A new type of gastropod proboscis: the foregut of Hastula bacillus (Gastropoda: Terebridae)

Hastula bacillus (Deshayes) is a small terebrid gastropod which inhabits sandy surf beaches in southern Thailand, where it feeds upon spionid polychaetes. It possesses a foregut anatomy unlike that of any other gastropod. An elongate arborescent muscular organ, known as the accessory proboscis structure, is extended through the mouth during foraging. When retracted, it is folded into an 's' shape in the permanent rhynchodeum. The accessory proboscis structure bears numerous tufts of short, stiff cilia which are associated with pairs or triplets of dome-like structures. It is suggested that the structures may be chemosensory and concerned with prey location. Hastula bacillus also possesses a retractable labial tube, a long proboscis and buccal tube, dart-shaped radular teeth, an odontophore, an accessory salivary gland, a pair of salivary glands and a well-developed venom gland with muscular bulb. A comparison with other terebrid species suggests that H. bacillus is the most plesiomorphic taxon yet described from the family.     

Loss of planktotrophy and speciation: geographical fragmentation in the deep-water gastropod genus Bathytoma (Gastropoda,Conoidea) in the western Pacific

Dispersal capabilities are crucial in how speciation patterns are determined in marine invertebrates. Species possessing a long-living planktonic larva apparently have a dispersal advantage over those with non-planktotrophic development, and their distant populations may exchange genetic material, maintaining a broad geographical range for the species. Recent species of the gastropod genus Bathytoma (Conoidea) are all characterized by non-planktotrophic development, having most probably lost a free-swimming larva in the pre-Pliocene, as Miocene fossils have protoconchs indicating planktotrophic larval development. All have a bathyal distribution (100–1500 m), which implies that their capability for direct expansion on the bottom is restricted by both deep-sea basins and shallow-water areas, especially in insular West and South-West Indo-Pacific. Therefore, it can be hypothesized that Bathytoma populations should represent numerous, mostly allopatric taxa restricted to a single or contiguous island groups. We tested this hypothesis using molecular and morphological characters independently. One hundred and thirty-eight specimens from the Philippines, Solomons, Vanuatu, and the Coral Sea were sequenced for one mitochondrial (COI) and one nuclear (ITS2) gene, and 14 operational molecular units were recognized. When these molecular units are overlaid over shell characters, 13 species (11 unnamed) and one form of uncertain status are recognized: three occur in the Philippines, six in the Solomons and one in New Caledonia. Broad distributions (inter-archipelagic) are uncommon (three species). On the whole, the phylogeographic pattern of the diversity in the genus is rather complex and probably also reflects processes of sympatric and fine-scale allopatric speciation, and local extinctions. The eleven new species are described and named.     

Revision of the genus Thetidos Hedley, 1899 (Gastropoda: Conoidea: Raphitomidae) in the Indo-Pacific with descriptions of three new species

The genus Thetidos was established to accommodate a single species Thetidos morsura, a minute turriform conoidean with an unremarkable paucispiral protoconch, but possessing characteristic globose whorls of the teleoconch and three strong denticles on the inside of outer apertural lip. Subsequently, Thetidos was considered synonymous with Lienardia, and has rarely been mentioned in literature until the recent discovery of a remarkably similar species Thetidos tridentata, though it is different in protoconch morphology. Both molecular data and protoconch morphology unequivocally suggested placement of the new species in Raphitomidae. Examination of shells from the Indo-Pacific identified a number of similar forms, all referable to the genus Thetidos. Six species are now recognized within the genus; of them three, Thetidos puillandrei n. sp., Thetidos minutissima n. sp., Thetidos pallida n. sp., are here described as new. Thetidos species are now known from subtidal depths from the Philippines and Sulawesi to French Polynesia. Thetidos morsura is the only species of the genus that possesses a paucispiral protoconch suggestive of a non-planktotrophic development, although it displays a wide geographic range and a high morphological variability.

http://zoobank.org/urn:lsid:zoobank.org:pub:1F2001CC-6BEA-4B26-AFB8-6B337E101FDB     

Exploring Species Level Taxonomy and Species Delimitation Methods in the Facultatively Self-Fertilizing Land Snail Genus Rumina (Gastropoda: Pulmonata)

