不同壳色菲律宾蛤仔品系间的双列杂交

于2006年秋,以"海洋红"(R)、白蛤(W)、斑马蛤(Z)为材料,开展了不同壳色菲律宾蛤仔品系间3×3的双列杂交.实验由3个自交组R×R、W×W、Z×Z和3个杂交组R×Z、W×Z、W×R,即6个正反交RZ、ZR、WZ、ZW、WR、RW组成,研究了子一代在不同阶段生长、变态、存活的杂种优势及壳色遗传机制.结果表明,在不同阶段,不同杂交组合的杂种优势表现程度不同.浮游期间,各杂交组幼虫生长优势(Hg)随着日龄而增大,存活优势(Hs)与日龄几乎无相关性,其值分别为Hg=6.20±2.43,Hs=14.83±0.28.W×Z杂交组合表现出明显的杂种优势,其值分别为Hg w×z=8.50±2.79,Hs w×z=20.59±0.98, 与R×Z、W×R杂交组差异显著(P ＜0.05).杂交有效地提高了变态率,缩短了变态时间;变态率的杂种优势为Hm=15.84,平均缩短变态时间2d.室内培育期间,刚刚完成变态的稚贝很快表现出生长优势,而后一段时间才表现出存活优势,其值分别为Hg=8.98±2.91,Hs=8.11±8.18;W×Z杂交组合的杂种优势为Hg w×z=15.93±6.47、Hs w×z=8.78±8.76,Hg w×z与R×Z、W×R杂交组差异显著(P ＜0.05),Hs w×z与W×R杂交组差异显著(P ＜0.05).养成期间,幼贝的杂种优势分别为Hg=12.77±1.20,Hs=49.85±1.93;W×Z杂交组合的杂种优势分别为Hg w×z=20.92±1.98,Hs w×z=61.60±1.38,与其它杂交组的显著性差异程度与稚贝期相同.从总体水平上分析,幼虫、稚贝、幼贝生长速度的杂种优势分别为15.06、17.40、15.77,彼此间无显著性差异(P ＞0.05);综合各阶段的杂种优势,3个杂交组的杂种优势大小顺次为:W×Z＞R×Z＞W×R.R×Z、W×Z、W×R的子一代的壳色分别表现为:红斑马、白斑马(左壳背部有一条深色条带)、中红(左壳背部有一条深色条带),且正反交的壳色表现一致,说明壳色表现形式与性别无关,为非伴性遗传.     

菲律宾蛤仔两道红与白斑马品系的三元杂交

为了提高菲律宾蛤仔壳色品系的生产性能,于2009年8月,以具有较快生长速度的两道红(R)F₂和具有显著杂种优势的白斑马(WZ)F₂为试验材料,开展了两个蛤仔品系的三元杂交。其中白斑马品系生长快,抗逆性强,是由生长最快的珍珠白(W)和抗逆性最强的斑马蛤(Z)杂交产生的二元品系。试验由RR(♀R×♂)、RWZ(♀R×♂)、WZR(♀WZ×♂R)、WZWZ(♀WZ×♂WZ)4个试验组组成。获得了三元正反交组合RWZ、WZR,比较了各试验组子代在不同阶段生长、存活的杂种优势并分析了壳色遗传机制。结果表明,正反交组的单亲杂种优势具有明显的不对称性,正交组RWZ的生长与存活性状得到了明显的改良;WZR的存活性状得到了一定程度上的改良。从生长上看,在浮游期,RWZ、WZR的单亲杂种优势分别为+1.70、-2.92;双亲生长优势为-0.68,主要受到卵源与配对策略交互作用的影响,其次为母本效应;在稚贝培育期,RWZ的单亲生长优势为+9.71,WZR单亲生长劣势为-6.57,总体上尚未表现出双亲生长优势,其大小仅为+0.90。从存活上看,RWZ、WZR在浮游期的单亲存活优势分别为+4.47、+3.05;双亲存活优势为+3.60,主要受到配对策略的影响,其次为母本效应;正反交组在稚贝阶段的单亲杂种优势分别为+13.09、+7.30;双亲存活优势为+9.00。R×R、R×WZ、WZ×R、WZ×WZ子代的壳色分别表现为两道红、两道红白斑马、两道红白斑马、白斑马;白斑马自交后代仍然为白斑马,未出现壳色分离,且三元正反交的子代壳色表现一致,说明壳色为非伴性遗传。     

