Estimates of heritability and genetic correlations for growth‐related traits in the tiger prawn Penaeus monodon

Heritabilities and genetic and phenotypic correlations were estimated for body weight (BW), body length (BL), carapace length (CL), carapace width (CW) and carapace height (CH) of the Penaeus monodon from measurements on progeny at 6 months of age resulting from a nested mating design. Estimation was made on data from 41 full‐sib and 10 half‐sib families. The estimated heritabilities for these traits were 0.13–0.24, and the significantly phenotypic and genetic correlations were 0.81–0.94 and 0.88–1.00, respectively. The present results indicate that genetic improvement through selective breeding conducted on P. monodon might be feasible and would be an efficient method to obtain a positive response to selection.     

Quantitative genetic parameter estimates for size and growth rate traits in Pacific white shrimp, Penaeus vannamei (Boone 1931) when reared indoors

Heritabilities of size traits and growth rate traits, as well as genetic, phenotypic and environmental correlations were estimated at three ages for a captive population of Pacific white shrimp (Penaeus vannamei) grown indoors. A covariate, mean size or mean growth rate during early growth in individual tanks before tagging and mixing, was introduced in the analyses to reduce the error caused by unique previous growth conditions on variance components. Heritabilities of size traits increased with age, with the h² for TL, AL, TWt and Wi1AS being 0.15, 0.20, 0.20 and 0.22, respectively, at 17 weeks, increasing to 0.28, 0.33, 0.34 and 0.35 at 29 weeks of age. Heritabilities of growth rate traits estimated between consecutive growth periods decreased from the first (h² for ΔTL 0.65, ΔAL 0.71, ΔTWt 0.63 and ΔWi1AS 0.84) to the second period (h² for ΔTL 0.34, ΔAL 0.50, ΔTWt 0.54 and ΔWi1AS 0.52). Phenotypic correlations were always larger than genetic correlations for both, size and growth rate traits. Genetic correlations between size traits within age were high (r_G >0.95), but those between the same size trait at different ages decreased as the age difference increased in spite of a consistently high environmental correlation (r_E 0.80–0.85) between the same trait at different ages. Phenotypic and genetic correlation's between the same growth rate trait at the two different growth periods evaluated were negative or zero (r_G TL –0.26, AL –0.24, Wi1AS 0.00) with the exception of total weight (r_G TW 0.35) and the environmental correlations between growth periods were also low (r_E 0.13–0.32).     

Time‐series analysis of native and non‐native crayfish dynamics in the Thames River Basin (south‐eastern England)

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Heritabilities and genetic correlation of shell thickness and shell length growth in a mussel,Mytilus chilensis (Bivalvia:Mytilidae)

Shell thickness in mollusks is generally considered adaptive because of their effects on fitness. However, little is known about the genetic basis of shell thickness. This is important, because the response to selection and the subsequent adaptive microevolution of a trait, such as thickness is only possible when that trait exhibits additive genetic variation. Here, we estimated the narrow‐sense heritability (h²: ratio between additive genetic variance and phenotypic variance) for the traits ‘shell thickness’ and ‘shell length growth’ in a 34‐month‐old cohort of the mussel Mytilus chilensis obtained by using a half‐full sib design and grown in the field. Also, phenotypic and genetic correlations were estimated between both traits. We found that h² showed significant values for shell thickness (0.294 ± 0.194) and length (0.731 ± 0.379). The phenotypic correlation between both traits was positive and significant; however, the genetic correlation between these traits was not. These results suggest both traits can evolve adaptively by selection, but because these traits did not show genetic correlation, it is possible that selection pressure affecting one trait may not affect the other.     

