Juvenile Redclaw Research Articles

Study of Dissolved Glucose Feeding on the Juvenile Redclaw Crayfish (Cherax quadricarinatus) Maintenance

Study of Dissolved Glucose Feeding on the Juvenile Redclaw Crayfish (Cherax quadricarinatus) Maintenance

Effects of Light Spectrum on Survival, Growth, Physiological, and Biochemical Indices of Redclaw Crayfish (Cherax quadricarinatus) Juveniles

The spectrum is a key environmental factor, and light-emitting diodes (LEDs) can influence the growth and development of crustaceans by altering the composition of the spectrum. This study conducted a 30-day experiment to investigate the effects of five LED spectra (red, yellow, blue, green, and white light) on the growth, antioxidant and immune enzyme activities, stress hormone levels, and the expression of α-amylase (α-AMY), ecdysone receptor (EcR) and retinoid X receptor (RXR) genes in juvenile redclaw crayfish (Cherax quadricarinatus). The results show that the survival rate of juveniles is markedly higher in the yellow and red-light groups than in the other three groups (P<0.05). The green light group exhibits the lowest survival rate, yet it demonstrates the highest weight gain rate and specific growth rate. Regarding enzyme activity and hormone levels, the yellow light group shows the lowest malondialdehyde content, with higher superoxide dismutase and acid phosphatase activity than the other groups; no significant differences are observed in lysozyme activity among the groups (P>0.05). The melatonin content in the green and blue light groups is significantly higher than that in the other three groups (P<0.01). In terms of growth gene expression, the expression of α-AMY, EcR, and RXR in juvenile C. quadricarinatus is regulated by the spectrum. In conclusion, when raised under the yellow light spectrum, juvenile C. quadricarinatus displays elevated survival rates, rapid growth, and robust antioxidant and immune defenses. This study provides important technical parameters for optimizing and enhancing the industrial cultivation of juvenile C. quadricarinatus.

A newly isolated strain of Bacillus subtilis W2Z exhibited probiotic effects on juvenile red claw crayfish, Cherax quadricarinatus

Aquaculture traditionally used antibiotics, leading to environmental contamination, food residue, and antibiotic-resistant superbugs. Probiotics offer a promising antibiotic alternative. In this study, a strain of Bacillus subtilis W2Z was isolated from aquaculture environments and can inhibit pathogens in aquaculture food production through chemical compounds. Eight-weeks C. quadricarinatus cultivation experiments revealed that B. subtilis W2Z, as a probiotic, contributes to increasing the yield of red claw crayfish. The supplementation of strain W2Z in the feed enhanced the crayfish's resistance to Aeromonas hydrophila by increasing immune-related enzyme activity and improving intestinal microbiota. B. subtilis W2Z has significant potential as a bioresource for exploring probiotics in crustacean aquaculture. Adding B. subtilis W2Z to C. quadricarinatus feed at a concentration of 1 × 108 to 1 × 109 colony forming unit (CFU)/g is recommended.

Evaluation of Dietary Essential Amino Acid Supplementation on Growth, Digestive Capacity, Antioxidant, and Intestine Health of the Juvenile Redclaw Crayfish, Cherax quadricarinatus.

