Stable isotope analysis of two species of anguilliform leptocephali (<Emphasis Type="Italic">Anguilla japonica</Emphasis> and <Emphasis Type="Italic">Ariosoma major</Emphasis>) relative to their feeding depth in the North Equatorial Current region

Anguilla japonica leptocephali are transported from their offshore spawning area to their recruitment areas in East Asia, but their depth distributions, food sources and feeding are still poorly known. This study analyzed carbon and nitrogen stable isotope ratios of leptocephali of A. japonica, Ariosoma major and Ariosoma spp., and of particulate organic matter (POM), their likely food source, at five different depths in 2004–2009. We used mixing models to show that A. japonica appeared to be feeding at depths between 5 and 50 m, but sometimes deeper. A. major appeared to have a tendency of mostly feeding at depths of 50 m or shallower. Although the A. japonica and Ariosoma spp. collected in the same area during the leptocephalus stage appeared to have different feeding ecologies possibly related to different types of POM, their different depth distributions, sizes and transport histories may also help explain these differences.     

Juvenile hormone–dopamine systems for the promotion of flight activity in males of the large carpenter bee Xylocopa appendiculata

The reproductive roles of dopamine and dopamine regulation systems are known in social hymenopterans, but the knowledge on the regulation systems in solitary species is still needed. To test the possibility that juvenile hormone (JH) and brain dopamine interact to trigger territorial flight behavior in males of a solitary bee species, the effects on biogenic amines of JH analog treatments and behavioral assays with dopamine injections in males of the large carpenter bee Xylocopa appendiculata were quantified. Brain dopamine levels were significantly higher in methoprene-treated males than in control males 4 days after treatment, but were not significantly different after 7 days. Brain octopamine and serotonin levels did not differ between methoprene-treated and control males at 4 and 7 days after treatment. Injection of dopamine caused significantly higher locomotor activities and a shorter duration for flight initiation in experimental versus control males. These results suggest that brain dopamine can be regulated by JH and enhances flight activities in males. The JH–dopamine system in males of this solitary bee species is similar to that of males of the highly eusocial honeybee Apis mellifera.     

Improvement of production of lipopeptide antibiotic iturin A using fish protein

To enhance the production of lipopeptide antibiotic iturin A, nutrient contents of the culture mediums were investigated in both submerged and biofilm fermentations. As a carbon source maltose and as nitrogen source, fish protein was used. In submerged fermentation maltose uptake was found lower (12%) compared to biofilm fermentation (15%) that was associated with higher cellular growth in biofilm. However, requirement of nitrogen (fish protein) concentration was found similar in both submerged and biofilm fermentations. Production of iturin A in submerged fermentation with 12% maltose and 5% fish protein was 4450 mg/L, and in biofilm fermentation it was 5050 mg/L when 15% maltose and 5% fish protein was used.     

Large- and small-size advantages in sneaking behaviour in the dusky frillgoby <Emphasis Type="Italic">Bathygobius fuscus</Emphasis>

Sneaking tactic, a male alternative reproductive tactic involving sperm competition, is generally adopted by small individuals because of its inconspicuousness. However, large size has an advantage when competition occurs between sneakers for fertilization of eggs. Here, we suggest that both large- and small-size advantages of sneaker males are present within the same species. Large sneaker males of the dusky frillgoby Bathygobius fuscus showed a high success rate in intruding into spawning nests because of their advantage in competition among sneaker males in keeping a suitable position to sneak, whereas small sneakers had few chances to sneak. However, small sneaker males were able to stay in the nests longer than large sneaker males when they succeeded in sneak intrusion. This suggests the possibility of an increase in their paternity. The findings of these size-specific behavioural advantages may be important in considering the evolution of size-related reproductive traits.     

感潮河段盐度和缺氧水体时空分布规律研究

感潮河段水体的物质输运规律及其时空分布不仅受径流、潮汐动力的双重影响,还受水闸调度等人类活动的影响.针对水闸调度影响下感潮河段复杂的水动力学及其伴随的物质输运过程,提出一种新的算盘式网格结构,建立了水动力学和物质输送的三维数学模型,考察了在径流、潮汐及水闸调度综合作用下,感潮河段水流密度分层的特点,并对水体中溶解氧和盐度的时空分布规律及其影响因素进行研究.结果发现,数值模拟计算结果与观测值吻合良好,表明所建立的三维数值模型可以很好地预测感潮河段的水流运动和物质输运规律.研究表明,感潮河段的缺氧水体首先出现在盐水楔的前端,在盐-淡水分层强度、盐水停留时间及水闸调度的综合作用下,出现溶解氧浓度持续降低的趋势,并导致缺氧水体范围从河口上游向下游扩展,随水闸的放流缺氧水体被冲刷的现象.