The labial gland system of larvae of the imported fire ant,Solenopsis invicta Buren

Summary The authors describe the ultrastructure of the labial gland system in imported fire ant larvae, Solenopsis invicta Buren and present an enzyme analysis of enzymes in labial-gland secretions and midgut contents. The tubes of the labial gland produce and secrete a proteinaceous substance rich in digestive enzymes. The narrow cells of the reservoir of the gland have little or no secretory function but the lumen stores the proteinaceous secretion. The labial-gland enzymes include proteases and amylases, which function in extraintestinal digestion of solid food placed on the anteroventral body region of 4th-instar larvae by adult workers. The midgut contains proteases, amylases, and upases. Lipids appear to be predigested by the workers before being fed to the larvae.Approved as TA 15262 by the Director of the Texas Agricultural Experiment Station in cooperation with ARS/USDA. Supported by the Texas Department of Agriculure interagency agreement IAC-0487 (78-79)We would like to thank Rosemary Kamas, Dr. John Mirenda, and Mike Strand for their help in dissections of larvae and Dr. Howard Williams for his advice and suggestions     

The enzyme 3-hydroxykynurenine transaminase as potential target for 1,2,4-oxadiazoles with larvicide activity against the dengue vector Aedes aegypti

The mosquito Aedes aegypti is the vector agent responsible for the transmission of yellow fever and dengue fever viruses to over 80 million people in tropical and subtropical regions of the world. Exhaustive efforts have lead to a vaccine candidate with only 30% effectiveness against the dengue virus and failure to protect patients against the serotype 2. Hence, vector control remains the most viable route to dengue fever control programs. We have synthesized a class of 1,2,4-oxadiazole derivatives whose most biologically active compounds exhibit potent activity against Aedes aegypti larvae (ca. of 15 ppm) and low toxicity in mammals. Exposure to these larvicides results in larvae pigmentation in a manner correlated with the LC₅₀ measurements. Structural comparisons of the 1,2,4-oxadiazole nucleus against known inhibitors of insect enzymes allowed the identification of 3-hydroxykynurenine transaminase as a potential target for these synthetic larvicides. Molecular docking calculations indicate that 1,2,4-oxadiazole compounds can bind to 3-hydroxykynurenine transaminase with similar conformation and binding energies as its crystallographic inhibitor 4-(2-aminophenyl)-4-oxobutanoic acid.     

刀鲚胚胎及胚后发育早期脂肪酸组成变化

为掌握刀鲚(Coilia nasus)胚胎及胚后发育早期的脂肪酸变化规律,采用生化分析手段对刀鲚的胚胎(原肠期,受精后7～9 h)、0日龄仔鱼(初孵仔鱼)、3日龄仔鱼和5日龄仔鱼(开口前)的脂肪酸组成和含量进行了检测分析。结果显示,刀鲚发育早期的总脂占干物质的相对含量均较高(53.10%～60.97%),干物质的总脂相对含量随个体发育显著降低,单个个体的总脂含量随个体发育呈现剧烈下降趋势,数值从胚胎的43.62μg/ind剧烈下降到5日龄仔鱼的16.27μg/ind;水分含量随个体发育而升高。刀鲚发育早期上述4个时期的干样中检出6种饱和脂肪酸(SFA)、4种单不饱和脂肪酸(MUFA)和8种多不饱和脂肪酸(PUFA)。4个发育时期脂肪酸相对含量,C18:1n9c占绝对优势(50.39%～57.00%),C16:1丰富且稳定(13.77%～14.24%),C16:0也较丰富(7.45%～9.15%)。单不饱和脂肪酸(MUFA)比例占绝对优势(65.14%～72.26%),n-3与n-6系列多不饱和脂肪酸含量的比值(∑n3PUFA/∑n6PUFA)较小(1.78～2.38)。刀鲚胚胎孵化出膜期间,单个个体单不饱和脂肪酸(MUFA)实际减少程度较高,尤其是C18:1n9c(减少量为13.21μg/ind,减少比例达到55.49%)和C16:1(减少量和比例分别为3.30μg/ind和53.12%),而二十碳五烯酸(EPA)加二十二碳六烯酸(DHA)的减少程度较低(1.44μg/ind和38.41%),尤其是DHA(0.95μg/ind和36.52%)。然而,出膜后,仔鱼对单不饱和脂肪酸(MUFA)的利用相对较低(1.94μg/ind和14.17%),尤其是C18:1n9c(13.21μg/ind和12.41%)和C16:1(0.63μg/ind和21.81%);而对EPA+DHA利用相对较高(1.04μg/ind和45.10%),尤其是DHA(0.71μg/ind和42.61%)。研究表明,刀鲚胚胎优先蓄留EPA和DHA,仔鱼在摄食前大量利用EPA+DHA(特别是DHA),呈现出海水鱼类脂肪酸的利用特点。因此,建议在刀鲚亲本强化培育及产后培育中,增加投喂富含单不饱和脂肪酸(MUFA)(特别是C18:1和C16:1)的饵料,以加强刀鲚亲本的营养积累和产卵后亲本生理机能的恢复;在刀鲚育苗前期,要及时补充富含DHA和EPA的饵料,如,单胞藻、蛋黄等,以提高刀鲚仔鱼开口期间的成活率。     

