Evaluation of limb autotomy as a promising strategy to improve production performances of mud crab (Scylla olivacea) in the soft‐shell farming system

Soft‐shell crab, a newly moulted crab having non‐calcified and hydrated soft exoskeleton, farming has been increasing tremendously in recent years throughout the world due to its high market price and consumer preferences. However, high aggressiveness and cannibalistic behaviour of mud crab limit its culture to an individual chamber system which ultimately makes the soft‐shell mud crab farming space and labour‐intensive. Therefore, the aim of this study was to improve the efficiency of soft‐shell crab production by autotomy of the claw and/or walking legs to reduce the moulting duration and intensify the culture system through double stocking in the existing individual chamber culture system. To achieve our objectives, a series of experiment were conducted at both indoor and on‐farm levels by removing the claw and/or walking legs of Scylla olivacea for two consecutive moulting cycles. Results showed that both claw ablation significantly (p < .01) shortened the moulting duration and increased the carapace width, weight gain, specific growth rate, feeding efficiency and yield parameter compared to the non‐ablated crabs more prominently at 1st moulting than the 2nd moulting in both indoor and on‐farm trials. Ablation of all walking legs while keeping the claw intact did not significantly influence (p > .05) the moulting duration and carapace width, but significantly (p < .01) improved the specific growth rate, weight gain, feeding efficiency and yield parameters at 1st moulting compared to the non‐ablation and unilateral three walking leg ablation groups. However, ablation of all appendages (both claw and walking legs) showed significant (p < .01) improvements of carapace width, weight gain, specific growth rate, feeding efficiency and yield parameters, and shortened the moulting duration up to 23 days from 34 days during 1st moulting and up to 27 days from 40 days at 2nd moulting. The survivals of different autotomized mud crabs were statistically non‐significant (p > .05) to the non‐autotomized crabs in various indoor and on‐farm trials. Besides improving the production performances, ablation of bilateral claw and all appendages allowed to double the stocking density in the existing individual chamber‐based soft‐shell crab farming that enhanced the production about threefold higher than the existing individual chamber‐based culture system. Finally, our results suggest that autotomy could be a promising technology for the commercial farming of soft‐shell mud crab in near future.     

Recent update on the prevalence of Vibrio species among cultured grouper in Peninsular Malaysia

Vibrio infections are common among marine fish and lead to serious problems in the aquaculture sector. This study reports a recent occurrence of Vibrio species (spp.) isolated from cultured groupers in Peninsular Malaysia using the gyrB and pyrH genes. A total of 147 Vibrio strains were successfully isolated from 77 (64%) groupers using culture method and subjected to gyrB and pyrH sequencing for species identification and confirmation. Results showed that 89% of Vibrio strains were identified and clustered to six groups of Vibrio spp., while 11% were not clustered to any Vibrio spp. using the gyrB sequences. Meanwhile, by analysis of the pyrH sequences all the 147 Vibrio strains (100%) were successfully identified and clustered into 11 groups of Vibrio spp., including the gyrB non‐identified strains. The pyrH gene provides a better resolution for identification of Vibrio spp. compared with the gyrB gene. Thus, the pyrH gene was more suitable for a rapid determination of Vibrio spp. distribution in Peninsular Malaysia. Using the pyrH gene, our study found higher prevalence of Vibrio vulnificus (33%), V. alginolyticus (24%) and V. parahaemolyticus (22%), followed by V. rotiferianus (5%), V. harveyi (3%), V. tubiashii (2%), V. campbellii (2%), V. ponticus (1%), V. diabolicus (1%), V. owensii (1%) and others Vibrio sp. (7%). Thus, the results of this study revealed that the occurrence of pathogenic vibrios among grouper fish is still high in Malaysian aquaculture. In addition, the pyrH gene was proved as a suitable marker for rapid identification of Vibrio species compared with the gyrB gene.     

Metagenomic analysis using 16S ribosomal RNA genes of a bacterial community in an urban stream,the Tama River,Tokyo

