Induction of spawning in Pacific white shrimp Litopenaeus vannamei (Boone, 1931) by injection of its molt inhibiting hormone isoform II produced in E. coli

The optimization of reproductive parameters in shrimp farming continues to be a challenge for most producing countries. Although the crustacean neuropeptides have been studied extensively in the last two decades, the functions of most of these neuropeptides remained putative. Among them, molt‐inhibiting hormone isoform II (MIH II) has shown an important role in vitellogenesis. In this study, the cDNA encoding mature MIH II peptide was isolated by RT‐PCR from the L. vannamei eyestalk. The cDNA was cloned into pET28a bacterial expression vector. Recombinant MIH II was obtained in the form of insoluble inclusion bodies and purified to ~88% purity. Two doses of rMIH II and a negative control group were assayed in vivo. The stages of ovarian maturation and spawning were recorded during 72 hr post‐injection. The results showed that ovarian maturation occurred approximately in 9% and 33% of females injected with rMIH II at the doses of 300 and 600 ng/gbw respectively. Neither maturation nor spawning was detected in the negative control group. Females injected with 600 ng/gbw, which showed vitellogenic stages III and IV, spawned. These preliminary results argue that the hormone rMIH II could be a promising candidate to induce spawning in L. vannamei shrimp.     

RH—2485对棉铃虫的室内药效试验

利用Rohm and Haas公司1996年推出的一种非甾醇类蜕皮激素竞争物RH-2485,用点滴法和喷雾法对棉铃虫防治效果进行了室内研究。结果表明,RH-2485可以引起棉铃虫非正常蜕皮。用25、50、100和150mg/L的RH-2485异丙醇溶液对2龄幼虫进行喷雾,阳性反应率为43.6％～94.9％。用RH-2485异丙醇溶液对6龄初蜕皮幼虫(进入6龄不超过1h)进行点滴,剂量为1、30、60、100和200ng/头,24h后阳性反应率为0～83.33％,而15d后的最终反应率为15.38％～96.67％。研究结果显示RH-2485对棉铃虫有显著引起非正常蜕皮的作用,可用于棉铃虫田间防治试验。     

脊尾白虾腺苷酸转移酶基因应答蜕皮的表达特征研究

蜕皮是脊尾白虾等甲壳类生物的一种特殊生活史,在前期克隆获得腺苷酸转移酶基因的基础上,研究了该基因在脊尾白虾蜕皮后不同组织和不同时间点(0、1、5、10、15min)的表达特征。试验结果表明,蜕皮后鳃组织中腺苷酸转移酶基因的表达量显著上升(P0.01);在蜕皮后1min,腺苷酸转移酶基因的表达量开始升高,至10min时达到峰值,随后下降。该结果显示,腺苷酸转移酶基因的表达特征与脊尾白虾蜕皮时的行为学特征一致,说明腺苷酸转移酶基因在甲壳动物蜕皮过程中起着非常重要的作用。     

Resistance and cross-resistance to the spinosyns - A review and analysis

The spinosyns were introduced in 1997 with the launch of spinosad. Since then, there have been several cases of resistance to spinosad in the field populations of insect pest species that have resulted in reduced efficacy. There have also been a number of studies where spinosad-resistant insect strains were created and characterized in the laboratory. Likewise many studies examining resistance to a variety of other classes of insecticides have included spinosad in the evaluation of their cross-resistance spectrum. Understanding mechanisms of resistance and cross-resistance can provide the basis for developing insecticide resistance management programs, as well as defining the most appropriate tools to address potential resistance issues. This review provides an overview and analysis of resistance and cross-resistance to the spinosyns (spinosad and spinetoram). Although there are more than 30 examples of resistance to the spinosyns, only half of these are related to selection in the field. The majority of these field selected examples occur in either the diamondback moth or western flower thrips. There have also been over 85 studies investigating cross-resistance to the spinosyns. However, in half of these studies spinosad showed no cross-resistance, and in another third of the total studies spinosad cross-resistance was minimal. Therefore, while resistance and cross-resistance to the spinosyns does occur, it is appears to be more limited in impact than might be implied from the large body of literature on the subject.     

