Direct and delayed effects of low temperature on the freshwater snail Indoplanorbis exustus (Deshayes, 1934), intermediate host of schistosomias

The direct and delayed effect of short-term exposure to low temperature (17.5 °C) on growth, reproduction and longevity of adolescent and mature freshwater Indoplanorbis exustus Deshyaes (Mollusca: Gastropoda) was studied in the laboratory. We found that growth and reproduction were retarded, but were enhanced when later they were returned to ambient temperature.     

Vertical variation in fecundity of the intertidal gastropodMonodonta labio caused by different growth rates between tidal zones

Monodonta labio (Gastropoda: Trochidae) occurs in a wide tidal zone on a boulder-covered shore in Amakusa, Japan. To investigate sources of variation in reproductive output within a population, the fecundity ofM. labio was estimated. Regressions of gonad egg counts on shell width were calculated from samples collected bi-weekly at three tidal zones: high, mid and low intertidal. Seasonal fluctuations in the regression revealed that individual females spawn at least three times a year. Variation in fecundity between the three tidal zones was not detected at any time in standard 12 mm snails. Due to the high growth rate in the low zone during the reproductive season, annual fecundity in the low zone was larger than that in the high and mid zones. Thus, tidal zone variation in fecundity ofM. labio was a result of growth variation between tidal zones.     

Food composition of the Near Eastern Fire Salamander,Salamandra infraimmaculata Martens, 1885 (Amphibia: Urodela: Salamandridae) from Eastern Anatolia

This study presents data on the food composition of the Near Eastern Fire Salamander, Salamandra infraimmaculata, from Bingöl, eastern Turkey. A total of 139 prey items was determined in the food content of 28 individuals (14 juveniles, 7 males, and 7 females). Insecta (N%= 37.4), Gastropoda (27.3%), and Isopoda (25.9%) constitute together 91% of the food items. The most frequent prey groups in the diet are Coleoptera (F%=50.0%), Isopoda (57.1%), and Gastropoda (46.4%). Coleoptera (V%= 34.6%), Gastropoda (28.0%), and Isopoda (23.5%) had the highest prey volumes. No significant difference was found between the sexes in food composition. The species generally feeds upon poorly flying or slow-moving invertebrates, but is opportunistic in taking up more mobile prey species as well. Diptera, Odonata and Hemiptera were found in small numbers only.     

The life-cycle of Echinostoma friedi n. sp. (Trematoda: Echinostomatidae) in Spain and a discussion on the relationships within the `revolutum' group based on cercarial chaetotaxy

The morphology of the different stages and life-cycle of Echinostoma friedi n. sp. are described and figured. The freshwater snail Lymnaea peregra (Gastropoda: Lymnaeidae) serves as the natural and experimental first intermediate host and L. corvus and Gyraulus chinensis (Gastropoda: Planorbidae) as experimental first intermediate hosts. These, and Physella acuta (Gastropoda: Physidae), also serve as second intermediate hosts. Adult worms, possessing 37 collar spines, were obtained from naturally infected Rattus norvegicus and experimentally from albino rats, golden hamsters and chickens. Mice were not suitable experimental definitive hosts. E. friedi differs from the most closely related species in the `revolutum' group mainly in terms of several morphological and biological features of the life-cycle stages and in its cercarial chaetotaxy. The chaetotaxy patterns of the species of the `revolutum' group are analyzed and the results show that a taxonomic comparison of these species may be carried out on the basis of the number of sensilla in the clusters CIII V₁, CIII V₂ (or CIII V₁ + CIII V₂), CIV DL and UV_b. These clusters appear adequate to establish taxonomic relationships between different species within the `revolutum' group.     

Environmental effects on the induction of wheat chemical defences by aphid infestation

The effects of temperature and photoperiod on the ability of wheat (Triticum aestivum L.) seedlings to show induced responses (increased accumulation of hydroxamic acids, Hx) upon infestation by the bird cherry-oat aphid, Rhopalosiphum padi L. were evaluated under laboratory conditions. Induction of Hx was significantly higher at lower temperatures. No such clear trend was found for the photoperiod effect. The significant effect of environmental conditions on growth rate of seedlings and the significant negative correlation between growth rate prior to infestation and induction of Hx suggested that environmental effects on induced responses were at least partially mediated through their effect on plant growth rate. After statistically uncoupling the effect of environmental conditions from the effect of plant growth rate, the effect of temperature on induction of Hx was no longer significant. Therefore, the temperature effect was mediated by plant growth rate.     

