In the past ∼155 years, professional and amateur malacologists have recorded ca. 90 described species of sacoglossan opisthobranchs in ∼25 genera on Japanese shores. In addition, there are at least 20 to 40 undescribed or unrecognized sacoglossans also recorded. The extraordinary species richness has been a source of admiration as well as vexation. Worldwide scientific excitement in this group was largely due to two pivotal discoveries by Japanese researchers: (1) the acquisition and retention of functional chloroplasts by the sacoglossan Elysia atroviridis Baba, 1955 and (2) the existence of extant populations of bivalved sacoglossans (initially Tamanovalva limax Kawaguti and Baba, 1959 and then related taxa). Eight of the nine sacoglossan families recognized by Jensen (1996, 2007) are represented in Japan. All the recognized sacoglossan genera are represented in Japan except: Roburnella Marcus, 1982; Platyhedyle Salvini-Plawen, 1973; Gascoignella Jensen, 1985; Olea Agersborg, 1923; Limapontia Johnston, 1836; and the Australian genera Edenttellina Gatliff and Gabriel, 1911 and Midorigai Burn, 1960. Taxonomic uncertainty has been caused by the absence of vouchers, incomplete and/or questionable descriptions, photographic misidentifications (books and internet), chronically unstable classification, and other scientific challenges; in particular, the small size, cryptic coloration, and patchy distribution of sacoglossans have contributed to limited collections of many species. Since 2000, we have collected, photographed, and preserved unusually large numbers of Japanese sacoglossans, including species traditionally considered rare by malacologists. Although it is premature to produce a comprehensive inventory of the Japanese sacoglossan fauna, we consider it necessary to describe explicitly the strengths and weaknesses of current information. This assessment should assist professional and amateur malacologists with future sacoglossan study, particularly in the areas of biogeography, phylogeny, and ecology.

Lake Biwa (Shiga Prefecture, Japan) is an ancient lake with many endemic species. In particular, 15 extant endemic species of the genus Semisulcospira (Caenogastropoda: Pleuroceridae) have attracted attention because they may represent a single species flock. Although many taxonomic studies have been conducted on these Lake Biwa species and on non-Biwa species of the genus, their genetic relationships remain unresolved. We use allozyme analysis to investigate the genetic differentiation of 12 species of the genus Semisulcospira, including nine Lake Biwa endemics: S. (Biwamelania) arenicola Watanabe and Nishino, 1995, S. (B.) decipiens (Westerlund, 1883), S. (B.) fluvialis Watanabe and Nishino, 1995, S. (B.) multigranosa (Böttger, 1886), S. (B.) nakasekoae Kuroda, 1929, S. (B.) ourense Watanabe and Nishino, 1995, S. (B.) fuscata Watanabe and Nishino, 1995, S. (B.) niponica (Smith, 1876), and S. (B.) habei Davis, 1969, and three non-Biwa species: S. (S.) libertina (Gould, 1859), S. (S.) reiniana (Brot, 1877), and S. (S.) kurodai Kajiyama and Habe, 1961. Based on their genetic features, the Lake Biwa endemics were divided into three groups, the S. (B.) decipiens group, S. (B.) niponica group, and S. (B.) habei group. The observed genotype frequencies of the Lake Biwa endemics within each group were similar to each other. We tested the observed genotype frequencies for each polymorphic locus in each local population of the Lake Biwa endemics for departure from Hardy—Weinberg equilibrium. Most of the eight polymorphic loci of the Lake Biwa populations did not deviate significantly from HWE, except for Aat of S. (B.) arenicola at the site B8, Pgm-1 of S. (B.) fluvialis at the site B9, and S. (B.) habei at the site B1 (level of significance α = 0.05). The S. (B.) niponica and S. (B.) habei groups showed similar genetic features to the non-Biwa S. (S.) libertina and S. (S.) reiniana groups, whereas the S. (B.) decipiens group was distinct from any other group. Our allozyme data suggest that Semisulcospira species in Japan are distinguished robustly into two major lineages, the S. (B.) decipiens group and a separate non-decipiens group, and that all extant Lake Biwa endemics do not form a single species flock, as proposed previously.