The present study was an 8-week feeding trial investigating the effects of lysine and threonine supplementation in vegetable-based diets on growth, antioxidative capacity, and gut microbiota of juvenile redclaw crayfish, Cherax quadricarinatus (initial weight 11.52 ± 0.23 g). The lysine and threonine were supplemented to formulate five isonitrogenous (37%) and isolipidic (9%) diets containing 0% (control), 0.2% lysine (L0.2), 0.2% threonine (T0.2), 0.4% lysine (L0.4), and 0.4% threonine (T0.4), respectively. Compared to the control, weight gain rate (WGR) and specific growth rate (SGR) of C. quadricarinatus significantly increased with increasing dietary lysine and threonine supplementation from 0.2% to 0.4% (P < 0.05). Hepatopancreas trypsin activity significantly increased with increasing levels of lysine and threonine in diets (P < 0.05). However, the pepsin, lipase, and amylase activities were not affected by dietary levels of lysine and threonine (P > 0.05). Compared with the control, crayfish in T0.4 and L0.4 showed significantly higher glutathione peroxidase (GPx) activity (P < 0.05), lower alanine aminotransferase (ALT) activity, and lower malondialdehyde (MDA) content (P < 0.05). Supplementation with 0.4% lysine significantly changed the composition of the gut microbiota (P < 0.05), which showed a significantly increased relative abundance of Proteobacteria and decreased Firmicutes, Actinomycetes, and Pontomyces (P < 0.05). The PICRUSt analysis demonstrated that the abundance of the metabolism and cellular processes pathways in the L0.4 group were markedly decreased compared with the control (P < 0.05). Meanwhile, a tighter interaction of the microbiota community in crayfish was observed in the T0.4 experimental group. In conclusion, these results suggested that dietary supplementation with 0.4% threonine could significantly promote growth and improve microbial health in juvenile C. quadricarinatus.

Evaluation of Black Soldier Fly Larvae Meal on Growth, Body Composition, Immune Responses, and Antioxidant Capacity of Redclaw Crayfish (Cherax quadricarinatus) Juveniles

This study investigated the effects of substituting fish meal (FM) with black soldier fly (Hermetia illucens) meal (BSM) on the growth performance, body composition, immune response, and antioxidant enzyme activity of juvenile redclaw crayfish (Cherax quadricarinatus). Four isonitrogenous (41%) and isolipidic (11%) diets (i.e., FM substitutes) were formulated from BSM prepared using larvae that were fed soybean meal (BSM-S), fishery byproducts (BSM-F), or pitaya (BSM-P). The experimental diets were fed twice daily to triplicate groups of juvenile redclaw crayfish (0.56 ± 0.04 g). After the feed trial, the FM and BSM-F groups exhibited significantly lower feed conversion ratios and significantly higher weight gain; specific growth rates; and concentrations of saturated fatty acids, highly unsaturated fatty acids, eicosapentaenoic acid, and docosahexaenoic acid in the muscle. Among the tested groups, the BSM-F group exhibited significantly enhanced immune responses and increased antioxidant enzyme activity (i.e., superoxide dismutase, phenoloxidase, and glutathione peroxidase); the BSM-P group exhibited a significantly higher feed intake and hepatopancreatic index; and the FM group exhibited a significantly higher muscle body index and apparent digestibility for the dry matter of crude protein. The findings indicate that the juvenile redclaw crayfish fed BSM-F achieved the highest weight gain among the groups.

Methodology for assessing the food attractiveness of feeding objects on the example of juvenile Australian red claw crayfish

The aim of the work: to identify behavioral responses that make it possible to characterize the food attractiveness of potential feeding objects for juveniles of the crayfish Cherax quadricarinatus.Used methods: the study was conducted on the juvenile Australian red-clawed crayfish C. quadricarinatus, in the aquarium room of aquaculture invertebrate department at VNIRO. 11 types of feeding objects of plant and 4 types of animal origin were studied, as well as TetraWaferMix compound feed as a control. A total of 616 experiments were performed.Newness: on the juveniles of the Australian red-clawed crayfish C. quadricarinatus, the methodology for assessing the nutritional attractiveness of feeding objects by the nature of behavior during feed consumption was tested.Result: the experiments conducted showed that a large proportion of individuals who threw, crumbled, held food with their oral limbs for a long time without attempting to mechanical processing it or did not eat the food, indicates its unsatisfactory nutritional qualities. The time spent by crayfish on eating food depends on the hardness of the proposed components, the rate of their softening in water, the size of individuals and therefore cannot directly characterize the nutritional attractiveness of the feed. Most of the proposed forage objects (11 out of 15) had attractive nutritional characteristics for juveniles of C. quadricarinatus crayfish. The most active juveniles consumed animal feed (larvae of Chironomus sp. and Hermetia illucens, squid meat, Gammarus sp.), and among the feeds of plant origin, the seeds of oats, wheat and fried buckwheat, as well as beets and potatoes had the greatest attractiveness.

