Changes in chemical components in the freshwater apple snail, Pomacea canaliculata (Gastropoda: Ampullariidae), in relation to the development of its cold hardiness

The apple snail, Pomacea canaliculata, is an invasive freshwater snail. It increases its cold hardiness before winter. However, the physiological mechanism of cold hardiness in molluscs is poorly understood, especially in freshwater molluscs. In this study, we examined the changes in low molecular weight compounds, glycogen and lipids, in the body of P. canaliculata in association with the development of cold hardiness. When snails without cold hardiness were experimentally cold-acclimated, the amount of glycerol, glutamine, and carnosine increased, while glycogen and phenylalanine decreased. Overwintering cold-tolerant snails collected from a drained paddy field in November also showed increased glycerol in their bodies with decreasing glycogen concentration, compared to summer snails collected from a submerged field. Water content also decreased during the cold acclimation, although the water loss was minimal. These results indicate that the freshwater snail, P. canaliculata enhances cold hardiness by accumulation of some kinds of low molecular weight compounds in its body as some insects do. However, the actual function of each low molecular compound is still unknown.     

Out of South America: multiple origins of non-native apple snails in Asia

Apple snails (Ampullariidae: Pomacea ) native to the New World have become agricultural and environmental pests widely in southern and eastern Asia since their introduction in about 1980. Although their impacts have been extensively documented, considerable confusion persists regarding their identities and geographical origins. Efforts to resolve the confusion have suffered from inadequate taxonomic and geographical sampling from both native and introduced ranges. Using phylogenetic and genealogical methods, we analysed 610–655 bp of cytochrome c oxidase subunit I DNA sequences from 783 apple snails from 164 Asian locations and 57 native South American locations. In Asia, we found four species of Pomacea in two clades: (1) Pomacea canaliculata and P. insularum , and (2) P. scalaris and P. diffusa . Parsimony networks and mismatch distributions indicate that the non-native ranges of the two most widespread species, P. canaliculata and P. insularum , probably result from multiple introductions. Molecular analyses are consistent with early accounts; non-native P. canaliculata populations trace back to multiple locations in Argentina and have probably been introduced more than once. In contrast, P. insularum was probably introduced from Brazil and Argentina independently. Multiple introductions may, in part, explain the success and rapid spread of these two species. Unlike P. canaliculata and P. insularum , P. scalaris and P. diffusa were probably introduced through the aquarium trade, derived originally from Argentina and Brazil, respectively. Possible physiological, ecological, and native range differences among these four species highlight the importance of accurate identification in understanding invasion patterns and processes, which is vital in developing and implementing management strategies.     

X-Ray and IR-Studies on the Dehydrated Fish Flesh

Many actinomycetes, newly isolated from soil, converted (?)-carvone to either (?)-trans-carveol or (?)-cis-carveol or to a mixture of both compounds, and known metabolic products, such as (+)-dihydrocarvone, (+)-isodihydrocarvone, (+)-neodihydrocarveol, (?)-dihydrocarveol, (+)-isodihydrocarveol and (+)-neoisodihydrocarveol.

Identification of the metabolic products and the metabolic pathways of (?)-carvone were described in a strain of Streptomyces, A-5–1 and a strain of Nocardia, 1-3-11. A summary shows the reaction mechanism pattern of (?)-carvone conversion by actinomycetes.     

Biosynthesis of Cobalamine,Erythromycin and Chlortetracycline by Streptomyces Species

Attempts were devoted to use Streptomyces aureofaciens and Streptomyces erythreus, the antibiotics producers as sources for the biosynthesis of cobalamine. The constituents of the fermentation medium and the strain play an important role in the biosynthesis of vitamin B₁₂. The same strain produced different amounts of antibiotic and vitamin on the two different constitutive media. The increase of the phosphorus concentration in the fermentation medium—within limits—increased the vitamin B₁₂ biosynthesis. The optimal concentration of phosphorus favourable for the synthesis of cobalamine was inhibitive for the antibiotic production. The phosphorus level in the fermentation medium plays an important role in the metabolism of carbohydrate and consequently on the biosynthesis of antibiotics. Low concentration of 5,6-dimethylbenzimidazole (cobalamine precursor) in the presence of suitable phosphorus induced the microorganism to increase its biosynthetic potentiality for the vitamin B₁₂ production.     

