Phospholipids Effect on Survival and Molting Synchronicity of Larvae Mud Crab Scylla serrata

Effect of phospholipids on survival and molting synchronicity of mud crab larvae Scylla serrata were examined using Artemia enriched with five treatments of emulsion oil i.e. treatment with different level of soybean lecithin (SL) together with a level of DHA70G (referred to as DHA-SL0, 20 and 40) and treatment with SL and cuttle fish phospholipids (CPL) at 40 uL/L without DHA70G (referred to as WDHA-SL and WDHA-CPL). Survival rate, intermolt period, carapace width, and molting synchronicity were evaluated. Additionally, lipid classes and fatty acid composition of enriched Artemia were analyzed. Survival rate, intermolt period, and carapace width at the first crab (FC) stage of mud crab larvae fed DHA-SL0 to 40 were similar to that of WDHA-CPL but higher than that of WDHA-SL (P < 0.05). Moreover, mud crab larvae fed DHA-SL20, DHA-SL40, and WDHA-CPL had a significantly higher molting synchronicity index compared to that of larvae fed WDHA-SL and DHA-SL0. It can be concluded that combination of phospholipids and essential fatty acids exhibited an additive effect in improving molting synchronicity of mud crab larvae

Emigration behaviour, moulting and survival during the sea-to-land transition of land hermit crabs Coenobita violascens and Coenobita rugosus under laboratory conditions: Effects of salinity and riverine odours

Coenobita rugosus is distributed along the entire coast, and the distribution of C. violascens is restrictedto the vicinity of rivers, mainly in the mangrove estuaries on southern Japanese islands. To infer theenvironmental cues affecting successful emigration from the sea to land on these species, we examined shellwearing and landing behaviour, moulting and survival for laboratory-raised megalopae and early juveniles under different seawater conditions: 1) high salinity (34 ppt, control), 2) low salinity (24 ppt), and 3) high salinity (34 ppt) with riverine odours (mangrove riverine water). In C. violascens, reduced salinity and riverine odours stimulated shell-wearing activity, and riverine odours enhanced the landing activity. In C. rugosus, reduced salinity and riverine odours stimulated both shell-wearing and landing activities, and the magnitude of the effects was larger in response to reduced salinity than riverine odours. These seawater conditions also tended to enhance the moulting and survival of the animals. Salinity reductions widely occur along the shoreline due to the inflow of groundwater as well as river water. Riverine odours and reduced salinity should be cues for emigration from the sea to land by megalopae of C. violascens and C. rugosus, respectively, thereby characterizing the distributions of these species on the islands

Settlement behaviour of the early megalopae of the land hermit crab Coenobita violascens (Decapoda: Coenobitidae) under laboratory conditions: Effects of inshore odours and salinity

The distribution of the land hermit crab Coenobita violascens is restricted to the vicinity of rivers,particularly mangrove estuaries. To infer the recruitment mechanisms of C. violascens, we examined settlement behaviour, such as swimming, walking, shell-inspection, and shell-wearing activities, in 0-day-old to 6-day-old megalopae under different seawater conditions: 1) offshore salinity (34 ppt, control), 2) offshore salinity (34 ppt) with inshore odours (riverine water), and 3) inshore salinity (24 ppt). Salinity was regulated using artificial sweater salts. Coenobita violascens megalopae exhibited nocturnal swimming activity, whereas other activities significantly increased during the daytime period. Inshore odours did not affect the swimming and walking activities, whereas the inshore salinity conditions decreased the swimming activity and enhanced the walking activity, i.e., stimulated the settlement behaviour of megalopae. Shell-related activities were not influenced by any of the seawater types. Our results suggest that megalopae might migrate to the coast using nocturnal flood-tide transport and settle on or near inshore habitats under the reduced salinity conditions that occur as a result of the inflow of groundwater and river water. Further studies are required to elucidate the role of inshore odours in the recruitment of C. violascens megalopae in mangrove estuaries

Distributions of land hermit crabs (Decapoda: Coenobitidae) on the coast of the tidal lagoon, Nagura Amparu, on Ishigakijima Island, Japan.

