Reproductive biology of the female Japanese mantis shrimp Oratosquilla oratoria (Stomatopoda) in relation to changes in the seasonal pattern of larval occurrence in Tokyo Bay, Japan

ABSTRACT:   The reproductive traits and the monthly larval abundance of the mantis shrimp Oratosquilla oratoria were investigated in Tokyo Bay, Japan, in 2002. The goal of the study was to elucidate the cause of changes in the monthly pattern of larval abundance from the 1980s to the 1990s as these changes relate to variation in the stock size of the adult shrimp. Oogenesis was divided into 10 stages by histological observation. The developmental stage of oocytes in an individual's ovary was synchronous, suggesting that almost all the oocytes in an ovary are spawned at the same time. The size at first maturity was estimated to be 7 ≤ body length ( BL ) < 8 cm. Fecundity was expressed as a function of BL , ranging from 19 300 eggs for 8 cm BL to 92 100 eggs for 14 cm BL . Small female shrimps (<10 cm BL ) spawned around August. Most large female shrimps (≥10 cm BL ) spawned around May, and some large female shrimps also spawned until September. Although most large female shrimps spawned in spring, the larval abundance was low before July and high from August onwards. The results suggest that a substantial decrease in the stock size of large individuals causes the low larval abundance before July.     

Purification and properties of pyrethroid carboxyesterase in rat liver microsome

Pyrethroid carboxyesterase which hydrolyzes the esters of chrysanthemumic acid was purified from rat liver microsome by cholic acid solubilization, ammonium sulfate fractionation, heat treatment, and DEAE-Sephadex A-50 column chromatography. The 45-fold purified enzyme (38% yield) is likely to consist of single protein, as evidenced by polyacrylamide gel disc electrophoresis and Sephadex G-100 column chromatography, and had a molecular weight of approximately 74,000 and a K_m of 0.21 mM. It is susceptible to inhibition by organophosphates and carbamate insecticides and insensitive to pCMB, mercuric ion, and cupric ion. It is capable of hydrolyzing trans isomers of synthetic pyrethroids much more rapidly (five to ten times) than the cis counterparts. The purified pyrethroid carboxyesterase is apparently identical in nature with malathion carboxyesterase and with p-nitrophenyl acetate carboxyesterase.     

Effect of infection timing on fusarium head blight and mycotoxin accumulation in open- and closed-flowering barley

ABSTRACT Barley has two flowering types, chasmogamous (open-flowering) and cleistogamous (closed-flowering). We examined the effect of the timing of Fusarium graminearum infection on Fusarium head blight (FHB) and mycotoxin accumulation in barley cultivars with different flowering types using greenhouse experiments. In the first experiment, 13 cultivars were spray inoculated at two different developmental stages, and the severity of FHB was evaluated. The effect of the timing of infection differed among cultivars. Cleistogamous cultivars were resistant at anthesis but susceptible at 10 days after anthesis, whereas chasmogamous cultivars were already susceptible at anthesis. In the second experiment, five cultivars were inoculated at three different developmental stages and the concentrations of deoxynivalenol (DON) and nivalenol (NIV) in mature grain were analyzed. Cleistogamous cultivars accumulated more mycotoxins (DON and NIV) when inoculated 10 or 20 days after anthesis than when inoculated at anthesis, whereas chasmogamous cultivars accumulated more mycotoxins when inoculated at anthesis. Thus, the most critical time for F. graminearum infection and mycotoxin accumulation in barley differs with cultivar, and likely is associated with the flowering type. Late infection, even without accompanied FHB symptoms, was also significant in terms of the risk of mycotoxin contamination.     

Efficacy of thiabendazole, mebendazole, levamisole and ivermectin against gullet worm, Gongylonema pulchrum: in vitro and in vivo studies

In vitro and in vivo studies were conducted to evaluate the effects of thiabendazole, mebendazole, levamisole and ivermectin against Gongylonema pulchrum. For in vitro assays, third-stage larvae (L3) incubated with the drugs were administered orally to mice and the ability of larvae to invade the gastric mucosa of the animals was examined. After incubation, only those larvae treated with high concentrations of levamisole (1 and 10 microg/ml) were tightly coiled with intestines exhibiting morphological abnormalities. Good dose-response data for the drugs tested was observed at the time of worm recovery from mice, with no worms recovered at the two highest concentrations of levamisole. In vivo efficacy of the drugs against adult worms was evaluated in six groups of three rabbits, each of which was infected with 30 L3 of G. pulchrum and treated with thiabendazole at 100 mg/kg for 3 days, mebendazole at 70 mg/kg for 3 days, levamisole as a single dose of 8 mg/kg, and subcutaneously injected ivermectin as a single dose of 0.2 mg/kg or vehicles of the drugs (control) at 4 months post-infection. Necropsy 14 days after treatment revealed that levamisole, mebendazole and ivermectin reduced worm burdens by 63.2%, 22.8% and 25.8%, respectively, with no reductions in worms observed with thiabendazole. The surviving worms were principally found in the esophagus with the remainder distributed among the buccal mucosa, the tongue, and/or pharyngeal mucosa in all groups. A number of morphologically abnormal eggs were observed within the uterus and ovijector in female worms recovered from the thiabendazole-treated group. These findings suggest that levamisole exhibits in vivo efficacy against G. pulchrum infection and that the larval invasion tests using mice could be used to screen for anthelmintic susceptibility of nematodes.     

