Hormonal regulatory role of eyestalk factors on growth of heart in mud crab,Scylla serrata

The present study was attempted to know the growth regulation of eyestalk factors on the growth of heart in Scylla serrata using eyestalk extractions and bilateral eyestalk ablations. The bilateral eyestalk ablation led to the maximum growth indices of the heart ((H) indices) to 0.162 and 0.158 in ablated male and female, respectively, in comparison to 0.153 and 0.167 in the control male and female and 0.147 and 0.157 in injected male and female, respectively. The data have shown that the heart of male crabs grows faster than female crabs. The study has also shown that bilateral eyestalk ablation resulted in a significant increase in the heart indices in males and has least effect on the growth of the female heart. The results presented strongly support a potential role of the eyestalk factors and molting hormone regulating the growth of the heart in S. serrata.     

Pathogenicity of fungi isolated from the larvae of the mangrove crab,Scylla serrata, in Indonesia

Heavy mortality reaching almost 100% occurred in the larvae of the mangrove crab,Scylla serrata, from July to December 1997 at the hatchery of Gondol Research Station for Coastal Fisheries in Bali, Indonesia. Mortality was observed in larvae after hatching from the eggs. The affected larvae were whitish and filled with numerous aseptate hyphae. Three fungi belonging to the order Lagenidiales,Lagenidium callinectes, Haliphthoros milfordensis, andHalocrusticida sp., were isolated from the infected larvae. Pathogenicity tests of the infected fungi against the larvae of mangrove crab demonstrated that all isolates were pathogenic.     

Development of cell line from the testicular tissues of crab <Emphasis Type="Italic">Scylla serrata</Emphasis>

This is the first report on development of a finite cell line from testicular tissues of crab, Scylla serrata. Both the explant and segregated tissues of testes yielded cells that could proliferate and grow. These cells ranged in size from 10 to 38 μm with distinct nuclei of varying shapes. The testicular cells survived and proliferated best in L-15-crab saline medium supplemented with epidermal growth factor (20 ng/mL) and glucose (1 mg/mL). The cell proliferation rate was assessed by Methyl tetrazolium assay in terms of change in optical density which clearly indicated a prominent increase in cell density. The testicular cells were subcultured at an interval of 4–6 days. These subcultured cells remained healthy and proliferated for 5 months with a minimum of ten subsequent passages. The finite cell line was characterized in terms of morphology, growth rate, lactate dehydrogenase release (for detecting health status) and 18S rRNA sequencing. This cell line could be a very useful tool for testing infections and replications of crustacean viruses. The present work provides a technique that could be extended for developing other crustacean cell lines.     

Lagenidium infection in eggs and larvae of mangrove crab (Scylla serrata) produced in Indonesia

A fungal infection occurred in the eggs and larvae of mangrove crab (Scylla serrata) in seed production in Bali, Indonesia. The causative fungus was classified as a member of the genusLagenidium (Oomycetes, Lagenidiales). After comparison of its biological and physiological characteristics with those ofL. callinectes ATCC 24973, a known parasite of various crustaceans, was concluded that the isolate is a new species ofLagenidium, L. thermophilum, because of its rapid and thermotolerant growth and unique discharge process. Fungal growth was observed on PYG agar containing 0–5.0% (w/v) NaCl and 0–2.5% (w/v) KCI. Similar pathogenicity toward the zoeae of swimming crab (Portunus trituberculatus) was demonstrated.     

Susceptibility of testicular cell cultures of crab, Scylla serrata (Forskal) to white spot syndrome virus

Testicular cell culture of crab, Scylla serrata (Forskal) was used to study the effects of White spot syndrome virus (WSSV). We are showing the susceptibility of cell culture of crabs to WSSV. The proliferating cell culture of testes were maintained for more than 4 months in a medium prepared from L15 and crab saline supplemented with epidermal growth factor. The cell cultures inoculated with different concentrations of virus showed distinct cytopathic effects such as change in cell appearance, shrinkage and cell lysis. WSSV infection of cultured cells was confirmed by Nested PCR technique. The incorporation of viral DNA in cultured cells was shown by RAPD profile generated using 10-mer primers. The controls that were not exposed to WSSV did not show cytopathic effects. This work shows the usefulness of proliferating testicular cell culture for studying WSSV infection using molecular tools. Thus, this report gains significance as it opens new vistas for diagnostics and drugs for WSSV.     