Potential effects of physiological plastic responses to salinity on population networks of the estuarine crab <Emphasis Type="Italic">Chasmagnathus granulata</Emphasis>

Chasmagnathus granulata is a South American crab occurring in estuarine salt marshes of the Brazilian, Uruguayan and Argentine coasts. Life history is characterized by an export strategy of its larval stages. I reviewed information on experimental manipulation of salinity during embryonic and larval development (pre- and posthatching salinities), and on habitat characteristics of C. granulata in order to determine potential effects of larval response to salinity in the field and to suggest consequences for the population structure. Local populations are spread over coastal areas with different physical characteristics. Benthic phases occupy estuaries characterized by different patterns of salinity variation, and release larvae to coastal waters characterized by strong salinity gradients. The zoea 1 of C. granulata showed a strong acclimatory response to low salinity. This response operated only during the first weeks of development (during zoeae 1 and 2) since subsequent larval survival at low posthatching salinities was consistently low. Larvae developing at low salinity frequently followed a developmental pathway with five instead of four zoeal stages. The ability to acclimate and the variability in larval development (i.e. the existence of alternative developmental pathways) could be interpreted as a strategy to buffer environmental variability at spatial scales of local or population networks. Early survivorship and production of larvae may be relatively high across a rather wide range of variability in salinity (5–32‰). Plastic responses to low salinity would therefore contribute to maintain a certain degree of population connectivity and persistence regardless of habitat heterogeneity. Electronic Publication     

Population dynamics of the invasive Pacific oyster Crassostrea gigas during the early stages of an outbreak in the Wadden Sea (Germany)

Since the late 1990s, the Pacific oyster (Crassostrea gigas) has spread into the East Frisian Wadden Sea (Germany). This invasion provided an opportunity to study the population dynamics and the patterns of spread during the initial bioinvasion process. With its source area in The Netherlands, the bioinvasion continues in an eastward direction, as documented by a gradient of high abundances in the west and low abundances in the east during the first study year. One year later, abundances of the Pacific oyster were more heterogenic and differed between adjacent tidal basins. The increase in population sizes at all study sites was very high, reaching levels similar to native occurrence populations. The growth constant (K) varied between 0.300 and 0.990 year⁻¹. The mussel bed with the highest densities had a mean abundance of >300 ind. m⁻², and a maximum of 1,460 ind. m⁻². Furthermore, the bioinvasion was facilitated by a low mortality (Z) found for populations between 0.5 and 1.5 years old (Z = 0.03–0.13 year⁻¹). At present, Pacific oysters are well established at several locations in the East Frisian Wadden Sea and may become with these reproductive potential self-sustaining populations.     