Thyroid hormone augments GLUT4 expression and insulin-sensitive glucose transport system in differentiating rat brown adipocytes in culture

The effects of triiodothyronine (T3) on differentiation-dependent expression of GLUT and responses of glucose transport to insulin and norepinephrine (NE) were investigated. Precursor cells of brown adipocytes isolated from the interscapular brown adipose tissue of newborn rats were cultured in the absence or presence of various concentrations of T3. Western bolt analysis revealed that treatment with T3 resulted in an increased expression of GLUT4, in a dose-dependent manner, whereas GLUT1 contents were unchanged. In parallel with the increase in GLUT4 expression, T3 improved insulin sensitivity for glucose transport, being accompanied by an increase in maximal transport rate and a reduction of ED(50). In contrast, T3-treatment of the brown adipocytes during the differentiation process had little effect on NE-regulatable glucose transport system. These results suggest that T3 plays a predominant role in the development of insulin-sensitive glucose transport during differentiation of brown adipocytes.     

Carbon dioxide exchange of a larch forest after a typhoon disturbance

A typhoon event catastrophically destroyed a 45-year-old Japanese larch plantation in southern Hokkaido, northern Japan in September 2004, and about 90% of trees were blown down. Vegetation was measured to investigate its regeneration process and CO₂ flux, or net ecosystem production (NEP), was measured in 2006–2008 using an automated chamber system to investigate the effects of typhoon disturbance on the ecosystem carbon balance. Annual maximum aboveground biomass (AGB) increased from 2.7 Mg ha⁻¹ in 2006 to 4.0 Mg ha⁻¹ in 2007, whereas no change occurred in annual maximum leaf area index (LAI), which was 3.7 m² m⁻² in 2006 and 3.9 m² m⁻² in 2007. Red raspberry (Rubus idaeus) had become dominant within 2 years after the typhoon disturbance, and came to account for about 60% and 50% of AGB and LAI, respectively. In comparison with CO₂ fluxes measured by the eddy covariance technique in 2001–2003, for 4.5 months during the growing season, the sum of gross primary production (GPP) decreased on average by 739 gC m⁻² (64%) after the disturbance, whereas ecosystem respiration (RE) decreased by 501 gC m⁻² (51%). As a result, NEP decreased from 159 ± 57 gC m⁻² to −80 ± 30 gC m⁻², which shows that the ecosystem shifted from a carbon sink to a source. Seasonal variation in RE was strongly correlated to soil temperature. The interannual variation in the seasonal trend of RE was small. Light-saturated GPP (P_max) decreased from 30–45 μmol m⁻² s⁻¹ to 8–12 μmol m⁻² s⁻¹ during the summer season through the disturbance because of large reduction in LAI.     

Avian predation on wild and cultured sea urchin <Emphasis Type="Italic">Strongylocentrotus intermedius</Emphasis> in a rocky shore habitat

ABSTRACT:   The present study reports the annual variation in consumption of the sea urchin Strongylocentrotus intermedius by avian predators on a rocky shore where the culture of sea urchins has been conducted. Carrion crow and a few gull species were the most abundant avian predators and consumed a large number of sea urchins. Crows consumed mostly natural sea urchins, approximately 36 kg ww/ha per year on the intertidal rocky bench, but the gull species consumed mostly cultured sea urchins, approximately 100 kg ww/ha per year in the culture area. The seasonal variation in the amount of sea urchins consumed by crows was higher than that by the gull species, presumably because of the difference in foraging behavior in association with the seasonal tidal cycle. The natural sea urchins consumed are an allochthonous input from the subtidal to the intertidal habitat, and thus, crow predation may not affect the natural and the cultured populations of the sea urchin. The gull species consumed much of the cultured sea urchin, and thus, may be regarded as an effective predator causing damage to sea urchin culture. The results suggest that further studies are needed to determine why the gull species selectively feed on cultured sea urchins.     

Loss of virulence of the phytopathogen Ralstonia solanacearum through infection by φRSM filamentous phages

φRSM1 and φRSM3 (φRSM phages) are filamentous phages (inoviruses) that infect Ralstonia solanacearum, the causative agent of bacterial wilt. Infection by φRSM phages causes several cultural and physiological changes to host cells, especially loss of virulence. In this study, we characterized changes related to the virulence in φRSM3-infected cells, including (i) reduced twitching motility and reduced amounts of type IV pili (Tfp), (ii) lower levels of β-1,4-endoglucanase (Egl) activity and extracellular polysaccharides (EPS) production, and (iii) reduced expression of certain genes (egl, pehC, phcA, phcB, pilT, and hrpB). The significantly lower levels of phcA and phcB expression in φRSM3-infected cells suggested that functional PhcA was insufficient to activate many virulence genes. Tomato plants injected with φRSM3-infected cells of different R. solanacearum strains did not show wilting symptoms. The virulence and virulence factors were restored when φRSM3-encoded orf15, the gene for a putative repressor-like protein, was disrupted. Expression levels of phcA as well as other virulence-related genes in φRSM3-ΔORF15-infected cells were comparable with those in wild-type cells, suggesting that orf15 of φRSM3 may repress phcA and, consequently, result in loss of virulence.