大连群体两种壳型菲律宾蛤仔的双列杂交

为探讨不同壳型菲律宾蛤仔的杂种优势，于2007年6月开展了壳宽型（W）和壳扁型（P）两种壳型菲律宾蛤仔的双列杂交。实验由2个杂交组PW（P♀×W♂）、WP(W♀×P♂)和2个自交组WW(W♀×W♂)、PP(P♀×P♂)组成。结果表明，杂交子代壳宽与壳长的比值、放射肋数介于两个自交子代之间，表现为中间型。浮游期间，幼虫未表现出生长优势，但表现出一定的存活优势，幼虫大小存在显著的母本效应。PW和WP子代的存活优势分别为（3.43±0.54）和（4.21±0.55）。室内培育阶段，杂交子代稚贝表现出明显的生长、存活优势，但母本效应逐渐减弱，PW和WP子代的生长优势分别为（10.76±2.25）和（8.28±1.88），存活优势分别为（5.52±0.62）和（11.10±2.41）。养成期间，杂交子代的生长、存活优势更加明显，母本效应消失，PW和WP子代的生长优势分别为（16.22±0.23）和（14.80±1.50），体重的杂种优势分别为（50.29±1.13）和（35.27±2.43），存活优势分别为（12.30±1.37）和（17.45±0.75）。以上结果说明两种不同壳型蛤仔杂交可以产生杂交优势，随着个体发育杂交优势越来越明显。     

中国蛤蜊的家系建立及早期生长发育研究

摘要：于2008年7月，采用不平衡巢式设计建立了中国蛤蜊家系（7个父系半同胞家系和21个全同胞家系：A1、A2、A3……G1、G2、G3），并对各家系的卵径、受精率、孵化率及生长、存活和变态等相关指标进行了分析。结果表明：各家系蛤蜊的卵径、受精率、孵化率及D形幼虫大小均无显著差异（P＞0.05）。 就其生长而言，不同发育阶段各家系的个体大小不同，生长速度不同，受父本效应、母本效应及雄内雌间作用的影响。幼虫浮游期，G1壳长最大，生长速度为10.04±1.67 μm•d-1；A2壳长最小，生长速度为6.07±1.32 μm•d-1。幼虫匍匐期，B3生长最快，其生长速度为29.93±3.67 μm•d-1；D1生长最慢，其生长速度为16.72±2.73 μm•d-1。稚贝期，G3壳长最大，生长速度为83.14±5.85μm•d-1；A2、A3的壳长较小，其生长速度分别为57.78±5.44μm•d-1，55.86±4.48μm•d-1。就其存活而言，幼虫浮游期，A2、C1、E3、F2、G1、G2的存活率较高（＞85%），B2、D1存活率最小（＜35%）；稚贝培育期，G1存活率（70.40%）最高；A1（23.40%）、C2（20.90%）、F1（19.30%）的存活率较低。变态期间，各家系的生长速度不同，G1、G3生长速度分别为7.94±1.53 μm•d-1、7.96±1.52 μm•d-1；D1生长速度最小，仅为5.23±0.75μm•d-1。各家系的变态率不同，B1、E1、G2变态率均在80%以上，E2（41.24%）、F1（43.25%）变态率较低。各家系的变态规格存在差异，随着变态时间的延长变态规格小型化；G1、G2、G3变态规格最大（240μm），变态时间最短（13d）；D1变态规格最小，仅为226.65±5.65μm,变态时间最长（17d）。综合各家系生长、存活等早期表型性状，G3生长最快，F2存活率最高，G1产量最高，可进一步作为中国蛤蜊的育种材料。     