Natural inducers for coral larval metamorphosis

 Coral gametes from Acropora millepora (Ehrenberg, 1834) and from multi-species spawning slicks provided larvae for use in metamorphosis assays with a selection of naturally occurring inducer chemicals. Four species of crustose coralline algae, one non-coralline crustose alga and two branching coralline algae induced larval metamorphosis. However, one additional species of branching coralline algae did not produce a larval response. Metamorphosis was also observed when larvae were exposed to skeleton from the massive coral Goniastrea retiformis (Lamarck, 1816) and to calcified reef rubble, demonstrating metamorphosis is possible in the absence of encrusting algae. Chemical extracts from these algae and the coral skeleton, obtained using either decalcification or simple methanol extraction procedures, also contained active inducers. These results extend the number of crustose algal species known to induce coral metamorphosis, suggest that some inducers may not necessarily be strongly associated with the calcified algal cell walls, and indicate that inducer sources in reef habitats may be more diverse than previously reported. Accepted: 21 May 1999     

温度对尖裸鲤胚胎发育及其仔稚鱼生长性状的影响

采用实验生态学方法研究温度对尖裸鲤（Oxygymnocypris stewartii）胚胎发育及仔稚鱼生长性状的影响,旨在掌握温度对其早期发育的影响。结果表明,随着温度的升高,胚胎的孵化时间缩短,发育速度加快。在平均水温5 ℃、8 ℃、11 ℃、14 ℃和17 ℃下,尖裸鲤的胚胎孵化时间分别为530.78 h、366.12 h、214.22 h、220.63 h、153.95 h,温度和孵化时间呈幂函数关系,有效积温在水温为11 ℃时最低,为2 356.4 h ·℃。尖裸鲤胚胎不同发育时期在不同温度下的累计时间均呈现指数函数关系。随着温度的升高,孵化率呈现先降低后升高的趋势,水温范围在11 ~ 17 ℃时,温度系数Q10值和Q13值最接近2。尖裸鲤初孵仔鱼全长与温度间呈现三次多项式函数,全长与温度之间不存在显著性关系;而初孵仔鱼卵黄囊体积与温度间呈现显著性的二次多项式函数。综合各项指标表明,尖裸鲤胚胎的适宜孵化水温为11 ~ 17 ℃,仔稚鱼的适宜生长水温为14 ~ 17 ℃。     

大豆品种(系)和种植密度对豆天蛾幼虫存活及生长发育的影响

豆天蛾Clanis bilineata tsingtauica Mell幼虫,是一种食用昆虫,富含蛋白质、维生素和矿质元素,具有很高的营养、药用和经济价值。了解适宜豆天蛾幼虫生长发育的大豆品种（品系）和种植密度,可为豆天蛾幼虫规模化饲养提供理论基础。研究通过设置两因素裂区实验,在10个品种（品系）大豆和2个种植密度水平下,测定豆天蛾幼虫生物学参数,明确适宜豆天蛾幼虫养殖的大豆品种（品系）和种植密度。结果表明,不同大豆品种（系）和种植密度对豆天蛾幼虫存活及生长发育均有显著影响;其中使用连151、淮豆9号、东辛3号和H0573大豆饲养的豆天蛾幼虫产量和存活率较高,虫体长度较长,发育历期较短;大青豆饲养的豆天蛾幼虫产量较低,幼虫发育整齐度较差,发育历期长。当种植密度为40 cm×30 cm时,豆天蛾幼虫存活和发育历期整齐度均显著高于种植密度40 cm×15 cm。综上所述,较适宜豆天蛾幼虫养殖的大豆品种（品系）为连151、淮豆9号、东辛3号和H0573,种植密度为40 cm×30 cm。     

Social organization and spawning in the Atlantic sharpnose puffer,Canthigaster rostrata (Tetraodontidae)

Synopsis Social organization and spawning in the sharpnose pufferCanthigaster rostrataere studied on a reef in the San Blas Islands, Panama. Sexes were dimorphic. In mixed coral and rubble habitat, females defended territories against other females and small males. From one to six female territories were included within the territories of certain large males. These haremic males visited their females and patrolled their territories throughout the day. Smaller, non-haremic males occupied territories or home ranges within or adjacent to those of haremic males or were wanderers. Spawning between a haremic male and a territorial female occurred within the female's territory. The female prepared an algal nest into which demersal eggs were deposited. There was no parental care. Eggs were spherical, translucent, and measured approximately 0.66 mm in diameter. Larvae were about 1.4 mm TL and closely resembled those of other species ofCanthigaster.