Fluctuating salinity effect on Sphoeroides annulatus (Jenyns 1842) physiological responses

Euryhaline fish, such as the Bullseye puffer Sphoeroides annulatus (Jenyns 1842), experience sudden salinity changes in their natural environment, which is more common than the exception, so they must adapt to survive and cope with extreme salt conditions. Therefore, Bullseye puffer juveniles were exposed to short‐term stress (39 hr) by fluctuating salinity conditions (41, 35, 29, 23, 17, 11, 5, 11, 17, 23, 29, 35, 41 psu) with a 3‐hr interval between each point at 26 ± 1ºC in a respirometer chamber and acclimation reservoirs. Responses to oxygen consumption rate (OCR: 23–35 mg O₂ h^–1 kg^–1), ammonium excretion rate (AER: 1–1.85 mg NH4⁺ h^?1 kg^?1), oxygen‐nitrogen atomic ratio (O:N 17–30), osmoregulatory pattern (blood osmotic pressure from 342.4 to 332.8 mmol/kg) and changes in expression levels of Na⁺/K⁺‐ATPase in the gills (higher values at higher salinities) were measured. Although some signs of stress were detected below the iso‐osmotic point (11.4 psu), the puffer fish is a strong euryhaline fish that survives under these conditions. Nonetheless, it could recover when salinity returned to the initial acclimation point because Sphoeroides annulatus is able to live in a wide range of environments with wide natural salinity fluctuations; thus, a common practice in aquaculture has been to expose fish to low salinity for several reasons discussed in this study. This capacity reveals its high plasticity to saline adaptation from 41 to 5 psu an up from 5 to 41 psu, all in less than 2 days.     

An intensive hatchery rearing protocol for larvae of the bullseye puffer,Sphoeroides annulatus (Jenyns)

In this study bullseye puffer, Sphoeroides annulatus larvae were reared from hatching through to 1 or 2 months after weaning on an experimental scale in three replicate 600 L tanks and on three occasions during the spawning season (nine tanks in total). The rearing protocol used was green water (Nannochloropsis oculata and Isochrysis sp.) 100 000 cells mL^?1 from 0 to 11 days after hatch (DAH), 5–10 rotifers, Brachionus rotundiformis mL^?1 from 2 to 26 DAH, 0.1–1 Artemia mL^?1 from 21 to 34 DAH and weaning from 29 to 34 DAH. Survival to a month after weaning was 1%, a total of 3153 juveniles were produced with an average wet weight of 0.29 ± 0.07 g and a length of 27.5 ± 0.82 mm.     

Interactive effects of salinity on oxygen consumption,ammonium excretion,osmoregulation and Na+/K+‐ATPase expression in the bullseye puffer (Sphoeroides annulatus,Jenyns 1842)

A physiological study was performed to explore the effects in Sphoeroides annulatus (Jenyns 1842) juveniles of exposure to different salinities 10, 17, 23, 29, 35 and 41‰ on oxygen consumption rate (OCR), ammonium excretion rate (AER), the oxygen‐nitrogen atomic ratio (O:N), osmoregulation and Na⁺/K⁺‐ATPase expression. The OCR values ranged from 27.9 to 30.9 mg O₂ h^?1 kg^?1, displaying a Type 1 response pattern Kinne (1977). AER ranged from 0.60 to 0.69 mg h^?1 kg^?1, and O:N values were from 53.12 to 59.26, indicating that the puffers use proteins and lipids as an energy‐substrate. Osmoregulation in S. annulatus was hyposmotic in salinities of 23, 29, 35 and 41‰ and hyperosmotic in a salinity of 10‰. The isosmotic point of the bullseye puffer was 356 mmol kg^?1 (10.5‰). The enzyme expression analysis indicates that the fish acclimated to 41‰ had the highest Na⁺/K⁺‐ATPase expression level, whereas, the lowest expression level was found close to the isosmotic point. Na⁺/K⁺‐ATPase expression in the gills was found to have a U‐shaped relationship with environmental salinity. We conclude that the bullseye puffer is strongly euryhaline and can be cultivated in a wide range of environments that has important economic implications.     

Comparison of egg quality between wild and captive bullseye puffer (Sphoeroides annulatus)

The quality of eggs from wild and captive bullseye puffer were compared. No significant differences were found between percentage hatch, percentage fertilization or egg size for eggs from wild and captive bullseye puffer.     

