Effect of Polianthes tuberosa (Amaryllidaceae) on the Reproduction and Biochemical Parameters in the Ovotestis of Snail Lymnaea acuminata (Mollusca,Pulmonata)

The present study elucidates the effect of powder of Polianthes tuberosa bulb and its sapogenins tigogenin and hecogenin on the reproduction of the snail Lymnaea acuminata. It has been reported that the two sapogenins tigogenin and hecogenin caused a significant reduction in fecundity, hatchability, and survival of young snails. Exposure to sublethal concentration caused a small but significant reduction in protein, amino acids, nucleic acids, and phosphatase activities in gonadal tissue of treated snails. Withdrawal after 7 days indicates that the effect of powder of P. tuberosa bulb, tigogenin, and hecogenin on the reproduction and different biochemical parameters is reversible.     

Synergistic Effect of Sulfoxide with Carbaryl on the in vivo Acetylcholinesterase Activity and Carbohydrate Metabolism of the Snail Lymnaea acuminata

The synergistic effects of sulfoxide on the effects of carbaryl in the snail Lymnaea acuminata were studied. Snails were exposed to 40 % and 80 % of 48 h LC⁵⁰ doses of synergist, carbaryl mixture (5 : 1). While the concentration of carbaryl present in the mixture would not bring about any change in carbohydrate metabolism, there was a marked decrease in the AChE activity, glycogen levels and an increase in lactic acid and a reduction of sugar levels when the snails were exposed to a carbaryl synergist mixture. Sulfoxide alone also caused a decrease in glycogen levels and an increase in lactic acid levels. These changes, however, were smaller as compared to those resulting from exposure to the mixtures.     

Changes in Transaminase Activity Following Treatment with Pesticide Mixtures

Changes in the activities of two enzymes, viz., glutamic oxalacetic transaminase (GOT) and glutamic pyruvic transaminase (GPT) following exposure to the pyrethroids fenvalerate and decis (deltamethrin), the carbamate sevin (carbaryl), singly, and the binary mixtures of fenvalerate + sevin and decis + sevin was studied in the nervous tissue of the fresh water snail Lymnaea acuminata. The total amount of the pesticides administered in the binary mixtures was very low as compared to the amount contained in the 40% LC₅₀ and 80% LC₅₀ of any of the pesticides when given alone. On the one hand, lower quantities of pesticides were administered, while on the other, there was greater enhancement in the activities of the two transaminases. Thus, synergism in case of transaminase activity was much more as compared to synergism when lethality was taken as a criterion. The order of effectiveness of the pesticides/mixtures was decis + sevin > fenvalerate + sevin > decis > fenvalerate > sevin.     

Acute Toxicity of Distillery Effluent on a Freshwater Fish and Three Pond Snails

The LC₅₀ for 12… 96 h of a distillery waste water were determined for Lebistes reticulatus, Lymnaea luteola, Lymnaea acuminata and Viviparus bengalensis in the batch experiment with daily exchange of the medium. The sensitivity of the species increases in the given sequence with values of the LC_{50,96 h} of 10.77 to 3.72 % proportion of wastewater in the medium. Compared with this, with values of the LC_{50,48 h} of 14.06… 15.71 % after 48 h of exposure there is no significant difference in sensitivity, whereas after exposure for 12 and 24 h the sensitivity grows in the following order: V. bengalensis, L. acuminata, L. luteola, Lebistes reticulatus. Toxicity is obviously primarily determined by the sulphides; with increasing time of exposure also the suspended matter and other factors act toxically.     

滇西北剑湖湿地海菜花（Ottelia acuminata）群落物种组成及种群分布格局

群落物种组成及种群分布格局特征是揭示种群发展趋势及与环境相互关系的基础.以滇西北剑湖湿地海菜花群落为对象,采用样方法与扩散系数法对其物种组成与种群分布格局进行研究.结果表明:群落共有物种18种,分属12科、14属,包括沉水、漂浮、浮叶及湿生4类生活型;海菜花(Ottelia acuminata)、豆瓣菜(Nasturtium officinale)、马来眼子菜(Potamogeton malaianus)和草茨藻(Najas graminea)呈集群分布,其余种群呈随机分布;海菜花种群个体间拥挤效应最大,种内竞争最为激烈.保育海菜花种源、开展流域和生境治理以减缓湖泊沼泽化进程,是目前剑湖海菜花群落保护的当务之急.     