Changes of heritability and genetic correlations in production traits over time in red abalone (Haliotis rufescens) under culture

Red abalone Haliotis rufescens is one of the most valuable mollusks in the international market, but it has a low growth rate. A breeding program is being developed to increase its growth rate in Chile. We estimated the changes in direct heritability (h²), maternal/common environments heritability (m²) and genetic correlations (r_G) of growth traits (shell length and width, total mass, flesh mass and foot protein as an indicator of meat quality) measured during 2 years (every 4 months) from the juvenile stage (27 months) to the adult harvesting age (51 months), in 60 full‐sib red abalone families. Heritabilities for growth traits measured in juveniles and young adults (27–35 months of age), were low (0.07–0.17) and not significant. Initial low h² were associated with significant amounts of maternal/common environmental effects (m² = 0.4). In young adults and abalone near the harvest age (39–51 months of age) h² were much higher (0.32–0.75). These results emphasize the importance of multiple estimations of h² over time. Among meat quality traits, only the h² for the flesh mass for adults at harvesting age was significant (0.15). We observed strong positive r_G (>0.9) between shell sizes (easy to measure) and total and flesh masses (trait more related to market value than shell sizes but harder to measure) for adults at harvesting age. Thus, if the 5% largest 51 month old abalone were selected from the population as broodstock we expect a positively correlated response on flesh mass of 23.4%.     

The effects of hairtail protein hydrolysate–Fe<Superscript>2+</Superscript> complexes on growth and non-specific immune response of red swamp crayfish (<Emphasis Type="Italic">Procambarus clarkii</Emphasis>)

The experiment was conducted to investigate the effects of prepared hairtail protein hydrolysate–Fe²⁺ (PH–Fe²⁺) complexes on growth and non-specific immune responses of crayfish (Procambarus clarkii). The diets with five different levels of PH–Fe²⁺ (200, 400, 600, 800, and 1000 mg/kg) were fed to crayfish for 60 days. The results indicated that the survival rate, weight gain percentage, specific growth rate, and muscle index of crayfish with 400–1000 mg/kg of PH–Fe²⁺ feeding were significantly higher, 9.94–10.10, 8.55–8.72, 0.24–0.29 %/day, and 2.39–3.05 %, respectively, than the control values after 60 days of feeding. Additionally, after 30 days of feeding, 200–400 mg/kg of PH–Fe²⁺ showed no significant (P > 0.05) improvement effect on activities of superoxide dismutase (SOD), phenoloxidase (PO), lysozyme (LSZ), and acid phosphatase (ACP) in serum or hepatopancreas of crayfish. However, significant improvement effects were observed in 800–1000 mg/kg groups. After 60 days of feeding, 400–600 mg/kg of PH–Fe²⁺ significantly (P < 0.05) improved the activity of SOD and LSZ, but did not affect the activity of PO and ACP significantly (P > 0.05). Moreover, the activities of SOD, PO, LSZ, and ACP in serum and hepatopancreas were all significantly enhanced upon treatment with 800–1000 mg/kg of PH–Fe²⁺. For these reasons, PH–Fe²⁺ can be recommended as a supplement in crayfish feed to increase the growth and immunity.     

克氏原螯虾的适宜蛋氨酸需求量

以酪蛋白、明胶、鱼粉、小麦面筋粉和晶体氨基酸为蛋白源配制了6组蛋白质水平为28.25%、能量为16.07 kJ/g的等氮等能的半纯合饲料, 各组蛋氨酸实际含量分别为0.39%、0.53%、0.71%、0.86%、0.98%和1.13%。以初始体质量为(9.80±0.15) g的克氏原螯虾(Proambarus clakii)为试验对象, 每组设4个重复, 每个重复12尾虾。养殖试验于室外网箱(规格为60 cm×60 cm×60 cm)中进行, 饲养周期为56 d。结果表明, 当饲料中蛋氨酸水平由0.39%升高至1.13%时, 克氏原鳌虾的增重率、特定生长率和饲料效率均显著升高(P<0.05)。当蛋氨酸水平为0.86%时, 三者均达到最大值。当蛋氨酸水平进一步升高时, 三者均呈下降趋势。试验各组的成活率为83.33%~91.67%, 但无显著差异(P>0.05)。当蛋氨酸水平为0.86%时, 全虾粗蛋白含量最高, 其显著高于0.39%组(P<0.05)。日粮蛋氨酸水平对全虾的水分、灰分和脂肪含量以及肝胰脏组成和肌肉氨基酸组成均无显著影响(P>0.05)。肌肉粗脂肪含量以蛋氨酸水平0.98%组最低, 其显著低于0.39%组(P<0.05)。饲料中蛋氨酸水平显著影响肠道蛋白酶的活性(P<0.05), 但对脂肪酶和淀粉酶活性均无显著影响(P>0.05)。以增重率为评价指标进行一元二次回归分析, 得出克氏原螯虾的适宜蛋氨酸需求量为0.94%, 占饲料蛋白质的3.36%。本研究通过分析饲料中不同蛋氨酸水平对克氏原螯虾生长、饲料利用、虾体组成、肌肉氨基酸组成和消化酶活性的影响, 确定克氏原螯虾的适宜蛋氨酸需求量, 以期为其人工配合饲料的研制提供基础数据和理论依据。