Expression of a glycoprotein hormone receptor gene in the ovary of the bullseye puffer (Sphoeroides annulatus)

A fragment of a glycoprotein hormone receptor (GpHR) gene was isolated from the ovary of the bullseye puffer. This cDNA fragment showed similarity to the thyrotropin (TSH) and gonadotropin (LH and FSH) receptors. GpHR mRNA expression in the ovary gradually increased during oocyte maturation.     

Weaning of bullseye puffer (Sphoeroides annulatus) from live food to microparticulate diets made with decapsulated cysts of Artemia and fishmeal

Two experiments were carried out to test microparticulate diets forweaning hatchery-produced larvae and juveniles of bullseye pufferSphoeroides annulatus. The diets were formulated with differentprotein sources: diet 1 with a combination of decapsulated cysts ofArtemia and fishmeal, and diet 2 with a combination offishmeal, squid, tuna gonad and shrimp meal. In the first experiment60-days-old fish were weaned with the microdiets over five days. Fishsurvival after 11 weeks of feeding was 92% for diet 1, 85%for diet 2, and 95% for the control fish fed Artemianauplii. Once it was determined that bullseye puffer can be adequatelyreared with artificial dry diets, diet 1 was used to test earlier timesfor weaning to reduce the period of Artemia feeding. In thesecond experiment, three different times were tested for initiation ofweaning in sibling fish larvae, i.e., at 29, 34, and 39 days post-hatch.Small differences in weight, length and survival were found amongweaning treatments after 23 days of feeding. When weaned at day 29post-hatch, fish larvae grew from an initial weight of 38.4 mg andlength of 11.1 mm to a final weight and length of 405.7 mg and 25.1 mmrespectively. Final survival in this treatment was 49.3%. Thereduced period of Artemia feeding would provide an economicalalternative for the species to take into consideration for its cultureat commercial scale.     

温度和盐度对日本黄姑鱼胚胎发育的影响

为了确定日本黄姑鱼（Nibea japonica）胚胎孵化的最适水温和盐度,采用不同水温和盐度对日本黄姑鱼受精卵进行了孵化试验。结果显示,在盐度为30的条件下,日本黄姑鱼受精卵在14～28℃范围内均能正常孵化,最适孵化水温为18～20℃。孵化时数与温度呈幂函数相关,孵化时间随温度升高而缩短。盐度试验表明,在水温为18℃的条件下,日本黄姑鱼受精卵在盐度25—32的海水中呈悬浮或者半悬浮状态,在盐度14～45范围内均能孵化,适宜孵化盐度为26～32。盐度对初孵仔鱼全长有显著影响,盐度较低组仔鱼全长显著大于高盐度组（P〈0．05）。     

Effects of salinity acclimation on the growth performance,osmoregulation and energy metabolism of the oriental river prawn,Macrobrachium nipponense (De Haan)

In this study, we evaluated the growth, osmoregulation and energy metabolism of the oriental river prawn, Macrobrachium nipponense, reared during 6 weeks with different salinities (0, 8, 14 and 22 g/L). The results showed that the haemolymph osmolality of M. nipponense increased with an increase in ambient osmotic pressure; the isosmotic point was 490 mOs/kg H₂O. The prawns showed a higher survival rate, weight gain rate and hepatopancreas index in salinity 14 g/L. Digestive enzymes were all affected by salinity, and the highest activities were observed in the salinity 14 g/L. The mRNA expression of Na⁺‐K⁺‐ATPase in gills and p53 in hepatopancreas were the highest in salinity 22 g/L. The expressions of heat shock protein 90 and glutathione S‐transferase genes in hepatopancreas were significantly higher in the salinity 8 g/L. Lipid metabolism‐related genes in hepatopancreas were significantly expressed in the salinity 14 g/L. The glucose‐6‐phosphatase gene in hepatopancreas was highly expressed in the salinity 8 and 22 g/L, and the expression of the ecdysone receptor gene in hepatopancreas was significantly higher in the salinity 14 g/L. The results showed that salinity 14 g/L could promote the growth of M. nipponense. However, higher salinity conditions may cause physiological damage, which provides a theoretical basis for brackish water culture of M. nipponense.     

