The effects of food and density of the movement ofArion ater andAriolimax columbianus (Pulmonata: Stylommatophora) between habitats

Experiments were conducted to determine if slug density, or food quantity and quality could cause dispersal by slugs. Arion ater dispersed quickly from overcrowded areas, where high mortality was incurred by this species. Poor food conditions, caused more dispersal than good food conditions, but food had no effect on the mortality of A. ater. Neither food nor density factors had significant effects on the dispersal of Ariolimax columbianus. However, more A. columbianus died in the high- than low-density treatments. A. columbianus mortality was unaffected by the food factor. Dispersing Arion were heavier than non-dispersers, but there was no difference between the weights of dispersing and non-dispersing Ariolimax. There were significant seasonal changes in the dispersal rate, mortality and weight of dispersing Arion, whereas only the mortality of Ariolimax changed significantly during the experiments. Since Arion ater did not markedly reduce its activity during unsuitable weather it was able to leave areas of poor food and high slug density fairly rapidly. Ariolimax columbianus' large size allowed it to remain inactive during unfavourable weather and permitted this species to be relatively unresponsive to the experimental treatments.     

The ultrastructure of the epicardium epithelium of the slug, Arion ater (Linnaeus, 1758), (Pulmonata, Stylommatophora)

In the present paper we investigated the fine structure of terrestial slug Arion ater (L.) Interacisternal microtubules were formed in Arion ater, however they do not correspond to interacisternal polycylinders because they differ in size and they are not continuous with the membrane cistern. From our study it may be concluded that these intracisternal microtubules suggest an accumulation of protein.     

The channel cell of the terrestrial slug Ariolimax columbianus (Stylommatophora,Arionidae)

Summary Studies were carried out to identify the route by which macromolecules and large volumes of fluid traverse the skin of terrestrial gastropods. Electron micrographs of the skin of the banana slug Ariolimax columbianus demonstrated that carbon particles can enter large, specialized cells and pass thence to the exterior. These cells, which are termed channel cells, range up to 500 m in length; they reach from the external surface of the skin to deep within the subepithelial interstitium. At the light-microscope level they show a large central channel or reservoir apparently filled with homogeneous fluid; after injection of ink into the body cavity this central channel becomes ink-filled. Electron micrographs show cisternae of the smooth endoplasmic reticulum, opening from the cell surface and occasionally traversing the entire cytoplasmic layer. The neurohormone arginine vasotocin stimulates fluid and particle movement through the channel cell; this response is inhibited by norepinephrine. Fluid output is dependent on the presence of a transwall hydrostatic pressure gradient of about 7 torr or above, as well as on activation of the channel cells.     

An analysis of intrinsic and extrinsic factors affecting the activity of a nocturnal species: The wild boar

Over the last century, the wild boar (Sus scrofa) has become an important wildlife species in both economic and ecological terms. Considered a pest by some and a resource by others, its rapid increase in population and distribution has raised management concerns. Studies on activity rhythms may provide useful insights into its overall ecology and help develop effective management strategies. By examining highly detailed activity data collected by means of accelerometers fitted on GPS-collars, we studied wild boar daily activity rhythms and the effect of environmental conditions on their diurnal and nocturnal activity. We thus provided evidence of the predominantly nocturnal and monophasic activity of wild boars. All year round, we reported low activity levels during the day, which opportunistically increased under the most favourable environmental conditions. Activity was found to be significantly affected by such weather conditions as temperature, precipitation and air relative humidity. Moreover, we found that nocturnal activity slightly increased as moonlight increased. Part of our analysis was focused on the hunting period in order to investigate whether wild boars modify their activity levels in response to hunting disturbance. Our results suggested that wild boar nocturnal habits are not directly influenced by the current hunting disturbance, though we hypothesised that they may have evolved over several decades of hunting harassment. Alternatively, but not exclusively, nocturnal habits may have evolved as a low-cost strategy to achieve an optimum thermal balance (i.e., behavioural thermoregulation).     

