Inhibitory effects of the androgenic gland on ovarian development in the mud crab Scylla paramamosain

Isolation and characterization of androgenic hormone in decapod crustaceans depend on an effective bioassay of its action. In the present study, the effect of androgenic gland on ovarian development in the mud crab Scylla paramamosain was investigated with a view to develop a bioassay for androgenic hormone. Ovarian regression with degeneration of oocytes occurred in some female crabs implanted with androgenic gland in vivo. In vitro incubation of ovarian tissues at secondary vitellogenesis in extract of androgenic gland resulted in a significant decrease in amino acid uptake by the tissues. We propose that this inhibitory effect could be established as an effective bioassay for the isolation of androgenic hormone in the mud crab. (c) 2005 Published by Elsevier Inc.

Improvement of polyploidy induction in Eriocheir sinensis

An incubating temperature of 15 degreesC is used to induce triploidy in Etiocheir sinensis through inhibition of the release of polar body H, and that of 18 degreesC to induce tetraploidy through inhibition of the first cleavage. Flow cytometry is used to identify the ploidy in different developmental stages. For induction of triploidy in fertilized eggs in vitro, the highest induction rate observed in blastula by cytochalasin B, 6-DMAP and KCI is 49.1%, 51.7% and 77.5%, respectively. In the KCI treatment of pregnant crabs with the fertilized eggs, the highest triploid induction rate observed in the zoea is 85.3%. For induction of tetraploidy, the highest induction rate observed in the blastula by cytochaslasin 13, 6-DMAP and KCI is 50.3%, 54.9% and 79.8% respectively. In the KCI treatment of pregnant crabs with the fertilized eggs, the highest induction rate in zoea is 27.3%. Through this study such difficulty as in vitro culture is overcome. Triploid zoea Etiocheir sinensis has been developed for the first time. The induction rate of tetraploid zoea has also been greatly improved.

Complete mitochondrial genome of the Asian paddle crab Charybdis japonica (Crustacea: Decapoda: Portunidae): gene rearrangement of the marine brachyurans and phylogenetic considerations of the decapods

Given the commercial and ecological importance of the Asian paddle crab, Charybdis japonica, there is a clearly need for genetic and molecular research on this species. Here, we present the complete mitochondrial genome sequence of C. japonica, determined by the long-polymerase chain reaction and primer walking sequencing method. The entire genome is 15,738 bp in length, encoding a standard set of 13 protein-coding genes, two ribosomal RNA genes, and 22 transfer RNA genes, plus the putative control region, which is typical for metazoans. The total A+T content of the genome is 69.2%, lower than the other brachyuran crabs except for Callinectes sapidus. The gene order is identical to the published marine brachyurans and differs from the ancestral pancrustacean order by only the position of the tRNA (His) gene. Phylogenetic analyses using the concatenated nucleotide and amino acid sequences of 13 protein-coding genes strongly support the monophyly of Dendrobranchiata and Pleocyemata, which is consistent with the previous taxonomic classification. However, the systematic status of Charybdis within subfamily Thalamitinae of family Portunidae is not supported. C. japonica, as the first species of Charybdis with complete mitochondrial genome available, will provide important information on both genomics and molecular ecology of the group.

Molecular cloning and characterization of a serine proteinase homolog prophenoloxidase-activating factor in the swimming crab Portunus trituberculatus

Serine proteinase homologues (SPHs), as one of prophenoloxiase-activating factors (PPAFs), play critical roles in innate immunity of crabs. Based on an EST from the eyestalk full length cDNA library, the complete cDNA (designated as PtSPH) and genomic DNA of SPH from the swimming crab Portunus trituberculatus were cloned in this study. The estimated molecular weight of mature PtSPH (354 amino acids) was 38.7 kDa and its isoelectric point was 5.08. Multiple sequence alignment revealed that PtSPH lacked a catalytic residue with a substitution of Ser in the active site triad to Gly. Phylogenetic analysis indicated PtSPH together with PPAFs of Callinectes sapidus (AAS60227), Eriocheir sinensis (ACU65942), Penaeus monodon (ABE03741, ACP19563) and Pacifastacus leniusculus (ACB41380), formed a distinct cluster which only included clip-SPHs. As the first analyzed genomic structure of PPAFs in crustaceans, two introns were found in the open reading frame region of this gene. The mRNA transcripts of PtSPH could be detected in all the examined tissues, and were higher expressed in the eyestalk than that in gill, hepatopancreas, haemocytes and muscle. Accompanied with the change in phenoloxidase (PO) activity and total haemocyte counts, the temporal expression of PtSPH gene in haemocytes after Vibrio alginolyticus challenge demonstrated a clear time-dependent expression pattern with two peaks within the experimental period of 32 h. These findings suggest that PtSPH is involved in the antibacterial defense mechanism of Portunus tritubercualtus crab. (C) 2010 Elsevier Ltd. All rights reserved.

