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尖膀胱螺Physa acuta是世界广泛分布的淡水螺类,在我国属外来入侵种.本文着重对该螺的形态特征、繁殖、发育及光照对螺生长和繁殖发育的影响等进行了实验观察和研究.尖膀胱螺个体中等,左旋,壳口无厣.喜聚居于水生植物较多、营养丰富的淡水区域.尖膀胱螺为雌雄同体,异体受精,有时也可自体受精.性成熟个体在条件适宜的情况下(温度、食物和光照)每天都可产卵,卵孵化率近100%.尖膀胱螺胚胎发育共经历卵裂期、囊胚期、原肠期、担轮幼虫期、面盆幼虫期、仔螺形成及出膜期7个时期.一般情况下,螺卵7~10 d可孵化,60 d即可性成熟.25℃、24 h连续光照条件下,尖膀胱螺体重明显增加,40 d就可以性成熟并产卵. 相似文献
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在开展四川省并殖吸虫病流行病学调查中,我们在并殖吸虫(Paragonimus)病流行区采集到七种淡水蟹,其中四种蟹类(威远华溪蟹 Sinopotamon weiyuanense,Dai & Chen,1990;陕西华溪蟹巫山亚种Sinopotamon Shansiense wushanense,Dai & Chen,1990;矮小华溪蟹 Sinopoysmon nanum,Dai& Chen,1990和屏山华溪蟹 Sinopotamon pinshanense,Dai & Liu,1994)体内发现非殖吸虫囊蚴。 相似文献
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We present data for seven new markers isolated from a microsatellite‐enriched DNA library from the freshwater snail Physa acuta. Six of them appear to be conserved in Physa cubensis. These loci might be useful for analysing population structure and reconstructing the story of invasion of freshwaters on a worldwide scale by P. acuta. 相似文献
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Body size-dependent gender role in a simultaneous hermaphrodite freshwater snail, Physa acuta 总被引:1,自引:0,他引:1
We examined whether gender role in the simultaneous hermaphroditefreshwater snail, Physa acuta, is determined by relative bodysize in a manner predicted by the size-advantage model. We observedthe body-size combinations of pairs in the laboratory by usingfield-collected populations. Smaller individuals tended to playthe "male" role (sperm donor), and larger snails the "female"(sperm recipient). Next, we analyzed the mating behaviors involvedin gender-role decision in snail pairs of three different body-sizecombinations, using "large" and "small" snails. Smaller snailswere more likely to approach the partner as a male in different-sizecombination (large/small), whereas frequent initial approachesas a male and rejection behavior as a female were observed inthe large/large combination. Third, we examined the body sizepreference when a snail can freely choose the partner from twoother individuals of different body sizes (large/large/smallor large/small/small). Small individuals had a significant tendencyto act as the male and positively selected large snails as thefemale partner in both triple combinations. However, the largeindividual acted as both the male and the female with nearlyequal frequency. In the size-differing pairings, copulationsoccurred after fewer male approaches and fewer rejections thanin pairings involving two large snails, suggesting that bodysize difference is one of the behavioral solutions in genderconflict. Clear gender-role switching associated with body sizewas not seen. Smaller snails thus have a tendency to play themale role more frequently but adopt both gender roles when theirbody size is sufficiently large. 相似文献
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The genetic structure, selfing rate and inbreeding depression of the hermaphroditic freshwater snail Physa acuta were jointly analysed in a population near Montpellier, France. Allozymic markers revealed moderate gene diversity (0.138), and no heterozygote deficiency. The mean outcrossing rate, estimated by using progeny arrays, was 0.9, with substantial variation among families. This also suggests that the number of fathers among outcrossed offspring of a given mother is low. Inbreeding depression was estimated over more than one generation using 83 first‐laboratory‐generation (G1) families. The main parameters measured were parental (G1) fecundity, offspring (G2) survival and fecundity. Size and growth were also monitored. Parental fecundity was analysed under several conditions (isolation, pair and quadruplet outcrossing). The self‐fertilization depression, including parental fecundity, offspring survival and fecundity, was about 0.9 at the population level. The genetic data obtained in the same population indicate a value of about 0.3 using Ritland’s (1990) technique, suggesting that the depression over the whole life‐cyle might be even higher than 0.9. Grouping affected neither fecundity nor self‐fertilization depression. Substantial variation in depression for survival was detected among individuals, from no survival in some selfed families to better survival than that of outbred families in others. The overall result (outbred population structure, high outcrossing rate and high self‐fertilization depression) is consistent with what is expected in large outcrossing populations in which inbreeding depression is maintained by mutation‐selection balance. 相似文献
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1. Few studies have directly addressed the role played by parasites in the structure and function of ecosystems. Parasites influence the behaviour, reproduction and overall fitness of their hosts, but have been usually overlooked in community and ecosystem‐level studies. We investigated the effects of trematode parasites on snail–periphyton interactions. 2. Physa acuta (Gastropoda: Pulmonata) snails infected with the trematode Posthodiplostomum minimum (often >30% of within‐shell biomass) grazed more rapidly than uninfected snails. Trematode effects on snail grazing indirectly affected the standing stock and community structure of periphyton. Populations of snails with 50% infected individuals reduced algal biomass by 20% more than populations with lesser (10% or 0%) infection rates. 3. The alga Cladophora glomerata dominated periphyton communities grazed by snail populations with 50% infection rates, whereas diatoms and blue–green algal taxa dominated when grazed by snail populations with lower infection rates. 4. Thus, trematodes indirectly affected periphyton communities by altering host snail behaviour, a trait‐mediated indirect effect. These results indicate that trematodes can indirectly influence benthic community structure beyond simple population fitness, with possible related effects on ecosystem function. 相似文献
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Abstract. Individual marking has long been used in many fields of biology. However, capture–mark–recapture (CMR) studies are not evenly distributed among taxonomic groups, with most studies focusing on vertebrates. For example, a limited number of studies have been conducted in gastropods, in sharp contrast to their important role as biological models or exploited natural resources. The lack of standard, validated marking techniques certainly contributes to the limited use of CMR. In this article, we evaluate two fundamental requirements for a marking technique to be suitable, i.e., tag loss (two experiments) and impact on life-history traits (survival, growth, and fecundity, in three experiments). Five marking techniques for hard-shelled gastropods were tested in the freshwater snail Physa acuta (Pulmonata). The tag-loss rate per month was lower for glued plastic marks (0.01) than for paint marks (0.03–0.07), and the tag-loss rate varied among colors (gouache paint). Under laboratory conditions, the life-history traits were not significantly affected by marking. We thus recommend using glued plastic marks for long-term studies, and paint marks for mass marking, with double marking to account for tag-loss rate. Based on an extensive literature survey, we also review current CMR practices in gastropod studies and suggest general improvements that would prove useful in both this group and invertebrates in general. 相似文献
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我国分布的宽耳蝠包括北京宽耳蝠(Barbastella beijingensis)和东方宽耳蝠(B. darjelingensis)2个物种。东方宽耳蝠在我国分布于内蒙古、新疆、青海、陕西、甘肃、河南、湖南、江西、四川、重庆、云南、贵州、台湾等省(自治区、直辖市),但北京宽耳蝠仅记录于北京。2022年7月于山西省祁县昌源河湿地公园林道中(37°19′15″ N,112°26′18″ E,海拔812 m),采集到1只雄性宽耳蝠。该蝠体型中等,前臂长43.7 mm。双耳在额部相连,外耳廓近方形,横嵴明显,耳廓中部外缘具有较小的耳突,其第三掌骨长大于第四掌骨长大于第五掌骨长。颅全长为14.6 mm,具有强壮的上前臼齿和下前臼齿。以上特征均与北京宽耳蝠相符。头骨特征中,与北京宽耳蝠相比其具有较小的颅基长和颅宽,其余头骨测量参数值均与北京宽耳蝠相近。基于Cyt b和ND1基因序列的系统发育学证据亦支持形态鉴定结果。结合外部形态、头骨参数及分子数据,将山西样本鉴定为北京宽耳蝠,为山西省翼手目分布新记录种。 相似文献