Prehistoric anthropogenic introduction of partulid tree snails in Papua New Guinean archipelagos

Aim Members of the tropical tree snail family Partulidae are endemic to Pacific high oceanic islands and typically have single‐island ranges. Two nominal Papua New Guinean species, Partula carteriensis and Partula similaris, deviate from familial norms by having extensive multi‐island ranges that include low islands. We hypothesized that undocumented anthropogenic introductions may underlie this regional biogeographical anomaly and evaluated this hypothesis with novel field distributional and genotypic data. Location Papua New Guinean archipelagos between 1.4 and 11.4° S and 146.5 and 154.2° E. Methods Ethanol‐preserved museum lots of P. carteriensis (from New Britain, Bismarck Archipelago) and P. similaris (from Woodlark, Boiaboiawaga and Goodenough islands) were genotyped for a standard mitochondrial marker, cytochrome c oxidase subunit I (COI), and the resulting haplotypes were subjected to phylogeographical analyses. Results All four genotyped populations showed very little genetic or conchological differentiation, irrespective of nominal taxonomic status, the archipelago sampled or whether the island was low, high, oceanic or continental. Partula carteriensis and P. similaris exhibit atypical distributions on larger high islands, being restricted to coastal villages and absent from native forest. Main conclusions Our results strongly indicate that P. carteriensis and P. similaris are conspecific, although a formal taxonomic revision is beyond the scope of this present study. They collectively exhibit the most heterogeneous geographical range known among partulids and their explicitly synanthropic association with high island coastal villages strongly implicates human introduction as the regional dispersal mechanism. We currently lack insights into the timeframe (apart from regional prehistory) and cultural context of these translocations. We also lack a convincing source population, and it may be necessary to survey the partulid fauna of the neighbouring Solomon Islands to identify one. Partulids are critically endangered throughout much of their range and the discovery of populations that apparently thrive in human‐altered landscapes is noteworthy. Their study may provide clues of broad relevance to partulid conservation.     

Patterns of introduction of non-indigenous non-marine snails and slugs in the Hawaiian Islands

The native snails of the Hawaiian Islands are disappearing. One cause is predation by introduced carnivorous snails. Habitat destruction/modification is also important, facilitating the spread of other non-indigenous snails and slugs. Eighty-one species of snails and slugs are recorded as having been introduced. Thirty-three are established: 12 freshwater, 21 terrestrial. Two or three species arrived before western discovery of the islands (1778). During the nineteenth century about one species per decade, on average, was introduced. The rate rose to about four per decade during the twentieth century, with the exception of an especially large number introduced in the 1950s as putative biocontrol agents against the giant African snail, Achatina fulica. The geographical origins of these introductions reflect changing patterns of commerce and travel. Early arrivals were generally Pacific or Pacific rim species. Increasing trade and tourism with the USA, following its annexation of Hawaii, led to an increasing proportion of American species. More general facilitation of travel and commerce later in the twentieth century led to a significant number of European species being introduced. African species dominated the 1950s biological control introductions. The process continues and is just part of the homogenization of the unique faunas of tropical Pacific islands.     

Host specificity and biology ofHeteropsylla spinulosa [Hom.: Psyllidae] introduced into Australia and Western Samoa for the biological control ofMimosa invisa

The biology and host specificity of the psyllidHeteropsylla spinulosa Muddiman, Hodkinson & Hollis collected fromMimosa invisa Von Martius, was studied in Brazil and in Australia. Oviposition was recorded on 19 of 100 plant species tested but nymphs died without feeding, except onM. invisa. H. spinulosa was shown to be specific toM. invisa and was subsequently released and established in Australia and Western Samoa.      

A tale of two snails: is the cure worse than the disease?