Genetic differentiation in the mud crab Scylla serrata (Decapoda: Portunidae) within the Indian Ocean

Scylla serrata (Decapoda: Portunidae) is a swimming crab that is widespread in the Indo-Pacific region and commonly found in estuarine and mangrove waters. An extended planktonic larval phase suggests high dispersal potential and the possibility of extensive gene flow between conspecific populations at least on a geographic mesoscale (tens to hundreds of kilometres).Intraspecific variation of the mitochondrial DNA cytochrome oxidase subunit I (mtDNA COI) gene was investigated in 77 individuals from four representative mangrove swamps of the African tropics (Kenya and Zanzibar) by means of DNA sequencing. We examined 535 base pairs (bp) and identified 24 different haplotypes. Each population sample is characterised by a single most frequent haplotype, shared among all four populations, and a small number of rare ones, typically present in only one or two individuals and representative of a specific population.Analysis of molecular variance (AMOVA), F_ST statistics and χ² contingency analysis of spatial distribution of mtDNA haplotype frequencies revealed in toto a significant genetic differentiation among populations. These results could indicate that gene flow might be reduced, even between geographically close sites, despite the high potential for dispersal; anyway, at the recorded level of divergence and owing to the abundance of rare haplotypes and singletons in our data set, repeated sampling over time is necessary to establish whether the recorded pattern of genetic differentiation is stable and biologically significant.Finally, integration of our data with those reported by Gopurenko et al. [Mar. Biol. 134 (1999) 227] on S. serrata from South Africa, Red Sea and Mauritius Islands allowed to infer S. serrata population structure within a larger area of the Indian Ocean region.     

Purification and part characterization of a novel antibacterial protein Scygonadin, isolated from the seminal plasma of mud crab, Scylla serrata (Forskål, 1775)

A novel protein was isolated from the seminal plasma of the mud crab, Scylla serrata (Forskål, 1775). It exhibited an antibacterial activity against the Gram-positive bacterium Micrococcus leteus with IC90 of 0.125 mg/ml. The extraction procedure for the protein included techniques of acid extraction, ion-exchange chromatography on SP-Sepharose Fast Flow and reverse-phase liquid chromatography on Source 5R RPC. It showed a molecular mass of 10.8 kDa by SDS-PAGE. A partial 20 residue NH₂-terminal sequence was determined by Edman degradation and MS-fingerprint of the protein was conducted. Similarity search in protein databases (BLAST) revealed that the protein exhibited no significant homology to any other reported antimicrobial peptides. We propose the name Scygonadin (from the gonad of S. serrata) for this antibacterial protein.     

Identification of lower fungi isolated from larvae of mangrove crab,Scylla serrata, in Indonesia

Since 1992, seed production of mangrove crab,Scylla serrata, has been attempted at the Gondol Research Station for Coastal Fisheries, Bali, Indonesia. During the production process, almost all of the larvae have died due to fungal infection. Fungi isolated from the larvae with fungal infection were classified into three species in the order Lagenidiales:Lagenidium callinectes, Haliphthoros milfordensis andHalocrusticida baliensis sp. nov. based on detailed morphological characteristics. The effects of temperature, pH and mineral content of the water on their growth were also examined.     