Effects of dietary chitosan oligosaccharide on the growth, intestinal microbiota and immunity of juvenile red claw crayfish (Cherax quadricarinatus)

This study aimed to evaluate the potential benefits of chitosan oligosaccharide (COS) on red claw crayfish (Cherax quadricarinatus) and explore its underlying mechanisms. The crayfish were randomly divided into six groups, and the diets were supplemented with COS at levels of 0 (C0), 0.2 (C1), 0.4 (C2), 0.6 (C3), 0.8 (C4), and 1 (C5) g kg−1. Treatment with COS significantly improved the growth performance of the crayfish with a higher weight gain rate (WGR) and specific growth rate (SGR) in the C2 group compared to the C0 group. Additionally, the content of crude protein in the crayfish muscles in the C1 group was significantly higher than that of the C0 group. Regarding non-specific immunity, the activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), and alkaline phosphatase (AKP), and the levels of expression of the genes related to immunity (SOD; anti-lipopolysaccharide factor [ALF]; thioredoxin1 [Trx1]; C-type lysozyme, [C-LZM]; and GSH-Px) in the hepatopancreas and hemolymph increased significantly (P < 0.05) after supplementation with 0.4 g kg−1 of COS, while the content of malondialdehyde (MDA) decreased (P < 0.05). The survival rate of C. quadricarinatus increased (P < 0.05) in the C2, C3, C4, and C5 groups after the challenge with Aeromonas hydrophila. This study found that COS has the potential to modulate the composition of the intestinal microbiota and significantly reduce the abundance of species of the phylum Proteobacteria and the genera Aeromonas and Vibrio in the gut of C. quadricarinatus, while the abundance of bacteria in the phylum Firmicutes and the genus Candidatus_Hepatoplasma improved significantly. This study suggests that the inclusion of COS in the diet of C. quadricarinatus can enhance growth, boost immunity, and increase resistance to infection with A. hydrophila, especially when supplemented at 0.4–0.8 g kg−1.

Response of growth performance, antioxidant capacity, and gut microbiota to dietary cholesterol and lecithin in the juvenile Redclaw crayfish, Cherax quadricarinatus

Dietary cholesterol and lecithin are two essential nutrients for the growth and health of crustaceans. A 56-day feeding trial was carried out to evaluate the effects of dietary cholesterol and lecithin on the growth performance, antioxidant capacity, intestinal digestive enzymes, and gut microbiota of the Redclaw crayfish, Cherax quadricarinatus. The crayfish (initial average weight 11.39 ± 0.28 g) were fed with six experimental diets formulated with different contents of cholesterol (0.5% and 1%) and lecithin (1%, 2%, and 3%). No additional cholesterol (0%) and lecithin (0%) were added to the diet of the control group. Crayfish fed the diet with 0.5% cholesterol and 2% lecithin improved growth performance, antioxidant capacity, and intestinal digestive enzyme activities than crayfish fed with other diets. Survival, condition factor, hepatosomatic index, and whole-body proximate composition of crayfish were not significantly affected by different dietary cholesterol and lecithin levels. The Proteobacteria, Firmicutes, and Actinobacteria dominate the gut microbiota community of C. quadricarinatus. In diets with 0.5% cholesterol and 2% lecithin, there were more positive connections and a more complex network structure, which may reduce the risk of pathogen infection. Overall, the combination of 0.5% cholesterol and 2% lecithin in C. quadricarinatus diets was optimal.

