Larval survival,development and growth in the horsehair crab,Erimacrus isenbeckii,cultured under different photoperiod conditions

Larval sinking causes larval mass mortality during seed production in the horsehair crab, Erimacrus isenbeckii. Under normal light conditions, horsehair crab larvae generally show negative phototactic behaviour and sink in their rearing seawater. It has been proposed that culturing larvae in the dark may prevent larval sinking. Herein, we examined the effect of photoperiods on horsehair crab larval survival and development to facilitate the development of larval rearing techniques that prevent sinking. Newly hatched larvae were reared with Artemia to the first crab stage in 2‐L beakers under five photoperiods: 0L:24D, 6L:18D, 12L:12D, 18L:6D and 24L:0D. Larvae survived and molted to the first crab stage under all tested photoperiod conditions. The survival rate improved with increasing light period, whereas the developmental period for each larval stage decreased with increasing light period. Longer light periods increased the carapace length at the first crab stage. Our results suggest that larvae could be cultured to the first crab stage in large‐scale tanks under constant darkness. However, significantly improved larval performance under longer photoperiodic conditions indicates a need for developing alternative culture techniques to control larval behaviour in the seed production tank.     

Grain yield responses of lowland rice varieties to increased amount of nitrogen fertilizer under tropical highland conditions in central Kenya

Tropical highland conditions in Mwea Kenya, ensure the high radiation and the large day–night temperature differences. Such conditions are generally believed to promote rice growth and yield, but the current grain yield is lower than the expectation. In the current standard N fertilizer practice in Mwea, 75 kg nitrogen (N) ha^?1 is applied in three splits at fixed timing. The effects of increases in N fertilizer amount (125, 175, and 225 kg N ha^?1) on rice growth and yield were evaluated to test the hypothesis that unachieved high rice grain yield in Mwea is due to insufficient amount of N fertilizer. Two popular lowland varieties in Mwea (Basmati 370 and BW196) and two varieties reported as high yielding in other countries (Takanari and IR72) were used. Shoot dry weight (DW) increased with increases in the amount of N fertilizer applied in three splits at fixed timing, irrespective of variety. It reached approximately 20 t ha^?1 under increased N conditions (>75 kg N ha^?1) in several cases, indicating that high biomass production could be achieved by increasing N application rate. However, the increased biomass did not increase grain yield, due to decreased grain filling under high N conditions in all varieties. Thus, N amounts above 75 kg ha^?1 were ineffective for increasing grain yields in Mwea, where N fertilizer was applied in three splits at fixed timing. Increasing influence of low temperature under high N conditions may be one of the reasons for the decreased grain filling in Mwea.     

水稻叶片含氮量无损快速测定方法

采用CCN6000水稻叶片氮素快速测定仪,以籼型常规早稻中早39为材料,研究了水稻叶片氮含量化学分析值、CCN值及SPAD值的关系。结果表明,早稻倒1叶叶片CCN值与含氮量呈近1.0∶1.0的关系,倒2叶叶片CCN值与含氮量呈近1.0∶1.1的关系,倒3叶叶片CCN值与含氮量呈近1.0∶1.2的关系,倒1叶CCN值与含氮量之间最为吻合,CCN值与SPAD值显著相关。水稻孕穗期叶片含氮量为倒3叶倒2叶倒1叶。研究表明,CCN值可以作为叶片含氮量的快速诊断依据。     

Age,growth and age at sexual maturity of fan ray <Emphasis Type="Italic">Platyrhina sinensis</Emphasis> (Batoidea: Platyrhinidae) in Ariake Bay,Japan

Abstract:   Age, growth and sexual maturity of the fan ray Platyrhina sinensis in Ariake Bay, Japan were determined from specimens collected from May 2002 to September 2006. Age determination was conducted by vertebral centrum analysis using soft X-radiography. Annual band pair deposition was determined by marginal increment and edge analyses. The von Bertalanffy growth model best described the overall pattern of growth for both males and females (males L _∝  = 455.2, k  = 0.56, t ₀ = −1.09; females L _∝  = 555.8, k  = 0.28, t ₀ = −1.77; L _∝ is the theoretical asymptotic total length in mm, k is the growth rate coefficient and t ₀ is the theoretical time at zero length). Parameter estimates suggest that females attain a larger asymptotic total length and grow more slowly than males. The observed maximum ages were 5 years for males and 12 years for females. Age at 50% sexual maturity was 2.1 years for males and 2.9 years for females. The results indicate that this species is relatively fast-growing, short-lived and early maturing compared with many batoid species.     

