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Despite being simultaneously male and female, hermaphrodites may still need to assume the male or female sexual role in a mating encounter, with the option to swap roles afterwards. For the great pond snail, Lymnaea stagnalis, deciding which sexual role to perform has important consequences, since sperm transfer and male reproductive success can be decreased. We hypothesised that detecting cues that indicate a possible mating encounter could help them to adapt their mating behaviour. Therefore, we experimentally assessed whether signalling the presence of a conspecific with an odour can affect the sexual role of Lymnaea stagnalis. The results showed that learning resulted in either an increased ability to mate as a male or in faster mating compared to the control group. These findings reveal that learning shapes the mating dynamics of Lymnaea stagnalis, thus showing that cognitive processes not only affect mating in separate-sexed species but also in hermaphrodites.

Background Spiral cleavage is a feature of non-ecdysozoan protostomes, in which left-right reversal frequently evolved in gastropod molluscs. In pulmonate gastropods, maternal molecules are responsible for chirality patterning, on which the polarities of visceral and coiling asymmetries depend. In the pond snail, Lymnaea stagnalis (the clade Hygrophila), a frame-shift mutation of one of tandem-duplicated, diaphanous-related formin genes (diaph) resulted in incomplete reversal from dextral to sinistral cleavage. Is this mechanism of chirality regulation common to, or shared with other pulmonates? To answer this question, we examined genes involved in chirality patterning in the land snail, Bradybaena similaris which belongs to the clade Stylommatophora. Results Both dextral and sinistral siblings develop from progeny of a racemic mutant of B. similaris. Differences in maternal mRNAs between the two strains were searched by transcriptome analyses. We found fifty maternal transcripts that exhibited less expression in early embryos of the mutant strain. The most conspicuous was a homolog of diaph. The diaph gene was duplicated in the stylommatophoran ancestor (diaph-a and diaph-b), as in the case of the ancestor of Lymnaea (Lsdiaph1 and Lsdiaph2). The quantity of maternal diaph-b mRNA was drastically reduced in early embryos of the racemic mutant compared to wild-type, while diaph-a expression was at nearly the same level in both strains. Unlike the case of Lsdiaph2, which is frame-shifted to produce truncated peptides in the mutant of L. stagnalis, however, Bsdiaph-b mRNA in the mutant strain is not frame-shifted and most probably produces normal Diaph-b protein. These results suggest the presence of regulatory mechanisms of gene expression for chirality patterning in pulmonate gastropods, although genomic analyses are required for confirmation. Conclusions Heterochirality resulting from the loss of polarity control in spiral cleavage does not require mutation of the diaph gene in B. similaris. The determination of left-right polarity instead depends on the expression of this diaph gene, which is duplicated in stylommatophoran Bradybaena, as well as in hygrophilan Lymnaea. Our results provide an avenue to identifying a regulatory mechanism that controls the direction of spiral cleavage in gastropods. Electronic supplementary material The online version of this article (10.1186/s40851-018-0120-0) contains supplementary material, which is available to authorized users.

International audience; Aim: We assess biogeographical patterns, population structure and the range of species in the pulmonate genus Siphonaria across the sub‐Antarctic. We hypothesized that locally endemic cryptic species will be found across the distribution of these direct‐developing limpets in the sub‐Antarctic.Location: The sub‐Antarctic coasts of the Southern Ocean including South America, the Falkland/Malvinas, South Georgia, Kerguelen and Macquarie Islands.Methods: Multi‐locus phylogenetic reconstructions, mtDNA time‐calibrated divergence time estimations and population‐based analyses of Siphonaria populations were used at the scale of the Southern Ocean.Results: We resolve two widely distributed lineages of Siphonaria (S. lateralis and S. fuegiensis) across the sub‐Antarctic. MtDNA divergence time estimates suggest that they were separated around 4.0 Ma (3.0 to 8.0 Ma). Subsequently both species followed different evolutionary pathways across their distributions. Low levels of genetic diversity characterize the populations of both species, reflecting the role of Quaternary glacial cycles during their respective demographic histories, suggesting high levels of dispersal among geographically distant localities.Main conclusions: Siphonaria lateralis and S. fuegiensis constitute sister and broadly co‐distributed species across the sub‐Antarctic. Unexpected transoceanic similarities and low levels of genetic diversity in both these direct‐developing species imply recurrent recolonization processes through long‐distance dispersal to isolated sub‐Antarctic islands. For such groups of Southern Ocean invertebrates, rafting may be more effective for long‐distance dispersal than a free‐living planktotrophic larval stage. This biogeographical model may explain why many marine species lacking a dispersal phase exhibit broad distributions, low genetic diversity and low population structure over thousands of kilometres.