Effects of dietary Radix bupleuri root extract on the growth, muscle composition, histology, immune responses and microcystin-LR stress resistance of juvenile red claw crayfish (Cherax quadricarinatus)

The current study was conducted to determine the effects of dietary Radix bupleuri root extract (RBE) on the growth performance, muscle composition, immune responses, and microcystin-LR (MC-LR) stress resistance of juvenile red claw crayfish (Cherax quadricarinatus). Crayfish (0.28 ± 0.02 g) were fed experimental diets containing graded RBE levels as 0 (Diet 1), 0.2 (Diet 2), 0.4 (Diet 3), 0.6 (Diet 4), 0.8 (Diet 5) and 1.6 (Diet 6) g/kg RBE for 8 weeks. The results showed that specific growth rate (SGR) and weight gain rate (WGR) were significantly increased in the Diet 4 and Diet 5 groups. The content of muscle crude protein was significantly increased in the Diet 4 and Diet 5 groups, and the crude lipid content was significantly decreased in the Diet 5 group. Dietary RBE did not alter the structure of the hepatopancreas. Total antioxidant capacity (T-AOC) and superoxide dismutase (SOD) activities in hepatopancreas and plasma were significantly increased in Diet 4 and Diet 5 groups compared to the control group, while the malondialdehyde (MDA) content in hepatopancreas and plasma was significantly decreased in the Diet 5 group. Plasma alkaline phosphatase (AKP) activity was significantly higher in the Diet 3, Diet 4, Diet 5 and Diet 6 groups. Hepatopancreas and plasma PO activities were significantly increased in Diet 4 and Diet 5 groups. The mRNA levels of extracellular copper/zinc superoxide dismutase (ecCu, Zn-SOD), hemocyanin, C-type lysozyme (C-LZM), GPx, and selenium-dependent glutathione peroxidase (Se-GPx) were significantly up-regulated in the hepatopancreas of crayfish fed Diet 5 than those of the control group. After MC-LR challenge, the survival rates of crayfish in the Diet 4 and Diet 5 groups were significantly higher than the control group. The findings suggest that 0.6–0.8 g/kg of RBE can improve growth and muscle composition and enhance immunity and microcystin-LR resistance.

Effects of eggshell and seashell powder as natural dietary calcium supplements on growth, molting frequency, and carapace calcium composition of juvenile red claw crayfish, Cherax quadricarinatus.

The growth performance of red claw crayfish, Cherax quadricarinatus, fed diets with different sources and concentrations of natural calcium was evaluated. Formulated diets containing 30% protein and 8% lipid were prepared using supplementation of 0 (control), 3%, 6%, 9% eggshell, and 6% seashell. C. quadricarinatus juveniles with an average total weight of 0.21 ± 0.01 g and length of 25.0 ± 0.10 mm were obtained from ten ovigerous females bred in captivity. An aquarium with a size of 0.72 m² was divided into eight compartments with an area of 0.09 m² per compartment and was individually stocked with juvenile crayfish. A total of eight juvenile crayfish were used per dietary treatment. There were five dietary treatments in total and each of these treatments were replicated three times. The addition of eggshell and seashell powder exerted positive effects on the growth performance, molting frequency, and survival of the crayfish. Crayfish fed with a 6% eggshell-supplemented diet exhibited the best overall growth performance. The calcium percentage of the carapace increased with the increase in calcium content of the diets. Meanwhile, the performance of diets comprising eggshells and seashells was not significantly different (P > 0.05). Considering the low cost and abundance of eggshells, the addition of 6% of this product to the diet is recommended for the best growth of juvenile C. quadricarinatus.

The effectiveness of using the microbial synthesis protein “Gaprin” in feeding juvenile Australian red-clawed crayfish

In the conditions of the scientific center “Breeding valuable breeds of sturgeon” of the Volgograd State Agrarian University, the effectiveness of replacing 75% of fishmeal in the feed for juvenile Australian red claw crayfish with microbial protein - haprin has been experimentally proven. The influence of experimental feeds on weight gain, linear indicators and survival of individuals was studied, and their economic efficiency was determined. Practical recommendations have been developed to allow the implementation of the developed recipe at aquaculture enterprises containing Australian red-claw crayfish.