Comparative Toxicity of Heavy Metals and Interaction of Metals on a Freshwater Pulmonate Snail Lymnaea acuminata (Lamarck)

In static bioassays the toxicity of heavy metal ions against Lymnaea acuminata over 24 … 96 h is tested. The values of the LC_50,96h for the metals tested are, in mg/l: Hg²⁺ ?0.023; Cu²⁺-0.034, Cd²⁺ ?0.872, Ni²⁺ ?2.78, Cr⁶⁺ ?5.97 and Zn²⁺ ?10.49. In the combined solutions of Cu²⁺, Ni²⁺ and Zn²⁺ at least an additive effect of toxicity occurs in the presence of two metals. The same holds for the presence of the three metals; in this case, the relative toxicity against the mixture of two metallic salt solutions appears to be slightly reduced. The acute manifestation of the toxic effect occurs within 48 h, subsequently the relative mortality decreases especially in the mixed solutions.     

Vergleichende Untersuchung der Diäten vonLymnaea auricularia undL. peregra (Gastropoda: Basommatophora) im Zürichsee

Two very similar species of freshwater snails,Lymnaea auricularia andL. peregra coexist in Lake Zürich. We examined their diets to determine possible differences. Microscopic analysis of stomach and hind gut contents revealed no marked differences between the diets of the two snail species collected from the same substrate. However, in both species we found significant differences between the composition of the substrate and that of the stomach contents, using discriminant analysis. We conclude that both species of snails feed preferentially on patches of favourable food supply and that their diets overlap almost totally. The coexistence of the two species under these conditions suggests that food does not limit their density in the area studied.     

光照对海菜花(Ottelia acuminata)种子萌发、幼苗生长及生理的影响

为研究滇池海菜花衰退消亡的原因,探讨其恢复的可能性,通过模拟实验研究了光照对海菜花种子萌发和幼苗生长及生理的影响.结果表明光照强度对海菜花种子萌发的影响不显著;光照强度显著影响海菜花幼苗的生长,其中71.8%和91.5%遮光条件下海菜花的平均叶片长度、叶片宽度和株高均显著高于无遮光和97.6%遮光条件下其平均叶片长度、叶片宽度和株高,平均生物量显著高于97.6%遮光条件下其平均生物量;实验中期不同光照条件下,海菜花叶片叶绿素a含量差异显著,其中71.8%遮光条件下海菜花叶片叶绿素a含量显著高于无遮光和97.6%遮光条件下其含量;光照强度对海菜花叶片过氧化物酶活性影响不显著.富营养化导致的水体透明度低、光照强度弱不影响海菜花种子萌发,但影响了海菜花的生长发育和生理特性,进而可能影响了海菜花的繁殖,这可能是滇池海菜花消亡的原因之一.因此恢复海菜花必须提高水体透明度,改善光照强度.     

Acute Toxicity of Mercury,Copper and Zinc to a Freshwater Pulmonate Snail,Lymnaea luteola (LAMARCK)

The short-term toxicity of mercury, copper and zinc was studied using a freshwater pulmonate snail, Lymnaea luteola (LAMARCK ). The median period of survival increases with decreasing the toxicant concentration. The 96 h LC₅₀ values and their confidence limits were 0.135 (0.112 … 0.186) ppm of Hg²⁺; 0.172 (0.118 … 0.355) ppm of Cu²⁺; and 6.13 (5.73 to 7.19) ppm of Zn²⁺. The relative potency ratio indicates that the Hg²⁺ ions were most toxic, followed by Cu²⁺ and Zn²⁺ ions.     