The giant African snail, Achatina fulica, has been introduced to many parts of Asia as well as to numerous islands in the Indian and Pacific Ocean, and has recently reached the West Indies. It has been widely decried as a disaster to agricultural economies and a threat to human health, leading to a clamor for the introduction of biological control agents. In fact, the lasting impact on agriculture may not be severe, and the human health risk is probably minor. This snail can be an aesthetic atrocity and a nuisance in other ways, however. Wherever A. fulica has achieved high densities, it has subsequently undergone a striking decline. Although this decline has been attributed to introduced predators, there is little evidence for this hypothesis; instead, epizootic disease seems to be at least part of the cause. However, the introduced predators, especially a New World snail, Euglandina rosea, have wrought havoc with the native land snails of many islands. They have already caused many extinctions and will almost certainly cause others. This predator was introduced by government agencies in many areas despite warnings from competent biologists that the effects could be disastrous. Pressures for such actions may become overwhelming in the face of a highly visible invasion, despite policies that should mandate extreme caution.     

Aquatic snails of the Bulinus africanus group in Zambia identified according to morphometry and enzymes

The Bulinus africanus species group (Planorbidae) of freshwater snails has been reported to be represented in Zambia by two species, B. africanus (Krauss) and B. globosus (Morelet), both named as intermediate hosts for Schistosoma haematobium. Uncertainty in identification of these snails from morphology led to the present investigation, combining morphometry (shell and copulatory organ) with enzyme analysis. Observations of both kinds were made usually on the same individual snails, from collecting sites mostly in the Lusaka area or at Lake Kariba. Particular attention was given to the proportional relationship between the penis sheath and the preputium of the copulatory organ, a character used previously to distinguish B. africanus from B. globosus in south-eastern Africa. The enzyme profile MDH-1, AcP-2, PGD-1 and PGM-2 was common to all snails examined from 25 populations; GPI and HBDH were polymorphic. The enzyme data indicate that the samples represent a single species. Shell characters varied continuously. The copulatory organ was generally of the form known for B. globosus. Although the copulatory organ of a few individuals had proportions overlapping the range reported for B. africanus, the present variation was continuous and was not bimodal. It is concluded that all these specimens are conspecific and may be identified as B. globosus. Previous identifications of B. africanus from Zambia appear to need substantiation and it seems that if this species is present at all in the sampled areas, it must be uncommon. It is relevant in regard to possible strain differences within S. haematobium in Zambia, that our observations indicate that only a single species of intermediate host is involved in transmission.     

Chiropterophily and ornithophily inFreycinetia (Pandanaceae) in Samoa

In Samoa, field observations, experiments, and SEM micrographs of hair and feather samples indicate the dioecious lianaFreycinetia reineckei to be both chiropterophilous and ornithophilous with the principal pollinators being an endemic flying fox,Pteropus samoensis, and an endemic starling,Aplonis atrifuscus. Nutritional analysis of staminate and pistillate inflorescenses indicate qualitative and quantitative differences between the rewards offered by the two sexes. No nectar is presented, the principal pollinator rewards being fleshy bracts and pollen. As a result, staminate and bisexual inflorescenses sustain higher levels of pollinator damage, a factor which may tend to maintain dioecism within the population.     

Detection of avian malaria (Plasmodium spp.) in native land birds of American Samoa

This study documents the presence ofPlasmodium spp. in landbirds ofcentral Polynesia. Blood samples collectedfrom eight native and introduced species fromthe island of Tutuila, American Samoa wereevaluated for the presence of Plasmodiumspp. by nested rDNA PCR, serology and/ormicroscopy. A total of 111/188 birds (59%)screened by nested PCR were positive. Detection of Plasmodium spp. was verifiedby nucleotide sequence comparisons of partial18S ribosomal RNA and TRAP(thrombospondin-related anonymous protein)genes using phylogenetic analyses. All samplesscreened by immunoblot to detect antibodiesthat cross-react with Hawaiian isolates of Plasmodium relictum (153) were negative. Lack of cross-reactivity is probably due toantigenic differences between the Hawaiian andSamoan Plasmodium isolates. Similarly,all samples examined by microscopy (214) werenegative. The fact that malaria is present,but not detectable by blood smear evaluation isconsistent with low peripheral parasitemiacharacteristic of chronic infections. Highprevalence of apparently chronic infections,the relative stability of the native land birdcommunities, and the presence of mosquitovectors which are considered endemic andcapable of transmitting avian Plasmodia,suggest that these parasites are indigenous toSamoa and have a long coevolutionary historywith their hosts.     