Effects of Dietary Eucommia ulmoides Leaf Extract on Growth, Muscle Composition, Hepatopancreas Histology, Immune Responses and Microcystin-LR Resistance of Juvenile Red Claw Crayfish (Cherax quadricarinatus)

The objective of the present study was to investigate the effects of different doses of dietary Eucommia ulmoides leaf extract (ELE) on juvenile red claw crayfish (Cherax quadricarinatus). A total number of 720 red claw crayfish (initial body weight of 0.24 ± 0.01 g) were randomly assigned to six groups and fed diets containing 0 (Diet 1), 0.5 (Diet 2), 1 (Diet 3), 2 (Diet 4), 4 (Diet 5) and 10 (Diet 6) g dry weight (dw) ELE kg (dw)−1 diets for eight weeks and challenged with microcystin-LR stress. The results indicated that dietary supplementation with 1–2 g dw ELE kg (dw)−1 diet could significantly improve the weight gain rate (WGR) and specific growth rate (SGR) of crayfish. Muscle crude protein contents of crayfish fed Diet 2, Diet 3, and Diet 4 were significantly higher than those of the control group. Compared with the control group, dietary ELE could increase total antioxidant capacity (T-AOC), superoxide dismutase (SOD), glutathione peroxidase (GPx), acid phosphatase (ACP), alkaline phosphatase (AKP), and phenoloxidase (PO) activities and decrease malondialdehyde (MDA) level of crayfish. Dietary ELE significantly increased the relative expression levels of SOD, thioredoxin 1 (TRX1), GPx, selenium-dependent glutathione peroxidase (Se-GPx), cytochrome P450 (CYP450), anti-lipopolysaccharide factor (ALF) and C-type lysozyme (C-LZM) mRNA of crayfish compared with the control group during the feeding experiment. When subjected to MC-LR stress for 48 h, the mRNA expression levels of SOD, GPx, Se-GPx, glutathione-s-transferase 1 (GST1), ALF, hemocyanin (HEM), and C-LZM in the hepatopancreas could be improved to varying degrees compared with the Diet 1. Supplementation of 1–2 g dw ELE kg (dw)−1 diet could improve the survival rate (SR) of crayfish under MC-LR stress. These results indicated that dietary ELE (1–2 g dw ELE kg (dw)−1 diet) could improve the growth performance, muscle protein, and non-specific immune response and increase the SR of crayfish under MC-LR stress by regulating the mRNA expression levels of the immune- and antioxidant-related genes.

EFFECTS OF DIFFERENT MINERAL INCLUSIONS IN ANCHOVY BYPRODUCT BASED FEEDS ON GROWTH PERFORMANCE OF RED CLAW CRAYFISH, Cherax quadricarinatus

The purpose of this study was to evaluate the effects of different mineral inclusion in anchovy by-product (ABP) based feeds on the growth performance of red claw crayfish juveniles, Cherax quadricarinatus. A total of five experimental feeds with the inclusion of different mineral levels from 0-2.0% of the diet (M0, M0.5, M1.0, M1.5, &amp; M2.0%) were fed to triplicate groups of 12 juvenile red claw crayfish with an average initial body weight of 2.20±0.10 g. There was no significant difference in terms of final body weight (g), final length (cm), weight gain (%), length gain (%), specific growth rate (%/d), and survival rate (%) of the juvenile red claw crayfish at the end of the feeding trial. Feed conversion ratio ranged from 1.60 (M0.5) to 1.76 (M1.0). Similar to the growth performance, the molting frequency was not affected by the different mineral inclusions in the feeds. Mineral inclusion in the feeds based on ABP can be reduced up to 0%, at least in a short culture period, and higher possibility of including minerals less than 2% in the feeds for juvenile red claw crayfish in a long-term culture period. Considering the good growth and survival of juvenile red claw crayfish in all treatments, the use of ABP as a source of protein and mineral in feeds for juvenile red claw crayfish is highly recommended as this will reduce the feed cost due to the much lower price of ABP. It can be concluded that the anchovy by-product meal used in the present study is a high potential ingredient to supply dietary protein and minerals in the formulated feeds for juvenile red claw crayfish

