Sexual behaviour in Isotomidae (Collembola)

We studied the sexual behaviour of three isotomid species Vertagopus cinereus, Vertagopus pseudocinereus, and Proisotoma clavipila including (1) stimulation of the female by the male, (2) deposition of spermatophores, and (3) pushing the female over the spermatophore. A variety of behaviour never described before in Isotomidae were observed including fastening of the female abdomen by the antennae of the male, repeated stimulation of the ventral region of the female, and repeated capture of spermatophore by the female. We propose a functional explanation of male sexual secondary characters and of the setae of the abdomen in V. pseudocinereus.     

Influence of cadmium,copper, and pentachlorophenol on growth and sexual development of Eisenia andrei (Oligochaeta; Annelida)

Summary In the existing guidelines for earthworm toxicity testing, mortality is the only test criterion. Mortality is, however, not a very sensitive parameter, and from an ecological point of view growth and reproduction are more important for a proper risk assessment of chemicals in soil. In this study the growth and sexual development of juvenile earthworms were considered as test criteria in a standardized earthworm toxicity test. The effect of Cd, Cu, and pentachlorophenol on the growth and sexual development of juveniles of the species Eisenia andrei was studied in an artificial soil substrate. Two tests with Cd were carried out to study the effects of the mode of application of the food source (cow dung). EC₅₀ (50% effective concentration) values for the effect of Cd, Cu and pentachlorophenol on the growth of E. andrei were 33–96, >100, and >32 mg kg^-1 dry soil, respectively, and there was no observed effect at 18–32, 56, and 32 mg kg^-1 dry soil, respectively. Sexual development of the earthworms was inhibited at 10 mg Cd kg^-1 and 100 mg Cu kg^-1 dry soil, but was not affected at the highest pentachlorophenol concentration tested (32 mg kg^-1 dry soil). The results were the same whether the food was applied in a hole in the middle of the soil or mixed homogeneously through the soil.     

The effect of acoustic harassment devices on harbour porpoises (Phocoena phocoena) in the Bay of Fundy, Canada

Many salmon aquaculture sites in the Bay of Fundy employ acoustic harassment devices (AHDs) to deter seals from approaching fish pens. These devices may also exclude harbour porpoises (Phocoena phocoena) from important habitat. To determine the effects of AHDs on harbour porpoises an AHD was deployed experimentally in the Bay of Fundy, Canada. Relative porpoise abundance (visual scans) and porpoise movements (tracked by theodolite) were recorded for separate, daily, 2-h periods in the vicinity of either an active (n=9) or inactive (n=7) AHD. Fewer porpoises were sighted during active periods (0.22±0.44, mean±SD ) than inactive periods (2.91±1.29; P<0.05). The mean closest observed approach of porpoises to the AHD during active periods (991±302 m) was significantly greater than during inactive periods (364±261 m; P<0.01). Porpoise density was therefore reduced in the vicinity of active an AHD. These results should be considered before AHDs are deployed in porpoise habitat.     

Protecting more than the wetland: The importance of biased sex ratios and habitat segregation for conservation of the Hine’s emerald dragonfly, Somatochlora hineana Williamson

Within species habitat use may depend on age, season or sex of an individual. The distribution of males and females may vary both temporally and spatially due to differences in the costs of reproduction and the distribution of critical resources. Conservation of a species requires knowledge of the habitat use of both sexes in order to predict the population size and protect all habitats that a species requires. Adult dragonfly populations often have highly male-biased sex ratios at the breeding habitat. This bias has been attributed to females using alternative habitats to avoid male harassment, or to high female mortality. We monitored adult Hine’s emerald dragonfly (Somatochlora hineana Williamson) populations, in breeding and non-breeding habitats in Door County, Wisconsin and found significant differences in habitat use between males and females. Males primarily used wetland habitats, while females primarily used dry meadows and marginal breeding habitats, only coming into wetlands to lay-eggs or find mates. We assessed food resources in the different habitats and found that high quality insect prey (primarily adult Diptera) were more available in the wetland habitat, indicating that these areas were likely a more productive foraging area for adult dragonflies. The fact that females appear to avoid the wetland habitat is consistent with the hypothesis that male harassment alters female distribution patterns. Consideration of the patterns of habitat use by S. hineana indicates the need to develop a broader understanding of the importance of non-wetland areas in the conservation of wetland species.     