温度和盐度对羊鲍胚胎发育及幼虫发育的影响

为探究水温和盐度对羊鲍胚胎发育和幼虫发育的影响,以人工驯化后的野生羊鲍为实验材料,采用温度、盐度单一和双因子组合方法设计实验。结果表明,羊鲍孵化率和成活率受温度、盐度影响显著,28°C时,胚胎发育时间最短,孵化率最高,26°C时,幼虫发育时间最短,成活率最高。胚胎发育适宜温度为24~28°C,最适温度为26~28°C。盐度为24时,羊鲍胚胎发育和幼虫发育时间最短,孵化率和成活率最低;盐度分别为30和32时,孵化率和成活率最高。胚胎发育和幼虫发育的适宜盐度为28~32,最适盐度为30~32。温度盐度交互作用对羊鲍孵化率影响差异不显著,对成活率影响差异显著。通过响应曲面模型优化,得出温度为24.61°C,盐度为32时,孵化率和成活率均达到最大值,分别为95.32%和81.20%,满意度为0.848。研究表明,羊鲍胚胎发育和幼虫发育对温度、盐度的敏感性不同,对高温高盐的耐受性强于低温低盐。     

温、盐度对鲻鱼胚胎发育和孵化的影响

本文探讨了不同温度、盐度条件下鲻鱼胚胎发育和孵化情况,结果表明:(1)鲻鱼胚胎发育的适宜水温为18—25℃;(2)适宜盐度为25—40;(3)最适孵化条件为温度25℃和盐度30—35。     

Comparative study of the effects of heavy metals on embryonic development of zebrafish

This study aimed to investigate the effects of heavy metals, such as copper, zinc, iron, cobalt, chromium, aluminium, manganese and molybdenum, on zebrafish egg hatching rate and the subsequent survival rate of the larvae. Each metal was used in the various concentrations of0.05 mg/L, 50 mg/L and 500 mg/L to detect the threshold limit of tolerance. The study's results showed significant differences in the hatching and survival rate of larvae between the control group and most of the experimental groups when adding heavy metals in various concentrations. The highest concentration (500 mg/L) of the induced heavy metals tested in this study resulted in total egg or larval mortality within 96 hr and significantly lower egg or larval life expectancy. Among the tested metals, zinc and molybdenum had the most significant impact on hatching time, in contrast to iron that did not differentiate the results from the control group. Copper, cobalt, chromium, aluminium and manganese did affect zebrafish eggs depending on their exposure concentrations, which differentiated the results from the control group. Also, the study's findings demonstrate a significant dependence of the hatched egg heart rate on the metal concentration, and in particular, higher concentrations of metals correspond to higher heart rate. Zinc, Molybdenum and copper was proved to be the most toxic heavy metals causing increased hazard rate to mortality up to 96 hr and shorter life expectancy. Finally, skeletal deformities that occasionally observed did not significantly affect the total life expectancy of the hatched eggs.     

盐度对山西盐池卤虫群体的影响

盐度对山西盐池卤虫群体的影响贾沁贤，王贻义，卢敬让，周望舒，杨孟科（青岛海洋大学，２６６００３）（山西省水产科学研究所，太原０３０００６）关键词盐度，卤虫，孵化率，存活率ＥＦＦＥＣＴＳＯＦＳＡＬＩＮＩＴＹＯＮＡＲＴＥＭＩＡＳＩＮＩＣＡＰＯＰＵＬＡＴＩ...     

疣吻沙蚕胚胎发育观察及盐度对其孵化的影响

采用显微镜观察了疣吻沙蚕(Tylorrhynchus heterochaeta)胚胎发育不同时期特征,并依据疣吻沙蚕人工孵化经验设置6个盐度梯度组(A:0,B:5,C:10,D:13,E:15,F:20),每组3个平行,研究了盐度对疣吻沙蚕受精率和孵化率的影响。结果表明,疣吻沙蚕胚胎发育可分为受精卵、卵裂期、囊胚期、原肠期、前担轮幼虫期、后担轮幼虫期、膜内三刚节疣足幼虫期和三刚节疣足幼虫期8个时期;盐度对疣吻沙蚕孵化影响显著(P0.05),C组受精率和孵化率最高,与其他组存在显著差异(P0.05)。适宜受精的盐度范围为10~13,最适孵化的盐度为10。     

Low salinity increases survival,body weight and development in tadpoles of the Chinese edible frog Hoplobatrachus rugulosus