西江广东鲂(Megalobrama terminalis)繁殖生物学及繁殖策略

探究鱼类繁殖策略是了解鱼类种群动态的关键.通过对珠江西江流域重要的经济鱼类广东鲂(Megalobrama terminalis)生殖周期、产卵时间、成熟期长度、生殖力类型和生殖力等方面进行研究,阐明在人类活动日益加强下,西江广东鲂的繁殖策略适应性变化情况.研究表明,广东鲂个体平均体长245 mm,优势体长集中在260~280 mm,平均体重347 g,优势体重集中在320~480 g.用L 50逻辑斯谛回归方法推算广东鲂雌鱼和雄鱼初次性成熟体长分别为244.5和232.2 mm.雌雄性比例为1.105∶1,且随着体长增加,雌雄性比呈现出先下降后上升的变化趋势.广东鲂繁殖群体在产卵季节为48月,产卵高峰为6月初持续到7月上旬,产卵季节内广东鲂鱼苗的密度与径流量显著相关.广东鲂绝对繁殖力平均为73069粒,相对繁殖力平均为118.7粒/g,绝对繁殖力与体长和体重均呈正相关.广东鲂繁殖群体性腺成熟系数与性腺重、肥满度以及体重密切相关.广东鲂种群繁殖策略在人类活动加剧影响下呈现出适应性变化:初次性成熟体长变小,绝对繁殖力下降.     

Effects of heavy metals on the survival and feeding behaviour of the sandy shore scavenging gastropod Nassarius festivus (Powys)

The effects of Cu, Cd, Zn and Cr on the survival and feeding behaviour of the sandy shore scavenging gastropod Nassarius festivus were compared. The 96-h LC₅₀ for Cu, Cd, Zn and Cr were 0.36, 1.52, 1.76 and 36.9 mg l⁻¹, respectively. Four sublethal concentrations of each metal plus a control were prepared and the snails were exposed to experimental solutions for 96 h. Feeding behaviour was studied after the snails were starved for five days. As compared with the control, the number of individuals feeding was significantly reduced by exposure to 0.05 mg l⁻¹ Cu, 0.2 mg l⁻¹ Zn, 0.5 mg l⁻¹ Cd and 5 mg l⁻¹ Cr. The time spent feeding was greater for individuals exposed to greater concentrations of Zn and Cd but no effect was found for Cu and Cr. Chemoreception of food was studied by placing the snails at a fixed distance of 15 cm from the bait. The success rate of reaching the bait was less for individuals exposed to Cr but no effect was found for Zn, Cu or Cd. The time required for an individual to reach the bait decreased as the concentration of Zn increased. In contrast, a longer time was required for individuals exposed to Cr whereas the effect of Cd and Cu was insignificant. The potential of using feeding behaviour and chemoreception in contaminant evaluations is discussed.     

Extended larval development compensates for sublethal effects of fish predation in a mayfly population (Rhithrogena semicolorata, Ephemeroptera)

Many predation experiments in streams are carried out in enclosures. Hence, the relevance of their results to predict population dynamics is often unclear due to the relatively small spatial and temporal scale of the experiments. To enhance the transferability of experimental results on the ecosystem scale the impact of fish predators on a prey population was observed in a reach scale approach over 2 years in a natural stream. A 400-m reach inhabited by the small benthivorous fishes gudgeon (Gobio gobio) and stone loach (Barbatula barbatula) was compared with a fishless reference reach.It was shown that fish predation may affect the population of the grazing mayfly Rhithrogena semicolorata on the ecosystem scale. Although the larvae grew slower in the fish reach than in the fishless reach, the adults reached the same size and fecundity because they emerged 2–3 weeks later. By this compensation, the prey species avoided a reduction of their individual fecundity. On the other hand, the extended exposure to the fish predators resulted in an enhanced mortality and a reduced density of adult mayflies. Thus, there was obviously a trade-off between maximising fecundity and minimising mortality from fish predation.The observed differences were almost certainly caused be fish predation and not by natural differences of the reaches. This was concluded from results gained after eliminating all benthivorous fish from the former fish reach.With the help of scenario analyses based on our empirical data and simple model assumptions we could demonstrate that compensating the potential loss in fecundity by extending development time led to higher average fitness of the prey population than emerging at an earlier fixed time to avoid additional predation losses. Therefore, we concluded that this strategy was adaptive in the presence of benthivorous fish.     