东北红豆杉有性繁殖播种育苗

东北红豆杉,又名紫杉,是第三纪孑遗的珍贵树种。红豆杉资源的保存和种苗的快速繁育,是解决紫杉醇用材林的基础,大面积营造红豆杉人工林是解决紫杉醇原料的关键。用红豆杉种子繁殖苗木时,要注意种子的储存方式,要沙种混藏或控温处理,这对越冬后出芽和打破休眠习性,具有很好的效果。播种前要搓伤种皮、温水浸种、药剂素处理。     

西南地区扁穗牛鞭草有性生殖多样性研究

通过对60份野生扁穗牛鞭草资源有性繁殖过程的测定，对有性繁殖花序开始及持续时间，单株直立与匍匐枝形成花序数、小穗数、小花数、花序柄长、花序长、花序宽、花序厚，开花时间及规律进行分析。结果说明：花序开始时间变异范围达25d，持续时间变异范围为32—116d；变异系数由大到小的顺序为直立枝有序比例〉直立枝最大花序数〉直立枝平均花序数〉直立枝产序节数〉匍匐枝平均花序数〉匍匐枝最大花序数〉匍枝有序比例〉匍匐枝产序节数，均在75％以上；花序性状变异程度较大，花序彬枝、小花彬花序、花序柄长、花序轴长、花序宽、花序厚均差异极显著；开花主要集中的07：00—09：00，11：00-13：00，17：00—19：00三个时间段，未发现结实。     

温度湿度及种球茎大小对花魔芋有性繁殖的影响

有性繁殖是促进魔芋种植业发展和品种改良的有效途径,引起了极大的兴趣。本文研究117个花魔芋(Amorphophallus konjac K.Coch)单株花粉成熟后连续5d的温度、湿度以及花芽种球茎对其有性繁殖的影响,结果表明:授粉期间的温度和湿度对其自花授粉结实影响大,结实株花粉成熟后连续5d的平均温度和湿度分别为24℃和64%,均显著高于不实株,高温高湿有利于散粉和花粉的萌发从而完成受精;花芽种球茎大小对有性繁殖也有影响,结实株平均种球茎重显著高于不实株,且与单株结实浆果数呈极显著的正相关(r=0.6096,N=29),因此,宜选用花芽球茎大的用于魔芋有性繁殖。     

农村出生性别比失衡的社会学解读

自20世纪80年代以来,中国的出生性别比就出现异常,尤其是农村出生性别结构失衡情况更加严重。运用社会学理论及相关方法,探讨造成农村出生性别比失衡的成因,并提出"计划生育政策的完善"、"传统养老保障模式潜能的挖掘"及"社会性别文化的创新"等对策思考。     

湖南壶瓶山藤本植物的有性系统及其环境适应性

采用踏查和样地调查相结合的方法,并查阅相关资料,对湖南壶瓶山藤本植物的有性系统及其对环境的适应进行了研究。结果表明:在本区330种藤本植物中,两性花202种,占总种数的61.2%,杂性花12种,占总种数的3.6%,单性花共116种,占总种数的35.1%,其中雌雄异株类明显多于雌雄同株类,占总种数的28.8%,占单性花类种数的81.9%;每个样地中,藤本植物的雌雄异株种数占总种数的平均比率(36.47%),明显高于全部种子植物的雌雄异株种占的平均比率(16.67%),也明显高于本区全部藤本植物中的雌雄异株的比率(28.8%);本区藤本植物开花的盛花期和结果的盛果期避开了温度最高的7月和8月,分别在最高温到来之前和之后,盛花期和盛果期同样避开了降水量最多的7月。结论认为:亚热带藤本植物中雌雄异株种所占的比率明显高于热带的同类比率;壶瓶山藤本植物与其它类群植物相比具有最有效的性系统,对环境具有更强的适应能力;合适的温度和降水量有利于藤本植物的开花结果。     

周氏新对虾群体雌雄性比例变化的分析

根据 198 0年、1981年、1982年、1984年 5～ 8月底栖生物组调查资料研究其雌雄比例问题 ,结果表明胶州湾周氏新对虾雌雄比例变化较大 ,4年间各月的平均值为 :5月 1.68;6月 1.59;7月 1.4 0 ;8月 0 .87,5～ 8月期间雌雄比值按 :Ｘ =- 7.0ｅ-0 .2 6 6ｔ 8.683规律呈负指数增长 ,主要是由于雄性交配后死亡 ,雌性经三次产卵逐渐死亡所至 ,种群从 5～ 8月期间雌雄比例很难保持 1∶1,一般情况下雌性个体多于雄性个体。图 1　试捕拖网取样站位Ｆｉｇ .1　Ｌｏｃａｔｉｏｎｏｆｔｒａｗｌｉｎｇｓｉｔｅｓ周氏新对虾广泛分布在我国东南沿海及日本、…