Zn~(2+)对青蛤的胁迫效应

在盐度25和水温26~28℃下,将壳长为(35.32±0.89)mm的青蛤暴露于Zn~(2+)质量浓度10.00、19.95、39.81、79.43、158.49、316.23mg/L试验组及空白对照组,得出Zn~(2+)的半致死质量浓度和安全质量浓度;之后又研究了Zn~(2+)在青蛤鳃和内脏团中的蓄积和血淋巴液中超氧化物歧化酶、过氧化氢酶、酸性磷酸酶的活性。试验结果表明,Zn~(2+)的96h半致死质量浓度为191.56mg/L,安全质量浓度为1.92mg/L;96h半致死质量浓度下,Zn~(2+)在青蛤鳃中蓄积速度快于内脏团,血淋巴液中超氧化物歧化酶、过氧化氢酶和酸性磷酸酶活性呈先诱导再抑制的趋势,安全质量浓度下无明显变化,但均高于对照组;两种组织中的Zn~(2+)质量浓度与处理时间呈正相关。本研究结果为青蛤健康养殖和毒理学研究提供了参考。     

4种重金属离子对菲律宾蛤仔的急性毒性及安全评价

为探究菲律宾蛤仔对Cd~(2+)、Mn~(2+)、Zn~(2+)、Cu~(2+)的耐受能力,采用毒理学试验方法研究4种重金属离子对菲律宾蛤仔的急性毒性效应。试验结果显示,菲律宾蛤仔的死亡率与4种重金属离子的质量浓度成正比,表现出明显的剂量—效应关系。4种重金属离子对试验菲律宾蛤仔24、48、72、96 h的半数致死质量浓度分别为:Cd~(2+),38.62、29.83、8.11、2.67 mg/L;Mn~(2+),712.58、421.57、188.74、61.27 mg/L;Zn~(2+),141.27、72.20、34.91、21.57 mg/L;Cu~(2+),29.88、12.06、3.62、0.79 mg/L;Cd~(2+)、Mn~(2+)、Zn~(2+)、Cu~(2+)对菲律宾蛤仔的安全质量浓度分别为0.03、0.61、0.22、0.01 mg/L。试验结果表明,4种重金属离子对菲律宾蛤仔毒性强弱依次为Cu~(2+)Cd~(2+)Zn~(2+)Mn~(2+),Cu~(2+)对菲律宾蛤仔的安全质量浓度低于渔业水质标准,在育苗和养殖过程中需特别关注。     

锌离子胁迫下青海湖裸鲤钙调蛋白磷酸酶的表达

为检测在重金属胁迫下青海湖裸鲤钙调蛋白磷酸酶(Calcineurin,CN)的动态变化,确定CN是否可以作为生物标志物对水环境中的重金属污染进行早期诊断,通过检测Zn~(2+)胁迫后青海湖裸鲤CN表达量的变化,研究了Zn~(2+)对青海湖裸鲤生存状态的影响。结果表明,Zn~(2+)对青海湖裸鲤的致死率与胁迫时间和离子浓度成正相关;通过实时定量PCR发现,CN在鳃、肌肉、肾脏和肝脏中均有表达;在Zn~(2+)浓度为1 mg/L时,随着胁迫时间的逐渐延长,鳃中CNAα、CNAγ和CNB均有逐渐增加的趋势,96 h时表达量达到最高水平;随着胁迫浓度的逐渐增加,CNAα、CNAγ和CNB表达量呈先升高后降低的变化趋势,在Zn~(2+)浓度为2 mg/L时,三者表达量均达到最高水平。研究结果显示,青海湖裸鲤钙调蛋白磷酸酶对锌离子胁迫产生了明显应答,可以作为重金属污染的候选生物标志物。     