Sexual dimorphism and the impact of temperature on the pupal and adult stages of Sepedon spinipes spinipes, a potential biological control agent of fascioliasis

The malacophagous feeding behaviour of larvae of members of the family Sciomyzidae makes the group ideal for the selection of potential biological control agents of snail hosts of trematode diseases. The aim of this study was to investigate the effects of temperature (14 °C, 17 °C, 20 °C, 23 °C, and 26 °C) on the pupal and adult stages of Sepedon spinipes spinipes (Scopoli) (Diptera: Sciomyzidae). Larval prey density effects on the pupal stage and the extent of sexual dimorphism within the species are also assessed. Optimum growth conditions for the pupal stage and pre‐oviposition/oviposition periods, and female fecundity are identified for mass culturing purposes. The tendency of mature third instar larvae to engage in wandering behaviour is highlighted, and the biological control implications of such behaviour are discussed. Female puparia were significantly (P<0.001) heavier than males for both larval prey densities. Such sexual dimorphism would enable the prediction of adult sex from puparial weight prior to eclosion, thereby facilitating culture establishment. The effect of three food types [honey/yeast mixture only, crushed Radix balthica (L.) (Gastropoda: Pulmonata: Lymnaeidae) only, and honey/yeast mixture plus a crushed snail] on adult longevity (laboratory conditions) was also determined and the results suggest that adults live longest when provided with a crushed snail and a honey/yeast mixture.     

Desiccation,predation, and mussel-barnacle interactions in the northern Gulf of California

Summary Field experiments were conducted in order to determine the potential for desiccation and predation to mediate the effect of mussels (Brachidontes semilaevis) on barnacles (Chthamalus anisopoma) in the highly seasonal northern Gulf of California. We did this by removing both mussels and a common mussel predator (Morula ferruginosa: Gastropoda) and by spraying selected sites with sea water during summertime spring low tides. We also determined the effect of crowding on resistance to desiccation in barnacles, and the effect of barnacles on colonization by mussels. The mussel-barnacle community was not affected by keeping experimental quadrats damp during daytime low tides throughout the summer. Exposure to summertime low tides, however, did affect the survivorship of isolated, but not crowded, barnacles; and barnacle clumps enhanced the recruitment of mussels. Hence crowding in barnacles had a positive effect on both barnacle survivorship and mussel recruitment. Morula had a negative effect on mussel density, and mussels had a negative effect on barnacle density. The effect of Morula on barnacle density was positive, presumably due to its selective removal of mussels. These results suggest an indirect mutualism between barnacles and the gastropod predator, because barnacles attract settlement or enhance the survival of mussels, and the predator reduces the competitive effect of mussels on barnacles.     

醉马草水浸液对豌豆蚜触杀活性及种群增长的影响

为探讨醉马草水浸液对豌豆蚜触杀活性及种群增长的影响,采用带虫浸叶法比较不同生育期醉马草带菌（E+）和不带菌（E-）水浸液对豌豆蚜触杀活性及种群生命表,测定了豌豆蚜的死亡率及触杀后对其生殖期,平均繁殖力,繁殖率及生命表参数的影响。结果表明,不同生育期醉马草带菌（E+）水浸液触杀豌豆蚜后对其各项指标均有显著影响。在苗期时,E+水浸液触杀豌豆蚜后校正死亡率最高,繁殖力最低,内禀增长率（r_m=0.145 d^-1）和净生殖率（R₀=4.802头）均为最小值。在成熟期时,E+水浸液触杀豌豆蚜24 h、48 h和72 h后校正死亡率分别为26.15%,19.01%,9.07%;繁殖期（3.87 d）,平均繁殖力（8.80头）,繁殖率（1.40%）,内禀增长率（r_m=0.208 d^-1）和净生殖率（R₀=8.820头）。在枯黄期时,E+水浸液触杀豌豆蚜后校正死亡率最低,繁殖力最强,内禀增长率（r_m=0.247 d^-1）和净生殖率（R₀=13.647头）均为最大值。不同生育期醉马草E-水浸液触杀豌豆蚜后对其种群繁殖无显著影响,与对照差异不显著（P>0.05）。综上,苗期醉马草E+水浸液对豌豆蚜有较好的触杀效果,校正死亡率高,且触杀后当代繁殖力减弱,种群扩建时间延长,不利于其种群繁殖和增长;故苗期醉马草E+水浸液具有很好的杀虫潜力,所采用水浸液方法制备简单,成本低,可为新型植物源农药研发提供重要理论依据。     