不同壳型菲律宾蛤仔杂交家系的建立及早期生长发育比较

利用3种壳型的菲律宾蛤仔,即壳宽型（H）、中间型（M）和壳扁型（P）,采取双列杂交方式,成功建立3种杂交组合（PH、HM和MP）,每个杂交组合由4个杂交家系组成,共12个杂交家系。结果表明,不同壳型亲本形态差异显著（P〈0.05,n=4）;各杂交组合的D形幼虫、附着规格、变态规格和单水管稚贝的大小彼此间差异不显著（P〉0.05,n=120）。幼虫浮游期间,3种杂交组合表现出不同程度的生长、存活优势。PH杂交组合表现出明显的生长优势,与HM、MP组幼虫大小差异显著（P〈0.05,n=120）,生长速度分别为（10.21±0.42）、（9.96±0.52）和（9.29±0.52）μm/d;从存活率上看,9日龄时,PH杂交组合存活率最高,与HM、MP组合差异极显著（P〈0.05,n=12）。变态期间,幼虫生长缓慢,PH、HM和MP杂交组合的生长速度分别为（1.72±0.48）、（1.93±0.53）和（2.08±0.39）μm/d,差异显著（P〈0.05,n=120）;变态率分别为（83.20±8.47）%、（6.45±3.06）%和（10.75±3.70）%,差异极显著（P〈0.01,n=12）。稚贝培育期间,3组稚贝的大小差异极显著（P〈0.01,n=120）,生长速度分别为（16.74±3.06）、（13.08±2.24）和（15.20±2.55）μm/d;本阶段3组存活率均较高,分别为（93.25±2.99）%、（90.75±2.22）%和（87.25±4.86）%,彼此间差异显著（P〈0.05,n=12）。     

中国刺参(Apostichopus japonicus)与韩国刺参杂交子一代生长和抗病力比较

采用完全双列杂交法对刺参中国群体(C)和韩国群体(K)进行群体间杂交和群体内自繁,获得C(♀)×C(♂)、K(♀)×K(♂)、K(♀)×C(♂)和C(♀)×K(♂) 4个交配组合的子一代。分析了各交配组受精率、孵化率、附着变态率、浮游幼体和幼参阶段的生长和抗病能力以及杂交子代的杂种优势。结果显示,杂交组与自繁组在受精率和孵化率等方面不存在显著性差异,杂交组附着变态率高于自繁组。C(♀)×K(♂)组在幼参期体长平均值均大于其他3个组,并表现出显著性差异,其体长杂种优势率在9.43%–23.75%之间;其体重从150日龄后表现出杂种优势,在4.09%–34.96%之间。而K(♀)×C(♂)组在幼参期体长和体重除在150日龄时表现为杂种优势,其他时间均表现为杂种劣势。K(♀)×C(♂)组抗灿烂弧菌病能力最强,杂种优势率为26.21%。     

虾夷扇贝与风向标扇贝种间杂交的初步研究

针对虾夷扇贝在养殖过程中出现的问题,本研究以风向标扇贝和虾夷扇贝为亲本进行了种间杂交实验,培育出了虾夷扇贝（♀）×风向标扇贝（♂）（PY♀×PC♂）及风向标扇贝（♀）×虾夷扇贝（♂）（PC♀×PY♂）两种杂交一代,并对其早期发育及幼虫期和稚贝期生长进行了比较。结果显示,PY♀×PC♂杂交一代的受精率、孵化率和幼虫期的生长和存活率介于双亲之间,而壳高和壳长的生长均高于双亲,表现出显著的杂种优势;PC♀×PY♂杂交一代的受精率、孵化率、幼虫期生长和存活率均低于双亲,表现为杂种劣势。在养殖第1年,PY♀×PC♂杂交一代的壳高、壳长、壳宽和体质量增长率均高于双亲,杂种优势显著。研究表明,卵子来源对后代的表现具有极其显著的影响,以雌性虾夷扇贝与雄性风向标扇贝进行种间杂交从而改良虾夷扇贝种质是可行的。     