     

Rapid measurements of fat content in live and slaughtered common carp (<Emphasis Type="Italic">Cyprinus carpio</Emphasis> L.)

The objective of this study on common carp (Cyprinus carpio) was to obtain and predict the first cross-validated data of the fat content on market size carps using a non-invasive or non-destructive method in situ. The carps (1680 ± 388 g; n = 136) used were from a semi-intensive system and were on a different diet (cereal, pelleted and extruded diet). For the evaluation of the fat content, a Fish Fatmeter FM 692 from Distell.com. (FFM) and a manual measurement of back fat height using a digital calliper were used. For the prediction model, the following basic body measurements (variables) were used: total body length, body length, body height, the width of the body, and the circuit of the body. The body weight, weight of intestines, weight of gonads, weight of hepatopancreas, and fillet yield (%) were measured, and the Fulton coefficient was calculated. The study was focussed on evaluating the applicability of these methods and the accuracy of the obtained result, respectively. Results showed that all the rapid methods had a strong correlation. Multiple regression models with forward selection of variables were used throughout. The final prediction model between predicted and observed values for the fat content for FFM and calliper being adjusted index of determination is shown here (R _adj ²  = 0.88; 5 variables and R _adj ²  = 0.91; 7 variables), respectively.     

Effect of irradiance on bioremediation capacity of the red algae Chondrus crispus and Palmaria palmata

To investigate the illuminance requirements for the culture of red algae in finfish effluent, both Chondrus crispus and Palmaria palmata were assessed simultaneously at three irradiances. Apical tips, 3.5 cm length, were stocked at 2 g L^?1 in 1-L glass flasks with enriched seawater in two 24-day experiments, at 10 and 14 °C, respectively. Palmaria grew up to 70 % better and up took more nutrients than Chondrus under five of the six experimental conditions, except at 14 °C and low irradiance (daily photon dose of 3.4 mol photon m^?2 day^?1). Specific growth rate of both species at high irradiance, 13.1 and 17.2 mol photon m^?2 day^?1, at each trial, 10 and 14 °C, respectively, was 40 and 20 % better than at medium irradiance, but nutrient uptake was similar at both medium and high irradiance. Chondrus growth rate was higher during Experiment 2 (14 °C and 17.2 mol photon m^?2 day^?1) than during Experiment 1 (10 °C and 13.1 mol photon m^?2 day^?1), while Palmaria growth rate was similar in both trials, but always significantly higher than Chondrus. In the range 10–14 °C, Palmaria is the best candidate for integration with Atlantic halibut juveniles (Hippoglossus hippoglossus).     

大口黑鲈生长性状的遗传参数和育种值估计

采用最佳线性无偏差预测法(BLUP法)对大口黑鲈(Micropterus salmoides)体质量、体长和体高的遗传参数和育种值进行估计.4月龄和6月龄的体质量遗传力分别为0.29±0.08和0.28±0.10、体长遗传力分别为0.31±0.08和0.26±0.10,6月龄的体高遗传力为0.29±0.10.这些性状的传力都属于中度遗传力(P＜0.01),表明在加性效应控制下,大口黑鲈生长性状具有较大的遗传改良潜力.6月龄的体质量与体长、体质量与体高及体长与体高的遗传相关分别为0.790±0.094、0.820±0.081和0.990±0.001,这些性状之间均表现为高的正遗传相关性(P＜0.01),说明在对体质量进行选择的同时,其他生长性状也可以获得相应的间接选择反应.从不同评定方法的秩相关来看,6月龄时综合育种值与体质量育种值、体长育种值以及体质量育种值与体长育种值的秩相关系数均达到了极显著(P＜0.01),分别为0.998、0.914和0.890,用综合育种值对大口黑鲈的评定名次排序与用单性状育种值排序的差异不大.本研究对大口黑鲈生长性状的遗传参数和育种值进行确定与分析,旨在为该物种的人工选育提供理论依据和技术参考.     