Functional morphology of the neuropeptidergic light-yellow-cell system in pulmonate snails

The light yellow neuropeptidergic cell system of the basommatophoran snail Lymnaea stagnalis is homologous to the R3-R14 system of the opisthobranch Aplysia californica, and produces three different neuropeptides. Systems homologous to the light yellow cells of Lymnaea stagnalis have been investigated morphologically in two Basommatophora (Lymnaea ovata, Bulinus truncatus) and three Stylommatophora (Helix aspersa, Cepaea nemoralis, Deroceras reticulatum). To this end, an antibody to synthetic light-yellow-cell peptide-II and oligonucleotides to mRNAs encoding parts of peptide-I and peptide-III, were used. The in situ hybridization probes gave negative results. On the other hand, neuronal cell clusters were observed in the central nervous system of all specias studied by immunocytochemistry. These clusters were located in the ganglia of the visceral complex. The neurons project axons into all nerves of these ganglia, especially into the pallial nerves, into the connective tissue of the central nervous system, and into the neuropile of various ganglia. The morphology of the systems is similar to that of the light-yellow-cell system of Lymnaea stagnalis. In all species, the wall of the aorta was innervated by immunoreactive axons. Peripheral innervation by the light-yellow-cell system was investigated in Helix aspersa and Deroceras reticulatum. Serial and alternate sections of whole snails were studied. Reconstructions were made of the heart-kidney-lung complex of these animals. In both species, the muscular vessels of the pulmonary system at the right side of the body were strongly innervated by immunoreactive axons. Furthermore, immunopositive innervation was observed to muscles in the secondary ureter-pneumostome area. The light-yellow-cell system of pulmonates is thus probably involved in the regulation of blood pressure and urine release.     

Neuronal background of activation of estivated snails,with special attention to the monoaminergic system: a biochemical,physiological, and neuroanatomical study

Osmotic stimulation activates both estivated and inactivated specimens of Helix pomatia and increases their central arousal. High-pressure liquid chromatography has shown that, during activation, the level of both serotonin and dopamine decreases in the central nervous system (CNS) but increases in the foot and heart, organs that are involved in the eversion of the body. In isolated CNS from activated animals, the firing frequency of the heart-modulator serotonergic (RPas) neurons is significantly higher than that in the CNS of estivated or inactivated animals. These neurons innervate both the heart and the anterior aorta. In semi-intact preparations, distilled water (an osmotic stimulus) applied to the mantle collar increases their firing frequency, whereas tactile stimulation evokes their inhibition. Extracellularly applied monoamines mimic the effect of peripheral stimuli: serotonin (0.1–10 μM) increases the activity of the RPas neurons, whereas dopamine (0.1–10 μM) inhibits their activity. Tyrosine-hydroxylase immunocytochemistry and retrograde neurobiotin tracing have revealed similar bipolar receptor cells in the mantle collar and tail, organs that are exposed to environmental stimuli in estivated animals. Serotonin immunocytochemistry carried out on the same tissues does not visualize receptor cells but labels a dense network of fibers that appear to innervate neurobiotin-labeled receptor cells. The combination of neurobiotin-labeling of RPas neurons and immunolabeling suggests that RPas neurons receive direct dopaminergic inputs from receptor cells and serotonergic inputs from central serotonergic neurons, indicating that central serotonergic neurons are interconnected. Thus, the RPas neurons may belong to neuronal elements of the arousal system. This work was supported by Hungarian OTKA grants T037389, T046580, T037505, and K63451.     

