Intensification of redclaw crayfish Cherax quadricarinatus culture: II. Growout in a separate cell system

In the process of exploring ways to intensify crayfish culture, a growout system of individual cages (cells) was designed to determine the effects of gender and cell size on the growth of the red claw crayfish Cherax quadricarinatus. Cells of three different diameters—large (25 cm), medium (20 cm) and small (16 cm)—were used. When crayfish were stocked at a mean weight of approximately 10 g, growth rate of males was significantly higher than that of females. The growth rate of the males in the large cells was 0.31±0.14 g/day, while that of the females was 0.18±0.09 g/day. The size of the cell had significant influence on the weight of males. Male crayfish in the large and medium cells grew better than those in the small cells. When males were stocked at a higher mean weight (about 23 g), their mean weight after 206 days was higher in the large cells (69.28±15.72 g) than in the small cells (58.11±12.66 g), suggesting that the growth of large males was also affected by cell size. Regardless of cell size, male animals of this species grew faster than females under conditions of individual cells. This intensive culture method appears to present a powerful improvement in yields, by as much as two orders of magnitude, in comparison with communal cultures.     

Intensification of redclaw crayfish Cherax quadricarinatus culture: I. Hatchery and nursery system

Intensification of an indoor hatchery and nursery system for the Australian redclaw crayfish Cherax quadricarinatus (von Martens) (Decapoda: Parastacidae) was obtained by increasing the surface area available for the crayfish juveniles and by synchronizing the age of the hatchlings held in each tank. The former improvement was facilitated by distributing an artificial seaweed-like material throughout almost the entire volume of small (275 l) hatching tanks. As the number of egg-bearing females was increased from 3 to 8 per hatching tank, the number of juveniles per liter also increased to as many as 6.5 juveniles/l, without reaching an apparent upper limit. The hatchlings were kept in the tanks for 75 days from the day females were found to be gravid and then harvested and graded according to size. The average juvenile weight at harvest was 0.34±0.04 g. The weight distribution of the juvenile males was not significantly different from that of the juvenile females on the day of harvest, and in both the distribution was positively skewed.     

亚硝酸盐对红螯光壳螯虾不同组织免疫相关酶活性及超微结构的影响

应用透射电镜技术,结合生物酶测定,研究了水体中不同浓度亚硝酸盐胁迫下红螯光壳螯虾肝胰腺、鳃和肌肉组织中免疫相关酶的活性变化,以及对肝胰腺和鳃的形态学影响。结果显示,与对照组相比,亚硝酸盐胁迫下,3种组织的ACP、AKP、SOD以及GSH-PX的活性都显著降低(P<0.05);随着亚硝酸盐浓度增加,酶活力呈现降低的趋势;鳃组织Na+,K+-ATPase和Ca2+,Mg2+-ATPase的活性也显示出随亚硝酸盐浓度升高而降低的趋势。超微结构显示,随着亚硝酸盐浓度增加,鳃角质层受损、断裂;上皮细胞排列疏松、空泡化;细胞器变形;鳃腔内也出现空泡化现象,血细胞变形。肝胰腺上皮细胞排列杂乱无章,细胞裂解,空泡化;微绒毛受损、断裂,肝小管间距扩大、结缔组织变得稀薄,血细胞变形;高浓度组R细胞的脂滴减少,核膜解体,细胞膜破裂,空泡化加剧;F细胞的核糖体减少,空泡化加剧,内质网水肿。研究说明亚硝酸盐对红螯光壳螯虾3种组织的免疫相关酶活产生影响,并损伤肝胰腺和鳃的形态学结构,影响其生物学功能。     

Characterisation of cellulase activity in the digestive system of the redclaw crayfish (Cherax quadricarinatus)

Endogenous cellulase activity was identified in the gastric fluid and digestive gland of the redclaw crayfish. Cellulase showed maximal activity from pH 4 to 5 and was stable for up to 2 h at 40°C. Cellulase activity in the digestive gland was unaffected by antibiotic treatment. Taken together these findings suggest a significant endogenous component for redclaw cellulase activity. Partial purification of cellulase activity was performed using anion exchange and gel filtration chromatography. One major and one minor band of activity were identified subsequently by SDS-PAGE and zymography. The molecular weight of the major band was estimated at 40 kDa while the minor band was estimated at 30 kDa. Redclaw cellulase enzymes demonstrated broad substrate specificity, hydrolysing polysaccharides containing β-1,4 and mixed β-1,4 and β-1,3 glycosidic bonds but showed a preference for soluble substrates. Hydrolysis products of cellodextrins of various lengths also showed that the enzymes liberated free glucose. Exposure of redclaw to antibiotics resulted in a dramatic decline in bacterial populations in the gastric contents (>90%) but only a 40% decline in cellulase activity.     