高分子吸附剂除去海水中重金属离子的研究

用高分子吸附剂从盐度30,pH8.30左右的海水中动态和半静态吸附除去铜、锌、铅、镉离子。动态吸附结果表明,对海水中重金属离子的吸附容量为Cu~(2+)>Pb~(2+)>Zn~(2+)>Cd~(2+),吸附选择性为Cu~(2+)>Zn~(2+)>Pb~(2+)>Cd~(2+)。半静态吸附17h,对12.1μg/L Cu~(2+)除去率为89.3％;对22.5μg/L Zn~(2+)为82.7％;对104.8μg/L Pb~(2+)为59.4％;200.8μg/L Cd~(2+)为59.0％。为消除重金属离子对海洋生物幼体的毒性,提供了一种极其有效的方法。     

四种重金属暴露对青鳉呼吸行为的毒性效应

研究青鳉对不同重金属污染物的敏感性和响应阈值,为水体污染特别是重金属污染的早期预警监测提供定量基础。青鳉3月龄,体长(1.5±0.1) cm,体重(0.15±0.01) g;4种重金属为Cd、Zn、Cu和Hg。研究结果表明:青鳉对Cu~(2+)、Zn~(2+)、Cd~(2+)和Hg~(2+)的急性致死毒性大小为Hg~(2+)Cu~(2+)Cd~(2+)Zn~(2+);Hg~(2+)、Cu~(2+)和Cd~(2+)暴露下青鳉呼吸频率和呼吸强度先升高再降低(P0.01),呼吸参数与重金属浓度间呈现倒"U"型关系;Zn~(2+)暴露下青鳉呼吸频率、呼吸强度显著下降(P0.01);青鳉呼吸行为对Cu~(2+)、Zn~(2+)、Cd~(2+)和Hg~(2+)4种重金属暴露的响应阈值和响应时间分别为0.15、0.95、0.15、0.045 mg/L和2 h 32 min、4 h 7.5 min、3 h 5.5 min、4 h 37 min,响应阈值与96 h LC_(50)的比值分别为0.43、0.19、0.33、0.77。青鳉对Cd~(2+)、Zn~(2+)、Cu~(2+)、Hg~(2+)污染较为敏感,其呼吸参数可作为突发性水体重金属污染的生物监测指标。     

重金属Hg~(2+)、Cu~(2+)、Cd~(2+)对渤海湾卤虫无节幼体的急性毒性

在水温(18±0.5)℃、盐度27‰的环境下,研究了重金属Hg~(2+)、Cu~(2+)、Cd~(2+)对渤海湾卤虫无节幼体的急性毒性效应。结果表明,Hg~(2+)对渤海卤虫无节幼体24h、48h的LC50分别为201.01mg/L和0.05mg/L,安全浓度分别为2.01mg/L和0.000 5mg/L;Cu~(2+)对渤海湾卤虫无节幼体24h、48h的LC50分别为197.17mg/L和7.50mg/L,安全浓度分别为1.97mg/L和0.08 mg/L;Cd~(2+)对渤海湾卤虫无节幼体24h、48h的LC50分别为331.30mg/L和8.13mg/L,安全浓度分别为3.31mg/L和0.08mg/L。毒性由强至弱依次为Hg~(2+)Cu~(2+)Cd~(2+),但Cu~(2+)与Cd~(2+)的毒性差异不明显。     

紫色土吸附Cu2+、Zn2+对水体中土壤颗粒凝聚沉降的影响

研究中性紫色土表面吸附Cu~(2+)、Zn~(2+)后对其在水体中凝聚沉降的影响,为重金属离子释放对三峡库区水-土界面生态系统造成的风险提供数据参考。2014年10月,采集西南大学桑园的中性紫色土表层土壤,以Cu-(NO_3)_2和Zn(NO_3)_2配制重金属离子,进行Cu~(2+)和Zn~(2+)对中性紫色土凝聚沉降实验、测定中性紫色土颗粒吸附Cu~(2+)和Zn~(2+)后zeta电位值。研究结果表明:(1)中性紫色土吸附Cu~(2+)、Zn~(2+)后水体中土壤颗粒含量随时间不断减小,并且呈先快速后缓慢减小的规律,在不同浓度条件下土壤颗粒含量变化规律表现差异较大,其临界浓度分别为0.3~0.5和0.5~0.7 mmol/L。(2)水体中中性紫色土颗粒平均沉降速率均随Cu~(2+)、Zn~(2+)浓度升高而增大,分别从1.01 cm/min增加到2.92和2.58 cm/min,表现为Cu~(2+)Zn~(2+);过程分为3个阶段:缓慢增加,快速增加和基本不变,平均沉降速率随浓度变化临界范围分别为0.3~0.5和0.5~0.7 mmol/L。(3)水体中中性紫色土颗粒zeta电位绝对值随Cu~(2+)、Zn~(2+)浓度升高而变小,同时表现为Ca~(2+)Zn~(2+)Cu~(2+),土壤颗粒吸附Ca~(2+)、Cu~(2+)和Zn~(2+)后zeta电位绝对值随浓度变化临界浓度范围分别为0.8、0.3~0.5和0.5~0.7 mmol/L。重金属离子吸附在中性紫色土表面减小zeta电位值和静电斥力,加速土壤颗粒凝聚沉降过程。     