The Optimum Lipid Level for the Juvenile Redclaw Crayfish Cherax quadricarinatus: Practical Diets with Soybean Oil as the Lipid Source.

As a new species in aquaculture, the lipid nutrition requirement for the juvenile redclaw crayfish Cherax quadricarinatus on a dietary basis on a practical formula needs to be evaluated accurately. In this study, the optimum dietary lipid level was explained by analyzing the growth performance, antioxidant state, lipid metabolism, and gut microbiota of C. quadricarinatus after an eight-week cultivation trial. Six diets with different soybean oil levels (named L0, L2, L4, L6, L8, and L10) were fed to C. quadricarinatus (11.39 ± 0.28 g). The results indicated that the specific growth rate and weight gain of crayfish fed the L4 and L6 diets were significantly higher than those of the other groups (P < 0.05). By the analysis of a second-order polynomial regression model according to growth performance (weight gain rate), the optimum lipid level in a practical diet for juvenile C. quadricarinatus was 9.67%. The survival, condition factor, and hepatosomatic index of crayfish were not significantly affected by dietary oil levels (P > 0.05). As the level of dietary lipids increased, the total antioxidant capacity and glutathione peroxidase activity in serum showed a tendency to rise and then fall and the enzyme activity was highest in crayfish fed the L6 diet. Gut lipase and pepsin activities showed the highest value in crayfish fed the L6 diet. There was no significant difference in acetyl-CoA carboxylase and carnitine palmitoyltransferase-1 contents in crayfish among all the groups (P > 0.05). The relative abundance of Proteobacteria in the phylum and Citrobacter in the genus showed a significant decrease in crayfish of the L10 diet, while the relative abundance of Firmicutes in the phylum markedly increased compared to that of the other groups (P < 0.05). In summary, the results indicated that the 10.39% (L6 diet) dietary lipid level could induce better growth performance, antioxidant ability, and digestive enzyme activity. Most of the fatty acid composition of muscle is not closely related to the fatty acid composition of the diet. Moreover, the composition and diversity of the gut microbiota of C. quadricarinatus were changed by high dietary lipid levels.

Efficiency assessment of the use of compound feeds with protein different levels for juveniles Australian red claw crayfish in RAS conditions

The aim of the work is to investigate the effect of compound feeds with different levels of protein on the growth of juveniles of the Australian red claw crayfish Cherax quadricarinatus. Used methods: To solve this problem, two experiments were carried out in the aquariums of aquaculture invertebrate department at VNIRO: the first was on juveniles weighing 0.017 ± 0.004 g and 0.87 ± 0.08 mm long; the second one was on juveniles weighing 0.31 ± 0.14 g and 23.7 ± 3.9 mm long. The duration of the experiments was 30 and 40 days, respectively. Feeding of juveniles was carried out with three variants of compound feed recipes with an estimated protein content of 25 %, 35 % and 45 %. The main part of the formulations consisted of components of plant origin. Tetra Wafer Mix food for fish and crustaceans (Germany) with a protein content of 45 % was used as a control. The duration of the experiments was 30 and 40 days, respectively. Feeding of juveniles was carried out with three variants of compound feed recipes with an estimated protein content of 25 %, 35 % and 45 %. The main part of the formulations consisted of components of plant origin. Tetra Wafer Mix food for fish and crustaceans (Germany) with a protein content of 45 % was used as a control. Newness: Development of a feed formulation for rearing juveniles of the Australian red claw crayfish in recirculating aquaculture systems (RAS). Results: These experiments showed that the growth rate of juvenile Australian red claw crayfish is directly dependent on the proportion of protein in the feed. It was established that the relative content of protein in the muscles of crayfish depends on its content in compound feed. An analysis of our own and published data indicates that feeds with protein content below 35 % cannot be recommended for growing of juveniles’ Australian red claw crayfish. Feeds with a protein content of 45 % are optimal for the growth of juveniles. It was established that the effectiveness of compound feeds depends not only on the protein content and energy value, but also on their taste attractiveness. Practical significance: The obtained results will be used in the development of mixed feed for juveniles Australian red claw crayfish.