魁蚶(Scapharca broughtonii)中国群体与韩国群体杂交子一代的生长和存活比较

以魁蚶(Scapharca broughtonii)中国群体(C)和韩国群体(K)为材料,进行了4个组合的杂交和自交实验,分析了各实验组的受精率、孵化率、幼虫和稚贝的生长、存活以及杂交子一代的杂种优势.结果显示,4个组的受精率和孵化率均较高(80％以上);自交组的受精率略高于杂交组,但孵化率无显著差异.在幼虫期,KK组和KC组的壳长平均值大于CK组和CC组,但存活率和变态率无显著差异;在稚贝期,KK组和KC组的壳长平均值也均大于CK组和CC组,但CC组和CK组的保苗率比KC组和KK组高.综合分析比较表明,杂交KC组的杂种优势率在幼虫期和稚贝期的壳长生长上均表现为正值,在稚贝期的存活率方面也表现为正值,杂交KC组结合了两群体的部分优良性状,是理想的育种材料.     

魁蚶(Scapharca broughtonii)中国群体与韩国群体杂交子一代的生长和存活比较

以魁蚶(Scapharca broughtonii)中国群体(C)和韩国群体(K)为材料,进行了4个组合的杂交和自交实验,分析了各实验组的受精率、孵化率、幼虫和稚贝的生长、存活以及杂交子一代的杂种优势。结果显示,4个组的受精率和孵化率均较高(80%以上);自交组的受精率略高于杂交组,但孵化率无显著差异。在幼虫期,KK组和KC组的壳长平均值大于CK组和CC组,但存活率和变态率无显著差异;在稚贝期,KK组和KC组的壳长平均值也均大于CK组和CC组,但CC组和CK组的保苗率比KC组和KK组高。综合分析比较表明,杂交KC组的杂种优势率在幼虫期和稚贝期的壳长生长上均表现为正值,在稚贝期的存活率方面也表现为正值,杂交KC组结合了两群体的部分优良性状,是理想的育种材料。     

长牡蛎3种壳色家系间杂交子代生长和存活比较

为了利用杂种优势培育长牡蛎优良新品种,实验以3种不同壳色长牡蛎家系(白色/W、黑色/B、紫色/P)为材料,采用3×3完全双列杂交法,建立了3个自交组合和6个正反杂交组合,分析了各实验组幼虫期和养成期的生长、存活以及杂交子代的杂种优势。结果表明,浮游幼虫期,杂交组PB表现出显著的生长优势;与自交组相比,各杂交组均有着较高的幼虫存活率;在幼虫存活率方面,所有杂交组均有较高的杂种优势率。在养成期,紫壳色自交组的壳高显著大于白壳色和黑壳色自交组;6个杂交组中,PB的壳高生长最快,BP次之,PW、WP的生长最慢;各杂交组与自交组的成活率差异均不显著;杂交组BP及其反交组PB的壳高、壳长、总重和存活率的杂种优势率分别介于3.71%~15.27%、-2.00%~13.10%、11.23%~41.56%、-2.77%~9.83%,其他4个杂交组在整个养成阶段没有表现出杂种优势。     

Protein and amino acid composition from the mantle of juvenile O ctopus vulgaris exposed to prolonged starvation

Protein and amino acid composition of the mantle of juvenile O ctopus vulgaris (Cuvier, 1797) during fasting for 27 days were determined. Average protein content of octopus mantle was of 711.19 ± 46.80 g kg^?1 DW, and it decreased with increasing fasting days. The non‐essential amino acids content was higher (486.18 ± 11.08 g kg^?1 protein) than essential amino acids (425.82 ± 9.15 g kg^?1 protein) at the start of the experiment (unstarved animals). The results suggest that the amino acid profile of the mantle where the most abundant amino acids are Arg, His, Lys, Gly, Leu and Pro could indicate a prolonged fasting condition (>20 days) or poor nutrition of O . vulgaris. This study supports the idea of using mantle for metabolic needs of starved O . vulgaris suggesting that the degradation pathway of amino acids to pyruvate and tricarboxylic acid cycle intermediates was favoured contrary to the degradation pathway of ketogenic amino acids. Special considerations should be taken concerning Thr, Ile, Ser, Ala, Asx (Asp, Asn), Glx (Glu, Gln) (because of their fast intake) and Lys and His (due to their stable contents) during a prolonged period of fasting.     

