Effect of temperature on survival,growth and malformation of cultured larvae and juveniles of the seven-band grouper Epinephelus septemfasciatus

The effects of rearing temperature (23–29 °C) during the larval and juvenile stage on survival, growth and skeletal malformations in the seven-band grouper Epinephelus septemfasciatus were investigated. The survival rate of juveniles 30–40 mm in total length emerging from eggs was higher at 25 and 26 °C (0.1–1.3 %) than at 23 °C or 27–29 °C (0.004–1.5 %). Growth (increase in total length) was accelerated at higher temperatures. The frequency of malformed individuals was lower at 25–27 °C (36.0–61.5 %) than at 23, 28 or 29 °C (65.3–76.9 %). Specific incidences of spinal curvature and centrum fusion or defects in juveniles were not related to rearing temperature. However, incidences of twisted or compressed vertebrae (6.5–64.0 %) were higher at higher temperatures, while the incidence of bifurcated neural spine was significantly higher at 23 °C (43.6–54.4 %) than at other temperatures (3.3–22.7 %). The incidence rate of spinal curvature (23.3 %) was significantly higher in juveniles with a deflated swim bladder, regardless of rearing temperature. The results of this study suggest that the optimum culture temperature for seven-band grouper is 25–26 °C, collectively considering the survival, growth and incidences of abnormalities. Our results also demonstrate the significance of identifying the conditions for swim bladder inflation to prevent spinal curvature in seven-band grouper.     

Genetic population structure of the Pacific bluefin tuna Thunnus orientalis and the yellowfin tuna Thunnus albacares in the North Pacific Ocean

The genetic population structure of the Pacific bluefin tuna (PBF) Thunnus orientalis and the yellowfin tuna (YFT) T. albacares in the North Pacific Ocean was investigated. The polymorphism of microsatellite (SSR) loci and sequences of mitochondrial DNA control region (mtCR) were analyzed for 71 samples of PBF from Japan and Mexico and 45 samples of YFT from Japan and Panama. In the SSR analyses, both single-locus (?0.010 to 0.008 in PBF and ?0.023 to 0.020 in YFT) and global multilocus (0.003 in PBF and ?0.002 in YFT) F _ST values among the geographic populations were low and not significant in these species. In the mtCR analyses, neither the neighbor-joining tree nor the minimum spanning network showed genetic differentiation among the geographic populations in each species. The pairwise F _ST values among the geographic populations of them (?0.005 in PBF and ?0.020 to ?0.014 in YFT) were low and not significant. Our SSR and mtCR data suggested that genetic differentiations were not evident among the eastern and western populations in the North Pacific Ocean either in PBF or in YFT. Mismatch distributions, demographic parameters, and neutrality tests suggested that sudden population expansion of PBF and YFT in the North Pacific Ocean occurred 628,000–731,000 and 450,000–525,000 years ago, respectively.     

Promotion of initial swimbladder inflation in Pacific bluefin tuna,Thunnus orientalis (Temminck and Schlegel), larvae

Initial swimbladder inflation (ISI) of Pacific bluefin tuna (PBT), Thunnus orientalis, larvae was studied to increase the survival of cultured larvae. Experiment 1 was conducted to explore promotion and inhibition of ISI under different water surface conditions; including the use of surface skimmer to remove autogenous surface substances (SS), covering the water surface with liquid‐paraffin‐layer (LP) and oil film (OF), and a control (non‐treatment, NT). Significantly higher inflation frequency was observed in SS (62.2%) than NT (11.9%), LP (2.7%) and OF (3.9%). This indicates that ISI in PBT larvae can be promoted by removal of surface substances on rearing water which inhibit larval air gulping. Experiment 2 aimed to elucidate proper day of larval age to start skimming for promoting ISI with four different periods of oil film removal: from 3 to 8 (SF3D), 4 to 8 (SF4D), 5 to 8 (SF5D), 6 to 8 (SF6D) days‐post‐hatch (dph). Significant improvement in ISI frequency was observed in SF3D (80.2%) but the frequency was very poor in SF4D, SF5D, and SF6D (17.8–7.5%). This implies the need of oil film removal without missing a narrow window, 1 day of 3 dph, to promote ISI in practical PBT larviculture.     