湖北道观河水库细鳞鲴的个体生殖力

研究了道观河水库细鳞鲴的个体生殖力。细鳞鲴样本由2~ -5~ 龄鱼组成,其个体绝对生殖力与体长、体重和年龄分别呈直线、对数函数和幂函数相关,体长相对生殖力与体长、体重和年龄分别呈双曲线、对数函数和幂函数相关,体重相对生殖力与它们相关不显著。多元逐步回归分析其绝对生殖力和体长相对生殖力均与体重和成熟系数密切相关,而体重相对生殖力仅与成熟系数相关。     

The trophic ecology of arctic char (Salvelinus alpinus) and brown trout (Salmo trutta) in Ellidavatn, a small lake in Southwest Iceland

In the lake Ellidavatn, southwest Iceland, fish samples were collected with gillnets of one mesh-size once or twice a month for two years. Stomach samples of 961 Arctic char and 429 brown trout were analysed. The annual diet of char consisted of chironomid larvae (31%), cladocerans Eurycercus lamellatus (19%), bivalves Pisidium spp. (16%), water snails Lymnaea peregra (15%), chironomid pupae (8%) and char eggs (5%) and that of trout consisted of sticklebacks (76%), salmonids (7%) and L. peregra (6%). The average percentage of indigestible plant remains and gravel in the stomach content was much higher for the char (14%) than trout (3%). There were large seasonal changes in the diet of char: char eggs were consumed in autumn, chironomid larvae mostly from autumn to spring, chironomid pupae in summer and E. lamellatus from summer to autumn. No seasonal changes in the diet of trout were seen. The diet overlap of char and trout was very low, usually about 10%, reaching a maximum of about 30% in late summer 1976 when the common diet was mainly E. lamellatus and chironomid pupae. The resource partitioning in Ellidavatn indicates that char are better adapted to preying on small benthic invertebrates than piscivorous trout. The segregation in the diet of the two species indicated competition for restricted food supply, which was also consistent with slow growth and low condition factor of char (0.8–1.0) and trout (1.0) in Ellidavatn. The prey of trout were two orders of magnitude larger than the prey of char which may explain why adult char grew more slowly (2 cm y⁻¹) than adult trout (4 cm y⁻¹) and reached sexual maturity at a smaller size (30 cm) than trout (40 cm).     

近30年滇西北高原湖泊海菜花(Ottelia acuminata)群落变化

采用对比研究法,研究了近30年来滇西北洱海、茈碧湖、剑湖、拉市海和泸沽湖5个高原湖泊海菜花(Ottelia acuminata)群落的变化,结果表明:与1980年相比,天然海菜花群落仅在泸沽湖和剑湖有分布.现时海菜花群落物种数增加,泸沽湖海菜花群落物种数由1980年的7种增至2008年的10种,剑湖海菜花群落物种数由1980年的6种增至2011年的12种.群落生活型构成变得复杂,泸沽湖海菜花群落由沉水植物和漂浮植物构成向沉水植物、浮叶植物和漂浮植物构成变化;剑湖海菜花群落由单一沉水植物构成向沉水植物、浮叶植物、漂浮植物和湿生植物构成变化.两湖海菜花群落物种组成均发生更替,但泸沽湖海菜花群落物种组成与30年前相似度较高,群落保存相对较好;剑湖海菜花群落物种组成则与30年前相似度较低,群落变化大.     