美人鱼发光杆菌对凡纳滨对虾非特异性 免疫功能及抗病力的影响

在基础饲料中分别添加0.1%和1%美人鱼发光杆菌灭活菌、0.1%美人鱼发光杆菌活菌配制成3种免疫实验饲料,以基础饲料为空白对照组饲料,每组设3个平行样。对个体质量为(4.83±0.36)g的凡纳滨对虾进行为期20 d的饲养实验,分别在0、5、10、15和20d进行取样,以血清中的酚氧化酶(PO)、酸性磷酸酶(ACP)、碱性磷酸酶(AKP)、超氧化物歧化酶(SOD)和溶菌酶(UL)活性为免疫指标,探讨了美人鱼发光杆菌作为免疫制剂对凡纳滨对虾非特异性免疫效应的影响;在投喂免疫饲料后的第22天,按0.004 2 kg/kg体重的剂量,直接投喂对虾白斑综合征病毒(WSSV)病料,并记录累积死亡率。结果表明,美人鱼发光杆菌免疫实验组对凡纳滨对虾血清中PO、ACP、AKP、UL和SOD活性影响明显高于对照组,并且在饲料中添加美人鱼发光杆菌后,明显提高了对虾抵御WSSV感染的能力。其中0.1%美人鱼发光杆菌活菌实验组的抗病毒感染能力最强,WSSV感染14d内累计死亡率为63.3%±5.8%;而对照组为96.7%±3.3%。研究表明,美人鱼发光杆菌添加在对虾饲料中能提高凡纳滨对虾非特异性免疫水平,增强抵抗疾病的能力,将其作为对虾免疫增强剂具有良好的应用前景。     

Effects of Spirulina platensis as a feed additive on growth and coloration of blue dolphin cichlids (Cyrtocara moorii Boulunger, 1902)

This study was carried out to investigate the effects of replacing fish meal with dietary Spirulina as a feed supplement on the growth performance and coloration of blue dolphin cichlids (Cyrtocara moorii). Five isonitrogenous (47% crude protein) and isocaloric (17.36 kJ/g digestible energy) diets were for formulated to replace FM with 0, 5, 10, 15 and 20% Spirulina (designated as Control, SP5, SP10, SP15 and SP20 respectively) and fed to the fish (initial body weight, 3.15 ± 0.01 g). Fish were randomly distributed into fifteen 120 L aquariums (26.5 ± 1.00°C), 15 fish per aquarium. The diets were tested in triplicate for 12 weeks. Experimental groups were fed twice daily (09:00 and 17:00) by hand to satiation. At the end of the feeding trial, significantly (p < 0.05) higher weight gain (WG), specific growth rate (SGR), protein efficiency ratio (PER) and lower feed conversion ratio (FCR) were observed in fish fed the SP10 diet when compared to the SP20 diet. There was no significant difference in these parameters between the other groups. The skin coloration of blue dolphin cichlid fed a diet containing Spirulina meal was enhanced. The best coloration was observed in the SP15 group. These impressions were objectively validated by chemical determinations of carotenoids extracted from fish skins and passed statistical tests of significance. The study findings show that Spirulina meal does not diminish growth rates except at very high levels.     