Trophic niche and habitat shifts of sympatric Gerreidae

The diet and mouth growth rates of three Gerreidae species (Eugerres brasilianus, Eucinostomus melanopterus and Diapterus rhombeus) were assessed at different ontogenetic phases (juveniles, sub‐adults and adults) in order to detect allometric growth, and whether they are related to habitat and seasonal changes in the Goiana Estuary, north‐east Brazil. The importance of each prey for each ontogenetic phase was described using the index of relative importance. The three species showed seasonal ontogenetic shifts in diet and allometric growth of mouth morphology. They also had an exclusively zoobenthic diet, comprising mainly Polychaeta, Copepoda, Ostracoda, Gastropoda and Bivalvia. Mouth development showed a possible influence on diet changes for E. melanopterus. Significant interactions (P < 0·01) were detected among seasons, areas and ontogenetic phases for the most important prey for E. brasilianus and E. melanopterus. Diet overlaps are evidence of intra and interspecific competition among gerreids for specific prey. A conceptual model of the competition and seasonal diet shifts among ontogenetic phases of gerreids is given. The sediment ingested due to the feeding mechanisms of Gerreidae species could also partially explain the ingestion of synthetic items observed for all ontogenetic phases, which indicates one of a myriad effects of human activities (e.g. artisanal fishery) in this estuary.     

Diversity and distribution of molluscan fauna of Asthamudi estuary,Kerala, India

The survey of molluscan fauna of Ashtamudi estuary of the southwest coast of India recorded the presence of 119 species classified under 3 classes (Polyplacophora, Gastropoda and Bivalvia), 57 families and 96 genera. The species diversity was dominated by the Gastropoda (69 species), followed by the Bivalvia (49 species) and the Polyplacophora (1 species). The report includes four species recorded for the first time from India: Desmaulus edgarianus (Melvill, 1898), Pilosabia trigona (Gmelin, 1791), Nassarius javanus (Schepman, 1891) and Jorunna labialis (Eliot, 1908). The true diversity of the mangrove region was as good as that of a community with 31.380 (=?31) equally common species; the respective values for the bar mouth and lake regions were 15.516 and 8.997, respectively, indicating that the molluscan species assemblage of the mangrove was the most diverse and of the lake, the least. True β-diversity across this gradient registered 1.792, which means that though there were three communities, they were equivalent to only 1.792 (=?2) effective communities, i.e., the three actual communities were as different from each other as 2 with equal weights and no species in common.

     

Partial 28S rDNA sequences and the antiquity of hydrothermal vent endemic gastropods

A molecular phylogenetic investigation of the hypothesized antiquity of the hydrothermal vent endemic Neomphalina (Mollusca; Gastropoda) is reported. Sequences of two domains of the gene encoding for 28S ribosomal RNA were acquired for 3 outgroup and 32 gastropod genera. Use of the likelihood ratio test indicated complex substitution patterns for these domains and taxa, corresponding to a general time-reversible model with among-site rate variation. Phylogenetic analyses were performed using this model under maximum likelihood criteria. The data lacked resolution of gastropod radiations of the Paleozoic and all three of the outgroup sequences were randomized relative to the ingroup. Acceleration of evolutionary rates had additionally randomized the sequences of the Patellogastropoda relative to the other Gastropoda. The data resolved radiations of the Mesozoic and supported monophyly of the sampled Neritopsina, Vetigastropoda, Neomphalina, Caenogastropoda (including Campanile and the Architaenioglossa), and Heterobranchia (Valvata + Euthyneura), although several results were not significantly different from nonmonophyletic alternatives. Mesozoic origins of the hydrothermal vent endemic Neomphalina are preliminarily supported and implications for the hydrothermal vent refugia hypothesis discussed. Issues related to phylogenetic resolution of the Gastropoda are additionally discussed.     

Effect of desalination on the littoral tecturid gastropods in early development

The effect of decreased salinity on the limpetsCollisella dorsuosa, C. versicolor, C. radiata, andNotoacmea concinna (Mollusca, Gastropoda) is studied at early stages of development. It is shown that, for normal development from fertilization to the veliger stage, the salinity must be not less than 22–24‰. A decrease in salinity depressed the behavior of larvae. At earlier stages, the larvae were less sensitive to changes in salinity than at later stages. At the same time, veligers were better able to adapt to changes in salinity than trochophores. The vertical water distribution of larvae depended on their age. Two days after fertilization, the larvae sank down to start a benthic life. It is proposed that the narrow tolerance range of littoral limpet larvae to changes in salinity is connected with the fact that they spend a relatively small part of their life in plankton.     