四川西北部巴蜗牛类研究兼一新种描述(腹足纲:肺螺亚纲:柄眼目)

对川西北陆生贝类巴蜗牛科进行了系统整理.其中对假弯巴蜗牛[Bradybaena (Bradybaena) pseudocampylaea (Moellendorff)]、松山巴蜗牛[Bradybaena (Bradybaena) sueshanensis Pilsbry]、单带反向巴蜗牛[Bradybaena (Bradybaena) controversa monotaeniata Pilsbry]进行了解剖.描述了新种茂县蛇蜗牛Pseudiberus (Pseudiberus) maoensis sp.nov.,其模式标本及其他研究标本均保存于中国科学院动物研究所.     

Evolutionary relationships among the Pulmonate land snails and slugs (Pulmonata, Stylommatophora)

We have incorporated an additional 56 species of land snails and slugs in our ribosomal (r) RNA molecular phylogeny. The new taxa include representatives of several important groups. The molecular tree now includes 160 species of stylommatophoran land snails and slugs in 144 genera in 61 families. In the rDNA tree, the Stylommatophora are principally divided into an 'achatinoid' and a 'non-achatinoid' clade. Within these clades, several major land snail groups, including the Orthurethra, Elasmognatha, Limacoidea, and Helicoidea, are supported. Overall, the rDNA molecular phylogeny has remained stable following the incorporation of the additional taxa, with these additions having little impact on the major evolutionary patterns in the tree. Taxonomic coverage of the Orthurethra, Orthalicidae, Camaenidae, and Bradybaenidae is increased significantly. The camaenids and bradybaenids form a complex, and both appear to be paraphyletic. Several families of uncertain affinity, such as the Sagdidae and Thyrophorellidae, are included for the first time. The Sagdidae are shown to belong to the Helicoidea, and the Thyrophorellidae to the Achatinoidea.  © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 87 , 593–610.     

The neck region of the spermatozoon of Discus rotundatus (Müller) (Pulmonata,Stylommatophora)

The neck region of the mature spermatozoon of Discus rotundatus is described. No evidence for a centriole or centriolar derivative is obtained. Nine striated coarse fibres and the two central fibres of the axoneme extend into the base of the implantation fossa. The axonemal doublet system is disrupted in the neck region. There are two fibrous accessory structures located between the central doublet and the striated coarse fibres.     

Oviposition behaviour of Tamarixia radiata: effects of host density and exposure time

1. The number of hosts attacked as a function of host density is considered to be an important characteristic of parasitoid behaviour and is used to estimate key parameters such as handling time and ‘instantaneous rate of discovery’. However, little has been done to validate functional response models by direct observation of parasitoid oviposition behaviour. 2. Tamarixia radiata is the most promising parasitoid for biological control attacking Diaphorina citri. Mass rearing and augmentative release seen as a potential strategy for suppression of D. citri has been documented in abandoned citrus, residential areas, and organic groves. Nevertheless, parasitism rates in culture and in the field are only moderate, leading to questions about oviposition behaviour in response to host density. 3. Behaviours of gravid T. radiata females presented with susceptible host instars were categorised and documented by direct observation for 30 min and by camera recordings made over 12 h. Frequency of searching and antennating increased with host density during the 30 min. Probing rejection rates and search duration increased significantly with host density over 12 h. These factors resulted in significantly lower fecundity than expected, possibly due to host mark‐mediated deterrence within the small searching area. Females took approximately 3.6–4.2 min to probe and parasitise a host regardless of host density and exposure duration. These results were markedly different from the 52.2 min estimated from the functional response equation. 4. Further experiments are required to assess the range and persistence of the putative host‐marking pheromone, and to better understand the relationship between functional response parameters and actual behaviour.     