Two additional new members of the onchidione family, 16-epi-onchidione (1) and 4-epi-onchidione (2), co-occurring with six previously reported bis-gamma-pyrone polypropionates including onchidione (3), were isolated from the marine pulmonate Onchidium sp. Their structures were determined by extensive spectroscopic analysis and by comparison with 3 and onchidione-related derivatives. The absolute configuration of 1 was established by X-ray diffraction analysis employing graphite monochromated Cu K-alpha radiation (lambda = 0.71073 angstrom) with small Flack parameter 0.08. In addition, the absolute stereochemistry of previously reported onchidionol (6) was confirmed by the X-ray diffraction analysis. Some of the isolated compounds showed significant activation effects on the splicing of XBP1 mRNA as ER stress modulators to inhibit the growth of tumors. (C) 2018 Elsevier Ltd. All rights reserved.

Sexual selection is generally predicted to act more strongly on males than on females. The Darwin-Bateman paradigm predicts that this should also hold for hermaphrodites. However, measuring this strength of selection is less straightforward when both sexual functions are performed throughout the organism’s lifetime. Besides, quantifications of sexual selection are usually done during a short time window, while many animals store sperm and are long-lived. To explore whether the chosen time frame affects estimated measures of sexual selection, we recorded mating success and reproductive success over time, using a simultaneous hermaphrodite. Our results show that male sexual selection gradients are consistently positive. However, an individual’s female mating success seems to negatively affect its own male reproductive success, an effect that only becomes visible several weeks into the experiment, highlighting that the time frame is crucial for the quantification and interpretation of sexual selection measures, an insight that applies to any iteroparous mating system. DOI: http://dx.doi.org/10.7554/eLife.25139.001, eLife digest Many factors affect an organism’s ability to survive and reproduce. These factors are often called “selection pressures” and include the availability of food and shelter, conditions in the environment such as temperature, and the presence of diseases and predators. Males and females experience different selection pressures so they often evolve to look different – consider, for example, the male deer’s antlers and the peacock’s colourful tail feathers. Such traits arise from a phenomenon called sexual selection, the selection pressures that act on an organism’s ability to obtain a mate. Measuring sexual selection is not only of interest to scientists looking to understand how evolutionary processes work; it also has wider applications, including in wildlife conservation. For instance, knowing which cues are important for successful reproduction could help efforts to breed endangered animals in captivity and stop them from going extinct. Scientists study sexual selection in a species by measuring how successful males and females are at mating and reproducing. Past studies have found that a female’s reproductive success mainly depends on there being enough resources available for her to produce eggs, while a male’s success depends on him getting access to these eggs. However, most research into sexual selection has been on species with separate sexes. It is more difficult to measure sexual selection in species – like snails and slugs – where each individual is male and female at the same time. As such, it is not clear if reproductive success in these species, which are known as simultaneous hermaphrodites, depends on the same factors as those species with separate sexes. To address this, Hoffer et al. measured sexual selection in the great pond snail Lymnaea stagnalis, a simultaneous hermaphrodite. Most studies estimate sexual selection based on measurements taken over several days. Instead, Hoffer et al. observed the great pond snail over a period of eight weeks, which is about a quarter of its reproductive life. The experiments showed that mating multiple times, especially with multiple partners, overall improves the development of the snail’s offspring. The male part of the great pond snail gains the most reproductive success from repeated mating, whereas the female part may in fact be negatively affected. These negative effects were only seen several weeks into the experiment, and so they show that sexual selection pressures change over time. Future research is needed to determine what causes the negative effects on the female part of the great pond snail. Overall, these findings stress the need for careful consideration of the time frame over which future measurements of sexual selection take place, not just in hermaphrodites, but in all species. DOI: http://dx.doi.org/10.7554/eLife.25139.002