Standard Metabolic Rate in Gastropoda Class

Abstarct—The relationship between oxygen consumption and soft tissue weight in the Gastropoda class (according to the obtained and published data) is expressed by the equation with coefficientsa = 0.71 and k = 0.78. Prosobranch and pulmonate snails have similar levels of oxygen consumption. Opisthobranch snails have higher oxygen consumption. No relationship has been revealed between the metabolic rate (coefficient a) and climatic zone of the gastropod habitat.     

Modelling the effect of temperature, water activity and pH on the growth of Serpula lacrymans

Aims: To predict the risk factors for building infestation by Serpula lacrymans, which is one of the most destructive fungi causing timber decay in buildings. Methods and Results: The growth rate was assessed on malt extract agar media at temperatures between 1·5 and 45°C, at water activity (a_w) over the range of 0·800–0·993 and at pH ranges from 1·5 to 11·0. The radial growth rate (μ) and the lag phase (λ) were estimated from the radial growth kinetics via the plots radius vs time. These parameters were then modelled as a function of the environmental factors tested. Models derived from the cardinal model (CM) were used to fit the experimental data and allowed an estimation of the optimal and limit values for fungal growth. Optimal growth rate occurred at 20°C, at high a_w level (0·993) and at a pH range between 4·0 and 6·0. The strain effect on the temperature parameters was further evaluated using 14 strains of S. lacrymans. The robustness of the temperature model was validated on data sets measured in two different wood‐based media (Quercus robur L. and Picea abies). Conclusions: The two‐step procedure of exponential model with latency followed by the CM with inflection gives reliable predictions for the growth conditions of a filamentous fungus in our study. The procedure was validated for the study of abiotic factors on the growth rate of S. lacrymans. Significance and Impact of the Study: This work describes the usefulness of evaluating the effect of physico‐chemical factors on fungal growth in predictive building mycology. Consequently, the developed mathematical models for predicting fungal growth on a macroscopic scale can be used as a tool for risk assessment of timber decay in buildings.     

Adaptive morphology of Capulus subcompressus Pelseneer, 1903 (Gastropoda: Capulidae) from Terra Nova Bay, Ross Sea (Antarctica)

Capulus subcompressus Pelseneer, 1903 (Gastropoda: Capulidae) is a small epibiont gastropod living at Terra Nova Bay (Ross Sea) down to 540 m on the calcareous tubes of its unique host, the serpulid Serpula narconensis Baird, 1865. This polychaete forms bush-like aggregates which host a rich microfauna of crustaceans, hydroids and molluscs. In contrast to all other capulids, C. subcompressus shows an evident oval shell aperture, which is due to an allometric growth that can be imputed to the Serpula tube morphology. Since the allometric growth is detectable in all size classes, it could be deduced that the compressed shape of the C. subcompressus shell is the stable result of a significant evolutionary history which binds tightly these two species in Antarctic waters. Accepted: 17 July 1999     

黄河三角洲芦苇湿地底栖无脊椎动物与环境因子的关系研究——以石油开采区与淡水补给区为例

分别于2018年5月和8月对黄河三角洲芦苇湿地19(淡水补给区11处,石油开采区8处)处采样点的底栖无脊椎动物和水体理化指标进行调查采样,运用统计方法分析两个区域物种组成、优势种、多样性、群落结构以及与环境因子的关系。结果表明:两季共采集到底栖无脊椎动物54种,主要以水生昆虫、腹足纲和软甲纲为主,淡水补给区和石油开采区各类群组成差异明显。独立样本T检验表明淡水补给区和石油开采区水体理化指标间差异显著(P0.05)。双因子方差分析显示,昆虫纲和腹足纲密度在两区域差异显著(P0.05),软甲纲和腹足纲密度在季节上差异明显(P0.05)。底栖无脊椎动物优势种共10种,淡水补给区指示物种8种,而石油开采区未发现有指示物种。聚类和非参数多维排序(nM DS)显示,底栖无脊椎动物群落结构相似性较低; RDA结果表明:淡水补给区底栖无脊椎动物群落结构主要受Cond,TDS,Sal,pH,Eh,HCO_3~-,SO_4~(2-)等环境因子的影响。石油开采区底栖无脊椎动物群落结构影响较大的环境因子为HCO_3~-、NH_4-N。     

Trade-offs between ontogenetic changes and food consumption in Brazilian silverside Atherinella brasiliensis from two tropical estuaries