路南海菜花的核型分析及其海菜花属的演化探讨

海菜花属(Ottelia Pers.)为沉水单子叶植物,只生长于淡水生境中,具有重要的生态价值、环境指示作用以及植物系统学研究意义.本文首次报道了特产于我国云南石林湖泊中的路南海菜花(Ottelia acuminata var.lunanensis H.Li)的体细胞染色体数目为22条,核型属"1B"型,核型公式2n=2x=22=18m+4sm.结合已研究的花部特征和核型资料讨论海菜花属种间的亲缘关系及演化,为海菜花(Ottelia)的利用和保护提供细胞生物学证据.     

Molluscicidal Activity of Euphorbiales against the Snail Indoplanorbis exustus

Mortality caused to the snail Indoplanorbis exustus by the latices of four species of plants belonging to the family euphorbiaceae has been reported. This snail is the vector of the liver fluke Fasciola hepatica and Fasciola gigantica. It was found that very low concentrations of the latex were effective in killing the snails. The order of toxicity of the four plants was E. royleana > E. antisyphilitica > E. lactea cristata > J. gossypiifolia. The toxic activity of these plants was marginally lost after extraction by organic solvents. The toxic effect of all the plants was both dose and time dependent. It has been suggested that the latex of these plants may eventually find use as molluscicides in the field.     

Survival of an invasive aquatic snail to overland translocation in non-aquatic media: Implications for spreading

Invasive species are a threat to aquatic ecosystems worldwide. Aquatic snails have a limited ability for an active dispersal. Therefore, their ability to survive to transport in non-aquatic media may help explain their spread across unconnected habitats. We assessed the ability of New Zealand Mud Snail (NZMS) (Potamopyrgus antipodarum) to survive attached to different materials. Two studies were conducted: (1) a laboratory study to assess the tolerance of a laboratory population of NZMS to non-aquatic media attaching snails to leaf litter, sediment and clay and (2) a field-laboratory study to assess the survival of an invasive field population after being left imbedded in clay in the laboratory and subsequently transferred to a new river reach. All laboratory animals died after 3 days in leaf litter, while in the case of sediment and clay all snails died after 5 days. After being imbedded in clay and subsequently transferred to the river, the survival of the field population was lower than that of the laboratory populations. We conclude that NZMS can be dispersed by mechanisms which imply spending some time in non-aquatic media, and that this species has a relatively high tolerance to translocation between reaches with contrasting environmental properties.     

Action Sites of Cypermethrin,a Synthetic Pyrethroid in the Snail Lymnaea acuminata

24 h of in vivo exposure to 40 and 80 = LC50 of the synthetic pyrethroid cypermethrin significantly reduced the acetylcholinesterase, cytochrome oxidase and lactic dehydrogenase activity in the nervous tissue of L. acuminata. Succinic dehydrogenase activity increased significantly after the same treatment. Fifteen minutes in vitro exposure to different doses of cypermethrin also significantly inhibited cytochrome oxidase and lactic dehydrogenase activity. However, acetylcholinesterase and succinic dehydrogenase activities remain unaltered. It is concluded that the cypermethrin on the one hand causes repititive discharges at the nerve terminal and on the other hand blocks the electron transport chain.     

Behavioral effects of titanium dioxide nanoparticles on larval zebrafish (Danio rerio)

In this study, zebrafish embryos were exposed to titanium dioxide nanoparticles (TiO₂ NPs at 0.1, 0.5, 1, 5, 10 mg/L or control) from fertilization to free swimming stage. Hatchability, survival, and malformation rate were not affected by TiO₂ NPs at these exposure levels. However, larval swimming parameters, including average and maximum velocity and activity level were significantly affected by TiO₂ NPs. Co-exposure to either the glutathione precursor, N-acetylcysteine (NAC), or the glutathione synthesis inhibitor, buthionine sulfoximine (BSO), did not significantly alter the behavioral effects resulting from TiO₂ NPs, suggesting that other factor(s) besides oxidative stress may contribute to the behavioral toxicity of TiO₂ NPs. Our study also demonstrated that the behavioral endpoints were more sensitive than the others (e.g., hatchability and survival) to detect toxicity of TiO₂ NPs on developing fish.