重金属Cu2+、Pb2+、Cd2+对太平洋牡蛎的急性毒性效应

采用单因子急性毒性实验研究Pb~(2+)、Cu~(2+)和Cd~(2+)对太平洋牡蛎(Crassostrea gigas)的96 h半数致死浓度(96 h LC_(50))及急性毒性效应。实验结果表明,Pb~(2+)、Cu~(2+)和Cd~(2+)对太平洋牡蛎96 h LC_(50)分别为22.99、21.75 mg/L和21.35 mg/L,急性毒性作用大小的顺序为:Cd~(2+)Cu~(2+)Pb~(2+)。Pb~(2+)、Cu~(2+)和Cd~(2+)对太平洋牡蛎的安全浓度(SC)分别为:2.30、2.18 mg/L和2.14 mg/L。总体而言,与Cu~(2+)和Pb~(2+)相比,太平洋牡蛎对Cd~(2+)毒性的耐受性较低。     

铬、锌、镉对黄颡鱼“全雄1号”的急性毒性及安全评价

在水温(28.0±1.5)℃、pH 6.5~7.0的条件下,采用静水试验法测定铬[Cr~(6+)]、锌[Zn~(2+)]和镉[Cd~(2+)]3种重金属对黄颡鱼"全雄1号"苗种的半数致死浓度(LC_(50))及安全浓度(SC)。结果显示,[Cr~(6+)]对黄颡鱼"全雄1号"苗种24 h、48 h、72 h、96 h的LC_(50)分别为168.71、84.85、52.23、34.46 mg·L~(-1);[Zn~(2+)]对黄颡鱼"全雄1号"苗种24 h、48 h、72 h、96 h的LC_(50)分别为5.36、3.34、3.12、2.75 mg·L~(-1);[Cd~(2+)]对黄颡鱼"全雄1号"苗种24 h、48 h、72 h、96 h的LC_(50)分别为1.87、1.74、1.63、1.15 mg·L~(-1);3种重金属对黄颡鱼苗种的SC分别为[Cr~(6+)]3.446 mg·L~(-1)、[Zn~(2+)]0.275 mg·L~(-1)、[Cd~(2+)]0.012 mg·L~(-1)。3种重金属对黄颡鱼苗种毒性大小为:[Cd~(2+)][Zn~(2+)][Cr~(6+)],[Cd~(2+)]和[Zn~(2+)]为中毒,[Cr~(6+)]为低毒。     

重金属镉和锌对可口革囊星虫的毒性试验

研究了镉、锌离子对可口革囊星虫的单一和联合毒性。结果显示:镉离子对可口革囊星虫的48 h和96 h半致死浓度分别为501 mg/L和175 mg/L,锌离子对可口革囊星虫的48 h和96 h半致死浓度分别为82 mg/L和61 mg/L,镉和锌对可口革囊星虫的安全浓度分别为17.5 mg/L和6.1 mg/L;镉和锌对可口革囊星虫的联合毒性在48 h和96 h时AI<0,相互拮抗作用明显。     