Water salinity affects survival, growth and metamorphosis of anuran tadpoles. Hoplobatrachus rugulosus is considered not only as a freshwater amphibian but is also found in brackish wetlands. However, whether salinity change interferes with hatching, survival, body mass and development of H. rugulosus tadpoles is unknown. We found that salinity levels of <4‰ did not affect of survival or hatching of H. rugulosus eggs. At an early larval stage, tadpoles could tolerate up to 9‰ salinity for 96 h; however, body water content decreased when salinity was >5‰. After a 3‐week experiment, body weights of tadpoles exposed to 2‰ and 4‰ salinities were higher but that of the 6‰ group was lower compared with the 0‰ group. More than 90% of tadpoles exposed to 2‰ and 4‰ salinity showed complete metamorphosis. Salinity levels <4‰ promoted survival of tadpoles better than 0‰, whereas none of tadpoles in the 6‰ group became juvenile frogs in 50 days. Time taken to reach metamorphosis was shorter for 2‰ and 4‰ (47.22 ± 0.28 and 47.26 ± 0.33 days, respectively) than for 0‰ (49.31 ± 0.35 days). Juvenile frogs in the 2‰ group had greater body weight than the control. It could be concluded that salinity of <4‰ increased survival and body weight of H. rugulosus tadpoles, and shortened the time taken to reach metamorphosis.     

Effects of salinity on the ions important and sodium‐potassium ATPase in osmoregulation,cortisol, amino acids,digestive and immune enzymes in Scylla paramamosain during indoor overwintering

Overwintering is an important part of the conservation of Scylla paramamosain, and salinity has an important effect on the conservation of S. paramamosain during overwintering. Three salinities (4‰, 12‰ and 25‰) were selected as the overwintering salinities to reveal the effects of different salinities on the relevant important ions in osmotic pressure regulation, plasma cortisol, digestive enzymes, immune enzymes and amino acids of S. paramamosain during indoor overwintering. Results indicated that after overwintering, Cl^‐, Na⁺ and the osmotic pressure of serum have the highest salinity at 25‰, and the lowest salinity at 4‰. Na⁺/K⁺‐ATPase activity and cortisol were found to increase with decreasing salinity. The activity of digestive and immune enzymes was highest at 25‰, and was the lowest at 4‰. The amount of total amino acids (TAA), umami amino acids (UAA) and essential amino acids (EAA) in 25‰ were significantly higher than in 4‰ and 12‰. After overwintering, the essential amino acid index (EAAI) in the salinity range of 12–25‰ was 54.04–59.00, compared to 48.56–54.04 in the salinity range of 4–12‰. As a result, S. paramamosain at 25‰ had higher digestion and immunity than at 4‰ and 12‰, due to requiring more energy for osmotic pressure adjustment. In addition, S. paramamosain at 25‰ had the best meat quality. The results of this study are helpful for aquaculture production for indoor overwintering of S. paramamosain.     

Effect of EPA/DHA ratios on the growth and survival of Galaxias maculatus (Jenyns, 1842) larvae reared under different salinity regimes

Despite the importance of certain highly unsaturated fatty acids in osmotic regulation, few studies have been addressed to determine the essential fatty acid requirements for a given species cultured under different salinities. As Galaxias maculatus is a diadromic species, the present study aimed to determine the effect of salinity on the optimum dietary EPA/docosahexaenoic (DHA) ratio for survival and growth during the larval stages. Larvae were fed for 20 days with rotifers containing two different EPA/DHA ratios (low: 0.64 and high: 2.18) at three different salinities (0, 10 and 15 g L^?1). The results of this study showed a marked effect of water salinity on larval dietary lipid utilization in G. maculatus larvae. These results suggested that G. maculatus larvae reared at higher salinities may have a higher dietary requirement for DHA, whereas larvae reared at 0‰ showed higher requirements for EPA. The overall results of the present study indicate that even small changes in salinity can determine the optimum dietary EPA/DHA ratio and the quantitative essential fatty requirements of fish. This may have important repercussions and affect the rearing performance of G. maculatus cultured under different salinities.     

水温对石磺胚胎发育的影响

通过实验室研究,对石磺（Onchidium sp．）胚胎发育过程进行了详细观察,比较了不同水温下石磺胚胎发育的速度,探讨了膜内面盘幼虫孵化出膜的主要条件。结果表明：石磺的胚胎发育过程类似于肺螺亚纲其他贝类,行体内受精,刚产出的卵为受精卵,细胞未进行分裂,卵裂从卵产出体外开始,分别经过卵裂期,囊胚期,原肠期,膜内担轮幼虫期,膜内面盘幼虫期,经过孵化期孵化出膜为自由生活的面盘幼虫期。对各阶段幼体的大小、形状、内部器官等特征以及发育变态过程进行了详细的显微观察和描述。26℃,28℃,30℃3个水温组中,从受精卵到膜内面盘幼虫孵化出膜分别需要300h,290h,288h;发现影响幼虫孵化出膜的主要因素是水温和海水的刺激作用;繁殖盛期卵群工厂化水泥池自然水温孵化时间为10～14d。并报道了水温低于23℃时石磺胚胎停止发育现象。