Implications of piscine predator control on the federally listed fountain darter

One strategy for protecting the federally listed fountain darter, Etheostoma fonticola (Jordan & Gilbert), during low flow conditions is the removal of piscine carnivores [in this case, largemouth bass, Micropterus salmoides (Lacepède)]. However, headwater spring communities of the Comal and San Marcos rivers include another potential predator [red swamp crayfish, Procambarus clarkii (Girard)]. Removal of piscine carnivores could produce cascading effects by increasing crayfish consumption of benthic fish. The purpose of this study was to evaluate if piscine carnivore removal will lessen predatory pressure or induce a trophic cascade with crayfish increasing and causing declines in fountain darter. The numbers of fountain darter consumed were quantified among three predator treatments (red swamp crayfish only, largemouth bass only and red swamp crayfish and largemouth bass combined) and vegetation treatments (vegetated and non‐vegetated) at three temperature regimes (18, 22, 27°C). Vegetation had no effect on fountain darter predation. Among temperature trials, largemouth bass only and red swamp crayfish and largemouth bass combined consumed similar numbers of fountain darter, and red swamp crayfish only consumed the least numbers of fountain darter, except at 22°C. Largemouth bass did not consume more red swamp crayfish than fountain darter. Therefore, largemouth bass removal appears to be a viable option for reducing fountain darter predation during periods of low flow.     

Characterization of a novel marine origin aerobic nitrifying–denitrifying bacterium isolated from shrimp culture ponds

A novel marine origin Bacillus subtilis strain H1 isolated from a shrimp culture pond effectively removed NH₄⁺‐N, ‐N and ‐N, with a maximum ammonium, nitrite and nitrate removal rate of 2.35 mg NH₄⁺‐N L^?1 hr^?1 per OD, 9.64 mg ‐N L^?1 hr^?1 per OD and 0.75 mg ‐N L^?1 hr^?1 respectively. The gas chromatography–isotope ratio mass spectrometry results indicated that N₂O was emitted when ¹⁵NH₄Cl, Na¹⁵NO₂ or Na¹⁵NO₃ was used. Additionally, N₂ was also produced when Na¹⁵NO₂ was used. Single‐factor experiments suggested that the optimal conditions for NH₄⁺‐N and ‐N removal were glucose as a carbon source, C/N 15, initial pH 7.5, 30 g/L NaCl, 28°C and a shaking speed of 160 rpm. Orthogonal tests showed that the optimal conditions for NH₄⁺‐N removal were C/N 15, pH 9, 10 g/L NaCl and shaking speed 160 rpm when ammonium chloride was used as the substrate. The optimal conditions for ‐N removal were C/N 10, pH 6, 10 g/L NaCl and a shaking speed of 160 rpm when sodium nitrite was used as the substrate. In summary, B. subtilis strain H1 had highly efficient aerobic nitrifying–denitrifying ability and high adaptability, suggesting that it is potentially valuable to marine aquaculture.     