Thermoregulation in leopard tortoises in the Nama-Karoo: The importance of behaviour and core body temperatures

Despite being ectotherms, reptiles have an ability to thermoregulate which is enhanced by adopting a variety of behavioural mechanisms. Different behavioural postures, the use of retreat sites and selection of microhabitats enable reptiles to maintain their core body temperatures (T_b) above that of ambient temperatures (T_a) in winter or below T_a maximum in summer. This study describes the daily activity patterns of leopard tortoises (Stigmochelys pardalis) in relation to T_b and T_a, and the extent to which leopard tortoises can manipulate their T_b in response to seasonal changes in T_a. Ten and nine leopard tortoises were radio-tracked in 2002 and 2003, respectively and cloacal T_b and behaviours observed. Core T_bs were measured using Thermocron iButtons^™ surgically implanted into the body cavities of 4 and 5 adult telemetered tortoises for summer and winter 2003, respectively. There were seasonal differences in the extent to which certain behaviours were practiced and the time of day that these occurred. Leopard tortoises generally had unimodal activity patterns in winter and bimodal ones in summer. In winter tortoises were active at lower T_bs, and at lower T_a, than in summer. Tortoises maintained their core T_b well below T_a minimum profiles in summer and well above these in winter. Core T_b closely followed the increase in T_a minimum profiles in the mornings, however tortoises exhibited an extended thermal lag when T_a minimum profiles cooled overnight. By using different behavioural mechanisms in summer and winter, leopard tortoises maintained their core T_b at different levels compared with T_a minimum and maximum profiles. Consequently although they are ectotherms, they maintained their core T_b independent of T_a.     

A comparative study of the ultrastructure and mineralogy of calcified land snail eggs (Pulmonata: Stylommatophora)

This study indicates that eggs containing calcium carbonate crystals occur in at least 36 of the 65 known families of the land snails (class Gastropoda: order Stylommatophora). Eggs from 22 of these families were available for examination. The x-ray diffraction data, available for the first time for 21 of these families, shows that these egg shells are all made of calcite only, or of a combination of calcite with smaller amounts of aragonite. All of the snail (body) shells examined were made of aragonite only. This is the first ultrastructural investigation of these egg shells, and it indicates that the eggs exhibit enough structural diversity to allow identification of parental animals to genus, and often to species level solely on the basis of egg shell ultrastructure. All of the calcified eggs may be divided into two groups: (1) partly calcified, with discrete crystals of CaCo₃ dispersed in the jelly layer, and (2) heavily calcified, with a hard, brittle egg shell made of fused crystals of CaCO₃ much like an avian egg. Both types of calcified eggs occur in oviparous as well as in ovoviviparous snails. Because of the wide distribution of calcified eggs in the Stylommatophora, and because of the occurrence of heavily calcified eggs in ancient families such as Partulidae, Endodontidae, and Zonitidae, the calcified egg is viewed as a primitive land snail trait associated with terrestrial adaptation. The function of the calcified egg shell, in addition to mechanical support of egg contents, is to supply the developing embryo with enough calcium to form the embryonic shell by the time of hatching.     

Extrinsic vs. intrinsic food shortage and the strength of feeding links: effects of density and food availability on feeding rate of Hyphydrus ovatus

Summary We use field and laboratory experiments to determine whether Hyphydrus ovatus, a predatory aquatic beetle, is food limited, and whether any food shortage results from depletion of prey by these predators (intrinsic food shortage) or is independent of predation by these beetles (extrinsic food shortage). In the laboratory, differences in feeding rate influence body fat content, thus making fat content a useful index of recent feeding history. H. ovatus collected during the breeding season have fat contents significantly greater than those of H. ovatus starved for 25 days, but not significantly different from those of H. ovatus fed ad libitum for 25 days, indicating that natural feeding rates are near the maximum possible. H. ovatus confined at a density 60 times greater than natural show reduced fat content and feeding rate relative to natural, indicating that at very high densities H. ovatus is capable of depleting its prey. Addition of supplemental natural prey (primarily Cladocera) to experimental enclosures resulted in an order of magnitude increase in prey availability, and a significant increase in fat content and feeding rate of confined H. ovatus. Adults of this species do not appear to be food limited during the breeding season, and extraordinarily high densities of adults seem to be necessary to produce intrinsic food shortage. These results suggest that feeding links between H. ovatus an its principal prey do not have major effects on population dynamics under typical field conditions, and call into question the assumption that closely coupled predator-prey interactions are the sole explanation for observed food-web patterns.     