In vivo dry matter and protein digestibility of three plant-derived and four animal-derived feedstuffs and diets for juvenile Australian redclaw, Cherax quadricarinatus

Dry matter and protein digestibility of three plant-derived and four animal-derived feedstuffs and diets in which they were included were evaluated for juvenile Australian redclaw. The ingredients evaluated were: soy paste, textured wheat, sorghum meal, two sardine meals (67% and 58% crude protein), squid meal, and red crab meal. A reference diet was formulated and produced in the CIBNOR nutrition laboratory. Seven experimental diets were then made including 15% of each ingredient in the reference diet. The experiment consists of a single-factor, completely randomized design with five replicates per treatment. Digestibility was measured indirectly, using chromic oxide as a marker. Plant-derived ingredients and the corresponding diets had, in general, a higher digestibility than animal ingredients. Soy paste and sorghum meals, and the diets in which they were included, showed an excellent dry matter (over 87%) and protein (approximately 90%) digestibility. Some of the animal ingredients such as sardine meal 67% CP and squid meal had a good dry matter digestibility (over 80%), but were significantly lower than plant-derived ingredients. The lowest dry matter and protein digestibility was recorded for sardine meal 58% CP and red crab meal. It is concluded that juvenile redclaw are omnivorous and able to efficiently consume diets containing plant- and animal-derived ingredients, but they can digest plant-derived ingredients more efficiently.     

红螯螯虾XO-SG神经细胞的原代培养

本研究采用酶解的方法获得红螯螯虾眼柄XO-SG复合体的单个神经细胞,并依据显微观察对XO-SG神经细胞进行分类,同时利用Leibovitz's L-15等作为基础培养基离体培养解离的神经细胞。目的是建立虾类XO-SG神经细胞的分类标准并确定合适的培养条件,便于在体内外开展神经内分泌系统的调控研究。结果显示,根据神经细胞形态特点,红螯螯虾XO-SG神经内分泌细胞分为6种类型,不同类型的细胞在细胞大小以及显微结构上存在明显差异;建立了红螯螯虾眼柄XO-SG神经元的体外原代培养方法,细胞在改良的L-15培养基中存活状态良好,原代培养的神经细胞可以在体外存活14 d。离体培养过程中,不同类型神经细胞的再生速率存在差异,部分细胞在第2天就出现再生的轴突或树突。再生过程基本可以持续7 d,随后细胞开始萎缩凋亡。本研究为红螯螯虾眼柄神经细胞的分类以及利用神经细胞在体外开展虾类的内分泌代谢和调节机制研究提供了基础依据和研究平台。     

饲料中非蛋白能源物质对红螯光壳螯虾幼虾生长、生理、生化指标的影响

在等蛋白质、等能量基础上,研究碳水化合物与脂类比例(CHO∶L)为10.75∶1、4.81∶1、2.66∶1、1.52∶1和0.87∶1的5组试验饲料对红螯光壳螯虾[初始体质量(1.72±0.01)g]相关生长、生理、生化指标的影响。8周试验结果表明,CHO∶L比例为2.66∶1时,红螯光壳螯虾的增重率、特定生长率和饲料利用率达到最高。高比例的CHO∶L(10.75∶1)和低比例的CHO∶L(0.87∶1)都会显著地抑制(P<0.05)红螯光壳螯虾的生长和饲料的利用。饲料脂肪水平为40～145 g/kg时,虾的脂肪酶和碱性磷酸酶活力显著升高(P<0.05),己糖激酶和丙酮酸激酶活力则呈显著降低趋势(P<0.05)。CHO∶L对虾胃蛋白酶活力影响显著(P<0.01),CHO∶L为2.66∶1和1.52∶1表现出比较高的活力,显著高于(P<0.05)其它试验组。碳水化合物为156.3～360.4 g/kg范围内,虾淀粉酶活力随饲料中碳水化合物的升高而显著升高(P<0.01)。红螯光壳螯虾增重率分别与饲料中碳水化合物和脂肪水平进行二次回归分析得出,红螯光壳螯虾对配合饲料中碳水化合物和脂肪的最适需求量分别为268.28和120.22 g/kg,相对应的CHO∶L为2.20∶1,且红螯光壳螯虾对碳水化合物的利用能力要高于对脂肪的利用。     

Percoll不连续密度梯度离心法分离红螯光壳螯虾血细胞

建立了利用Percoll不连续密度梯度离心分离红螯光壳螯虾血细胞的方法,并对配制分离体系的缓冲液以及分离体系的密度组成进行了优化。结果显示,由20%、65%和100%的Percoll组成的分离体系分离效果最优。在转速为1 810 r/min的条件下离心20 min之后,可将红螯光壳螯虾血细胞分为SGC与GC 2个细胞层。经流式细胞术分析,发现细胞层纯度均在95%以上,细胞死亡比率低于1.5%,可用于后续的细胞功能分析。此方法简单有效,为后续研究螯虾的免疫防御机制及病害防治方法奠定了基础。     

Electrical stimulation of spermatophore extrusion in the freshwater yabby (Cherax destructor)

A technique for collecting spermatophores from male yabbies (Cherax destructor) is described. This technique consists of applying an electrical stimulus of between 5 and 10 mA and 40–50 Hz around the coxa of the fifth walking leg, and was found to have a success rate of 76% in 100 males tested. Furthermore, this approach enabled the collection of spermatophores from intersex individuals, indicating that intersex animals have the ability to function as males.