Reproductive success is a critical fitness attribute that is directly influenced by resource availability. Here, we investigate the effects of diet-based resource availability on three interrelated aspects of reproductive success: a change in mating system based on mate availability, consequent inbreeding depression, and the deterioration of reproductive efficiency with age (senescence). We employed a factorial experimental design using 22 full-sib families of the hermaphroditic freshwater snail Physa acuta to explore these interactions. Individual snails were reared in one of two mate-availability treatments (isolated [selfing] or occasionally paired [outcrossing]) and one of two diet treatments (boiled lettuce or Spirulina, an algae that is rich in protein, vitamins, and minerals). Spirulina-fed snails initiated reproduction at a 13% earlier age and 7% larger size than lettuce-fed snails. Spirulina also resulted in a 30% reduction in the time delay before selfing. Compared to lettuce, a diet of Spirulina increased inbreeding depression by 52% for egg hatching rate and 64% for posthatching juvenile survival. Furthermore, Spirulina led to a 15-fold increase in the rate of reproductive senescence compared with a diet of lettuce. These transgenerational, interactive effects of diet on inbreeding depression and reproductive senescence are discussed in the context of diet-induced phenotypic plasticity.

The first record of aChilean gastropod of the Late Oligocene of Argentina is described. Thespecimens show a typical general morphology and a characteristic nepionicsculpture of Chiliborus (Mollusca: Gastropoda), being the first fossilof this genus of Strophocheilidae. The locality of Quebrada Fiera (Malargüe,Mendoza Province) had provided vertebrates (a small lizard, birds and manymammals, such as notoungulates, litopterns, carnivorous marsupials), but thisis the first record of an invertebrate.The mammal assemblage has been assigned to the Deseadan Mammal Age andcorresponds to an open woodland environment that developed in semiaridconditions during a period of volcanic activity. The extant species of Chiliborus live in a warm oceanic climate on westcoast of Chile, in areas with vegetation that varies from sclerophyllous shrublands,small forests to transitional and mixed forests. Fil: Miquel, Sergio Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales ; Argentina Fil: Cerdeño Serrano, Maria Esperanza. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina

Diverse animals exhibit left–right asymmetry in development. However, no example of dimorphism for the left–right polarity of development (whole-body enantiomorphy) is known to persist within natural populations. In snails, whole-body enantiomorphs have repeatedly evolved as separate species. Within populations, however, snails are not expected to exhibit enantiomorphy, because of selection against the less common morph resulting from mating disadvantage. Here we present a unique example of evolutionarily stable whole-body enantiomorphy in snails. Our molecular phylogeny of South-east Asian tree snails in the genus Amphidromus indicates that enantiomorphy has likely persisted as the ancestral state over a million generations. Enantiomorphs have continuously coexisted in every population surveyed spanning a period of 10 years. Our results indicate that whole-body enantiomorphy is maintained within populations opposing the rule of directional asymmetry in animals. This study implicates the need for explicit approaches to disclosure of a maintenance mechanism and conservation of the genus.

Background Mitochondrial (mt) genome sequences are widely used for species identification and to study the phylogenetic relationships among Gastropoda. However, to date, limited data are available as taxon sampling is narrow. In this study we sequenced the complete mt genomes of the freshwater gastropods Radix swinhoei (Lymnaeidae) and Planorbarius corneus (Planorbidae). Based on these sequences, we investigated the gene rearrangement in these two species and the relationships with respect to the ancestral gene order and assessed their phylogenetic relationships. Methods The complete mt genomes of R. swinhoei and P. corneus were sequenced using Illumina-based paired-end sequencing and annotated by comparing the sequence information with that of related gastropod species. Putative models of mitochondrial gene rearrangements were predicted for both R. swinhoei and P. corneus, using Reishia clavigera mtDNA structure as the ancestral gene order. The phylogenetic relationships were inferred using thirteen protein sequences based on Maximum likelihood and Bayesian inference analyses. Results The complete circular mt genome sequences of R. swinhoei and P. corneus were 14,241 bp and 13,687 bp in length, respectively. Comparison of the gene order demonstrated complex rearrangement events in Gastropoda, both for tRNA genes and protein-coding genes. The phylogenetic analyses showed that the family Lymnaeidae was more closely related to the family Planorbidae, consistent with previous classification. Nevertheless, due to the position recovered for R. swinhoei, the family Lymnaeidae was not monophyletic. Conclusion This study provides the complete mt genomes of two freshwater snails, which will aid the development of useful molecular markers for epidemiological, ecological and phylogenetic studies. Additionally, the predicted models for mt gene rearrangement might provide novel insights into mt genome evolution in gastropods. Electronic supplementary material The online version of this article (doi:10.1186/s13071-016-1956-9) contains supplementary material, which is available to authorized users.