In an effort to determine genus- or species-level taxonomic profiles and diversity of bacterial consortia in the Tama River around urban Tokyo, next-generation sequencing technology targeting a 16S ribosomal RNA (rRNA) gene amplicon was employed. Metagenomic analysis performed by an Ion Personal Genome Machine after sequentially filtering samples through 5-, 0.8- and 0.2-μm filters yielded 1.48 Gb of 16S sequences (average 2.38 M reads/sample). The results indicated that half of the bacterial sequences belonged to Proteobacteria, followed by Bacteroidetes, Actinobacteria and Cyanobacteria. Flavobacterium (Bacteroidetes), possibly including a potential fish pathogen, was the most numerous genera in the Tama River metagenome, and accounted for?~?16% of assigned 16S reads, followed by Mycobacterium. Other dominant bacterial genera including Zoogloea, Sediminibacterium, Hyphomicrobium, Sphingopyxis, Thiothrix and Lysobacter, were thought to be associated with waste water and sludge. MiSeq metagenomic analysis revealed that environmental factors, particularly water temperature, influenced the bacterial composition throughout the year, with a strong negative correlation observed for Proteobacteria and a positive correlation for Bacteroidetes. In terms of bacterial genera, Flavobacterium was positively correlated with temperature, while Polaromonas, Pseudomonas and Bradyrhizobium were negatively correlated with this, suggesting dynamic change in the free-living bacterial population throughout the year and versatile adaptation strategies in relation to environmental factors.     

Synergy between grapevine vitiviruses and grapevine leafroll viruses

An interactive relationship between vitiviruses and grapevine leafroll viruses was characterized in grapevine. Grapevine viruses A and B (GVA and GVB) were found more frequently in the presence of co-infecting Grapevine leafroll associated viruses (GLRaV-1, ?2 or ?3) than in their absence. The titers of the vitiviruses in co-infection with leafroll viruses were found to be higher than were their titers in the absence of leafroll virus infection. The occurrence of vitivirus-associated stem-pitting symptoms was correlated with leafroll virus co-infection. Specific pairing associations on the species level were found between different viti- and leafroll virus species: GVB was associated preferentially with GLRaV-2; GVA was associated preferentially with GLRaV-1 and GLRaV-3. In contrast to the increase in vitivirus titer seen with leafroll virus co-infection, the incidence and titer of grapevine leafroll virus appeared to be unaltered by vitivirus co-infection. The potential for a synergistic enhancement of grapevine disease in co-infected vines is discussed.     

Salty stories,fresh spaces: Lessons for aquatic protected areas from marine and freshwater experiences

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Immobilization of Cationic Titanium Dioxide (TiO<Subscript>2</Subscript><Superscript>+</Superscript>) on Electrospun Nanofibrous Mat: Synthesis,Characterization, and Potential Environmental Application

We report a facile approach to fabrication and characterization of cationic titanium dioxide (TiO₂⁺) on poly (vinyl alcohol)/poly (acrylic acid) (PVA/PAA) composite electro-spun nanofibrous mat. The aim of this study is to develop a “functional electrospun nanofibrous mat” as a sustainable approach to superior photocatalytic degradation of organic colorants. For that, the PVA/PAA nanofibrous mat was prepared by electrospinning of PVA and PAA solution according to an aspect ratio of 1:1 and later water stability was induced by the thermal cross linking at an elevated temperature of 145 °C for 30 minute. By means of electrostatic layer-by-layer (LbL) assembly, cationic titanium dioxide (TiO₂⁺, ~19 nm) was immobilized on the surface of the water stable nanofibrous mat. As functionalized composited nanofibrous mat was characterized by using scanning electron microscope (SEM), fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) analysis and thermogravimetric analysis (TGA). Superior competency of the functionalized nanofibrous mat towards photocatalytic degradation of organic dye (methyl blue) in aqueous solution was observed by using UV-visible spectrophotometer with quantitative measuring method. The result indicates a complete degradation of methyl blue within 40 mins and superior reusability upto 5 cycles application. The study signifies the prospect of using electrospun nanofibers to manipulate the catalytic activity, which could be a foundation for further rational design of various composite nanofibrous materials.     

A survey of entomopathogenic nematodes of the families Steinernematidae and Heterorhabditidae (Nematoda: Rhabditida) in Damascus countryside of Syria

A survey of entomopathogenic nematodes was conducted in Damascus countryside from January 2011 to December 2013. Soil samples were tested for the presence of steinernematid and heterorhabditid nematodes by baiting with Galleria mellonella larvae. Of the 189 soil samples studied 17 were positive for entomopathogenic nematodes (9%), with 11 of these positive samples (65%) containing Heterorhabditis and 6 (35%) Steinernema isolates. Morphological studies were carried out to characterize eight isolates. The Heterorhabditis isolates collected in Syria were identified as Heterorhabditis zealandica (Poinar, 1990), Heterorhabditis indica (Poinar et al., 1992) and Heterorhabditis bacteriophora (Poinar, 1990). Heterorhabditis zealandica was isolated from 4 sites. Heterorhabditis indica and H. bacteriophora were isolated from two sites each. Entomopathogenic nematodes were mainly found in stone fruit orchards and apple orchards but also in citrus groves, vineyards, and walnut orchards.