Using this technique, it was shown that spermatophore development is correlated with water temperature and that it is possible to elicit spermatophores from males in the non-reproductive season simply by raising water temperatures. The ability to non-invasively collect spermatophores from yabbies will facilitate the development of artificial fertilization techniques in this species.     

白斑综合征病毒对红螯光壳螯虾幼虾肝胰腺免疫酶活性及其超微结构的影响

利用生物化学方法和电镜技术,研究人工注射免疫多糖及WSSV对红螯光壳螯虾幼虾肝胰腺POD、LSZ、SOD、PO的活性变化及肝胰腺超微结构的影响。试验分对照组、实验组Ⅰ(注射WSSV)、实验组Ⅱ(注射免疫多糖)、实验组Ⅲ(注射免疫多糖48 h后注射WSSV)4组,结果显示,随着处理时间的增加,实验组Ⅰ与对照组相比POD、PO、LSZ活性均呈现明显降低趋势(P<0.01),而SOD活性呈现先升高后降低的趋势(P<0.01);实验组Ⅱ的螯虾4种酶活性呈现先升后降,与对照组相比酶活性增加(P<0.05);实验组Ⅲ4种酶活性均高于实验组Ⅰ(P<0.05),但与对照组相比SOD、POD、LSZ活性降低(P<0.01)。红螯光壳螯虾幼虾肝胰腺组织由肝小管组成,肝小管由基膜和上皮细胞组成。超微结构显示,对照组螯虾幼虾肝胰腺单层柱状上皮细胞的表面微绒毛排列整齐,各细胞器结构完整;实验组Ⅰ上皮细胞微绒毛受损、断裂,核膜解体,细胞核破裂,粗面内质网断裂;实验组Ⅱ上皮细胞粗面内质网核糖体增多;实验组Ⅲ与实验组Ⅰ相比,细胞核结构完整,粗面内质网肿胀,线粒体部分畸变。结果说明感染WSSV的幼虾肝胰腺形态结构受损,并进一步影响其生物学功能。人工注射免疫多糖能提高幼虾免疫相关酶活性,在一定程度上能抵抗WSSV的侵染。     

氨氮急性胁迫及其毒后恢复对红螯光壳螯虾幼虾相关免疫和代谢指标的影响

应用实时荧光定量PCR技术,结合生物酶和代谢产物测定,研究了氨氮急性胁迫对红螯光壳螯虾幼虾代谢及免疫系统的毒性影响及其毒后恢复情况。实验首先进行3 d的氨氮胁迫,取样后剩余虾移入曝气自来水进行7 d的毒后恢复实验。结果表明,3 d氨氮胁迫后,肌肉ACP、AKP、SOD活性表达均受到显著影响,随着氨氮浓度的升高酶活性分别降低,最高浓度组(16 mg/L)降低为对照组的76%、68%和62%。线粒体MnSOD、胞外Cu/ZnSOD的mRNA表达量也随着氨氮浓度增加而下降,最高浓度组降低至对照组的69%和68%。CAT、GPX活性以及GPX和GST的mRNA表达量变化不显著。肝胰腺中可溶性蛋白和甘油三酯含量随着氨氮浓度升高而降低,最高浓度组分别降低至对照组的72%和59%,AST活性在12 mg/L浓度组显著升高至对照组的134%。7 d恢复期过后,ACP和AKP活性以及各代谢指标恢复到正常水平;而SOD和GPX活性高于对照组。各抗氧化基因的表达量都不同程度高于对照组。实验表明,高浓度氨氮胁迫能抑制部分免疫相关酶的活性及基因表达,对免疫系统造成损害。氨氮胁迫下,红螯光壳螯虾动员蛋白质和脂肪来供能应对胁迫。7 d的恢复时间不足以让红螯光壳螯虾从胁迫中完全恢复,其肌肉仍处于轻度氧化应激状态。     

Partial and total replacement of fish meal with soybean meal and brewer's grains with yeast in practical diets for Australian red claw crayfish Cherax quadricarinatus