　We investigated the distributions of land hermit crabs on the coast of the tidal lagoon, Nagura Amparu, on Ishigakijima Island, Japan, through six surveys conducted during the period from October 2011 to September 2013. Nagura Amparu is a brackish estuary system with a tidal flat and mangrove tree areaseparated from the outer sea bay by a sandbank. Land hermit crabs were captured using bait traps at three sites along the shoreline of the sandbank facing the inner tidal flat and at one site in the coastal forest on the sandbank. Four land hermit crab species, Coenobita brevimanus, C. cavipes, C. rugosus, and C. violascens, were collected. Almost all collected crabs were C. violascens, and a few C. rugosus were collected on the shoreline. On the other hand, C. cavipes was dominant, followed by C. violascens, and a few C. brevimanus were captured in the coastal forest. Coenobita violascens were juveniles and adults, and they widely inhabited the shoreline and coastal forest. All C. cavipes were juveniles, suggesting that this species utilizes the coastal forest as a nursery ground. Our results highlight the importance of the Nagura Amparu as habitat for juveniles and adults of C. violascens and juveniles of C. cavipes

Sexual Dimorphism and Reproductive Status of the Red Swamp Crayfish Procambarus clarkii

The red swamp crayfish Procambarus clarkii is native to northeastern Mexico and the south-central USA, and it has expanded its distribution worldwide and negatively impacted the ecosystems in the invaded regions. The dynamics of the P. clarkii populations have been studied as the basis for the development of effective control measures against this invasive alien species. Adult males of P. clarkii exhibit a cyclical dimorphism between two sexual morphotypes; reproductive form I has large chelae and non-reproductive form II has small chelae. However, whether P. clarkii females have two sexual morphotypes and exhibit form alternation has not been resolved, and little is known about the degree of intra-sexual dimorphism of the chelae, even among males. We employed allometric growth analysis on the chelae dimensions of P. clarkii females and males that were collected from a small pond in Yokohama, Japan. Our analysis demonstrated the existence of form I, which has larger chelae, and form II, which has smaller chelae, in P. clarkii females and highlighted the intra- and inter-sexual dimorphisms in the chelae of this species. The reproductive cycle of the population was successfully traced by the reproductive status of P. clarkii based on the occurrence patterns of each sexual morphotype; the form I crayfish occurred throughout the sampling period from April to December, while the occurrences of form I females and males were highly correlated, peaking in October. Our results suggested that alternation of sexual forms occurs in P. clarkii females. The ability to discriminate between the sexual morphotypes based on chelae allometric growth would allow us to evaluate the female reproductive status more easily ansd precisely in invasive P. clarkii populations

Characterization of Aquimarina hainanensis isolated from diseased mud crab Scylla serrata larvae in a hatchery

Mass mortality due to necrosis signs occurred in hatchery‐reared zoea stage larvae of the mud crab Scylla serrata in Okinawa, Japan, and a causative bacterium was isolated. In this study, we identified and characterized the bacterium by genome analysis, biochemical properties and pathogenicity. The bacterium was a Gram‐negative, non‐motile, long rod, forming yellow colonies on a marine agar plate. It grew at 20–33°C (not at 37°C) and degraded chitin and gelatin. Phylogenetic analysis of the 16S rRNA gene sequence identified the bacterium as Aquimarina hainanensis. Genome sequence data obtained from Illumina MiSeq generated 29 contigs with 3.56 Mbp in total length and a G + C content of 32.5%. The predicted 16 chitinase genes, as putative virulence factors, had certain homologies with those of genus Aquimarina. Experimental infection with the bacterium conducted on larvae of four crustacean species, brine shrimp Artemia franciscana, freshwater shrimp Caridina multidentata, swimming crab Portunus trituberculatus and mud crab S. serrata, revealed that this bacterium was highly virulent to these species. The present study suggests that the bacterium caused mass mortality in mud crab seed production was A. hainanensis and can be widely pathogenic to crustaceans

How Are Statistical Parameters of the Velocity Vector of Body Sway Distributed in Normal Human Subjects?

The velocity vector when the human body sways has been qualitatively evaluated in clinical sessions. We quantitatively measured the velocity vector for 1 min in 89 normal subjects standing in a stable posture, and examined distributions of quantities of the velocity vector. The velocity vector was measured with a stabilometer, which visualizes the vector as magnitudes radially projected from the center to the periphery into 36 directions by 10°. The 3 quantities we calculated from the 36 scalars of the vector per subject were the coefficient of correlation (CV), skewness and kurtosis, which were analyzed statistically. Values of skewness were normally distributed. Values of CV and kurtosis were log-normally distributed when adjusted with log transformation. Then, we calculated standardized values of the normal distributions, from which the lower and upper cutoff values in the 95% and 99% areas were available. The 3 quantities showed statistically significant correlations with one another, although the levels were low. Thus, in the present study, use of the 3 parameters enabled us to quantitatively evaluate the whole image of velocity vector, which would simplify the procedures of examination and shorten the time required for differential diagnosis