Dietary thiamin and pyridoxine requirements of fingerling Indian major carp,Cirrhinus mrigala (Hamilton)

Two experiments were conducted to quantify the dietary thiamin (experiment I) and pyridoxine (experiment II) requirements of fingerling Cirrhinus mrigala for 16 weeks. In experiment I, dietary thiamin requirement was determined by feeding seven casein–gelatin‐based diets (400 g kg^?1 CP; 18.69 kJ g^?1 GE) with graded levels of thiamin (0, 0.5, 1, 2, 4, 8 and 16 mg kg^?1 diet) to triplicate groups of fish (6.15 ± 0.37 cm; 1.89 ± 0.12 g). Fish fed diet with 2 mg kg^?1 thiamin had highest specific growth rate (SGR), protein retention (PR), RNA/DNA ratio, haemoglobin (Hb), haematocrit (Hct), RBCs and best feed conversion ratio (FCR). However, highest liver thiamin concentration was recorded in fish fed 4 mg thiamin kg^?1 diet. Broken‐line analysis of SGR, PR and liver thiamin concentrations exhibited the thiamin requirement in the range of 1.79–3.34 mg kg^?1 diet (0.096–0.179 μg thiamin kJ^?1 gross energy). In experiment II, six casein–gelatin‐based diets (400 g kg^?1 CP; 18.69 kJ g^?1 GE) containing graded levels of pyridoxine (0, 2, 4, 6, 8 and 10 mg kg^?1 diet) were fed to triplicate groups of fish (6.35 ± 0.37 cm; 1.97 ± 0.12 g). Fish fed diet containing 6 mg kg^?1 pyridoxine showed best SGR, FCR, PR, RNA/DNA ratio, Hb, Hct and RBCs, whereas maximum liver pyridoxine concentration was recorded in fish fed 8 mg kg^?1 dietary pyridoxine. Broken‐line analysis of SGR, PR and liver pyridoxine concentrations reflected the pyridoxine requirement from 5.63 to 8.61 mg kg^?1 diet. Data generated during this study would be useful in formulating thiamin‐ and pyridoxine‐balanced feeds for the intensive culture of this fish.     

Sea bream culture in Egypt; status, constraints and potential

Marine fish farming in Egypt began in 1976 with the culture of gilthead sea bream, (Sparus aurata) as this fish was notably adaptable to brackish and marine pond conditions. Today, marine fish and shrimp farms amount to about 19,000 ha, out of which 42% is already in production while the rest, i.e., 58% is still under construction. In 1997, cultured gilthead sea bream production of 2,250 tons made up 3% of the 75,000 tons total aquaculture catch. In polyculture, usually with the grey mullet and sea bass, gilthead sea bream contributed 440 kg ha^–1 to the total yield of 1,700 kg ha^–1 (26%) over a period of 16 months. For the same period, the yield of monoculture ponds averaged 100 kg ha^–1, while in marine cages, yields ranged from 4–10 kg m³. In 1996–1997, fry of 0.25–1 g and fingerlings 1–10 g with a total of 3 million, were collected from the wild and 1 million fry were produced in the three marine hatcheries out of the four existing ones. The development of sea bream culture in Egypt is now severely inhibited by the shortage of seeds and adequate feeds. Exports of both sea bream and sea bass, during 1994–1996 averaged 1,300 tons per year.     

A Minchinia mercenariae‐like parasite infects cockles Cerastoderma edule in Galicia (NW Spain)

The cockle Cerastoderma edule fishery has traditionally been the most important shellfish species in terms of biomass in Galicia (NW Spain). In the course of a survey of the histopathological conditions affecting this species in the Ria of Arousa, a haplosporidan parasite that had not been observed in Galicia was detected in one of the most productive cockle beds of Galicia. Uni‐ and binucleate cells and multinucleate plasmodia were observed in the connective tissue mainly in the digestive area, gills and gonad. The parasite showed low prevalence, and it was not associated with abnormal cockle mortality. Molecular identification showed that this parasite was closely related to the haplosporidan Minchinia mercenariae that had been reported infecting hard clams Mercenaria mercenaria from the Atlantic coast of the United States. The molecular characterization of its SSU rDNA region allowed obtaining a fragment of 1,796 bp showing 98% homology with M. mercenariae parasite. Phylogenetic analysis supported this identification as this parasite was clustered in the same clade as M. mercenariae from the United States and other M. mercenariae‐like sequences from the UK, with bootstrap value of 99%. The occurrence of M. mercenariae‐like parasites infecting molluscs outside the United States is confirmed.     