The growth of juvenile snails in water conditioned by snails of a different species

Summary Two species of freshwater snails, Physa acuta and Lymnaea sp. aff. columella, were collected from Asabata marsh, Shizuoka Japan. Individuals of both species inhabit the same plants. Individuals of P. acuta are more abundant than those of L. sp. aff. columella. Experiments were conducted to examine the effect of water conditioned by snails on the growth of 10-day-old juvenile P. acuta snails. Juvenile snails in water conditioned by L. sp. aff. columella grew faster than those in water conditioned by P. acuta or only lettuce. The effects of water conditioned by P. acuta differed among the litters. The results suggest that juvenile P. acuta snails experience accelated growth in the presence of L. sp. aff. columella. The freshwater snails interacted through resource competition as well as through substances disolved in the water.     

Water balance and resistance to desiccation in rock-dwelling snails

We have examined the resistance to desiccation among rock-dwelling land snails of various phylogenetic groups:Cristataria genezarethana (Clausiliidae),Rupestrella rhodia (Chondrinidae) andLevantina caesareana (Helicidae), all from the same location in Israel.L. caesareana was the most resistant andR. rhodia the least resistant to desiccation andC. genezarethana was of intermediate resistance. Differences in the rates of water loss during desiccation were determined mainly by rate of water loss during the first 2 days of desiccation. The high rates of water loss in rock-dwelling species exceed those of other snails in the Mediterranean habitat of Israel. However, snails collected in the field at the end of aestivation were in only a mild state of dehydration, suggesting that the rocky habitat protects its occupants against desiccation. We also suggest that among the rock-dwelling species, the protective role of the rock is more important in the more evolutionarily primitive genera (the chondrinidRupestrella and the clausiliidCristataria) and that physiological capacities are more effective in the more highly evolved helicidLevantina.     

Exotic Lepidopteran Leafminers in North American Apple Orchards: Rise to Prominence, Management, and Future Threats

The European tentiform leafminers, Phyllonorycter blancardella (Fabricius) and P. mespilella (Hübner) (Lepidoptera: Gracillariidae), have infested apple, Malus domestica Borkhausen, in North America for at least 60–70 years. Unreliable taxonomic methods and lack of voucher specimens, however, have contributed to poor understanding of precisely when, where, and how these leafminers were introduced. Tentiform leafminers developed into significant foliar pests at about the time when adult resistance to broad-spectrum insecticides was detected in the 1970s and 1980s. At present, growers manage leafminers with insecticides and, to a lesser extent, with biological control. Most management programs for orchard pests rely on insecticides that are highly toxic to parasitic wasps, which hampers biological control. New techniques promoted in the context of integrated pest management (IPM) may improve biological control by reducing insecticidal use, but their adoption will depend on cost, labor, need to control other pests, and demands of the marketplace. Management programs must be flexible enough to accommodate changes in the species composition of leafminers and their parasitoids. Procedures to exclude pests may slow the rate of new introductions of leafminers and other pests, but they will not entirely protect the North American apple industry. Once new apple pests reach North America, they face few obstacles to further dispersal. The abundance of potential host plants, the lack of rigorous inspections, and new retail practices may facilitate the dispersal of exotic pests.     

Aspergillus on tree nuts: incidence and associations

California exports tree nuts to countries where they face stringent standards for aflatoxin contamination. Trade concerns have stimulated efforts to eliminate aflatoxins and Aspergillus flavus from almonds, pistachios and walnuts. Incidence of fungi on tree nuts and associations among fungi on tree nuts were studied. Eleven hundred pistachios, almonds, walnuts and brazil nuts without visible insect damage were plated on salt agar and observed for growth of fungi. Samples came both from California nut orchards and from supermarkets. To distinguish internal fungal colonization of nuts from superficial colonization, half the nuts were surface-sterilized before plating. The most common genera found were Aspergillus , Rhizopus and Penicillium . Each species of nut had a distinct mycoflora. Populations of most fungi were reduced by surface sterilization in all except brazil nuts, suggesting that they were present as superficial inoculum on (rather than in) the nuts. In general, strongly positive associations were observed among species of Aspergillus ; nuts infected by one species were likely to be colonized by other species as well. Presence of Penicillium was negatively associated with A. niger and Rhizopus in some cases. Results suggest that harvest or postharvest handling has a major influence on nut mycoflora, and that nuts with fungi are usually colonized by several fungi rather than by single species. This revised version was published online in June 2006 with corrections to the Cover Date.     