An investigation of the status of the terrestrial slugs Arion ater ater (L.) and Arion ater rufus (L.) (Mollusca, Gastropoda, Pulmonata) in Britain

Three types of evidence, variation in external coloration and patterning. characters of the distal genitalia and biochemical variation, were used to determine if A. a. ater and A. u. rufus could be recognized in Britain. From these studies it was possible to recognize the two taxa, but the variation of the morphological characters was continuous between them. The range of variation, in particular that of the distal genitalia of A. a. ater , was much wider than indicated by previous studies. The biochemical results from the use of zone electrophoresis and staining for non-specific esterases indicated that there was a high level of similarity between the taxa. It was not possible to determine whether the continuity in the variation resulted from hybridization or an overlap between two separate ranges. Consequently, although the results agreed with A. ater being two subspecies, more work is needed both in Britain and on the Continent to extend these observations and to determine the status of the two taxa.     

Molecular phylogeny of Australian Helicarionidae, Euconulidae and related groups (Gastropoda: Pulmonata: Stylommatophora) based on mitochondrial DNA

The delineation and phylogenetic relationships of the pulmonate family Helicarionidae are currently poorly understood. We have undertaken a phylogenetic analysis of Australian members of Helicarionidae. Three consecutive mitochondrial genes (COI, tRNA-val and 16S rRNA) were sequenced for 36 species from Helicarionidae and related groups. Helicarionidae grouped with Ariophantidae and Urocyclidae with good support in all trees, as did Microcystinae with Trochomorphidae, corresponding to the results of a previous morphological study, but the relationships of Euconulinae and Limacidae could not be resolved. Cystopeltidae never grouped with Helicarionidae and should be regarded as a separate family. The position of tRNA-val in the mitochondrial genome provided a new synapomorphy for Microcystinae. In addition, the COI and 16S rRNA sequences showed a high degree of compositional heterogeneity and incompatibility of phylogenetic signals, highlighting the importance of testing for the decay of the historical signal prior to the phylogenetic analysis.     

The spermatheca in the land snail, Arianta arbustorum (Pulmonata: Stylommatophora): muscle system and potential role in sexual selection

Abstract. Previous studies have shown variable patterns of paternity after multiple mating, and also variation in sperm storage among individuals of Arianta arbustorum , which suggests that the spermatheca may influence paternity in this promiscuous land snail. To identify possible morphological correlates of sperm manipulation, we investigated arrangement and ultrastructure of the muscles of the spermatheca. The musculature surrounding the 2–9 spermathecal tubules is arranged in a complex three dimensional network. In addition, each tubule has a thin sheath in which longitudinally oriented cells make up the innermost layer. Usually, the smooth muscle cells are enclosed by connective tissue. Only occasionally is direct muscle-muscle contact established through dense plaques. The short thick filaments, their small diameter, the relatively weak development of the tubular system and sarcoplasmic reticulum, and the low density of mitochondria indicate that the muscle cells contract relatively fast but with little strength, that they recover slowly, and have low endurance. A single muscle cell may be innervated by several axons and one axon may contact several muscle cells. Combining evidence of the present paper and a foregoing investigation on the spermathecal epithelium, we suggest that the main function of the spermathecal muscles is to expel sperm stored for fertilization, while the ciliation of the common duct is probably responsible for the distribution of sperm among the tubules.     