福寿螺3个地理群体遗传多样性的AFLP分析

应用AFLP分子标记技术对我国江苏苏州、福建漳州和广东珠海3个地理群体福寿螺进行了遗传多样性分析.8对选择性引物在3个群体的90个个体中,共扩增出382个位点,多态位点369个.江苏、福建和广东3个福寿螺群体的多态位点比率和Shannon's指数分别为84.82%、85.08%、79.06%,0.4259、0.4308、0.4079;表明3个群体遗传多样性在同一水平上.不同地理来源的福寿螺个体归群分析聚成3类,与地理分布一致,表明3个地理群体间已出现遗传分化,广东群体和福建群体首先聚在一起,再与江苏群体聚类.Shannon's指数和AMOVA分析估算均显示福寿螺的遗传变异主要来自于群体内个体间.综上所述,3个福寿螺群体具有丰富的遗传多样性而且已形成相对独立的遗传结构;并找到了3个群体间遗传特异性AFLP标记,可用于群体间分子鉴定和辅助分类.     

蓖麻籽提取液对福寿螺毒杀效果及作用机制

采用生物浸泡法,以草本植物蓖麻籽提取液制备植物源毒杀剂,研究不同提取液浓度(0、0.5、1.5、3.0、4.5、6.0 g/L)对福寿螺毒(Pomacea canaliculata Lam)杀作用效果,并通过福寿螺在亚致死浓度1.58(LC25)、3.82(LC50)和6.05 g/L(LC75)处理条件下的肝脏组织生...     

不同浓度下四种除草剂对福寿螺和坑螺的生态毒理效应

以化学除草剂应用为前提的水稻免耕抛秧栽培技术是近年来推广的节本栽培新技术。为更好地评价除草剂的环境风险,为防治除草剂的负效应提供科学依据,采用室内静水模拟实验研究了4种免耕稻田除草剂丁草胺、苄嘧磺隆、丁苄混剂和氯酸钾的3种浓度梯度下对典型水生动物福寿螺、坑螺的影响。结果表明,各除草剂对水生动物的代谢都有不同程度的影响, 氯酸钾和苄嘧磺隆对2种水生动物的呼吸作用影响不大,而丁草胺和丁苄混剂对3种水生动物的呼吸作用的影响有显著的抑制作用,且呈现一定的剂量效应;在本实验染毒剂量下, 丁草胺和丁苄混剂对2种水生动物的存活率影响很大,而氯酸钾和苄嘧磺隆对其存活率影响较小。丁草胺和丁苄混剂处理对福寿螺的氮代谢影响远远大于氯酸钾和苄嘧磺隆处理,而从水体总氮和总磷含量的影响来看,4种除草剂对其影响都较大。总之,从4种除草剂对实验用螺存活率和主要代谢生理指标的综合影响大小来看,丁草胺>丁苄混剂>苄嘧磺隆>氯酸钾。     

应用多个生态位模型预测福寿螺在中国的潜在适生区

高危性外来入侵种福寿螺严重危害我国的农业生产、生态系统完整性和人体健康.为制定有效的防控策略提供科学依据,本研究通过选取最适的生态位模型以预测福寿螺在我国的潜在适生区.结合福寿螺在我国的337条分布记录和年均温、年降水量等19个生物气候变量数据,本文采用MaxEnt、GARP、BIOCLIM和DOMAIN等4种生态位模型分别模拟预测了福寿螺在我国的潜在适生区,并利用受试者工作特征曲线(ROC)和Kappa统计量分析比较不同模型的预测效果.结果表明: 4种模型均能较好地模拟福寿螺在我国的分布,其中MaxEnt模型的模拟准确度最高(受试者工作特征曲线下的面积AUC=0.955±0.004,Kappa=0.845±0.017),其次是GARP和DOMAIN,准确度相对较小的是BIOCLIM,但其平均AUC也达0.898±0.017,平均Kappa值为0.771±0.025.MaxEnt模型的预测结果显示,福寿螺的潜在适生区主要分布在30° N以南地区,但其中也有部分地区地处30°N以北.适生区面积占国土面积的13.2%,广东、广西、湖南、重庆、浙江和福建沿海地区具有高度潜在入侵风险.本研究可以为福寿螺的科学防控提供参考,并且对大尺度上外来水生生物的适生区预测具有一定的借鉴意义.