A novel approach to denitrification processes in a zero-discharge recirculating system for small-scale urban aquaculture

This paper presents an innovative process to solve the nitrate build-up problem in recirculating aquaculture systems (RAS). The novel aspects of the process lie in a denitrification bioreactor system that uses solid cotton wool as the primary carbon source and a unique degassing chamber. In the latter, the water is physically stripped of dissolved gaseous O₂ (by means of a Venturi vacuum tube), and the subsequent denitrification becomes more efficient due to elimination of the problems of oxygen inhibition of denitrification and aerobic consumption of cotton wool. The cotton wool medium also serves as a physical barrier that traps organic particles, which, in turn, act as an additional carbon source for denitrification. Operation in the proposed system gives an extremely low C/N ratio of 0.82 g of cotton wool/g of nitrate N, which contributes to a significant reduction of biofilter volume. The additional advantage of using solid cotton wool as the carbon source is that it does not release organic residuals into the liquid to be recycled. Operation of the system over a long period consistently produced effluents with low nitrate levels (below 10 mg N/l), and there was only a very small need to replace system water. The overall treatment scheme, also incorporating an aerobic nitrification biofilter and a granular filtration device, produced water of excellent quality, i.e., with near-zero levels of nitrite and ammonia, a sufficiently high pH for aquaculture, and low turbidity. The proposed system thus provides a solution for sustainable small-scale, urban aquaculture operation with a very high recovery of water (over 99%) and minimal waste disposal.     

Fertilization by refrigerator stored sperm of the Indian major carp, Labeo calbasu (Hamilton, 1822)

This study reports on the spermatological properties, and on the development of a protocol for refrigerator storage (4°C) of Labeo calbasu (Hamilton, 1822) sperm for artificial breeding. Volume, motility, concentration and pH of the freshly collected sperm were 2.21 ± 0.53 (μL g^?1 of fish weight) (mean ± SD), 95 ± 1 (%), 1.93 ± 0.44 × 10⁹ (cells mL^?1) and 7.56 ± 0.17 respectively. Sperm activation was evaluated at different osmolalities of NaCl solution, and motility ceased completely when osmolality of the extender was ≥287 mOsmol kg^?1. Sperm retained motility for 24, 72 and 108 h, after refrigerator storage when sperm were undiluted, suspended in Alsever's solution and suspended in Alsever's solution containing 5% methanol respectively. Fertilization rate of fresh eggs with sperm stored at 4°C in Alsever's solution and Alsever's solution containing 5% methanol was 77% and 60% with a hatching rate of 60% and 43% respectively. The fertilization and hatching success of the stored sperm suggests potential to use refrigeration for transporting genetic material to hatcheries for artificial breeding of L. calbasu in Bangladesh.     

Effects of metomidate anaesthesia or transfer to pur sea water on plasma parameters in ammonia-exposed Atlantic salmon (Salmo salar L) in sea water

Atlantic salmon (Salmo salar L) postsmolts weighing 150 ± 53 g were exposed to 14–15 mg l^–1 TA-N (total ammonia-N) in sea water in 1 m³ tanks for 24h. Blood samples were then taken A) immediately after the fish were netted from the exposure tanks and stunned by a blow to the head; B) 2–20 min after the fish were transferred to 15 l of an anaesthetic solution of metomidate in ammonia-free sea water; or C) 2–20 min after the fish were transferred to 15 l of ammonia-free sea water. Plasma TA-N level was 18% lower in the anaesthetised fish compared to in the fish sampled directly from the exposure tanks (p 0.05), and accordingly 16% lower in the fish transferred to pure sea water although this difference was not significant (p = 0.07). Plasma glucose level was higher in the fish transferred to pure sea water than in the fish receiving the two other treatments (p 0.05), but plasma urea, osmolality, Na^{+, Cl–, Ca2+ or Mg2+} levels did not vary significantly between the different treatments. Plasma TA-N level increased with time in the fish in the metomidate solution (p 0.02).