Changes of lipid composition and fatty acid content in the hepatopancreas and expression of FABP before and after molting in red claw crayfish (Cherax quadricarinatus)

AbstractTo explore energy utilization during molting stage, matured and juvenile red claw crayfish were selected to determine changes in lipid composition and fatty acid contents of hepatopancreas. Moreover, the expression of the fatty acid binding protein (FABP) gene was determined to verify changes of fatty acids at the molecular level. Results showed that after molting, the crude lipid content was significantly lower than before molting (p &lt;.05). Among them, the triglyceride content in the hepatopancreas showed no significant differences both before and after molting. The cholesterol content only increased significantly after the matured red claw crayfish had molted. Phospholipids of matured red claw crayfish decreased significantly after molting, but increased significantly after molting in juvenile (p &lt;.05). Saturated fatty acid content did not differ significantly before and after molting in matured red claw crayfish, while it increased after molting in juveniles. The monounsaturated fatty acid content increased, while polyunsaturated fatty acid content decreased significantly after molting (p &lt;.05). The expression of FABP was consistent with the phospholipids change trend of both matured and juvenile red claw crayfish, which may be the molecular indicator of phospholipids during the molting stage. The specific lipid metabolism pathway still needs further exploration.

Effects of dietary trehalose on growth, trehalose content, non-specific immunity, gene expression and desiccation resistance of juvenile red claw crayfish (Cherax quadricarinatus)

This study was performed to investigate the effects of dietary trehalose on growth, muscle composition, non-specific immune responses, gene expression and desiccation resistance of juvenile red claw crayfish (Cherax quadricarinatus). A total of 540 (body weight of 0.41 ± 0.05) crayfish were randomly divided into six groups for a feeding experiment. Six diets with trehalose levels at 0 (Diet 1), 1 (Diet 2), 2 (Diet 3), 5 (Diet 4), 10 (Diet 5) and 15 (Diet 6) g kg−1 were prepared to feed juvenile red claw crayfish for 8 weeks. The results showed that the weight gain rate (WGR) and specific growth rate (SGR) of crayfish in Diet 4, Diet 5 and Diet 6 groups were significantly improved compared with the control group (Diet 1). Muscle crude protein contents of crayfish fed Diet 4, Diet 5 and Diet 6 were significantly higher than those of the control group. The activities of superoxide dismutase (SOD) and alkaline phosphatase (AKP) in hepatopancreas and hemolymph of crayfish for Diet 4, Diet 5, and Diet 6 groups were significantly increased while malondialdehyde (MDA) content was significantly reduced when compared with the control. The total antioxidant capacity (T-AOC), catalase (CAT) and glutathione peroxidase (GPx) activities in the hepatopancreas and hemolymph of crayfish fed Diet 5 and Diet 6 were significantly higher than those in the control group. However, acid phosphatase (ACP) activity was not significantly different among all experimental groups. The hepatopancreas and intestine trehalose contents of crayfish showed an upward trend with the increase of dietary trehalose levels. Compared with the control group, supplementation of 5–15 g kg−1 trehalose in the feed up-regulated the expression levels of GPx, C-type lysozyme (C-LZM), antilipolysacchride factor (ALF), facilitated trehalose transporter homolog isoform X2 (Tret1-2) and facilitated trehalose transporter isoform X4 (Tret1-4) mRNA. In addition, supplementation of 5–15 g kg−1 trehalose in the feed could improve the survival rate of red claw crayfish under desiccation stress. These results suggested that supplementation of 5–15 g kg−1 trehalose in feed could significantly improve the growth performance, muscle protein, non-specific immunity and desiccation resistance of juvenile red claw crayfish.

