Intraspecific life-history variation in Radix plicatulus (Gastropoda: Pulmonata: Lymnaeidae)

Life-histories of Radix plicatulus (Benson, 1842) populations inhabiting two neighbouring sites on a Hong Kong stream were investigated. In one of the two sites, R. plicatulus co-occurred with high densities of Pomacea levior which is known to prey on the egg capsules and hatchlings of sympatric gastropods. On the basis of general life-history theory, I hypothesized that R. plicatulus which co-occurred with P. levior should exhibit a life-history strategy characterized by a delayed reproduction, a longer recruitment period and a larger number of breeding bouts per year as compared with contemporaries inhabiting the other site with low P. levior abundance. Reproductive patterns of the two populations observed in the field accorded with the expectations of general life-history theory, and lent support to the hypothesis. However, laboratory culture experiments revealed no evidence of a genetic basis for the interpopulation differences. The importance of establishing a genetic basis for the interpopulation divergence before invoking an evolutionary explanation was discussed.     

Examining the phylogeny of the Australasian Lymnaeidae (Heterobranchia: Pulmonata: Gastropoda) using mitochondrial, nuclear and morphological markers

We examined the species groups relationships of the freshwater snail genus Austropeplea using mitochondrial, nuclear and morphological markers in addition to traditional methods of shell shape analysis. Based primarily on the results of a combined molecular and morphological analysis, samples of the nominal species A. tomentosa form distinct lineages. The New Zealand populations of A. tomentosa are a very distinct lineage from any of the Australian populations attributed to A. tomentosa. Furthermore, within the Australian group, three lineages, south Australia, Tasmania and eastern Australia, appear to have undergone recent and/or rapid speciation events. Samples assigned to A. lessoni were resolved as two distinct lineages, representing the eastern and northern Australian populations. Kutikina hispida was resolved within the Australian A. tomentosa clade. Molecular results for A. viridis suggests that it is also composed of at least two distinct lineages that could be treated as species. Incongruence observed between the single mitochondrial, nuclear and morphological topologies highlight the importance of using a number of different datasets in the delimitation of species-group taxa.     

Sphincterochilidae from Tunisia, with a note on the subgenus Rima Pallary, 1910 (Gastropoda, Pulmonata)

In order to establish an updated checklist of terrestrial gastropod from Tunisia, a revision of the species of Sphincterochilidae is presented, using bibliographic and museum records and the results of our own field work. As a result, only two species, Sphincterochila candidissima and Sphincterochila tunetana, are accepted to occur in Tunisia, and their type specimens are illustrated. The study of the morphological characters of the genital organs of both species clarified their subgeneric affiliation. Comparison of Sphincterochila tunetana with Sphincterochila cariosa from Lebanonshowed that the first has to be classified within the subgenus Albea, and the latter within Sphincterochila s. str.; the subgenus Rima Pallary, 1910 remains in the synonymy of Sphincterochila s. str. Bibliographic records of Sphincterochila baetica and Sphincterochila otthiana from Tunisia could not be confirmed, the latter probably lives close to the border with Algeria.     

Bridging gaps in the molecular phylogeny of the Lymnaeidae (Gastropoda: Pulmonata), vectors of Fascioliasis

Background  

Lymnaeidae snails play a prominent role in the transmission of helminths, mainly trematodes of medical and veterinary importance (e.g., Fasciola liver flukes). As this family exhibits a great diversity in shell morphology but extremely homogeneous anatomical traits, the systematics of Lymnaeidae has long been controversial. Using the most complete dataset to date, we examined phylogenetic relationships among 50 taxa of this family using a supermatrix approach (concatenation of the 16 S, ITS-1 and ITS-2 genes, representing 5054 base pairs) involving both Maximum Likelihood and Bayesian Inference.     

The karyological features of the genus Planorbarius (Gastropoda, Pulmonata, Bulinidae) of the Ukrainian fauna

The absence of significant distinctions between the species of the genus Planorbarius in the narrow sense (P. corneus, P. banaticus, P. purpura and P. grandis) has been established. All investigated species had identical chromosomal formulas (2n = 30m + 6sm = 36) and fundamental numbers (FN=72). Reliable distinctions between them were not found by total complement length (TCL), relative length of chromosomes (RL) and centromeric indexes. The species selected on the basis of genetic marking differed clearly by centromeric index of chromosome 12 that confirms the allospecies frame of P. corneus s. lato.     

A comprehensive phylogeographic study of Arion vulgaris Moquin-Tandon, 1855 (Gastropoda: Pulmonata: Arionidae) in Europe

Organisms Diversity & Evolution - Arion vulgaris Moquin-Tandon, 1855 is regarded as one of the 100 most invasive species in Europe. The native distribution range of this species is uncertain,...     