锌和氨氮对对虾肝胰脏的毒性作用

本文研究了中国对虾经锌和氨氮的毒性作用后肝胰脏内部结构发生的变化和损伤。结果表明,当锌和氨氮的不同浓度试验液对对虾经不同时间的中毒试验后,构成对虾肝胰脏肝小管的细胞组成、肝小管结构等发生不同程度的变化和损伤。在低浓度的锌和氨氮试验液的毒性作用下,构成肝小管管壁的分泌细胞增多,吸收细胞减少,且分泌细胞内形成较多的分泌小泡;当经高浓度的试验液作用后,不但肝小管管壁内的吸收细胞减少,分泌细胞增多及产生大量分泌小泡,而且因分泌细胞的破裂解体导致部分肝小管损伤或破坏。文中并就对虾肝胰脏在锌和氨氮的毒性作用下发生的变化与肝胰脏自身的解毒作用机理进行了初步的探讨。     

Requirements of vitamin C (l-ascorbyl-2-sulphate and l-ascorbyl-2-polyphosphate) and its effects on non-specific immune responses of grouper, Epinephelus malabaricus

An 8‐week feeding trial was conducted to determine two vitamin C derivatives, l ‐ascorbyl‐2‐sulphate (C2S) and l ‐ascorbyl‐2‐polyphosphate (C2PP), to satisfy vitamin C requirement and to test their effects on the non‐specific humoral immune responses of juvenile grouper, Epinephelus malabaricus. C2S and C2PP were each supplemented at 20, 50, 80, 150, 250 and 400 mg kg^?1 diet in the semi‐purified basal diet providing of 7, 16, 28, 55, 86, 142 mg ascorbic acid (AA) equivalent of C2S kg^?1 diet and 4, 9, 15, 31, 49, 75 mg AA equivalent of C2PP kg^?1 diet, respectively. Basal diet without AA supplemented was included as a control. Each diet was fed to triplicate groups of grouper (mean initial weight: 6.69 ± 0.07 g). Fish fed diets with ≥28 mg AA equivalent of C2S or ≥4 mg AA equivalent of C2PP kg^?1 had significantly (P < 0.05) greater weight gain (WG) than fish fed the unsupplemented control diet. Liver AA concentrations were higher in fish fed diets with ≥16 mg AA equivalent of C2S or ≥9 mg AA equivalent of C2PP kg^?1 than fish fed the control diet. Alternative pathway of complement activation (ACP) was higher in fish fed diets with ≥55 mg AA equivalent of C2S or ≥15 mg AA equivalent of C2PP kg^?1 than fish fed the control diet. Lysozyme activity was higher in fish fed ≥86 mg AA equivalent of C2S or ≥15 mg AA equivalent of C2PP kg^?1 than fish fed the control diet. Analysis by broken‐line regression of WG indicated that the adequate dietary vitamin C concentration from each vitamin C derivative in growing grouper is 46.2 mg AA equivalent of C2S kg^?1 diet and 17.8 mg AA equivalent of C2PP kg^?1 diet, and it also indicated that C2S is approximately 39% as effective as C2PP in meeting the vitamin C requirement for grouper. The data suggest that both C2S and C2PP supplementation support non‐specific immune responses of grouper.     

Characterization of grouper nervous necrosis virus (GNNV)

Grouper nervous necrosis virus (GNNV) was isolated from moribund grouper larvae, Epinephelus sp., using a fish cell line GF-1. The present study describes the biochemical and biophysical properties of GNNV and the expression of GNNV in diseased grouper larvae. Viral protein was detectable in most of the GNNV-infected GF-1 cells by the fluorescent antibody technique (FAT) after 12 h post-infection (p.i.), although no cytopathic effect (CPE) appeared at that time. Clear CPE developed on the third day, and complete disintegration of the monolayer occurred over the subsequent two days. The infectivity of GNNV can be blocked following treatment at 60 °C for 1 h. GNNV was sensitive to pH 3 and pH 10–12 with a 4 log₁₀ drop in infectivity. Purified GNNV was analysed by SDS–PAGE, and then stained with periodic acid silver. The positive staining indicated that its two capsid proteins were glycoproteins. Genomic RNAs of GNNV were extracted from purified virions and analysed. The molecular weights of genomic RNAs were 1.02 × 10⁶ and 0.50 × 10⁶ Da. The T2 region of the coat protein gene of GNNV was amplified by polymerase chain reaction (PCR), and the multiple alignment of the T2 sequence of two GNNV isolates with four genotypes of fish nodaviruses revealed that these two isolates (GNNV9410 and GNNV9508) belong to the red-spotted grouper nervous necrosis virus (RGNNV) genotype. The tissue distribution of GNNV in naturally infected grouper larvae was investigated by in situ hybridization using a dig-labelled probe, which showed that GNNV was not only detected in the brain and retina, but also in the gill, skeletal muscle, liver, pyloric gland, intestine and blood cells in the heart.     

