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Abstract: Over past decades, the farming of mud crab Scylla paramamosain has expanded rapidly in China. In our previous experiments, the results showed that the mud crab S. paramamosain in China could be divided into northern and southern populations and these two populations had differences in the adaptive capacity to cultivation environmental conditions. In order to verify this, the present study measured and compared the mitochondrial function and metabolic enzyme activity of these two populations during seasonal acclimatization. It was shown that the mitochondrial respiration rates in the gill, hepatopancreas and muscle of the northern population were significantly higher than those of the southern population in winter, spring and summer although the differences in summer were less pronounced than in winter and spring. In winter and spring, both state 2 and 3 mitochondrial respiration rates measured using either succinate or pyruvate+malate as the substrate in the gill of the northern population were consistently significantly higher than those of the southern population. The measurement of metabolic enzyme activity during different seasons showed that for the mitochondrial cytochrome C oxidase in the gill, hepatopancreas and muscle, the differences in activity between the northern and southern populations were in general consistent with those of the mitochondrial function. For example, the mitochondrial cytochrome C oxidase activities in the gill of the northern population were significantly higher than those of the southern population in winter, spring and summer. However, activity of lactate dehydrogenase, pyruvate kinase and hexokinase in the muscle were slightly different between the northern and southern populations. Only in summer the lactate dehydrogenase and pyruvate kinase activities in the muscle of the southern population were significantly higher than those of the northern population. In summary, the results of the present study showed that compared to the southern population, the northern population had a better compensation mechanism in mitochondrial metabolite level during cooler seasons, which might indicate that the northern population adapts better to low temperature than the southern population. Therefore, the temperature for the farming of the southern population and northern population should be different. [Copyright &y& Elsevier]

Abstract: Juvenile crabs are small, frail and frequently molt, which poses a great challenge to individual identification. This study evaluated the use of single and double visible implant elastomer marks in juvenile mud crabs Scylla paramamosain (1.57–2.50cm carapace width). Elastomer was injected ventrally in body sites adjacent to the second, third and fourth pair of pereiopods. After eight weeks, the untagged, single-tagged and double-tagged treatments showed no differences in survival, development or growth. For the three treatments, there were also no differences in the amylase, trypsinase and SOD (superoxide dismutase) activities in the hepatopancreas. However, the lactate dehydrogenase, adenosine triphosphatase and SOD levels in crab muscle where elastomer was implanted were higher than respective muscle in untagged crabs. Although most crabs had gone through three ecdyses, all surviving crabs in the tag treatments retained visible elastomer material. Except for elastomer implanted ventrally adjacent to the fourth, left pereiopod, elastomer at the other five sites were mostly clear and intact during cultivation with no difference between single-tagged and double-tagged treatments. Finally, dissection revealed that tags mainly migrated to the surface of the gill with the degree of tag migration dependent on the depth of injection. [Copyright &y& Elsevier]

Abstract: The antimicrobial peptide scygonadin (Scy) was first isolated from the gonad of Scylla serrata and its gene is predominantly expressed in the ejaculatory duct of adult males. Thus, its function was predicted to be associated with reproductive immunity, but this is still unclear and needs further investigation. In our study, the expression pattern of Scy at different developmental stages of both male and female S. paramamosain was investigated, so that the potential function of this peptide could be examined. Using real-time quantitative PCR, Scy mRNA transcripts were demonstrated obviously in the vulnerable embryos and larvae-zoea I but very weakly detected in the larvae-zoea III, megalops and juveniles. The gene expression pattern showed a decreasing trend during the early developmental stages. The Scy gene had low expression in the ejaculatory duct of small and medium crabs (100g and 200g in weight) whose gonads were underdeveloped. However, the level of Scy expression was significantly increased in large crabs (300g in weight), which had normally become sexually mature at this size. It was further observed that the numbers of Scy mRNA transcripts in sexually mature crabs were significantly more abundant than in immature ones. In addition, the Scy gene was significantly expressed in the ejaculatory duct of mature male crabs during the mating period (April and May) and reached their highest expression in May. Using immunohistochemistry, the Scy protein was strongly detected in the testis and seminal vesicle of small crabs. However, in large crabs, Scy protein was intensively present in more tissues than in small crabs, including the ejaculatory duct, posterior ejaculatory duct, gill and muscle of males, and also in the spermatheca, gill and muscle of females. It is also interesting to note that Scy mRNA transcripts were detected in other crab species and showed similar expression pattern to those in S. paramamosain. This study extended our knowledge concerning the antimicrobial peptide scygonadin, which has its function principally in the ejaculatory duct of males but which may also play a role at different developmental stages of S. paramamosain from embryogenesis to maturation, and is also widely distributed in other crabs. [Copyright &y& Elsevier]