Flocculation of Artemia induced by East Asian common Octopus octopus sinensis paralarvae under culture conditions

Artemia are potential food organisms for the mass culture of common octopus paralarvae but cause poor paralarval growth and mortality. To understand problems arising from Artemia use, we focused on Artemia flocculation in paralarval culture tanks; Artemia get caught up with each other, exhibit disrupted swimming, are deposited on the tank bottom and eventually die. To clarify whether paralarvae induce the flocculation of food organisms or not, we cultured newly hatched Artemia nauplii, 3-day-old metanauplii and decapod crustacean zoeae with or without paralarvae at different growth stages (weight). Flocculation occurred only when Artemia were cultured with paralarvae; metanauplii had a higher susceptibility for flocculation than nauplii. Flocculated Artemia proportion increased with increasing paralarval weight. Scanning electron microscopy revealed that flocculated metanauplii had deformed setules on their setae, with hook-shaped tips and adhesion of neighbouring tips, suggesting that flocculation may occur via a mechanism similar to the ‘hook-and-loop fastener’. As octopus paralarvae exhibit external digestion, digestive enzymes secreted by paralarvae may deform Artemia setules and result in flocculation. As flocculation did not occur when metanauplii were cultured in water in which paralarvae were cultured and then removed, causative enzymes were probably rapidly inactivated after secretion

Effects of rotifer and Artemia enrichment in the first feeding and larval morphogenesis of purple mud crab, Scylla tranquebarica larvae

The effects of feeding rotifers and Artemia enriched with different types of enrichment in the first feeding and later stages of Scylla tranquebarica larvae were investigated. Two different experiments were conducted each with five enrichment treatments including live and digestible Nannochloropsis sp. and Tetraselmis sp. or commercial product. In Experiment I, the zoea 1 (Z1) larvae were fed with enriched or unenriched rotifers as their first feed until they moulted into the zoea 2 (Z2) stage, while in Experiment II, the zoea 3 (Z3) larvae were fed with enriched or unenriched Artemia until they metamorphosed into megalopa stage. In Experiment I, Z1 fed enriched rotifers showed higher survival, larval stage index (LSI) and carapace length than those in unenriched treatment. However, the highest survival was recorded in larvae fed Nannochloropsis sp. treatment. In Experiment II, Z3 fed Artemia enriched with digestible Tetraselmis sp. exhibited the highest survival and LSI, lowest chela-carapace length ratio and abnormal moulting frequencies. In comparison to live microalgae, digestible treatment resulted in a smaller chela-carapace length ratio with lower abnormal moulting. In conclusion, enrichments tested in this study can be used to enrich rotifers for the first feeding of Z1, while later stage (Z3 onwards) fed Artemia enriched with digestible Tetraselmis sp. improved survival and decreased the abnormal moulting frequencies of Z5 to megalopa stage

First report of plant fungal pathogen Zasmidium musae associated with moribund eggs of ornate spiny lobster (Panulirus ornatus) in Sabah

Fungal infections have been reported as one of the main hindrances for successful crustacean seed production. In a shrimp hatchery of Universiti Malaysia Sabah, abnormal sponge development of the ornate spiny lobster Panulirus ornatus was observed and it was suspected as fungal infection due to a change in sponge colour. Fungus was isolated from egg samples of P. ornatus and transferred to Peptone-Yeast-Glucose-Seawater (PYGS) agar to identify and to reveal its morphological characteristics. Interestingly, the isolate in PYGS broth transferred into sterilized seawater did not show any characteristic feature of any asexual reproduction of Oomycete infection on crustacean. Consequently, slide culture was performed for a more detailed examination, where the fungus isolate showed septate hyphae and vesicle-like fruiting body only upon staining via Iodine-Glycerol stain. Based on the morphological characteristic features, the present isolate was determined as a non-oomycete organism and designated as IPMB LE01 strain. According to the ITS nucleotide sequence analyses of IPMB LE01, it has matched to Zasmidium musae. This species was mainly reported in plant fungal infection and rarely observed in aquatic animals. Hence, it is considered as the first report of fungus-associated on the moribund eggs of ornate spiny lobster in Sabah