Identification of polymorphic microsatellite loci in the mud crab Scylla serrata (Brachyura: Portunidae)

Five microsatellite loci are identified and characterized from the genome of Scylla serrata, a widespread and commercially important species of coastal marine crab. The loci were detected by randomly screening for di‐ and tri‐nucleotide repeat units within a partial genomic library developed for the species. The five loci consist of dinucleotide repeats and are both co‐dominant and polymorphic within the species. A sample (N = 36) of S. serrata from one Australian population has an average observed heterozygosity of 0.875 and provides no evidence of either linkage among loci or significant deviation from random mating expectations across loci. PCR products for each of the five loci were also observed from a small sample of three other species within the Scylla genus. These markers may provide genetic information that will be useful for both aquaculture and studies of natural populations of the genus.     

Molecular cloning and expression profiles of nitric oxide synthase (NOS) in mud crab Scylla paramamosain

The importance of the nitric oxide synthase (NOS) gene family is demonstrated by many studies in vertebrates and invertebrates in recent years. However, it keeps unknown of nitric oxide (NO) system and NOS gene family in mud crab Scylla paramamosain, an important cultured commercial crustacean in China and Pacific area. In this report, the cDNA of NOS containing full-length ORF was cloned from mud crab, S. paramamosain. It was of 4424 bp, including a 5′-terminal untranslated region (UTR) of 239 bp, a 3′-terminal UTR of 540 bp, which contained two ATTTA motifs, and an open reading frame (ORF) of 3645 bp encoding a polypeptide of 1214 amino acids. Structural analysis indicated that NOS contained a typical NO synthase domain at the N-terminal, next to a flavodoxin 1 domain, a flavin adenine dinucleotide (FAD) binding domain, respectively, and a conservative nicotinamide adenine dinucleotide (NAD) binding domain structure at the C-terminal. Quantitative real-time PCR analysis revealed S. paramamosain NOS (SpNOS) to be expressed in all tissues examined, with the highest expression in midintestine and the weakest level in heart and eyestalk. The expression profiles of SpNOS indicated that the NOS expression levels were significantly induced in midintestine, hepatopancrease and hemocytes after challenged with Vibrio Parahaemolyticus, the synthetic double-stranded RNA polyinosinic polycytidylic acid (poly I:C) and lipopolysaccharides (LPS). The NOS activity in hemocytes showed significant increase during at 24 h-48 h time period after immune challenges with V. Parahaemolyticus, poly I:C and LPS. Results here may suggest that the inducible NOS play an important role in mud crab’s defense against pathogenic infection.     

A new shell disease in the mud crab Scylla serrata from Port Curtis, Queensland (Australia)

In 1994 a previously unreported rust spot shell disease was seen in mud crabs Scylla serrata - Forskal from Port Curtis, central Queensland, Australia. Of 673 crabs surveyed, 21.7% had shell lesions. Of these, 82.9% had rust spot lesions on the carapace. The majority of rust spot-affected crabs (78.8%) were female. Rust spot lesions were predominantly non-perforated (89.4%) and 54.8% were bilaterally symmetrical. There was also a gender difference in the areas of the carapace most commonly affected. The main histological features of the rust spot lesion included: a cavity in the upper endocuticle; indentation of the endocuticle below the cavity; remains of muscle attachment adhesive epithelium within the cavity; fibrous connective tissue between the damaged carapace and the attached muscle; and islands of endocuticle in this fibrous connective tissue. Histopathology of the internal organs failed to find evidence of an infectious or parasitic cause of the rust spot lesions. The cause(s) of the syndrome appear(s) to be non-infectious.     

The breeding cycle of Scylla serrata (Forskal, 1755) at Ramisi River estuary,Kenya

The mud crab Scylla serrata was collected from Ramisi river estuaryfor a period of 14 months (January 1990–February 1991) using madema traps. For each crab, the carapace width (mm), sex and weightwere noted, and the number of ovigerous female crabs was recorded. Both ovigerous and non-ovigerous females were dissected in order to observeof the maturity stages of ovaries. The ovarian maturity stages weredescribed as stage zero – virgin/resting, stage one – developing, stage two– well developed and stage thre e– ripe. The most abundant was stage twothroughout the study period. The smallest ovigerous crab had a carapacewidth of 139 mm. A test of homogeneity of the binomial distributionof the sex ratio showed homoscedasticity (² = 14.615; d.f. = 13; p> 0.05) and the overall sex ratio did not differ from 1:1 (² = 0.776; d.f. = 1; p> 0.05). The variance test ofhomogeneity of the binomial distribution of sex in relation to size showeda very significant heterogeneity (² = 32.83; d.f. = 9; p< 0.05). There was no significant difference when the overall mean sizesfor males and females were compared using t-test (t = 4.26; d.f. = 18;p< 0.001). The relatively high numbers of females with stage two ovariesindicated that spawning took place throughout the year with a possible peakin the second half of the year.     