The effects of enhancing cage complexity on the behaviour and welfare of laboratory rats

This experiment was carried out to investigate the long-term effects of enhancing cage complexity on behavioural measures of welfare in laboratory rats. We housed 72 rats in groups of four in either ‘enriched’ or ‘unenriched’ cages for six weeks. Scan and focal animal sampling were conducted in both the light and dark phase of the second, fourth and sixth weeks. Results revealed that rats in the ‘enriched’ cages showed longer durations of sleep behaviour, and low levels of agonistic behaviour compared to rats in the ‘unenriched’ cages. Results importantly demonstrated that the behavioural changes observed in the enriched environment were due to the presence of the enrichments themselves in the cages (indirect effects) and not due merely to rats interacting with the enrichment items in their environment. Thus, enhancing the complexity of conventional laboratory cages can promote behaviour such as longer bouts of sleep that is likely to be indicative of good welfare, and diminish levels of behaviour such as aggression that is likely to lead to poor welfare.     

中国喇叭螺属的研究及一新种记述

笔者整理和厘清了Boysidia Ancey,1881已记载的中国喇叭螺属的种类,共计24种,其中有1新种,即清凉峰贝喇叭螺新种Boysidia(Bensonella)qingliangfengensis sp.nov.,对喇叭螺各亚属、贝喇叭螺亚属的已知种列出检索表,并对新种的形态特征、栖息环境进行了记述,与相似种进行了讨论。新种模式标本分别保存在中国科学院动物研究所标本馆和昆明医科大学细胞生物学与医学遗传学系标本室。     

The fine structural localization of acid phosphatase in pore cells of embryonic and newly hatched Deroceras reticulatum (Pulmonata: Stylommatophora)

Summary The fine structure of the pore cells in pre- and post-hatched Deroceras reticulatum is described. The cells have been divided into three main types on morphological grounds, one type being particularly rich in glycogen. Certain pore cells contain haemocyanin granules in grooves below cytoplasmic tongues, and in characteristic double-membrane-bounded vesicles within dilated cisternae of rough endoplasmic reticulum, as well as in other identified areas. All types of pore cells show fine fibres reminiscent of collagen associated with the basal lamina and pore complexes.In addition to acid phosphatase activity in lysosomes and Golgi elements, intra- and extracisternal activity has been demonstrated in association with the rough endoplasmic reticulum. The intracisternal activity is in close proximity to the Golgi apparatus and may represent enzyme that is about to enter the GERL system. Extracisternal activity may be associated with cellular lysis and death, or may represent local areas of degradation leading to cytodifferentiation. Remnants of lysed pore cells appear to be taken up by connective tissue amoebocytes.The authors wish to acknowledge the financial support of the Agricultural Research Council (G.B.) Grant No. AG 72/21, the photographic assistance of Mr. Nigel Green, and some technical assistance from Miss Jane Morgans     

A histochemical study of the secretions of reproductive glands and of the egg envelopes of Achatina fulica (Pulmonata: Stylommatophora)

Histochemical investigations of the secretions of reproductive glands—albumen gland, apical uterus, basal uterus and prostate gland—indicate the presence of galactogen in the albumen gland, acid mucopolysaccharide in the apical uterus, and lipoprotein in the basal uterus and prostate gland of A. fulica. The proteinaceous secretions produced by the glands do differ in their terminal reactive sites. Intense alkaline phosphatase reaction is found in albumen gland and apical uterus; carbonic anhydrase activity could be detected mainly in the uterine glands. The cyclical secretory activity of the reproductive glands has been studied preparatory to egg-laying and in the spent phase. Histochemical characteristics of the egg envelopes—albumen, shell membrane and egg-shell—suggest a possible sequential deposition of glandular products during the descent of eggs through the repv. ductive tract. The factors contributing to the stability and resistant nature of the egg envelopes, and the possible role of nutritive materials contained in reproductive gland secretions in the development of the embryo (even while the eggs are inside the uterus), are discussed.