三角帆蚌紫色选育系1龄阶段内壳色及生长性状的遗传参数估计

采用群体选育辅助种内群体间杂交选育的方法,以内壳色、体质量作为选育性状,经过连续4代的选育获得了紫色选育系F4。本实验以F4为亲本进行繁殖,利用6对微卫星标记,对15个同批繁育的F4母蚌的1龄后代进行亲子鉴定,鉴别出了来自12个父本、15个母本的42个全同胞家系,使用ASREML软件的约束极大似然法对三角帆蚌内壳色及生长性状进行了遗传参数分析。结果显示,内壳色颜色参数L*、a*、b*、dE*的遗传力分别为0.31±0.22、0.11±0.08、0.36±0.18、0.29±0.19,L*、a*、b*之间的遗传相关和表型相关均较低,范围为0.08~0.47和0.04~0.32,L*与dE*相关性最大,遗传相关为-0.94±0.06,表型相关为-0.96±0.01;生长性状壳长、壳高、壳宽、体质量和壳重的遗传力分别为0.24±0.19、0.37±0.27、0.26±0.16、0.26±0.17、0.31±0.19,各性状间遗传相关和表型相关均为正相关,分别为0.71~0.92、0.66~0.94;颜色参数与生长性状的遗传相关和表型相关均很低,为0.02~0.18。三角帆蚌紫色选育系1龄阶段内壳色和生长性状的遗传力多为中高水平,对其继续进行遗传改良预期能够获得良好遗传进展。内壳色与生长性状的相关度很低,无法实现相互选择,体质量与其他生长性状相关均较紧密,表明将内壳色、体质量作为目标性状进行同步选育的方法合理,可实现同时改良壳色及生长性能的目的。     

In vitro monoamine oxidase A and B inhibitory activity and molecular docking simulations of fucoxanthin

Fucoxanthin is the primary carotenoid found in edible seaweeds, such as Eisenia bicyclis, Undaria pinnatifida, and others. The aim of this study was to determine the effectiveness of fucoxanthin against Parkinson’s disease (PD) by inhibiting monoamine oxidase (MAO) A and B because MAO inhibitors are used in early management of PD. A sensitive enzyme-based chemiluminescent assay and kinetics methods were used to investigate the enzyme inhibitory activities and mode of inhibition. A molecular docking simulation was performed to clarify the binding characteristics of fucoxanthin to hMAO-A (2z5x) and hMAO-B (2v5z). Our results suggest that fucoxanthin shows significant inhibitory activity against hMAO-A and hMAO-B with IC₅₀ values of 197.41 ± 2.20 and 211.12 ± 1.17 μM, respectively. Selegiline was used as the positive control (IC₅₀: 10.54 ± 1.25 and 0.128 ± 0.01 μM for hMAO-A and hMAO-B, respectively). The enzyme-based kinetics results demonstrated that fucoxanthin inhibited both hMAOs in a reversible competitive manner. The molecular docking simulation predicted that fucoxanthin exhibits higher binding affinity towards hMAO-A and hMAO-B through hydrogen bonding and hydrophobic interactions. These findings suggest that fucoxanthin is a reversible competitive hMAO inhibitor that could be used to manage PD.     

Effects of partial replacement of fish meal with Spirulina platensis meal in practical diets on growth,survival, body composition,and reproductive performance of three-spot gourami (Trichopodus trichopterus) (Pallas, 1770)

This study investigated the effects of fish meal replacement by Spirulina platensis meal on growth, survival, body biochemical composition, and reproductive performance of Trichopodus trichopterus until the first spawning for 16 weeks. The fish fed dietary algal meal at levels of 2.5, 5, 10, and 20 % against those received fish meal only as control. The results showed that indicators such as belly diameter, feed intake, feed conversion ratio (FCR), and viscerosomatic index were significantly different between treatments with 5 and 10 % algal replacements (P < 0.05). The growth factors including final weight, weight gain, total length, fork length, and body height of fish did not show significant differences (P > 0.05) between the treatments. Feed intake increased up to 10 % replacement level and then decreased, though the best FCR values (0.77–0.79) were obtained with 2.5 and 5 % substitutions. The body lipid content showed a statistically marked decrease (P < 0.05) as a result of the algal replacements, but the amounts of protein and moisture were not significantly (P > 0.05) different between treatments. All fish fed S. platensis meal had greater gonadosomatic indices (19.4–21.85 %) than that of the control in spite of insignificant differences (P > 0.05) in their ovary weights (2.07–2.21 g). Absolute fecundity ranged between 7300 and 12,700 eggs/female with the highest amount in fish fed with replaced S. platensis levels of 2.5–10 %. The second-order polynomial regression analysis between absolute fecundity and substitution levels of algal meal was y = ?0.5319x ² + 106.87x + 7812.9 (R ² = 0.9642), and the optimal substitution level was determined to be 8.13 % for maximum absolute fecundity. Hatching percentages in the control and 20 % replacement were much lower (P < 0.05) than those in the other treatments (78–86 %). Given the relative enhancement of growth parameters and significant improvement in reproductive performance of broodstock three-spot gourami, 8.1–9.6 % S. platensis meal instead of fish meal is recommended in the diets.     