Delimiting species in facultatively selfing taxa is a challenging problem of which the terrestrial pulmonate snail genus Rumina is a good example. These snails have a mixed breeding system and show a high degree of shell and color variation. Three nominal species (R. decollata, R. saharica and R. paivae) and two color morphs within R. decollata (dark and light) are currently recognized. The present study aims at evaluating to what extent these entities reflect evolutionary diverging taxonomic units, rather than fixed polymorphisms due to sustained selfing. Therefore, a phylogenetic analysis of nuclear (ITS1, ITS2) and mitochondrial DNA (COI, CytB, 12S rDNA, 16S rDNA) sequences was performed. Putative species in Rumina, inferred from the mitochondrial DNA phylogeny, were compared with those proposed on the basis of the COI gene by (1) DNA barcoding gap analysis, (2) Automatic Barcode Gap Discovery, (3) the species delimitation plug-in of the Geneious software, (4) the Genealogical Sorting Index, and (5) the General Mixed Yule Coalescent model. It is shown that these methods produce a variety of different species hypotheses and as such one may wonder to what extent species delimitation methods are really useful. With respect to Rumina, the data suggest at least seven species, one corresponding to R. saharica and six that are currently grouped under the name R. decollata. The species-level status of R. paivae is rejected.     

The Model Organism Hermissenda crassicornis (Gastropoda: Heterobranchia) Is a Species Complex

Hermissenda crassicornis is a model organism used in various fields of research including neurology, ecology, pharmacology, and toxicology. In order to investigate the systematics of this species and the presence of cryptic species in H. crassicornis, we conducted a comprehensive molecular and morphological analysis of this species covering its entire range across the North Pacific Ocean. We determined that H. crassicornis constitutes a species complex of three distinct species. The name Hermissensa crassicornis is retained for the northeast Pacific species, occurring from Alaska to Northern California. The name H. opalescens is reinstated for a species occurring from the Sea of Cortez to Northern California. Finally, the name H. emurai is maintained for the northwestern species, found in Japan and in the Russian Far East. These three species have consistent morphological and color pattern differences that can be used for identification in the field.     

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.     

The Substantial First Impact of Bottom Fishing on Rare Biodiversity Hotspots: A Dilemma for Evidence-Based Conservation

This study describes the impact of the first passage of two types of bottom-towed fishing gear on rare protected shellfish-reefs formed by the horse mussel Modiolus modiolus (L.). One of the study sites was trawled and the other was scallop-dredged. Divers collected HD video imagery of epifauna from quadrats at the two study sites and directed infaunal samples from one site.The total number of epifaunal organisms was significantly reduced following a single pass of a trawl (90%) or scallop dredge (59%), as was the diversity of the associated community and the total number of M. modiolus at the trawled site. At both sites declines in anthozoans, hydrozoans, bivalves, echinoderms and ascidians accounted for most of the change. A year later, no recovery was evident at the trawled site and significantly fewer infaunal taxa (polychaetes, malacostracans, bivalves and ophuroids) were recorded in the trawl track.The severity of the two types of impact reflected the undisturbed status of the habitats compared to previous studies. As a ‘priority habitat’ the nature of the impacts described on M. modiolus communities are important to the development of conservation management policy and indicators of condition in Marine Protected Areas (EU Habitats Directive) as well as indicators of ‘Good Environmental Status’ under the European Union Marine Strategy Framework Directive.Conservation managers are under pressure to support decisions with good quality evidence. Elsewhere, indirect studies have shown declines of M. modiolus biogenic communities in fishing grounds. However, given the protected status of the rare habitat, premeditated demonstration of direct impact is unethical or illegal in Marine Protected Areas. This study therefore provides a unique opportunity to investigate the impact from fishing gear whilst at the same time reflecting on the dilemma of evidence-based conservation management.     