Salinity variation in estuarine environments influences the distribution of fish species as well as the availability of food resources to be used by them. This study examines the effect of the range of salinity on the trade-off between growth and feeding intensity of Atherinella brasiliensis from two tropical estuaries (positive and hypersaline). To investigate the effects of salinity, we hypothesized that hypersalinity negatively affects foraging intensity, consumption and prey selection by the Brazilian silverside, leading to differences in body condition. Sampling was carried out using the beach seine method in two areas of the estuaries (upper and lower zone) during rainy and dry periods. A total of 2549 stomachs (1124 for the positive estuary and 1425 for the hypersaline estuary) were examined, and the results indicated a dissimilarity of 92.7% of the diet between environments. In the positive estuary, there was more predation on Calanoida, Gastropoda, Hymenoptera, Ceratopogonidae larvae and Decapoda larvae, while Alga and plant-material characterized the diet in the hypersaline estuary. Significant correlations between the volume of food and salinity were observed in both estuaries. The vacuity index indicated that hypersaline environments presented higher contributions of semifull stomachs, indicating an intense consumption of algae. On the other hand,in the positive estuary, these values were less intense, but the stomachs were always with animal items. The variation found for both environments reinforces the effect of salinity on the physiological mechanism of the populations once the higher proportions of filled stomachs in the hypersaline environment indicate the need for constant and high ingestion of prey to guarantee the pronounced energy expenditure with osmoregulation.     

The abundance of phytophilous invertebrates on different species of submerged macrophytes*

SUMMARY. 1. We tested Krecker's model (1939) which states that the abundance of invertebrates per unit macrophyte biomass varies with plant species and is higher on plants with finely dissected leaves than on plants with broad leaves. The abundance of invertebrates was measured in thirteen lacustrine macrophyte beds in southern Québec, Canada. The model was tested for the total abundance of invertebrates and for the abundances of Chironomidae, Cladocera, Cyclopoida, Gastropoda, Hydracarina, Ostracoda and Trichoptera. 2. More epiphytic invertebrates were found on the dissected Myriophyllum spp. than on the broad-leaved Potamogeton amplifolius Tuckerm, P. robbinsii Oakes and Vallisneria americana Michx. (P<0.01). More invertebrates were also found on P. amplifolius than on P. robbinsii or V. americana (P<0.01). The total abundance of invertebrates was not systematically related to the degree of plant dissection. 3. The abundances of Chironomidae, Cladocera, Cyclopoida, Gastropoda, Hydracarina, Ostracoda and Trichoptera varied on different plant species (P<0.01). Contrary to Krecker's hypothesis, however, macrophytes with finely dissected leaves (Ceratophyllum demersum and Myriophyllum spp.) did not in general support more invertebrates per unit plant biomass than plants with large leaves (Potamogeton amplifolius, P. robbinsii and Vallisneria americana).     

Culture of Isolated Single Cells from <Emphasis Type="Italic">Taxus</Emphasis> Suspensions for the Propagation of Superior Cell Populations

Single cells isolated from aggregated Taxus cuspidata cultures via enzymatic digestion were grown in suspension culture. High seeding density (4×10⁵ cells/ml) and the addition of cell-free conditioned medium were essential for growth. Doubling the concentration of the nutrients [ascorbic acid (150 g/l), glutamine (6.25 mm), and citric acid (150 g/l)] had no effect on single cell growth or viability. A specific growth rate of 0.11 days⁻¹ was achieved, which is similar to the observed growth rate of aggregated Taxus suspensions. The biocide, Plant Preservative Mixture, added at 0.2% (v/v) to all single cell cultures to prevent microbial contamination, had no significant effect on growth or viability. Following cell sorting, single cell cultures can be used to establish new cell lines for biotechnology applications or provide cells for further study.     

Foraging in the ant-lionMyrmeleon mobilis hagen 1888 (neuroptera: Myrmeleontidae): Behavioral flexibility of a sit-and-wait predator

The relative effects of foraging benefits (food intake) and costs (disturbance = pit destruction) on growth rate and foraging behavior of larvae of the ant-lionMyrmeleon mobilis were investigated. In a laboratory experiment second-instar larvae were subjected to combinations of three rates of feeding and three rates of disturbance. Pit relocations were generally rare but occurred more often in starved larvae. Disturbance rate had no significant effect on pit relocation rate. Feeding rate was a major determinant of the energy allocated in pit construction and maintenance (positive relationship). In a second experiment third-instar larvae encountered changing rates of disturbance. Pit size was reduced as a response to increased rates of disturbance. Disturbance had no detectable effect on growth. In general,M. mobilis larvae were cost-conservative, foragers.