Brood sex ratios of the solitary parasitoid wasp, Coccophagus atratus

Abstract.

• 1 Female eggs of Coccophagus atratus are deposited within the haemolymph of coccoid scale insects. Male eggs are deposited on to late larval and prepupal stages of parasitoids of scale insects, including conspecifics.
• 2 When presented with either one host type or a combination of both host types, female C.atratus deposit all their available eggs, assigning the appropriate sex egg to each host encountered. Brood sizes are not adjusted for different combinations of hosts.
• 3 Behavioural observations show that females do not move away from patches of hosts until all their eggs are laid, regardless of the host type.
• 4 Brood sex ratios varied with changes in the relative availability of hosts for males and hosts for females. When both host-types were present in equal numbers, male biased sex ratios resulted (mean ±SEM =0.71 ± 0.009) and when 70% of hosts provided were suitable for female eggs, mostly female-biased sex ratios resulted (mean ± SEM = 0.37±0.01).
• 5 Our results do not fit predictions based on the assumption that a sex ratio of 0.5 should be expected in C.atratus. Observed sex ratios indicate that the unusual life histories of these parasitoids need to be taken into account in explanations of their sex ratios.

     

Some Characteristics of Pseudomonas 0–3 which Utilizes Polyvinyl Alcohol

Pseudomonas 0–3 strain which was isolated from soil can grow on polyvinyl alcohol (PVA) as a sole carbon source. When 0.5 per cent of PVA (500, 1500 or 2000) was employed as the carbon source in the culture medium, PVA was almost completely lost from the culture fluid after a week and the concentration of total organic carbon measured by a TOC analyzer decreased from the initial value of about 2700 ppm to 250~300 ppm after 7~10 days culture. This bacterium was found to produce and secrete an inducible enzyme which degrade PVA. The way by which this enzyme degrades PVA was examined and the results were obtained which suggested that PVA was broken down oxidatively in a way of endowise splitting. However, the mechanism of PVA degradation has not been clarified yet. The optimum pH and temperature for enzyme activity were examined and they were 7.5~8.5 and 35~45°C, respectively. Morphological and biological characteristics of this bacterium were examined and it was similar to a strain of Pseudomonas boreopolis.     

Targeted discovery and identification of novel nucleoside biomarkers in Apostichopus japonicus viscera using metabonomics

In this study, we investigated the metabonomic profiles of Apostichopus japonicus using an LC-MS-based method in conjunction with multivariate data analysis. Based on the PLS-DA model, 85 differential metabolites (VIP value >1.0) were obtained from viscera and body wall samples. The MS/MS and NMR experiments were used for the qualitative identification of the characteristic peaks. Sphingoid-based nucleoside analogues were the main components in Chinese A. japonicus viscera. Our findings demonstrate that A. japonicus viscera contain a large number of compounds that may have applications as nutraceuticals or pharmaceuticals.     

Effect of the ascidian Styela clava on the growth of small holothurians of the species Apostichopus japonicus

We studied the effect of the common ascidian Styela clava on the growth of small holothurians of the species Apostichopus japonicus (Selenka, 1867). In a traditional aquaculture system, the oxygen consumption rates, ammonia excretion rates, and ingestion rates of small A. japonicus were reduced significantly, which suggested that this group was stressed by the presence of large A. japonicus, and that this stress grew stronger with time. Oxygen consumption rates, ammonia excretion rates, and ingestion rates of small A. japonicus in an integrated aquaculture (IA) system with S. clava, microalgae, and A. japonicus were higher than those observed in the traditional culture system. Metabolic and digestive enzymes were more active in small A. japonicus in the IA system than in those in the traditional aquaculture system. These results suggest that the IA model did not affect the growth of large A. japonicas, but produced a marked positive impact on the growth of small individuals.     

Possible Mechanism of Oxygen Activation in Linoleate Peroxidation by Fusarium Lipoxygenase

The Oxygen activating mechanism of Fusarium lipoxygenase, a heme-containing dioxygenase, was studied. The enzyme did not require any cofactors, such as H₂O₂, however, both superoxide dismutase and catalase inhibited linoleate peroxidation by Fusarium lipoxygenase. A low concentration of H₂O₂ caused a distinct acceleration in enzymatic peroxidation. These results indicate that both O₂? and H₂O₂ are produced as essential intermediates of oxygen activation during formation of linoleate hydroperoxides by Fusarium lipoxygenase. This peroxidation reaction was also prevented by scavengers of singlet oxygen (¹O₂), but not by scavengers of hydroxy 1 radical (OH). Generation of O₂? in the enzyme reaction was detected by its ability to oxidize epinephrine to adrenochrome. Moreover, the rate of peroxide formation was greater in the D₂O than in the H₂O buffer system. These results suggest that the Haber–Weiss reaction (O₂^?+H₂O₂→OH^?+OH^·+¹O₂) is taking part in linoleate peroxidation by Fusarium lipoxygenase, and the ¹O₂ evolved could be responsible for the peroxidation of linoleate. H₂O₂ produced endogenously in the enzyme reaction might act as an activating factor for the enzyme. This possible mechanism of oxygen activation can explain the absence of a need for exogenous cofactors with Fusarium lipoxygenase in contrast to an other heme-containing dioxygenase, tryptophan pyrrolase, which requires an exogenous activating factor, such as H₂O₂.     

Microsatellite DNA markers for population-genetic studies of blue mackerel (Scomber australasicus) and cross-specific amplification in S. japonicus

Blue mackerel (Scomber australasicus) is targeted by large-scale purse-seiners in the western North Pacific, and its stock structure is still contentious. Herein, we described 10 polymorphic microsatellite loci for blue mackerel. The number of alleles among 32 individuals surveyed ranged from five to 27 (average of 16.2 alleles per locus). Departures from Hardy-Weinberg expectation were observed at two loci. Cross-specific amplification in the congener, S. japonicus, was successful, except for one locus, revealed to be diagnostic for these congeners. These microsatellite loci will be useful tools to address queries in population genetic structure, fishery management unit and taxonomic species status in the genus Scomber.     

Amphibian chytridiomycosis in Japan: distribution,haplotypes and possible route of entry into Japan

A serious disease of amphibians caused by the chytrid fungus Batrachochytrium dendrobatidis was first found in Japan in December 2006 in imported pet frogs. This was the first report of chytridiomycosis in Asia. To assess the risk of pandemic chytridiomycosis to Japanese frogs, we surveyed the distribution of the fungus among captive and wild frog populations. We established a nested PCR assay that uses two pairs of PCR primers to amplify the internal transcribed spacer (ITS) region of a ribosomal RNA cassette to detect mild fungal infections from as little as 0.001 pg (1 fg) of B. dendrobatidis DNA. We collected swab samples from 265 amphibians sold at pet shops, 294 bred at institutes and 2103 collected at field sites from northern to southwestern Japan. We detected infections in native and exotic species, both in captivity and in the field. Sequencing of PCR products revealed 26 haplotypes of the B. dendrobatidis ITS region. Phylogenetic analysis showed that three of these haplotypes were specific to the Japanese giant salamander (Andrias japonicus) and appeared to have established a commensal relationship with this native amphibian. Many other haplotypes were carried by alien amphibians. The highest genetic diversity of B. dendrobatidis was found in the American bullfrog (Rana catesbeiana). Some strains of B. dendrobatidis appeared to be endemic to Japanese native amphibians, but many alien strains are being introduced into Japan via imported amphibians. To improve chytridiomycosis risk management, we must consider the risk of B. dendrobatidis changing hosts as a result of anthropogenic disturbance of the host‐specific distribution of the fungus.