Three feeding studies were conducted to evaluate the effects of total replacement of fish meal (FM) with a combination of soybean meal (SBM) and brewer's grains with yeast (BGY) in diets for two separate strains of juvenile Australian red claw crayfish. In Experiment 1, three practical diets were formulated to be isonitrogenous (40% protein) and isocaloric (4.0 kcal available energy/g diet) and contained either 25%, 10%, or 0% fish meal. Variable percentages of SBM (35%, 46.8%, and 79.8%, respectively) and BGY-35 (0%, 30%, and 5%, respectively) replaced the fish meal. In Experiments 2 and 3, four practical diets were formulated to be isonitrogenous (40% protein) and isocaloric (4 kcal available energy/g diet) containing 24% or 0% fish meal. Diet 1 contained 24% fish meal, 23% SBM, and 0% BGY-35. A variable percentage of SBM (56.75%, 47.75%, and 40.75%, respectively) and BGY-35 (10%, 20%, and 30%, respectively) replaced the fish meal in the remaining three diets.

In Experiment 1, after 8 weeks, juvenile red claw fed all three diets had no significant difference (P>0.05) in final weight, percentage weight gain, or survival, which averaged 7.90 g, 3848%, and 83%, respectively. In Experiment 2, after 8 weeks, juveniles fed all four diets had no significant difference in final weight, percentage weight gain, or specific growth rate which averaged 11.46 g, 977%, and 3.08%/day, respectively. Percentage survival was not significantly different among treatments and averaged 79%. In Experiment 3, after 8 weeks, juvenile red claw fed all four diets had no significant difference in final weight, percentage weight gain, or specific growth rate which averaged 16.22 g, 457%, and 2.34%/day, respectively. Percentage survival was not significantly different among treatments and averaged 98%.

These results indicate that fish meal and shrimp meal can be totally replaced with soybean meal and BGY in diets for juvenile red claw crayfish. This may allow for less expensive diets by red claw producers, which may increase profitability.     

Potential fecundity of an introduced population, Keban Dam Lake, Elazı , Turkey, of freshwater crayfish, Astacus leptodactylus leptodactylus (Esch., 1852)

Potential fecundity of an introduced population, Keban Dam Lake, Elazı , Turkey, of freshwater crayfish, Astacus leptodactylus leptodactylus (Esch., 1852), was investigated in the present study. The results showed that there was not a linear relationship between female size and pleopodal egg number. The results also showed that although there is an increase in the mean pleopodal egg number with an increase in size (carapace length, CL), it is not the most important factor affecting potential fecundity in A. leptodactylus (slope=1.9294). Mean pleopodal egg number was 305.93 (S.E.=8.82) for the size range of 47–76 mm CL (N=96). The maximum pleopodal egg number was 588 for the crayfish in a 72-mm CL. The present study showed that Keban Dam Lake population of A. leptodactylus has more potential fecundity than the other populations in Turkey. The egg-bearing capacity of female A. leptodactylus caught from Keban Dam Lake could improve efficiency in controlled hatchery production of juveniles.     

Influence of environmental variables on the distribution of Squatina guggenheim (Chondrichthyes, Squatinidae) in the Argentine–Uruguayan Common Fishing Zone

The environmental variables affecting the spatial distribution of Squatina guggenheim Marini, 1936, an important commercial resource, are unknown. Here the influence of temperature, salinity and depth on the distribution of S. guggenheim in the Southwest Atlantic was analyzed. The species–habitat associations were evaluated for the S. guggenheim population as a whole as well as segregated by sex and by size classes (group 1, 23–44 cm; group 2, 45–74 cm; group 3, 75–91 cm L_T). Sampling took place during four bottom trawl surveys conducted in the Argentine–Uruguayan Common Fishing Zone (AUCFZ) during spring (October 1997) and fall (March 1997, March–April 1998, May–June 1998). The sharks were captured using an Engel bottom trawl and the hydrographical information was obtained using a CTD. Bottom depth was measured with an echo-sounder. The distribution of the population was affected (P ≤ 0.05) by temperature during spring and fall, while it was affected by salinity only in spring. S. guggenheim showed preference for temperatures ranging from 7.0 to 18.5 °C and salinity values ranging from 33.4 to 33.8. Generally, the distribution of males was affected (P ≤ 0.05) by temperature during both seasons, while females were influenced by temperature only in spring. The distribution of both sexes was affected by salinity in spring but not in fall. The distribution of adults sharks (group 3) was more affected by temperature and salinity than that of juveniles sharks (groups 1 and 2). Depth had no effects on the distribution of adults (males or females); however, juveniles belonging to size-group 2 were associated with depth during both spring and fall. High population catches were associated to thermal fronts during all surveys suggesting that these oceanographic structures play an important role as feeding areas for S. guggenheim. A population strategy of spatial segregation by size was proposed and discussed.