Cryopreservation of sperm from natural and sex-reversed orange-spotted grouper (Epinephelus coioides)

The shortage of males and/or sperm has been an impediment to the aquaculture of orange-spotted grouper (Epinephelus coioides). This study reversed orange-spotted grouper females into males using hormone implants. A cryopreservation protocol for sperm was developed using normal males, and then using similar procedures the cryopreservation of sperm from sex-reversed males was compared. Immature, young and mature female fish were injected with 4 mg kg⁻¹ BW 17α methyltestosterone as implants and the gonad development stage was monitored over a 120-day period. All treated females converted into functional males within 120 days of the experimental period. Younger females (2Y) were all males within 30 days, although not all were capable of fertilizing fresh ova until day 60. The time after injection to sex reversal in immature fish was 50% shorter than in older females. Postthaw fertilization (81%, 82%) and hatching (45%, 47%) of cryopreserved sperm from natural males were the highest in trehalose (15–20%) with 150 mmol NaCl treatment; however, it was less than the control (89% fertilization and 69% hatch). There was no difference in the postthaw fertilization and the hatch percentages between sex-reversed male sperm (64% and 46% respectively) compared with natural male sperm (59% and 49%). The findings of this study suggest the potential use of sex-reversed males and cryopreserved sperm for commercial production of orange-spotted grouper seed for aquaculture.     

牛蛙繁殖及养殖试验报告

为了使牛蛙能在沈阳地区繁殖和生长,研究了牛蛙繁殖和养殖的主要技术要点,包括牛蛙的产卵、孵化、蝌蚪培育、幼蛙养殖、幼蛙疾病防治、投喂的饵料等,为沈阳地区的牛蛙繁养提供了一条新路子。     

温度对不同规格珍珠龙胆石斑鱼(棕点石斑鱼♀×鞍带石斑鱼♂)呼吸和排泄的影响

应用实验生态学方法,研究了不同水温(15.8℃、21.0℃、26.6℃、30.9℃、36.5℃)对小[(28.1?1.1)g]、中[(278.9?20.1)g]、大[(575.8?37.4)g]3种规格的珍珠龙胆石斑鱼(棕点石斑鱼♀×鞍带石斑鱼♂)(Epinephelus fuscoguttatus♀×Epinephelus lanceolatus♂)呼吸和排泄的影响。实验结果表明,温度和规格对珍珠龙胆耗氧率和排氨率的影响均达到显著水平(P0.05);小、中、大3种规格珍珠龙胆耗氧率和排氨率随水温的增加呈现先升高后降低、再升高的变化规律,当水温为26.6℃时达到最大值,分别为(1.510±0.124)mg/(g·h)、(0.306±0.007)mg/(g·h)、(0.161±0.010)mg/(g·h)和(47.739±21.048)μg/(g·h)、(13.956±1.783)μg/(g·h)、(6.811±1.882)μg/(g·h),耗氧率和排氨率与温度之间的回归关系均符合一元四次方程,相关系数R2均为1.000。在水温15.8~36.5℃范围,相同水温下,珍珠龙胆的耗氧率和排氨率随其个体的增大而降低,耗氧率和排氨率与规格之间的回归关系均符合一元二次方程,相关系数R2均为1.000。不同温度条件下,小、中、大3种规格珍珠龙胆的耗氧率Q10和排氨率Q10在21.0~26.6℃时均达到最大,且其均在26.6~30.9℃时最小。小、中、大3种规格O/N比值平均值变化范围分别为21.535~113.541、15.713~32.193、12.097~27.094,表明实验水温条件下小规格珍珠龙胆的供能物质为蛋白质、脂肪和碳水化合物,而中、大规格珍珠龙胆的主要能量物质为蛋白质和脂肪。     