Pallial systems in the Athoracophoridae (Gastropoda: Pulmonata)

Abstract

Pallial systems are described for 10 athoracophorid species: Athoracophorus bitentaculatus, Pseudaneitea dendyi, P. gigantea, P. papillata, P. pallida, P. aspera, P. schauinslandi, P. multistriata, and Palliopodex verrucosus from the New Zealand and sub antarctic area; and Triboniophorus graeffei from Australia. In the New Zealand and subantarctic species the kidney is invariably bilobed, the ureter is extensively folded and connected to the intestine by an elongate tubule running initially through the lung, and the pneumostome, anus, and excretory pores are widely sepamted. Triboniophorus graeffei has the pneumostome, anus, and excretory pore closely associated, a compact kidney, and a more simply folded ureter. The New Zealand and subantarctic representatives are considered to be more advanced. Reasons for the development of the features they display are discussed, as is the function and evolution of the entire pallial system. An account of the variation in the pallial complex of Athoracophorus bitentaculatus is included.     

Habitat and distribution of perforatella rubiginosa (Gastropoda,Pulmonata) in the freshwater tidal region of the Scheldt estuary,Belgium

The amphibious land-molluse,Perforatella rubiginosa, is a common, wide-spread and characteristic inhabitant of the freshwater tidal region of the river Scheldt and its tributaries in NW Belgium. The species occupies a rather narrow zone in the uppermost intertidal area, which is characterized by large amounts of tidal drift covering the bottom, and usually by a luxuriant vegetation of tall, nitrophilous herbs, often withUrtica dioica dominant. Other characteristic molluscs of this zone areCarychium minimum, Oxyloma pfeifferi, O. sarsi, Deroceras laeve, Vitrea crystallina andZonitoides nitidus, locally alsoNesovitrea hammonis. Communication nr. 143 of the Delta Institute for Hydrobiological Research, Yerseke, The Netherlands     

The first record and occurrence of Stagnicola turricula (Held, 1836) (Gastropoda: Pulmonata: Lymnaeidae) in Upper Silesia (Southern Poland) in relation to different environmental factors

The degradation of freshwater environments, e.g.: eutrophication, drainage, water pollution, has led to the decline of lymnaeid species distribution. Some of them are recorded in the Red Book and Red List of species as rare, vulnerable or legally protected. The survey was carried out in Upper Silesia (Southern Poland), which is one of the biggest coal basins in the world. This region is devoid of natural water bodies; only reservoirs of an anthropogenic origin are common. Anthropogenic reservoirs, which are not very degraded, constitute important lentic habitats in Upper Silesia and they provide refuges for wildlife including rare and vulnerable molluscan species. This survey uncovered the first occurrence of Stagnicola turricula in the anthropogenic reservoirs in this area. S. turricula has been subdominant in molluscan communities. Sixteen molluscan species, including 11 gastropod and 5 bivalve species, were recorded at the sampling sites. Based on a redundancy analysis (RDA), the organic matter content in the bottom sediments and pH were the parameters most associated (statistically significant) with the distribution of molluscan species including S. turricula.     

On the reality of local and ecological races in lymnaeid snails (Mollusca,Gastropoda, Lymnaeidae)

The reality of ecological and local races was investigated in two widespread Palearctic species of lymnaeid snails (Lymnaea stagnalis and Radix auricularia). Several methods of statistical analysis were used, including two-way ANOVA, cluster analysis, and discriminant analysis for six plastic shell characters. It was shown that none of the methods used could convincingly demonstrate that ecological and local races were present in the studied species. Even in cases when statistically significant differences among the populations in the morphology of shells were revealed, these differences were very small and did not correspond to the meaning that was put into the concept of “race” by malacologists in the past. Perhaps, the formation of such races in pond snails is possible only in case of populations being formed in suboptimal conditions, for example, in thermal springs or at large depths. This being the case, the distinguishing of races requires using other shell characters, both quantitative and qualitative ones.     

A phylogeny of the land snails (Gastropoda: Pulmonata)

We have undertaken the first large-scale molecular phylogenetic analysis of the Stylommatophora. Sequences of the ribosomal RNA gene-cluster were examined in 104 species of snails and slugs from 50 families, encompassing all the currently recognized major groups. It allows an independent test of the present classification based on morphology. At the level of families our molecular phylogeny closely supports the current taxonomy, but the deep branches within the tree do not. Surprisingly, a single assemblage including the families Achatinidae, Subulinidae and Streptaxidae lies near the base of the tree, forming a sister group to all remaining stylommatophorans. This primary division into 'achatinoid' and 'non-achatinoid' taxa is unexpected, and demands a radical reinterpretation of early stylommatophoran evolution. In particular, the Orthurethra appear to be relatively advanced within the 'non-achatinoid clade', and broadly equivalent to other super-familial clusters. This indicates that supposedly primitive features such as the orthurethran kidney are derived. The molecular tree also suggests that the origin of the Stylommatophora is much earlier than the main period of their diversification.     