Genetic diversity status of Pacific white shrimp (<Emphasis Type="Italic">Litopenaeus vannamei</Emphasis>) using SSR markers in Iran

Genetic diversity is vital for the maintenance of genetic pool in cultured shrimps. In order to estimate the current status of genetic diversity in Litopenaeus vannamei shrimp in Iran, as an exotic species, a total of 45 individuals from Amiri and Gorgeaj farms in Jask port of Hormozgan province and one hatchery in Gomishan city of Golestan province, were detected using four microsatellite loci. The number of alleles per locus was 5–10, and the mean effective number of alleles (N _e) across populations and loci ranged from 4.834 to 5.148. The overall mean observed heterozygosity (H _o) ranged from 0.450 to 0.479, which was lower than the expected one (0.789–0.794). There was nothing remarkable about any of the allele frequencies across populations or loci. The mean inbreeding coefficient (F _IS) and pairwise genetic differentiation (F _ST) among populations were 41.6 % and 0.133, respectively. The three studied populations departed from Hardy–Weinberg equilibrium (HWE). Analysis of molecular variance revealed 14 % variability among and 86 % within populations. However, considering departing from HWE and the high F _IS and F, the moderate pairwise F _ST values, importance of introducing genetically diverse broodstock and monitoring to control inbreeding is discussed.     

The harvest of the freshwater crayfish <Emphasis Type="Italic">Astacus leptodactylus</Emphasis> Eschscholtz in Turkey: harvest history,impact of crayfish plague,and present distribution of harvested populations

This review focuses on the present distribution of populations of the crayfish Astacus leptodactylus that are harvested in Turkey. It also examines the history of this harvest and the impact that crayfish plague has had on them. Crayfish plague, caused by the fungus-like organism, Aphanomyces astaci Schikora, 1906, is a severe parasite of freshwater crayfish and has caused a lot of damage to A. leptodactylus populations in Turkey since 1984. Turkey was the largest provider of A. leptodactylus to Western Europe from 1970 (or possibly earlier) until 1986. For example, the peak production was reached in the early 1980s, with over 5,000 tonnes being exported in 1984. On the other hand, as a result of the crayfish plague the harvest of A. leptodactylus was reduced severely in most populations in Turkey after 1985. The harvest was only 320 tonnes in 1991. After the occurrence of crayfish plague in Turkey, in order to increase crayfish production uncontrolled A. leptodactylus stockings have been carried out in many waterbodies throughout Turkey. These introductions have caused an increase in the number of A. leptodactylus populations, but exploitation of A. leptodactylus is still under the pressure of the plague, although there has been a steady increase in crayfish production in recent years. The harvest increased to 2,317 tonnes in 2004. Fortunately, among those populations affected by crayfish plague, large amounts of A. leptodactylus can still be harvested from three lakes, ?znik (Bursa), E?irdir (Isparta) and Çivril (Denizli). Thus, it seems that A. leptodactylus has a degree of resistance to crayfish plague. It is therefore interesting to investigate the resistance of A. leptodactylus caught from these populations to crayfish plague.     

Estimation of genetic parameters for growth traits of Japanese flounder <Emphasis Type="Italic">Paralichthys olivaceus</Emphasis> using an animal model

To estimate genetic parameters of growth traits in Japanese flounder Paralichthys olivaceus, full-sib and half-sib families were produced in three consecutive years at the Beidaihe Central Experiment Station in China. Each year 8–28 families were produced. The body weight, body length and body depth at 180, 240, and 360 days of age were measured for 5,224 individuals. Four animal models were used to examine the phenotypic variation of growth traits and were compared using the likelihood ratio test. The results showed that estimates for additive genetic effect heritabilities varied greatly depending on the model, trait and age. The maternal effect had a significant impact on phenotypic variation only for body depth at 180 days of age, which explained 49% of the phenotypic variance. The ratio of full-sib effect to phenotypic variation ranged from 0.09 to 0.22. Growth traits all exhibited low heritability (0.13–0.39), indicating that there is the potential for family selection breeding for these traits in Japanese flounder. Using the full model with the fixed, full-sib family, additive and maternal genetic effects, genetic correlations among the three traits for fish of the same age were estimated to be more than 0.80. Generally, the genetic correlations gradually increased as age increased.     