Predicting the Fate of Biodiversity Using Species�� Distribution Models: Enhancing Model Comparability and Repeatability

Species distribution modeling (SDM) is an increasingly important tool to predict the geographic distribution of species. Even though many problems associated with this method have been highlighted and solutions have been proposed, little has been done to increase comparability among studies. We reviewed recent publications applying SDMs and found that seventy nine percent failed to report methods that ensure comparability among studies, such as disclosing the maximum probability range produced by the models and reporting on the number of species occurrences used. We modeled six species of Falco from northern Europe and demonstrate that model results are altered by (1) spatial bias in species’ occurrence data, (2) differences in the geographic extent of the environmental data, and (3) the effects of transformation of model output to presence/absence data when applying thresholds. Depending on the modeling decisions, forecasts of the future geographic distribution of Falco ranged from range contraction in 80% of the species to no net loss in any species, with the best model predicting no net loss of habitat in Northern Europe. The fact that predictions of range changes in response to climate change in published studies may be influenced by decisions in the modeling process seriously hampers the possibility of making sound management recommendations. Thus, each of the decisions made in generating SDMs should be reported and evaluated to ensure conclusions and policies are based on the biology and ecology of the species being modeled.     

A cladistic phylogeny of the family Patellidae (Mollusca: Gastropoda)

A phylogenetic hypothesis for the patellid limpets is reconstructed by cladistic analysis of morphological characters from 37 species, representing all but one of the living members of the family. Characters included in the analysis are derived from shell shape and microstructure, headfoot and pallial complex, radula and sperm. The species fall into four clades, providing the basis for a new phylogenetic classification into four monophyletic genera: Helcion (four species; southern Africa), Cymbula (eight species; southern Africa, eastern Atlantic, southern Indian Ocean), Scutellastra (17 species; southern and southwestern Africa, Australia, Indo-West Pacific, Eastern Pacific) and Patella (nine species; northeastern Atlantic and Mediterranean). The analysis suggests sister-group relationships between Helcion and Cymbula, and between Scutellastra and Patella. In combination with present-day patterns of geographical distribution, this phylogenetic hypothesis is used to discuss the historical biogeography of the Patellidae. Scutellastra may have originated in southern Africa and dispersed across the Pacific, or alternatively may be a primitively Tethyan group. Both Helcion and Cymbula appear to have originated in southern Africa, but three Cymbula species have dispersed respectively to northwest Africa, St Helena and the southern Indian Ocean. The patellids of the northeastern Atlantic form a single clade, Patella (including P. pellucida), which may have arrived by northward dispersal of an ancestor from southern Africa, or possibly by vicariance of a widespread ancestral Tethyan distribution. The known fossil record of patellids is too fragmentary to permit choice between these alternatives.     

Genetic divergence and geographic variation in the deep-water Conus orbignyi complex (Mollusca: Conoidea)

Puillandre, N. et al. (2010) Genetic divergence and geographic variation in a deep-water cone lineage: molecular and morphological analyses of the Conus orbignyi complex (Mollusca: Conoidea).The cone snails (family Conidae) are a hyperdiverse lineage of venomous gastropods. Two standard markers, COI and ITS2, were used to define six genetically-divergent groups within a subclade of Conidae that includes Conus orbignyi; each of these was then evaluated based on their shell morphology. We conclude that three forms, previously regarded as subspecies of Conus orbignyi are distinct species, now recognized as Conus orbignyi, Conus elokismenos and Conus coriolisi. In addition, three additional species (Conus pseudorbignyi, Conus joliveti and Conus comatosa) belong to this clade. Some of the proposed species (e.g., Conus elokismenos) are possibly in turn complexes comprising multiple species. Groups such as Conidae illustrate the challenges generally faced in species delimitation in biodiverse lineages. In the case of the Conus orbignyi complex, not only are there definable, genetically divergent lineages, but also considerable geographic variation within each group. Our study suggests that an intensive analysis of multiple specimens within a single locality helps to minimize the confounding effects of geographic variation and can be a useful starting point for circumscribing different species within such a confusing complex.     