Occurrence of additional Zoea-VI larvae in the mud crab, Scylla paramamosain (Estampador), reared in the laboratory

Mud crabs, Scylla spp. , are commercially important in many Indo-Pacific countries. The larval development of mud crabs has been reported previously as five zoeal and one megalopal stages. This paper reports larval rearing experiments that revealed variability in larval developmental stages in the mud crab Scylla paramamosain, one of four mud crab species. In addition to normal five zoeal stages, an alternative pathway of developing through six zoeal stages was observed for the crab. There were evidences suggested that the appearance of the additional Zoea-VI larvae was associated with unfavourable dietary conditions, including poor quality of diet, inadequate quantity of dietary supply and a period of starvation for newly hatched larvae. Based on exuviae and larval specimens, the morphology of the additional Zoea-VI larvae was described.     

Survival of the marine crab,scylla serrata exposed to thermal shock under different experimental conditions

Survival of the edible crab, Scylla serrata Subjected to endocrinological and pharmacological procedures, was examined after exposing them to 40°C for 3 hr. Only normal, intact crabs could withstand the thermal shock but not reserpinized intact, eyestalkless, sinus glandectomised (SGE), SGE and reserpinized (RSP), SGE injected with sinus gland homogenate and SGE injected with SG homogenate and reserpinized crabs. The possible involvement of endocrine centres in S. serrata in sustaining the environmental thermal shock is discussed.     

Nosema ceranae, a new microsporidian parasite in honeybees in Europe

Twelve samples of adult honey bees from different regions of Spain from colonies with clear signs of population depletion, positive to microsporidian spores using light microscopy (1% of total positive samples analysed), were selected for molecular diagnosis. PCR specific primers for a region of the 16S rRNA gene of Microsporidia were developed and the PCR products were sequenced and compared to GenBank entries. The sequenced products of 11 out of the 12 samples were identical to the corresponding Nosema ceranae sequence. This is the first report of N. ceranae in colonies of Apis mellifera in Europe. The suggested link of the infections to clinical disease symptoms makes imperative a study of the virulence of N. ceranae in European races of honey bees.     

汕头牛田洋沿海围垦区锯缘青蟹病害爆发的环境因素

锯缘青蟹(Scylla serrata)是汕头市的传统特色和优势养殖品种,也是拥有3万多亩海水养殖池塘的牛田洋围垦区的主养品种。近年来,每年9-11月份,牛田洋的青蟹病害严重,经济损失较大。为探讨青蟹发病与养殖环境的关系,于2007年4月至12月份对牛田洋养殖区的水体理化因子和生物因子进行连续监测研究,结果发现:各因子呈现出明显的季节性变化。在发病前的7-8月份,青蟹处于较高水温(≥28℃)和较低盐度(≤6)环境中。在发病期(9-11月份),各种环境因子恶化,其中铵态氮(NH4+-N)和亚硝态氮(NO2--N)在9月份达到峰值,分别为235.63μg·L-1和27.75μg·L-1;硝态氮(NO3--N)(10.85μg·L-1)、无机磷(PO34—P)(39μg·L-1)及生物因子(水体异养菌157.93×105cfu·L-1、弧菌116.75×103cfu·L-1,干重底泥异养菌157.93×105cfu·g-1、弧菌141.65×103cfu·g-1)在10月份达到峰值。结果说明:水体理化因子的恶化和条件致病微生物的大量增生是青蟹病害爆发的重要原因。