Effects of body weight, water temperature and ration size on ammonia excretion by the areolated grouper (Epinephelus areolatus) and mangrove snapper (Lutjanus argentimaculatus)

The effects of body weight, water temperature and ration size on ammonia excretion rates of the areolated grouper Epinephelus areolatus and the mangrove snapper Lutjanus argentimaculatus were investigated. Under given experimental conditions, L. argentimaculatus had a higher weight-specific ammonia excretion rate than E. areolatus. Weight-specific ammonia excretion rates of fasted individuals of both species showed an inverse relationship with body weight (W, g wet wt.), but a positive relationship with water temperature (t, °C). The relationships for total ammonia nitrogen (TAN) were: E. areolatus: TAN (mg N kg⁻¹ d⁻¹)=21.4·exp^0.11t·W^−0.43 (r²=0.919, n=60); L. argentimaculatus: TAN (mg N kg⁻¹ d⁻¹)=121.5·exp^0.12t·W^−0.55 (r²=0.931, n=60). Following feeding, the weight-specific ammonia excretion rate of E. areolatus increased, peaked at 2 to 12 h (depending on temperature), and returned to pre-feeding levels within 24 h. A similar pattern was observed for L. argentimaculatus, with a peak of TAN excretion being found 6 to 12 h after feeding. Stepwise multiple regression analysis indicated that weight-specific TAN excretion rates of both species increased with increasing temperature and ration (R, percent body wt. d⁻¹): E. areolatus: TAN (mg N kg⁻¹ d⁻¹)=22.8·t−28.8·R−378.2 (r²=0.832, n=24); L. argentimaculatus: TAN (mg N kg⁻¹ d⁻¹)=22.9·t−25.4·R−216.4 (r²=0.611, n=24). The effect of body weight on weight-specific postprandial TAN excretion was not significant in either species (p>0.05). This study provides empirical data for estimating ammonia excretion of these two species under varying conditions. This has application for culture management.     

投喂策略对牛蛙蝌蚪生长发育及肝肠功能的影响

为研究投喂策略对牛蛙蝌蚪生长发育的影响，建立科学的投喂标准，实验分别设置了4种投喂频率(1、2、3和4次/d)与4个投喂水平(4%、6%、8%和10%)饲养牛蛙蝌蚪，以探究牛蛙蝌蚪合适的投喂策略。投喂频率实验表明，投喂3次/d或4次/d的牛蛙蝌蚪在实验周期内的变态率显著高于投喂1次/d或2次/d的牛蛙蝌蚪，且投喂3次/d的牛蛙蝌蚪增重率最大。变态率与投喂量的比值(MFR)随投喂频率增加而上升，2、3或4次/d显著高于1次/d。投喂频率对已变态牛蛙蝌蚪的肝脏组织结构及肠道蛋白酶、脂肪酶、淀粉酶活性无显著影响。投喂水产实验结果显示，实验周期内牛蛙蝌蚪变态率随投喂水平增加而上升，且8%与10%组已变态牛蛙蝌蚪的均重显著高于4%与6%组，但已变态牛蛙蝌蚪肠道蛋白酶活性随投喂水平升高而降低。8%与10%组已变态牛蛙蝌蚪肝细胞脂滴含量明显增多，脂肪沉积现象明显。8%投喂水平组有益菌属暖绳菌属(绿弯菌门)与鲸杆菌属(梭杆菌门)相对丰度较高，一定程度改善了肠道微生物结构。研究表明，牛蛙蝌蚪每日投喂3次，综合投喂水平8%左右，蝌蚪的生长发育性能较优，兼顾了牛蛙养殖生产效益与蝌蚪肝肠健康，促进了牛蛙产业健...     