The second anti-lipopolysaccharide factor (EsALF-2) with antimicrobial activity from Eriocheir sinensis

The anti-lipopolysaccharide factor CALF) is a small basic protein that can bind and neutralize lipopolysaccharide (LPS), mediating degranulation and activation of an intracellular coagulation cascade. In the present study, cDNA of the second Eriocheir sinensis ALF (designated as EsALF-2) was cloned and the full-length cDNA of EsALF-2 was of 724 bp, consisting of an open reading frame (ORF) of 363 bp encoding a polypeptide of 120 amino acids. The deduced amino acid of EsALF-2 shared 82% similarity with EsALF-1 from E. sinensis and about 53-65% similarity with ALFs from other crustaceans. The potential tertiary structures of EsALF-1 and EsALF-2 contained two highly conserved-cysteine residues to define the LPS binding site, but the N-terminal of EsALF-1 formed a single additional alpha-helix compared to EsALF-2, implying that EsALF-1 and EsALF-2 might represent different biological functions in E. sinensis. The mRNA transcript of EsALF-2 was detected in all examined tissues of healthy crabs, including haemocytes, hepatopancreas, gill, muscle, heart and gonad, which suggested that EsALF-2 could be a multifunctional molecule for the host immune defense responses and thereby provided systemic protection against pathogens. The mRNA expression of EsALF-2 was up-regulated after Listonelln anguillarum and Pichia pastoris challenge and the recombinant protein of EsALF-2 showed antimicrobial activity against L. anguillarum and P. pastoris. indicating that EsALF-2 was involved in the immune defense responses in Chinese mitten crab against L. anguillarum and P. pastoris. These results together indicated that there were abundant and diverse ALFs in E. sinensis with various biological functions and these ALFs would provide candidate promising therapeutic or prophylactic agents in health management and diseases control of crab aquaculture. (C) 2010 Elsevier Ltd. All rights reserved.

青蟹属的系统进化和中国沿海拟穴青蟹的群体遗传结构研究

为了进一步研究青蟹属系统进化的科学问题，并揭示我国东南沿海青蟹群体遗传结构和群体进化细节信息，本论文主要开展了以下两个方面的研究：（1）基于线粒体12S rRNA、16S rRNA和COI三种基因序列探讨中国东南沿海青蟹的种类归属与青蟹属的系统进化；（2）利用线粒体COI基因标记分析中国东南沿海拟穴青蟹的群体遗传结构。序列特征、遗传距离和系统进化分析结果都表明本文研究的青蟹均为S. paramamosain。NJ、BAYES和ML系统进化树显示S. paramamosain与S. tranquebarica互为姐妹种，S. olivecea应该是4种青蟹中最早分化出来的种类。10个地理群体130只拟穴青蟹的线粒体DNA（mitochondrial DNA，mtDNA）细胞色素氧化酶亚基I（COI）基因序列Mantel检验结果显示群体间的遗传分化程度与地理距离没有显著的相关性。分子进化中性检验结果表明自然选择在分子进化过程中起了重要作用，并暗示该物种在最近经历了一个快速的群体爆发及扩张事件。

First record of the genus Gigantione (Epicaridea: Bopyridae: Pseudioninae) from Chinese waters, with description of three new species

The parasitic isopod genus Gigantione is first recorded from China. Four species are reported infesting xanthid and goneplacid crabs, three are new to science, and one is a new record from China. Gigantione ishigakiensis Shiino, 1941, infesting Liagore rubromaculata (De Haan); G. hainanensis sp. nov., infesting Atergatis floridus (L.) and Atergatis sp., which differs from other recorded species in the shape of its barbula, first oostegite and subrectangular maxilliped; G. rhombos sp. nov., infesting Heteroplax dentata Stimpson, Eucrate alcocki Serene and Eucrate sp., its female distinguished from other species of Gigantione by having a prominent rhombic projection on the barbula; and G. tau sp. nov., infesting Carcinoplax longimanus (De Haan), the female of which differs from other species mainly by its T-shaped pigmentation on the head. Four brachyuran crabs are first reported as hosts of bopyrids. A list of all brachyuran species so far recorded as bopyrid hosts in China is provided.

A new species and two new record species of genus Allokepon Markham, 1982 (Isopoda : Epicaridea : Bopyridae) from China

Descriptions of a new species and two new records of species of the genus Allokepon Markham, 1982 from Chinese waters are presented. The host species were portunid crabs. Allokepon hendersoni (Giard & Bonnier 1887) was found infesting Charybdis bimaculata (Miers), A. monodi (Bourdon, 1967) infesting Portunus pelagicus (L), Portunus trituberculatus ( Miers), and Thalamita sp. and A. longicauda n. sp. infesting Portunus pulchricristatus (Gorden). Three of the host species were recorded for the first time harboring isopod parasites, and the male of A. monodi is presented. Allokepon longicauda n. sp. is distinguished from the other four species found in China by the long slender uropods of females.