Influence of heating history on dynamic viscoelastic properties and dimensions of dry wood

To obtain new information about the mechanical and physical properties of dry wood in unstable states, the influence of heating history on viscoelastic properties and dimensional changes of dry wood in the radial, tangential, and longitudinal directions was studied between 100° and 200°C. Unstable states of dry wood still existed after heating at 105°C for 30 min and were modified by activated molecular motion in the first heating process to temperatures above 105°C. This phenomenon is thought to be caused by the unstable states reappearing after wetting and drying again. Dry wood components did not completely approach the stable state in the temperature range tested, because they did not entirely surpass the glass transition temperatures in most of the temperature range. In constant temperature processes at 135° and 165°C, E′ increased and E″ decreased with time regardless of the direction. This indicated that the unstable states of dry wood components were gradually modified with time at constant temperatures. On the other hand, anisotropy of dimensional change existed and dimension increased in the longitudinal direction, was unchanged in the radial direction, and decreased in the tangential direction with time at constant temperatures. Part of this report was presented at the 13th Annual Meeting of the Chubu Branch of the Japan Wood Research Society, Shizuoka, August 2003     

Uptake of dissolved free amino acids by spiny lobster <Emphasis Type="Italic">Panulirus japonicus</Emphasis> phyllosoma larvae

This study examined the ability of late stage (instar XXVI) Japanese spiny lobster Panulirus japonicus phyllosoma larvae to uptake seven l-type amino acids (AAs; aspartic acid, Asp; threonine, Thr; glutamic acid, Glu; glycine, Gly; alanine, Ala; valine, Val; and methionine, Met) from the rearing medium. The time course uptake during incubation for 5 h in solutions containing 1, 2, 5, 10, or 20 μM of each AA was determined using high performance liquid chromatography. There was considerable individual variation in uptake rates and even occasional release of AAs, but larvae showed net uptakes of all seven AAs. Two polar acidic AAs (Glu and Asp) were readily taken up whereas neutral AAs, including three considered as essential for crustaceans (Val, Met, and Thr), had lower uptake rates. Transient releases of AAs by the larvae were common for the AAs with the lowest uptake rates at 1–2 h of incubation. Uptake rates increased with increasing AA concentration but less so for those taken up in larger amounts. Larvae took up AAs to a total of 16.4 μmol/g/h for incubation in the 20 μM solution. The ability to uptake nutrients directly from the medium may be important for the well-being of the larvae.     

Spawning induced by cubifrin in the Japanese common sea cucumber <Emphasis Type="Italic">Apostichopus japonicus</Emphasis>

The neuropeptide cubifrin-I and its derivative cubifrin-L have recently been shown to be potent substances that induce in vitro oocyte maturation and spawning in the Japanese common sea cucumber Apostichopus japonicus. We have examined the reproductive behavior of A. japonicus in vivo following the injection of cubifrin-L into the body cavity with the aim of determining the practical value of using this peptide to induce spawning in the hatchery setting. The responsiveness of ovarian fragments with oocytes >155 μm in diameter to cubifrin-L in vitro was well correlated with the spawning success induced in vivo by a cubifrin-L injection. Mature sea cucumbers injected with cubifrin-L displayed sequential reproductive behaviors, which comprised climbing up the side wall of the tank toward the water surface, waving of the head, and shedding of gametes. Gamete shedding started about 60 and 80 min after the injection of cubifrin-L in males and females, respectively, and was completed almost simultaneously in the two sexes about 2 h post-injection. Repeated injections of cubifrin-L at intervals of about 10 days successfully induced multiple spawnings in males and females. These results demonstrate that cubifrin-L can be used as an effective inducer of spawning in Japanese sea cucumber cultivation.     

Fusarium rot of hyacinth caused by <Emphasis Type="Italic">Gibberella zeae</Emphasis> (anamorph: <Emphasis Type="Italic">Fusarium</Emphasis><Emphasis Type="Italic"> graminearum</Emphasis>)

Severe rot of leaves, peduncles and flowers caused by Gibberella zeae (anamorph: Fusarium graminearum) was found on potted plants of hyacinth (Hyacinthus orientalis), a liliaceous ornamental, in greenhouses in Kagawa Prefecture, Japan, in January 2001. This disease was named “Fusarium rot of hyacinth” as a new disease because only the anamorph, F. graminearum, was identified on the diseased host plant. The authors contributed equally to this work. The fungal isolate and its nucleotide sequence data obtained in this study were deposited in the Genebank, National Institute of Agrobiological Sciences and the DDBJ/EMBL/GenBank databases under the accession numbers MAFF239499 and AB366161, respectively.     

Pathology of female mice experimentally infected with an in vitro cultured strain of Trypanosoma equiperdum

Dourine, caused by infection with Trypanosoma equiperdum, is one of the trypanosomiasis in equids. The clinical course of dourine is long-term, ranging from 1–2 months to several years. Since the pathogenesis of dourine has not yet been elucidated, experimental studies using mouse infection models are needed. Although mice are not susceptible to most T. equiperdum strains, some strains can infect mice. Even in such strains, infected mice develop rapidly transient parasitemia and die within 2–8 days. Therefore, mice experimentally infected with these T. equiperdum strains are not suitable for mouse infection models to analysis the pathogenesis of dourine. A sequential method of isolating parasites from dourine-affected horses and adapting them to in vitro cultures using soft agarose media was recently developed. Various T. equiperdum strains adapted to in vitro conditions have been established using this technique. We used one of these strains, the T. equiperdum IVM-t2 strain. In the present study, T. equiperdum IVM-t2 strain inoculated mice developed periodic parasitemia during the experimental period of 60 days. Histopathologically, vaginitis and dermatitis were observed. These findings were comparable to those of dourine-affected horses. Therefore, mice infected with T. equiperdum IVM-t2 strain may be a valuable tool for pathological, immunological, and parasitological in vivo research, and will contribute to investigations on the mechanisms underlying the disease process and the host-parasite relationship.