Requirements of vitamin C (L-ascorbyl-2-monophosphate-Mg and L-ascorbyl-2-monophosphate-Na) and its effects on immune responses of grouper, Epinephelus malabaricus

An 8‐week feeding trial was conducted to evaluate two vitamin C derivatives, L‐ascorbyl‐2‐monophosphate‐Mg (C2MP‐Mg) and L‐ascorbyl‐2‐monophosphate‐Na (C2MP‐Na), to satisfy the vitamin C requirement and to test their effects on the immune responses of juvenile grouper, Epinephelus malabaricus. C2MP‐Mg and C2MP‐Na were each supplemented at 20, 50, 80, 150, 250, and 400 mg kg^?1 diet in the basal diet providing of 7, 18, 31, 51, 93, 145 mg ascorbic acid (AA) equivalent of C2MP‐Mg kg^?1 diet and 4, 10, 17, 31, 47, 77 mg ascorbic acid (AA) equivalent of C2MP‐Na kg^?1 diet, respectively. Basal diet without AA supplementation was included as control. Each diet was fed to triplicate groups of grouper (mean initial weight 3.20 ± 0.05 g). Fish fed diets supplemented with either C2MP‐Mg or C2MP‐Na had significantly (P < 0.05) greater weight gain (WG), feed efficiency and survival than those fed the unsupplemented control diet. Liver ascorbate concentrations in fish generally increased as dietary C2MP‐Mg or C2MP‐Na supplementation level increased. Haemolytic complement activity was higher in fish fed diets supplemented with 92 mg AA equivalent of C2MP‐Mg kg^?1 or 10–17 mg AA equivalent of C2MP‐Na kg^?1 than fish fed the unsupplemented control diet. Lysozyme activity was higher in fish fed ≥51 mg AA equivalent of C2MP‐Mg kg^?1 or ≥47 mg AA equivalent of C2MP‐Na kg^?1 than fish fed the unsupplemented control diet. Analysis by broken‐line regression of WG indicated that the adequate dietary vitamin C concentration from each vitamin C derivative in growing grouper is 17.9 mg AA equivalent of 2MP‐Mg kg^?1 and 8.3 mg AA equivalent of C2MP‐Na kg^?1, and it also indicated that C2MP‐Mg is about 46% as effective as C2MP‐Na in meeting the vitamin C requirement of grouper.     

Efficacy of 17 α‐methyl testosterone and letrozole on sex reversal of protogynous grouper,Epinephelus tauvina (Forskal, 1775) and spawning performance of sex‐reversed males

This study aimed to test the efficacy of 17 α‐methyl testosterone (17 α‐MT) alone and in combination with letrozole, an aromatase inhibitor, for the induction of sex reversal in protogynous greasy grouper, Epinephelus tauvina. Further, the long‐lasting effects of these treatments and spawning performance of sex‐reversed males were also investigated. Greasy grouper with oocytes in the perinucleolus stage were implanted with 5 mg 17 α‐MT kg^?1 body weight (T₁), 5 mg 17 α‐MT and 0.2 mg letrozole kg^?1 body weight (T₂) and 5 mg 17 α‐MT with 0.4 mg letrozole kg^?1 body weight (T₃) and no androgens/enzyme inhibitor implanted (C). The 17 α‐MT alone and in combination of letrozole‐induced sex reversal in greasy grouper, whereas untreated control fish (C) showed normal ovarian development. However, T₂ and T₃ group showed 100% sex reversal and completion of spermatogenesis up to functional male phase in 2 and 3 months, respectively, whereas T₁ group resulted in only 66.67% functional male with motile spermatozoa after 4 months. Sex‐reversed males successfully fertilized the eggs during induced spawning. There were significant differences on fertilization and hatching rates between T₂ group (79.00 ± 4.36%; 77.67 ± 2.87%, respectively) and T₁ group (57.67 ± 3.17%; 63.87 ± 2.91%, respectively). The result suggested that 17 α‐MT (5.0 mg kg^?1 BW) in combination with letrozole (0.2 mg kg^?1 BW) has the potential to produce 100% sex‐reversed male in short period in greasy grouper, which might greatly help in seed production of greasy grouper.