Growth and health status of the red claw crayfish, cherax quadricarinatus , fed diets with four typical plant protein sources as a replacement for fish meal

Four isonitrogenous (350 g/kg protein) diets were formulated for juvenile red claw crayfish, Cherax quadricarinatus, with half of the dietary fish meal replaced by four commonly used plant protein sources (cottonseed meal, soybean meal, rapeseed meal and peanut meal). A diet without fish meal replacement was used as a control. An eight-week growth trial was conducted to evaluate the growth and health of crayfish juveniles (6.71 ± 0.08 g) fed diets containing the five different protein sources. The weight gain and specific growth rate significantly decreased in the crayfish fed the peanut meal diet compared with those fed the control diet. Survival, hepatosomatic index and whole-body proximate compositions were not significantly influenced by different dietary plant protein sources. Intestinal damage is accompanied by higher activities of glutathione peroxidase, alanine aminotransferase and aspartate aminotransferase, and decreased lipase activities were observed in the crayfish fed the peanut meal diet. Crayfish fed the rapeseed diet also showed the detached peritrophic membrane and the lower lipase activities than those in control. Moreover, the malondialdehyde content increased and acid phosphatase activity decreased in the haemolymph of crayfish fed the soybean meal diet compared with those fed the control diet. Compared with those fed the control diet, the significantly increased valine contents, the activities of alkaline phosphatase and amylase were found in the crayfish fed the cottonseed meal diet. All these results suggest that soybean meal, rapeseed meal and peanut meal were not suitable substitute sources of plant protein for fish meal because of their adverse influences. On the contrary, cottonseed meal can be a good choice for fish meal replacement in the diet of juvenile Cherax quadricarinatus, as it does not have adverse effects on growth and could even increase amino acid nutrition, immunity and digestion.

Monosex male formation of juvenile redclaw crayfish using natural steroid hormone from gamma sea cucumber and different doses of honey bee

In a new commercial commodity aquaculture, tropical freshwater crayfish Cherax quadricarinatus, it is known that female has a slower growth rate than male. One way to increase production rate is through monosex cultures comprising all-male population by using genital reversion technique. This biotechnology method can be applied by using hormones and natural products. The natural hormones extracted from gamma sea cucumber, Stichopus variegatus has bioactive substances including steroid compounds, while honey bee contains chrysin compounds that act as aromatase inhibitors. Therefore, the combination of both substances expected can increase in testosterone level and accelerate production in the male monosex population of juvenile crayfish. The purpose of the study is to determine the most effective dose of honey bee in masculinization of juvenile freshwater crayfish combined with 2 mg. L−1 steroid extract of gamma sea cucumber. Furthermore, a Completely Randomized Design (CRD) was designed in the experiment with five different dose of honey bee treatment and dipping method in 2 mg. L−1 steroid extract of gamma sea cucumber for 18 h. Each treatment with four replications. The highest male formation was found in the dose of 20 ml. L− 1 honey bee at 83.75% and the lowest was in control. The present of honey bee at different doses in 2 mg. L−1 of gamma steroid extract did not significantly give an effect on percentage of female, intersex formation, survival, and growth rate of juvenile redclaw crayfish.

Growth, antioxidant capacity, intestine histology and lipid metabolism of juvenile red claw crayfish, Cherax quadricarinatus , fed different lipid sources

Growth, antioxidant capacity, intestine histology and lipid metabolism of juvenile red claw crayfish, <i>Cherax quadricarinatus</i> , fed different lipid sources