Impact of simulated herbivory on Alliaria petiolata survival, growth, and reproduction

In weed biological control, insect damage to target weeds can be simulated in invaded habitats to study potential responses of the plant to introduced natural enemies. In the present study, we investigated the impact of two levels of manual flower-shoot damage (shoots cut at tip or base) on Alliaria petiolata (garlic mustard) survival, size, and reproduction. Experiments were conducted in 2002 and 2003 using invasive field populations of A. petiolata under naturally varying plant densities. Plant survival was recorded, and size and reproduction parameters were measured. Manual flower-shoot damage had a significant effect on plant survival. In both years, fewer plants survived in the basal-cut treatment than in either the control (un-cut) or tip-cut treatment. Plant size and reproductive output were likewise reduced in the basal-cut treatment. In both years, total seed production was significantly lower in the basal-cut treatment than either the control or tip-cut treatment. When combined, increased mortality and reduced seed production of basal-cut plants greatly reduced the contribution these plants made to the seed bank. Plant density did not affect reproduction or plant size. The impacts of cutting were consistent across years and sites with distinct biotic and abiotic conditions, and A. petiolata densities. We anticipate that herbivore damage to A. petiolata populations by introduced biological control agents will likewise remain consistent under varying biotic and abiotic conditions if the agents are equally adapted to these.     

The control of Galba truncatula (Gastropoda: Lymnaeidae) by the terrestrial snail Zonitoides nitidus on acid soils

Field investigations on the control of Galba truncatula by Zonitoides nitidus were carried out over the past 30 years in the different types of lymnaeid habitats located in central France. When a layer of mowed vegetation was used to cover G. truncatula habitats at the end of June, the introduction of adult Z. nitidus (20/m²) eliminated lymnaeid populations after 2 years of control in habitats located in swampy meadows, around the heads of intermittent springs, in areas trampled by cattle, and along river or pond banks. In the case of wild watercress beds, 3 years were necessary. The best results (elimination of G. truncatula after a single year of control) were obtained using an association of snails (Z. nitidus + Oxychilus draparnaudi), or a mixed control (a first application of 0.1 mg/l CuCl₂, followed 3 months later by the introduction of Z. nitidus). Recolonization of treated habitats by G. truncatula coming from downstream populations was noted 3 years following the last application of biological control. Apart from the regular introduction of Z. nitidus in several watercress beds, the use of this snail to control G. truncatula has not become generalized in cattle- and sheep-breeding farms. The reasons for this situation are probably the complexity of applying this control in the field by nonspecialists and the difficulty of selecting the period of snail control at the end of June due to frequent local rainfall at this time.     

Heavy metal concentrations in common freshwater snails of Azraq Oasis,Jordan

Heavy metal concentrations in three freshwater snails, an aquatic plant, sediment, and water from Azraq Oasis pools in the Jordanian desert were measured by atomic absorption spectrophotometry. There were significant differences in metal accumulation among snail species. These snails are ranked according to their metal accumulation capacity in the order: Melanoides tuberculata > Melanopsis praemorsa > Theodoxus jordani. Although there were no significant differences among the size classes of these snails in metal concentrations, larger snails contained generally higher levels of metals than the smaller ones. The concentration factors for the selected snails exceeded 10³, while it ranged from 0.1–10.2 × 10³ for Typha angustata plants. Among sampling sites, metal concentrations in M. praemorsa, T. angustata, sediment, and water were not significantly different, except for Fe in M. praemorsa which was highest at station 3, and Cd and Cr which were highest in water and sediment of station 4. The seasonal variation in metal content was found to be species and metal-dependent.     