Waves of dispersal in island-hopping Chondrina species (Gastropoda, Pulmonata, Chondrinidae)

The aim of this study was to unravel the historical biogeography of the speciose land snail genus Chondrina. To this end phylogenetic hypotheses were tested using mitochondrial DNA sequence data.Mitochondrial DNA sequences of the Cytochrome Oxidase subunit I region were obtained for 89 individuals, representing just over 70% of the extant Chondrina species. The extent of molecular genetic diversity and phylogeographical patterns were investigated by using neighbour joining, parsimony and bayesian methods for phylogeny reconstructions. The resulting data were used to infer historical biogeographical patterns for the genus Chondrina.The three phylogenetic methods yielded congruent topologies for the phylogeny reconstruction. Six clades were identified, each of which with at least one taxon that is known from the Iberian peninsula. The most parsimonious scenario indicates at least three waves of dispersal out of the Iberian peninsula into the North and East of Europe and Northern Africa.The phylogenetic relationships combined with the distributional patterns of the various species, indicate that only vicariance events cannot explain the actual situation. Apparently, separate waves of dispersal and subsequent speciation occurred, each time starting from the southwestern part of the present generic range. Until recently, this was obscured by repetitive cases of parallel or convergent evolution in shell characters, as became evident with the use of molecular methods.     

The fine structure of the spermatozoa of Siphonaria algesirae (Gastropoda,Pulmonata)

The sperm of Siphonaria algesirae (Gastropoda, Pulmonata), a species with internal fertilization, was studied by light and electron microscopy. The spermatozoon is a very long, uniflagellate cell composed of a conical head with an apical acrosome, a midpiece with a helically coiled external sheath containing a complex mitochondrial derivative with a wavelength of ～ 5.5 μm, and an endpiece. There are no axonemal microtubules. Instead, nine homogeneous coarse fibers with transverse striations in the apical zone project toward the anterior section of the midpiece. In the posterior zone of the midpiece the coarse fibers are differentiated in a common microtubular axoneme. The complex mitochondrial derivative of the midpiece shows an organized group of 100 Å diameter spherical particles. Externally the midpiece is surrounded along its length by a cylinder formed by two membranes. A complex structure separates the transitional zone between the midpiece and the endpiece.     

Terrestrial slugs (Gastropoda, Pulmonata) in the NATURA 2000 areas of Cyprus island

Terrestrial slugs of the Island of Cyprus were recently studied in the framework of a study of the whole terrestrial malacofauna of the island. The present work was carried out in the Natura 2000 conservation areas of the island in 155 sampling sites over three years (2004-2007). Museum collections as well as literature references were included. In total six species are present in the Natura 2000 areas of the island, belonging to three families: Limacidae, Agriolimacidae and Milacidae. One of the species, Milax riedeli, is a new record for the island. The distribution of the species across the island and in the surrounding areas is discussed.     

The introduced slugs of New Zealand (Gastropoda: Pulmonata)

Abstract

Eleven species of slug introduced into the New Zealand fauna are discussed: Testacellidae - Testacella haliotidea Draparnaud, 1801 (T. vagans Hutton, 1882 n.syn.); Arionidae - Arion intermedius (Normand, 1852), A. hortensis Férussac, 1819 (A. incommodus Hutton, 1879 n.syn.); Milacidae - Milax gagates (Draparnaud, 1801), M. budapestensis (Hazay, 1881), M. sowerbyi (Férussac, 1823); Limacidae - Deroceras reticulatum (Müller, 1774) (Limax molestus Hutton, 1879 n.syn.), D. panormitanum (Lessona & Pollonera, 1882), Limax maximus Linnaeus, 1758, Lehmannia flava (Linnaeus, 1758), L. nyctelia (Bourguignet, 1861). Of these, T. haliotidea, M. budapestensis, M. sowerbyi, D. panormitanum, and L. nyctelia are recorded from New Zealand for the first time. A key for the identification of these species is provided. Species thought to be doubtfully established are discussed, and a list is given of recent interceptions at New Zealand ports.     

On the occurrence of Lymnaea auricularia (Gastropoda: Lymnaeidae) in New Zealand

Abstract

The occurrence in New Zealand of Lymnaea auricularia (L.) is recorded for the first time, and its status world-wide is briefly discussed, with particular reference to its role in economic parasitology. The lymnaeid fauna of New Zealand is briefly reviewed.     

Dorid nudibranchs from eastern Australia (Gastropoda, Opisthobranchia)

Collections of nudibranch gastropods made in 1968 are described. All the 18 eastern Australian species of doridaceans (excluding chromodoridiform species) obtained are illustra-ed and investigated anatomically, often for the first time since their original discovery over a century ago. A list of the dorid nudibranches reliably recorded from Australian waters (compiled by R. Burn) supplements the paper.