RFMix: A Discriminative Modeling Approach for Rapid and Robust Local-Ancestry Inference

Local-ancestry inference is an important step in the genetic analysis of fully sequenced human genomes. Current methods can only detect continental-level ancestry (i.e., European versus African versus Asian) accurately even when using millions of markers. Here, we present RFMix, a powerful discriminative modeling approach that is faster (∼30×) and more accurate than existing methods. We accomplish this by using a conditional random field parameterized by random forests trained on reference panels. RFMix is capable of learning from the admixed samples themselves to boost performance and autocorrect phasing errors. RFMix shows high sensitivity and specificity in simulated Hispanics/Latinos and African Americans and admixed Europeans, Africans, and Asians. Finally, we demonstrate that African Americans in HapMap contain modest (but nonzero) levels of Native American ancestry (∼0.4%).     

Immunocytochemical Localisation of Glycosaminoglycan-Like Activity in the Mucus and Associated Tissues of Terrestrial Slug Species (Gastropoda: Pulmonata)

Indirect immunofluorescence assays were conducted on cryotome sections of four terrestrial slug species from three distinct phylogenetic groups, Arion ater (L.), Arion hortensis (Férussac), Tandonia (Milax) budapestensis (Hazay), and Deroceras reticulatum (Müller) using monoclonal antibodies for two glycosaminoglycans (GAGs), heparan sulphate, and chondroitin sulphate. Specific staining for a heparan sulphate-like component was demonstrated in the foot and tail regions of each species and was particularly intense in A. ater and A. hortensis, notably in the epidermis and associated mucus-like material, and in mucus-like material from the pedal gland region of the latter species. Subsequent studies with A. ater confirmed the presence of heparan-sulphate–like activity in the caudal gland duct region. No evidence of specific staining for chondroitin sulphate-like activity was found in any of the slug species. This work suggests that a specific GAG, or a group of closely related GAGs, is a common component of mucus in a range of slug species and of different types of mucus, including trail (pedal) mucus and the more viscous mucus produced by the caudal gland.     

A molecular phylogenetic framework for the subfamily Ocenebrinae (Gastropoda,Muricidae)

The Ocenebrinae is a subfamily of marine predatory gastropods known as oyster and mussel drills. Their current phylogenetic framework is traditionally based on shell and radular characters, but a consensus on relationships among genera is still lacking. We investigated the molecular phylogeny of Ocenebrinae using 50 species and DNA data from one nuclear (28S) and two mitochondrial (COI and 16S) genes, the largest data set so far assembled for this subfamily. We found support for the monophyly of the Ocenebrinae, and species were divided into four major lineages. Within groups, genera had similar geographic distributions, suggesting that except in a few cases, species diversification within clades occurred without range expansions. We discuss the phylogenetic distribution of a labral tooth and a sealed siphonal canal, two characteristic ocenebrine features. We also show that Ocinebrina species in the north‐eastern Pacific are not monophyletic with north‐eastern Atlantic and Mediterranean species, and that the Ocinebrina edwardsii species complex belongs to Ocenebra.     

Snails in the desert: Species diversification of Theba (Gastropoda: Helicidae) along the Atlantic coast of NW Africa

The spatial subdivision of species often plays a pivotal role in speciation. Across their entire range, species are rarely panmictic and crucial consequences of spatial subdivision are (1) random genetic drift including historical factors, (2) uniform selection, and (3) divergent selection. Each of these consequences may result in geographic variation and eventually reproductive isolation, but their relative importance in speciation is still unclear. In this study, we used a combination of genetic, morphological, and climatic data to obtain a comprehensive picture of differentiation among three closely related, parapatrically distributed taxa of the land snail genus Theba occurring along the Atlantic coasts of South Morocco and Western Sahara. We conducted Mantel and partial Mantel tests to relate phenotypic and genotypic variation of these species to geography and/or climate. As null hypothesis for an evolutionary scenario, we assumed nonadaptive speciation and expected a pattern of isolation by distance among taxa. Rejection of the null hypothesis would indicate isolation by environment due to adaptation. Generally, genetic drift plays an important role but is rarely considered as sole driver of speciation. It is the combination of drift and selection that predominantly drives speciation. This study, however, provides a potential example, in which nonadaptive speciation, that is, genetic drift, is apparently the main driver of shaping the diversity of Theba in NW Africa. Restriction of gene flow between populations caused by geographic isolation probably has played an important role. Climate oscillations during the Plio‐ and Pleistocene may have led to repeated ecological changes in NW Africa and disruptions of habitats promoting differentiation by geographic isolation. The inferred evolutionary scenario, however, did not fully explain the incongruence between the AFLP‐ and mtDNA‐tree topologies. This incongruence might indicate past hybridization among the studied Theba forms.     