Sensory cells in the head skin of pond snails

Summary Several types of receptor endings were identified with scanning electron microscopy and silver-impregnation techniques in the skin of the tentacles, lips, dorsal surface of the head and mouth region of the pond snails Lymnaea stagnalis and Vivipara viviparus. Sensory endings at the tips of dendrites of primary receptor neurones, scattered below the epithelium, differ in structure, i.e., the endings exposed to the surface of the skin possess different proportions of cilia and microvilli, which vary in number, length, and packing. Type-I endings have microvilli and a few (1–5) cilia, 5–12 m in length. Type-2 endings have abundant (20–40), interwoven long (9–12 m) cilia and random microvilli. Type-3 endings show typical packing of 10–25 cilia in the form of bundles or brushes. They may be composed either of long (9–18 m) or short (2–7 m) cilia, or of both long and short ones. Microvilli here are absent. Type-4 endings have only microvilli. Two other types of skin receptors do not extend their sensory endings to the surface and can be indentified only in silver-stained preparations. Type-5 endings are branching dendrites of skin receptors cells that terminate among epithelial cells. In type-6, the sensory endings also terminate among epithelial cells but their cell bodies are located outside of the skin. In both species all skin regions examined possess the receptors of all six types differing only in their relative proportion. Possible functional roles of different receptors are discussed.     

Induced resistance in intertidal macroalgae modifies feeding behaviour of herbivorous snails

Herbivory in terrestrial and marine systems can induce changes in plant chemistry affecting the foraging behaviour of herbivores. A model based on terrestrial plant-herbivore interactions predicts herbivory-induced changes in leaf chemistry to be manifested in (1) increased herbivore mobility, (2) increased feeding dispersal and (3) reduced tissue consumption by herbivores. This study is the first to demonstrate that herbivory-induced changes in the tissue chemistry of the brown seaweed Ascophyllum nodosum elicit the same response in the feeding behaviour of the gastropod Littorina obtusata as predicted for herbivorous insects, providing good evidence for the models validity across different ecosystems. The potential benefit of increased feeding dispersal to terrestrial plants as suggested by the model is the prevention of concentrated damage to apical tissues thereby preserving the plants ability to compete for light; A. nodosum does not conform to these predictions. Increased dispersal of feeding damage on A. nodosum away from primary frond tissues would reduce the likelihood of frond breakage implying a fitness benefit of induced resistance.     

Bioprocessing of polluted suspended matter from the water column by the zebra mussel (Dreissena polymorpha Pallas)

Measurements of pseudofaeces production of Dreissena polymorpha were carried out with the aim of developing a biological filter at the freshwater inlet of Lake Volkerak-Zoommeer, the Netherlands. Bioprocessing of polluted suspended matter by suspended cultures of D. polymorpha occurs by filtration and sedimentation of the suspended matter as pseudofaeces. The measurements were conducted under semi-natural conditions.Pseudofaeces production was mainly determined by the dry matter content of the water; the relation is linear. Temperature was of much less importance. This agrees with earlier investigations of the filtration rate of D. polymorpha. Even at the lowest temperature measured during the experiments (6.4 °C) no large decrease in activity was observed. The relation of pseudofaeces production with shell length was sigmoid in shape, in accordance with measurements of the filtration rate.The pseudofaeces produced was slightly more polluted than suspended matter, partly due to a finer grainsize. D. polymorpha from Lake IJsselmeer exposed for 217 days at the intended location of the filter showed bioaccumulation of toxicants, especially organic pollutants and Polycyclic Aromatic Hydrocarbons (up to 10-fold accumulation). The required number of D. polymorpha in the biological filter to treat the waterflow of 14 m³ s^–1 entering Lake Volkerak-Zoommeer is 1.24 * 10⁹. The purification efficiency of the filter, the reduction of the amount of toxicants, partly depends on the binding properties of the toxicants and is highest for those strongly bound to suspended matter.