Feeding experiments were conducted using amino acid test diets to determine the optimal dietary requirement for arginine and lysine of the Chinese mitten-handed crab Eriocheir sinensis juvenile. Crab megalopae with an average weight of 6.86 mg were randomly assigned to different tanks and reared on six experimental diets for 25 d. The six experimental diets were formulated for different combinations of arginine (0, 0.4, 0.8, 1.2, 1.6, and 2.0 g per 100-g diet) and lysine (0, 0.3, 0.6, 0.9, 1.2, and 1.5 g per 100-g diets), respectively. Survival and molting frequency were calculated at the termination of feeding trials. Optimal arginine and lysine equirements were determined by the diets at which the highest survival and molting frequency was reached. The highest survival and molting frequency were 41.75% and 2.4, respectively, and were reached when the crabs were fed with 2% arginine. After juveniles were fed with the diets with 2.55% lysine, survival was the highest (44.0%) and the molting frequency was 2.31. We suggest that the requirement of juvenile crabs for arginine is 2.0% in diet or 3.3% of dietary protein, and the requirement for lysine is 2.55% in diet or 4.25% of dietary protein. This study provides critical information in formulating cost-effective aquaculture diets for the Chinese mitten-handed crab juvenile.

Biochemical composition and digestive enzyme activities of eggs during embryonic development were studied in the freshwater prawn, Macrobrachium rosenbergii. Proteins, lipids and carbohydrates were the main components in the embryos of M. rosenbergii. The proteins in yolk were used mainly as the structural substance, whereas the lipids and carbohydrates were used mainly as the energy sources. Protein content generally increased while lipid and carbohydrate contents decreased during the embryonic development. Seventeen amino acids, including eight essential amino acids, were found in every stage of embryonic development. The ratio of the contents of each essential amino acid (EAA) to total essential amino acid (TAA) remained unchanged during the different stages of embryonic development. The proportional content of glutamic acid was the highest among all the amino acids, and leucine content was the highest among the EAAs. The predominant fatty cids, in terms of relative proportion, were C16:0, C18:1n-9, C18:2n-6, C18:0 and C16:1 in each embryonic development stage. The monounsaturates (MUFA) were the preferentially utilized components of the unsaturates (UFA). C18:1n-9c was mainly used as an energy source during embryonic development, whereas C18:3n-3 and ARA mainly acted as the structural substances in embryos. SFA acted as the main energy source during early stages, from fertilized egg to gastrula stage, and MUFA acted as the main energy source from egg nauplius to egg metanauplius stage. HUFA were used mainly as energy sources during late stages. Of the five digestive enzymes assayed, activities of pepsin, trypsin and amylase were relatively high. Activities of pepsin, trypsin, amylase and cellulase increased during both the early and later embryonic stages, but decreased during the middle stages. The activity of lipase decreased after the gastrula stage. The gastrula stage was a special stage of embryonic development where organ anlage came into being. Activities of pepsin, trypsin, amylase and cellulase reached the highest level during the zoea stage. Variations of biochemical compositions and digestive enzyme activities were closely related to events in morphogenesis during the embryonic development of M. rosenbergii.

Antimicrobial peptides (AMPs) are important components of the host innate immune response against microbial invasion. In addition to the previously known four classes of antimicrobial peptides, a fifth class of ntimicrobial peptides has been recently identified to include NK-lysins that have a globular three-dimensional structure and are larger with 74–78 amino acid residues. NK-lysin has been shown to harbor antimicrobial activities gainst a wide spectrum of microorganisms including bacteria, fungi, protozoa, and parasites. To date, NK-lysin genes have been reported from only a limited number of organisms. We previously identified a NK-lysin cDNA in channel catfish. Here we report the identification of two novel types of NK-lysin transcripts in channel catfish. Altogether, three distinct NK-lysin transcripts exist in channel catfish. In this work, their encoding genes were identified, sequenced, and characterized. We provide strong evidence that the catfish NK-lysin gene is tripled in the same genomic neighborhood. All three catfish NK-lysin genes are present in the same genomic region and are tightly linked on the same chromosome, as the same BAC clones harbor all three copies of the NK-lysin genes. All three NK-lysin genes are expressed, but exhibit distinct expression profiles in various tissues. In spite of the existence of a single copy of NK-lysin gene in the human genome, and only a single hit from the pufferfish genome, there are two tripled clusters of NK-lysin genes on chromosome 17 of zebrafish in ddition to one more copy on its chromosome 5. The similarity in the genomic arrangement of the tripled NK-lysin genes in channel catfish and zebrafish suggest similar evolution of NK-lysin genes. © 2005 Elsevier Ltd. All ights reserved.

The goals of this study were to evaluate the acute and sublethal toxicity of copper (Cu2?) on the marine gastropod, Onchidium struma, and to examine the utility of enzymatic parameters as indicators of Cu2? exposure. In a semistatic renewal test, the 96-hour median lethal concentration of Cu2? for O. struma, 74.80 mg/L, was higher than that for other intertidal species. The activities of the antioxidative enzymes, Cu/Zn superoxide dismutase (Cu/ Zn-SOD) and catalase (CAT), and those of the metabolic enzymes-acid phosphatase (ACP), alkaline phosphatase (AKP), glutamic- xaloacetic transaminase (GOT), and glutamic-pyruvic transaminase (GPT) -in both hepatopancreas and muscle were determined after a 1-week exposure to Cu2? (range 1.35 to 4.20 mg/L). The activities of both Cu/Zn-SOD and CAT were higher in hepatopancreas than muscle. In addition, there wasa egative correlation between Cu2? concentration and Cu/Zn-SOD activity in hepatopancreas, whereas a positive correlation was observed for CAT activity. Concentration-dependent changes in ACP and AKP activity showed a similar trend in hepatopancreas, increasing then decreasing and, finally, a slight increase. In contrast, ACP activity was positively correlated with Cu2? across the concentration range tested. In both hepatopancreas and muscle, both GOT and GPT were activated by lower concentrations of Cu2? and inhibited at higher concentrations.

To identify distinctive genes associated with immunity in the Chinese mitten crab (Eriocheir sinensis), an expressed sequence tag (EST) library was constructed from haemocytes of this economically important species. 3118 clones were unidirectionally sequenced and analyzed by homology searches against sequences in the GenBank, KEGG and Uniprot. Significant homology (BLASTX, e-values b10−5) to known genes was found in 488 of the 1039 unique sequences. The automatic functional classification based on KEGG and Gene Ontology revealed 26 putative immune-related genes (2.5% of all unique sequences, 18.9% of all ESTs). These 26 genes coded for enzymes and proteins in the clotting and prophenoloxidase-activating system, antioxidative enzymes, antimicrobial peptides, and pattern recognition molecules. The existence of these molecular processes in the activation of cellular defense in crab has not been previously reported. According to EST abundance, the major immune-related genes were the Kazal-type proteinase inhibitor (337, 11.1% of all ESTs) and the C-type lectin (72, 2.4%). The EST sequences of mitten crab haemocytes provide important information for understanding the evolution of the immune system among crustaceans in general. This study lays the groundwork for development of molecular markers related to disease resistance in the crab.