Background With a diversity of pigmented shell morphotypes governed by Mendelian patterns of inheritance, the common grove snail, Cepaea nemoralis, has served as a model for evolutionary biologists and population geneticists for decades. Surprisingly, the molecular mechanisms by which C. nemoralis generates this pigmented shelled diversity, and the degree of evolutionary conservation present between molluscan shell-forming proteomes, remain unknown. Results Here, using next generation sequencing and high throughput proteomics, we identify and characterize the major proteinaceous components of the C. nemoralis shell, the first shell-proteome for a pulmonate mollusc. The recent availability of several marine molluscan shell-proteomes, and the dataset we report here, allow us to identify 59 evolutionarily conserved and novel shell-forming proteins. While the C. nemoralis dataset is dominated by proteins that share little to no similarity with proteins in public databases, almost half of it shares similarity with proteins present in other molluscan shells. In addition, we could not find any indication that a protein (or class of proteins) is directly associated with shell pigmentation in C. nemoralis. This is in contrast to the only other partially characterized molluscan-shell pigmentation mechanism employed by the tropical abalone Haliotis asinina. Conclusions The unique pulmonate shell-forming proteome that we report here reveals an abundance of both mollusc-specific and pulmonate-specific proteins, suggesting that novel coding sequences, and/or the extensive divergence of these sequences from ancestral sequences, supported the innovation of new shell types within the Conchifera. In addition, we report here the first evidence that molluscs use independently evolved mechanisms to pigment their shells. This proteome provides a solid foundation from which further studies aimed at the functional characterization of these shell-forming proteins can be conducted. peerReviewed

Invertebrates are used extensively as model species to investigate neuro-endocrine processes regulating behaviors, and many of these processes may be extrapolated to vertebrates. However, when it comes to reproductive processes, many of these model species differ notably in their mode of reproduction. A point in case are simultaneously hermaphroditic molluscs. In this review I aim to achieve two things. On the one hand, I provide a comprehensive overview of the neuro-endocrine control of male and female reproductive processes in freshwater snails. Even though the focus will necessarily be on Lymnaea stagnalis, since this is the best-studied species in this respect, extensions to other species are made wherever possible. On the other hand, I will place these findings in the actual context of the whole animal, after all these are simultaneous hermaphrodites. By considering the hermaphroditic situation, I uncover a numbers of possible links between the regulation of the two reproductive systems that are present within this animal, and suggest a few possible mechanisms via which this animal can effectively switch between the two sexual roles in the flexible way that it does. Evidently, this opens up a number of new research questions and areas that explicitly integrate knowledge about behavioral decisions (e.g., mating, insemination, egg laying) and sexual selection processes (e.g., mate choice, sperm allocation) with the actual underlying neuronal and endocrine mechanisms required for these processes to act and function effectively. © 2010 Koene.