First report of Melon yellow spot virus infecting balsam pear (<Emphasis Type="Italic">Momordica charantia</Emphasis> L.) in Japan

A new disease causing necrotic spots and yellowing on leaves of balsam pear (Momordica charantia) was found in Kochi Prefecture, Japan. In this study, we identified the causal pathogen as Melon yellow spot virus (MYSV) based on morphology of virus particles, serology, and the nucleotide sequence of the nucleocapsid protein gene. This is the first report of natural infection of balsam pear by MYSV. We propose the name spotted wilt for this new disease of balsam pear.     

Myrmecofaunal change with bamboo invasion into broadleaf forests

Recently, it is documented that bamboo (Mousouchiku:Phyllostachys pubescens Mazel) invasion deteriorates ecological and/or landscape diversity. In order to investigate the ecological effects on forest-floor arthropods caused by bamboo invasion, we compared the myrmecofauna among broadleaf forests, bamboo-broadleaf mixed forests, and bamboo forests in Hiroshima City and its vicinity. Myrmecofauna in bamboo forests were more impoverished than in broadleaf forests. Myrmecofauna in the mixed forests, however, were similar to that in broadleaf forests in both species diversity and species composition. The change in myrmecofauna may occur relatively late after the initial bamboo invasion.     

Seroprevalence of antibody to NcSAG1 antigen of Neospora caninum in cattle from Western Java,Indonesia

Neospora caninum can cause fetal abortion and neonatal mortality in cattle, and is a cause of economic concern worldwide. This study aimed to determine the prevalence of Neospora caninum-specific antibodies in cattle from Western Java, Indonesia. Serum samples from 991 cattle from 21 locations were tested for antibodies to N. caninum by using an enzyme-linked immunosorbent assay (ELISA) on the basis of recombinant NcSAG1. The overall seroprevalence was 16.6%, ranging from 0 to 87.5% in the sampled locations. The results of this study indicate latent infection rates of sampled animals were different in each location. Further studies are necessary to elucidate the relationship between N. caninum infection and abortion in cattle, and to identify risk factors for infection in high-prevalence environments.     

Physiological and psychological responses to a heavy floor-impact sound generated by dropping an automobile tire in a wooden house

We investigated the physiological and psychological responses of ten healthy male volunteers to a single heavy floor-impact sound generated by dropping an automobile tire from heights of 50, 100, and 150cm in a wooden house. Blood pressure and peripheral blood flow were measured simultaneously, and sensory evaluation was conducted using the semantic differential method. The results obtained were as follows: (1) the systolic blood pressure increased and the peripheral blood flow decreased when the subjects heard the heavy floor-impact sound; (2) the heavy floor-impact sound caused the subjects to feel uncomfortable, but there was no significant change in sharp and monotonous feelings; and (3) for the heavy floor-impact sound for 100cm and that for 150cm, the subjects showed no difference in comfortable feeling, but we detected differences in the variations of both the systolic blood pressure and the peripheral blood flow.Part of this research was presented at the 48th Annual Meeting of the Japan Wood Research Society, Shizuoka, April 1998.     

桑蚕消化道中肠球菌的部分特性的研究

在发现健康桑蚕幼虫消化道中存在β－溶血性的肠球菌的基础上，首次证实了肠球菌中只在厌氧条件下发生β－溶血反应菌的存在．Ｃｒａｉｇｉｅ试管法和毛细管法进一步确认了分离肠球菌菌株的生物性运动．“００８２”分离菌株在接种菌量较多、培养温度较高和碱性较大（ｐＨ值９～１０）条件下显示了较强的运动性．因此，它也将较容易地附着在桑蚕幼虫的围食膜上     

A mesoscale iron enrichment in the western subarctic Pacific induces a large centric diatom bloom

We have performed an in situ test of the iron limitation hypothesis in the subarctic North Pacific Ocean. A single enrichment of dissolved iron caused a large increase in phytoplankton standing stock and decreases in macronutrients and dissolved carbon dioxide. The dominant phytoplankton species shifted after the iron addition from pennate diatoms to a centric diatom, Chaetoceros debilis, that showed a very high growth rate, 2.6 doublings per day. We conclude that the bioavailability of iron regulates the magnitude of the phytoplankton biomass and the key phytoplankton species that determine the biogeochemical sensitivity to iron supply of high-nitrate, low-chlorophyll waters.