Ulva (Chlorophyta,Ulvales) Biodiversity in the North Adriatic Sea (Mediterranean,Italy): Cryptic Species and New Introductions

Ulva Linnaeus (Ulvophyceae, Ulvales) is a genus of green algae widespread in different aquatic environments. Members of this genus show a very simple morphology and a certain degree of phenotypic plasticity, heavily influenced by environmental conditions, making difficult the delineation of species by morphological features alone. Most studies dealing with Ulva biodiversity in Mediterranean waters have been based only on morphological characters and a modern taxonomic revision of this genus in the Mediterranean is not available. We report here the results of an investigation on the diversity of Ulva in the North Adriatic Sea based on molecular analyses. Collections from three areas, two of which subject to intense shipping traffic, were examined, as well as historical collections of Ulva stored in the Herbarium Patavinum of the University of Padova, Italy. Molecular analyses based on partial sequences of the rbcL and tufA genes revealed the presence of six different species, often with overlapping morphologies: U. californica Wille, U. flexuosa Wulfen, U. rigida C. Agardh, U. compressa Linnaeus, U. pertusa Kjellman, and one probable new taxon. U. californica is a new record for the Mediterranean and U. pertusa is a new record for the Adriatic. Partial sequences obtained from historical collections show that most of the old specimens are referable to U. rigida. No specimens referable to the two alien species were found among the old herbarium specimens. The results indicate that the number of introduced seaweed species and their impact on Mediterranean communities have been underestimated, due to the difficulties in species identification of morphologically simple taxa as Ulva.     

Phylogeny and biogeography of the Vitrinidae (Gastropoda: Stylommatophora)

The phylogeny of the Vitrinidae is reconstructed in a cladistic analysis based on characters of the genitalia, the copulation behaviour and the radula. The genera with an atrial stimulator turned out to be the earliest branches of the Vitrinidae, whereas the genera with a glandula amatoria form a monophyletic, taxonomically apomorphic group. The differences between the proposed phylogeny and previous hypotheses are discussed. The ancestral areas of the Vitrinidae and its sister group, the limacoid slugs Boettgerillidae–Limacidae–Agriolimacidae, are estimated using weighted ancestral area analysis. The Vitrinidae and the limacoid slugs might have originated by a vicariance event between Central Europe and the Near East. © 2002 The Linnean Society of London. Zoological Journal of the Linnean Society , 2002, 134 , 347–358.     

A phylogenetic analysis of rissooidean and cingulopsoidean families (Gastropoda: Caenogastropoda)

The Rissooidea is one of the largest and most diverse molluscan superfamilies, with 23 recognized Recent families including marine, freshwater and terrestrial members. The Cingulopsoidea are a group of three marine families previously included within the Rissooidea. A previous molecular analysis including two rissooideans and one cingulopsoidean, indicated the possibility that the Rissooidea is at least diphyletic. We use new molecular data to investigate the polyphyly of Rissooidea and test the monophyly of Cingulopsoidea with a greatly increased taxon set. This study includes the greatest sampling to date with 43 species of 14 families of Rissooidea and all families of Cingulopsoidea. Bayesian and maximum likelihood analyses of 16S and 28S show that there are two major clades encompassing taxa previously included in Rissooidea. These are the Rissooidea s.s. containing Rissoidae and Barleeiidae and the Truncatelloidea containing Anabathridae, Assimineidae, Falsicingulidae, Truncatellidae, Pomatiopsidae, Hydrobiidae s.l., Hydrococcidae, Stenothyridae, Calopiidae, Clenchiellidae, Caecidae, Tornidae, and Iravadiidae. Rissoidae is not monophyletic, with Lironoba grouping with Emblanda (Emblandidae) and Rissoina forming a separate clade with Barleeiidae. Iravadiidae is not monophyletic, with Nozeba being sister to the Tornidae. Tatea, usually included within Hydrobiidae, is distinct from that family and Nodulus, previously included in Anabathridae, groups with the hydrobiids.