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University. Recent evidence suggests that molluscs may be sensitive to the effects of endocrine disrupting chemicals (EDCs) in a similar manner to vertebrates, such as fish. Despite this (with the exception of TBT-induced imposex in marine gastropods), molluscs have been largely overlooked in the field of endocrine disruption. Life-cycle studies were conducted in which two species of native UK freshwater gastropod molluscs (the hermaphrodite Planorbarius corneus and the gonochorist Viviparus viviparus) were exposed to either 17β-oestradiol or environmentally relevant mixtures of chemicals known to be oestrogenic to vertebrates and to be present in UK treated sewage effluents (TSE) and rivers. Adult snails were exposed for four months in outdoor mesocosms, fed by river water, over the spring and summer (breeding season) in order to examine effects on reproductive output, growth and mortality. Furthermore, offspring (F1s) were also developmentally exposed over the same period. F1 juvenile snails were then depurated in river water for nine months (over winter) after which time their growth, survival, and reproductive success were measured in further un-dosed river water mesocosm studies in the following spring/summer. Histopathology was used to determine immediate effects of chemical exposure on adult and F1 snails’ reproductive health. Histopathology was also used to determine long lasting effects of chemical exposure on depurated F1s. Exposure to oestrogenic chemicals resulted in a range of effects, including modulated fecundity and growth in F0 adults, to retardation of growth, sexual development and fecundity in developmentally exposed F1s. Exposure to mixtures of oestrogenic chemicals also resulted in possible modulation of the immune system, resulting in increased parasitism and over winter mortality of exposed F1s compared to snails exposed to river water alone. Differences in sensitivity and response to exposure between the two species and the generations were also observed.

5 pages, 2 figures, 1 table.-- Printed version published Jun 23, 2003., Four new labdane diterpenes, 1-4, with an unusual oxidation pattern have been isolated from the marine pulmonate Trimusculus peruvianus. The structure and stereochemistry of these compounds were determined by spectroscopic data and chemical transformations. The absolute stereochemistry of 4 was assigned by application of the modified Mosher method. These compounds exhibit in vitro moderate cytotoxic activity against human colon carcinoma cell lines., This work was supported by the Ministerio de Ciencia y Tecnología (MCYT), project ref: PPQ2002-02494, DGUI of the Canary Islands Government PI2002/044, DID project CSMAR 02/6-2 of the Universidad de Chile, Cooperation Programme between CSIC (Spain)–CONICYT (Chile), and DI of the Universidad de Antofagasta. We are grateful to BIOMAR, S.A. for performing the bioassays. A. R. D.-M. acknowledges an I3P grant from the CSIC and E. D. an FPI grant from the MCYT.

Background Gastropods are among the most diverse animal clades, and have successfully colonized special habitats such as the marine sand interstitial. Specialized meiofaunal snails and slugs are tiny and worm-shaped. They combine regressive features – argued to be due to progenetic tendencies – with convergent adaptations. Microscopic size and concerted convergences make morphological examination non-trivial and hamper phylogenetic reconstructions. The enigmatic turbellarian-like Rhodopemorpha are a small group that has puzzled systematists for over a century. A preliminary molecular framework places the group far closer to the root of Heterobranchia – one of the major gastropod groups – than previously suggested. The poorly known meiofaunal Helminthope psammobionta Salvini-Plawen, 1991 from Bermuda is the most worm-shaped free-living gastropod and shows apparently aberrant aspects of anatomy. Its study may give important clues to understand the evolution of rhodopemorphs among basal heterobranchs versus their previously thought origin among ‘higher’ euthyneuran taxa. Results We describe the 3D-microanatomy of H. psammobionta using three-dimensional digital reconstruction based on serial semithin histological sections. The new dataset expands upon the original description and corrects several aspects. Helminthope shows a set of typical adaptations and regressive characters present in other mesopsammic slugs (called ‘meiofaunal syndrome’ herein). The taxonomically important presence of five separate visceral loop ganglia is confirmed, but considerable further detail of the complex nervous system are corrected and revealed. The digestive and reproductive systems are simple and modified to the thread-like morphology of the animal; the anus is far posterior. There is no heart; the kidney resembles a protonephridium. Data on all organ systems are compiled and compared to Rhodope. Conclusions Helminthope is related to Rhodope sharing unique apomorphies. We argue that the peculiar kidney, configuration of the visceral loop and simplicity or lack of other organs in Rhodopemorpha are results of progenesis. The posterior shift of the anus in Helminthope is interpreted as a peramorphy, i.e. hypertrophy of body length early in ontogeny. Our review of morphological and molecular evidence is consistent with an origin of Rhodopemorpha slugs among shelled ‘lower Heterobranchia’. Previously thought shared ‘diagnostic’ features such as five visceral ganglia are either plesiomorphic or convergent, while euthyneury and a double-rooted cerebral nerve likely evolved independently in Rhodopemorpha and Euthyneura.