Estimates of heritabilities and genetic correlations for growth and gonad traits in the sea urchin Strongylocentrotus intermedius

The present study is the first estimate for the sea urchin, Strongylocentrotus intermedius, of genetic parameters for growth and gonad traits during the entire reproductive period. 2165–5764 sea urchins were sampled from 74 to 120 families at six different growth stages. Six hundred individuals were sampled from 20 randomly chosen families at harvest. Coefficients of variation for most growth and gonad traits were high (18.08–78.66%) suggesting a good variation foundation for breeding. Point estimate for heritabilities based on the sire components of variance were moderate to high for test height (0.24–0.39), test diameter (0.21–0.48) and body weight (0.16–0.49). Heritabilities of gonad wet weight, gonad index and gonad moisture at harvest were 0.17, 0.41 and 0.50 respectively (moderate or high). Gonad colour parameters, L^* (lightness) and a^* (redness) have a heritability of 0, while b^* (yellowness) and colour difference ΔE₁ and ΔE₂ have very similar heritabilities of 0.2, 0.18 and 0.21 respectively. Heritabilities of β‐carotene concentration and content were 0.89 and 0.44 respectively. The genetic correlations between the two measured traits ranged from ?0.984 to 0.999. Gonad wet weight, L^*, b^*, β‐carotene concentration and β‐carotene content had significant positive genetic correlations with all the growth traits. However, gonad index, gonad moisture and colour differences ΔE₁ and ΔE₂ had significant negative genetic correlations with growth traits. The present study indicates that growth, gonad yield and most gonad quality traits could be improved by selection with moderate to high potential. Indirect selection should be applied on gonad traits using growth traits as secondary traits. The present study provides important theoretical guidance for future selective breeding programmes for S. intermedius.     

饲料中赖氨酸水平对克氏原螯虾生长、体组成与消化酶活性的影响

克氏原螯虾(Procambarus clarkii)购自盱眙某龙虾养殖场,初始体质量为(7.60±0.01)g。以酪蛋白、明胶、小麦面筋粉和晶体氨基酸为蛋白源配制7组蛋白质水平为28.26%、能量为17.15 kJ.g 1的等氮等能半纯和饲料,各组赖氨酸质量分数分别为0.76%、1.00%、1.22%、1.47%、1.69%、1.89%和2.18%。实验虾分为7组,每组设4个重复,每个重复12尾虾,分别投喂以上7种饲料。养殖实验于室外网箱(规格为60 cm×60 cm×60 cm)中进行,饲养周期为60 d。结果表明,随着饲料中赖氨酸水平的升高,增重率、特定生长率和饲料效率均显著升高(P<0.05),分别在赖氨酸水平1.69%、1.69%和1.22%组时,三者达到最大值;当赖氨酸水平进一步升高,三者均呈下降趋势。各组的成活率为89.58%~97.92%,组间无显著差异(P>0.05)。全虾水分含量以赖氨酸水平1.22%组最低,显著低于0.76%组(P<0.05)。全虾粗蛋白和粗脂肪含量分别以赖氨酸水平1.89%组和1.69%组最高,均显著高于0.76%组(P<0.05)。各组之间的全虾灰分含量、肌肉组成、肌肉氨基酸组成和消化酶活性均无显著差异(P>0.05)。以增重率为评价指标进行一元二次回归分析,得出克氏原螯虾的适宜赖氨酸需求量为1.66%,占饲料蛋白的5.87%。本研究旨在通过确定克氏原螯虾对饲料中赖氨酸的适宜需求量,为其人工配合饲料的研制提供基础数据和理论依据。