activity in the shrimp Litopenaeus schmitti,Pérez‐Farfante and Kensley (1997) exposed to low salinity

Phenoloxidase and peroxidase activity were analysed in haemolymph of juvenile shrimp, Litopenaeus schmitti, exposed to different salinity levels (35%, 18%, 8%) for 48 h. A significant reduction (P<0.05) in total glucose and phenoloxidase activity in animals exposed to lower salinities (18% and 8%) was recorded, while peroxidase activity and total protein concentration did not vary. Histology revealed the occurrence of oedema in gills in shrimp exposed to 8%. The work demonstrates for the first time that in L. schmitti, low salinities can decrease glucose levels in haemolymph and create an immunosuppressive state by reducing phenoloxidase activity.     

低盐度养殖的凡纳滨对虾体长和体重的增长规律

通过池塘陆基围隔实验，研究了凡纳滨对虾在最适水温、溶氧、pH及低盐度(2～6)养殖环境的生长特性及规律。实验结果，低盐度养殖健康对虾体长和体重平均生长率分别为1.398 mm·d^-1和0.169 g·d^-1，对虾前期体长呈线性生长，中后期体重呈加速增长。非线性拟合结果，对虾体长生长为二次曲线，符合Quadratic模型，体重增长为S型曲线，符合Boltzmann模型，生长观测值与模型拟合相关系数R²均达到0.99；凡纳滨对虾低盐度养殖典型体长和体重生长模型为L=7.843+2.297t-0.0105t²和W=16.541+(-0.621-16.541)/(1+e^{(t-54.809)/15.456})。低盐度养殖，对虾体长与体重呈立方关系，符合幂指数模型W=aL^b，a值范围4.9～9.0×10^-6，b值范围2.9495～3.0716，相关系数R²在0.99以上，典型幂指数模型为W=4.9×10^-6L^3.0716。     

环境因子变化对锯缘青蟹后期幼体及仔蟹变态存活率的影响

通过实验对锯缘青蟹Z、M、C1～C4仔蟹在不同温度、盐度及干露时间的条件下，观察变态及存活率的差异。结果表明：1．温度改变对Z5变态率有影响，30—26℃温度突变其变态率为53％，30-28～25℃温度渐变变态率为60％，对照组(30℃)为57％；温度改变对M的变态存活率和变态时间间隔无影响．但C1变态为C2的时间间隔比对照组延长24～48h。2．盐度改变对青蟹Z5及C1-C4。仔蟹存活和变态的影响不同,在直接由盐度33移至28、21、15、8的不同条件下，Z5和M的盐度忍耐下限分别为21和15；C1-C4仔蟹在以上的盐度变化条件下均能成活、变态，但C4仔蟹在28、33高盐度下部分个体蜕壳不遂或蜕壳后死亡。3．蟹苗及仔蟹耐干露能力随着个体长大而增强；同规格蟹苗在干露6～18h条件下，变态时间间隔随着干露时间的增加延长24．48h；M在潮湿海绵和不透风的条件下放置12h，可正常变态，离开海绵则在6h内全部死亡；但C1-C4仔蟹即便离开海绵18h，也能正常存活变态。     

Optimum temperature and salinity conditions for growth of green algae <Emphasis Type="Italic">Chlorella ellipsoidea</Emphasis> and <Emphasis Type="Italic">Nannochloris oculata</Emphasis>

ABSTRACT:   The effects of temperature and salinity on growth of green algae Chlorella ellipsoidea and Nannochloris oculata were determined to compare the optimum culture conditions. A four-temperature (15, 20, 25, and 30°C) × three-salinity (10, 20, and 30) factorial design with triplicates was applied. Specific growth rate (SGR), maximum density, and duration to reach maximum density of C. ellipsoidea were significantly affected by both temperature and salinity. The highest SGR was observed in C. ellipsoidea at 25°C and salinity 10, but the maximum density was very low. The highest maximum density was achieved in C. ellipsoidea at 15°C and 10. The slope constant of the linear relationship between semilogarithmic growth of C. ellipsoidea and day of culture was highest at 15°C and 10. The SGR and duration to reach maximum density of N. oculata were significantly affected by both temperature and salinity. However, maximum density of N. oculata was significantly affected by temperature, but not salinity. The highest maximum density was achieved in N. oculata at 25°C and 30, but SGR was significantly lower than that of N. oculata at 25°C and 10. The slope constant of the linear relationship between semilogarithmic growth of N. oculata and day of culture was highest at 25°C and 30. Based on these results, the condition of 15°C and salinity 10 seemed to be optimal for maximum density of C. ellipsoidea , and the condition of 25°C and 10 and 30 for SGR and maximum density for N. oculata , respectively.     

The relationship between `deep-hole' mitochondria-rich cells and salinity adaptation in the euryhaline teleost, Oreochromis mossambicus

The present study elucidates the relationship between deep-hole MR cells (Lee et al. 1996) and salinity adaptation in tilapia (Oreochromis mossambicus). Freshwater tilapia were transferred to salt water of various salinities, i.e., 5 (hypotonic), 10 (isotonic), 20 (hypertonic), and 30 (hypertonic), for 2 weeks. The density of MR cells, protein content, activity, and localization of the sodium pump were examined. There was no significant difference in serum osmolarity and Na⁺, K⁺, Cl^– levels in fish of the various treatment groups. The amounts of protein and activity of Na,K-ATPase were elevated in fish from SW with the highest salinity. MR cells observed by scanning electron microscope revealed small pits (0.5–1.0 m in diameter) in groups from hypotonic and isotonic water and large crypts (2.4–3.8 m in diameter) in fish from hypertonic water. Moreover, the density of these deep-hole MR cells increased significantly in fish adapted to hypertonic SW. Larger and more numerous deep-hole MR cells of euryhaline tilapia may account for higher protein amounts and activities of Na,K-ATPase, probably to meet the physiological demand of euryhaline teleosts engaged in hyporegulation.