Persistence of insect growth regulators against the rice weevil,sitophilus oryzae,in grain commodities

Ten insect growth regulators (IGRs): four juvenile hormone analogs (JHAs) — fenoxycarb, MV-678, R-20458 and dofenapyn, and six molt inhibitors (MIs) — triflumuron, chlorfluazuron, hexaflumuron, teflubenzuron, Dowco 439 and flufenoxuron; and the organophosphate malathion, were evaluated for residual activity in stored grain for 2 years against the rice weevil,Sitophilus oryzae (L.). Triflumuron, flufenoxuron, teflubenzuron, chlorfluazuron, hexaflumuron and fenoxycarb, each at a concentration as low as 1 ppm a.i., were superior to 10 ppm malathion throughout the experiment. The six MIs, each tested at 50 and 100 ppm a.i., gave complete control for 2 years. Moreover, a concentration as low as 1 ppm a.i. of triflumuron, teflubenzuron, flufenoxuron and chlorfluazuron had good residual activity for 1 year post-treatment and provided almost complete grain protection during this period. Among the JHAs, fenoxycarb had the best residual activity. It gave almost complete control (96.6%) ofS. oryzae at 10 ppm for 18 months post-treatment. The other JHAs at the four test concentrations failed to produce this level of control. The viability of the wheat grain was not affected by any of the insecticidal treatments, with 90% germination recorded in treated and control, grains at all intervals tested.     

Feeding Hens During Alternating a.m. and p.m. Time Blocks to Induce Zero Egg Production During the Molt

There is a need to evaluate the position paper and guidelines set forth by the United Egg Producers (Washington, DC) and the American Veterinary Medical Association (Schaumburg, IL) on feeding practices and nutrient levels provided during a molt. This pilot study was undertaken to learn if a complete cessation of lay could be achieved with daily feeding while using an alternate morning and evening feeding schedule. This was an effort to mimic the fast that a bird experiences in a natural setting. The hens were fed the amount they would eat in 4 h during the morning one day and again the evening of the next day. Some hens ceased production in the third week and others in the fourth week, with zero production for all hens occurring during the fifth week. The return to 50% egg production was achieved from wk 7 to 8. Peak egg production occurred from the eleventh to twelfth weeks postmolt, reaching a level only 5 to 6 percentage points below the first cycle. This feeding protocol resulted in complete cessation of lay, allowing for a more uniform and complete restoration of the ovarian and oviductal tissues. This restoration is necessary for an effective economical postmolt period of egg production.     

KK-42对日本沼虾幼虾蜕皮周期的影响及其可能机制

为了探索KK-42对日本沼虾幼虾蜕皮周期的影响及其可能的机制,以水产基地自行繁殖的2月龄幼虾(体长1.2~2.0 cm)为材料,捕捞后暂养于流水养殖水槽,水温(26±1)°C,每天投喂2次,1周后用于实验研究。用1.95×10–4 mol/L的KK-42溶液(处理组)或不含KK-42溶液(对照组)浸润1 min,取出,一部分用于幼虾生长速率、蜕皮周期的测定;从剩余部分中选择处于蜕皮间期(C)和蜕皮前期(D)的幼虾,Real-time PCR分析表皮几丁质酶1基因(Mnchi-1)的转录水平,同时进行表皮几丁质酶的活力测定。在实验观察期间,KK-42处理组平均体质量均显著高于对照组,体质量增长率的升高出现在处理后的前2周。随着幼虾的生长,蜕皮周期的持续时间均趋于延长,在4个连续测定的蜕皮周期中,KK-42处理能明显缩短前2个周期的时程,分别从(8.70±1.07)、(9.81±0.43)d/周期缩短为(6.93±0.97)、(8.11±1.20)d/周期。KK-42处理可显著上调C期表皮Mnchi-1的表达,在第3、6和9 h,其m RNA水平比对照组高10倍以上,酶活性同比提高2倍以上;KK-42对D期的影响相对较弱,该基因的表达水平及酶活性仅在12 h显著升高。结果表明,KK-42能显著诱导D期、尤其是C期表皮Mnchi-1基因的表达,提高几丁质酶活性,推测幼虾对旧表皮的分解提前至C期,这可能是KK-42缩短幼虾的蜕皮周期、促进其生长的分子机制之一。