With the collapse of the offshore whelk trawl fishery in Georgia, interest has increased in harvesting whelk from inshore areas where trawling is prohibited. This study examines the effects of hand harvesting on local intertidal populations of whelk. Over a 34 day period from 27 February to 1 April 2006, 1,824 whelk were hand harvested at low tide: 91.2% knobbed, Busycon carica (Gmelin, 1791); 4.7% lightning, Busycotypus sinistrum (Hollister, 1958); 4.1% channeled, Busycotypus canalicalatus (Linnaeus, 1758); and one pearwhelk, Busycotypus spiratus (Lamarck, 1816). Significantly greater numbers of knobbed and lightning female whelk were found than males. Mean shell lengths for females were consistently larger than males of all species. The study period was divided into three collection periods that were separated by approximately one week. The numbers of whelk harvested and their mean shell lengths significantly decreased between sampling periods as stocks were depleted. All species and sexes were active in both daytime and nighttime; however, significantly more knobbed and channeled whelk were harvested when sampling occurred closer to the middle of the night and significantly fewer toward the middle of the day. Nocturnal feeding is likely a cryptic adaptation to avoid predation and desiccation, and many whelk presumably remain buried on the intertidal flats during diurnal exposure. This study was conducted in the period leading up to copulation and egg-laying on the intertidal sandy-mud flats in inshore areas in coastal Georgia. Nocturnal hand harvesting at this time of the year could very quickly have detrimental impacts to local whelk stocks. Further implications of this work for an intertidal hand harvest supplemental whelk fishery are discussed.

Morphological and molecular data are used to address the taxonomic status of two uncommon species of opisthobranch molluscs from the Gulf of Mexico. Chromodoris fentoni is a new species closely related to other Atlantic and eastern Pacific congeneric species. It is characterized by having a whitish background color almost completely covered with irregular red pigment. Glossodoris punctilucens Bergh, 1890 is a rare species known from only a handful of specimens. Morphological and molecular data confirm that it is distinct from other similarly colored species from the eastern Atlantic.

Seagrass canopies harbor many different mollusc species, but information about the interaction of these seagrass residents with their host plants remains scarce. Most gastropods inhabiting seagrass meadows are believed to feed on epiphytes rather than directly on living seagrass tissues. In laboratory experiments, we demonstrate that the gastropod Smaragdia viridis (Linnaeus, 1758) feeds preferentially on three seagrass species that are common in the Caribbean and Bermuda, including Thalassia testudinum, Halodule wrightii, and Syringodium filiforme. The percentage of lysed over intact seagrass cells egested was significantly higher in gastropods fed either T. testudinum or H. wrightii (80.3 ± 4.7% and 84.6 ± 11.4%, mean ± SD) but not for S. filiforme (59.7 ± 15.9%). Diet versatility for both pioneer (H. wrightii and S. filiforme) and climax (T. testudinum) Caribbean seagrass species allows S. viridis to adapt to small-scale disturbances that are common in these habitats, but a diet specializing in seagrass may make this animal vulnerable to large-scale seagrass declines occurring worldwide.

A test system was evaluated for assessing chronic toxicity of waterborne chemicals with early life stage mussels. To determine if the test system could result in ≥80% survival in a control (unexposed) group, fat mucket mussels (Lampsilis siliquoidea Barnes, 1823) and plain pocketbook mussels (L. cardium Rafinesque, 1820) 1 day post transformation were stocked into test chambers (250 mL beakers, water volume, 200 mL, 21 °C, 40 mussels of 1 species per chamber) within a test system constructed for conducting chronic, continuous exposure, flow-through toxicity tests. The test system contained 60 chambers containing silica sand, 30 chambers with L. siliquoidea, and 30 with L. cardium. Each chamber in the continuous feeding system received 1 of 6 food types prepared with concentrated algal products. After 28 days, mussels were harvested from chambers to assess survival and growth. For L. siliquoidea, mean survival ranged from 34 to 80% and mean shell length ranged from 464 to 643 µm. For L. cardium, mean survival ranged from 12 to 66% and mean shell length ranged from 437 to 612 µm. The maximum mean growth rate for L. siliquoidea was 12.7 µm/d and for L. cardium was 11.8 µm/d. When offered a continuous diet of Nannochloropsis, Tetraselmis, and Chlorella for 28 days in the test system, the survival of 1 day post transformation L. siliquoidea was 80%. The test system can be easily enhanced with a pumping system continuously delivering test chemical to the test system's flow stream allowing for chronic toxicity tests with 1 day post transformation mussels.

The extensive fossil record of coiled nautiloids indicates that they comprised a diverse assemblage of species in ancient oceans. Today they are represented by the genera Nautilus Linnaeus, 1758 and Allonautilus Ward and Saunders, 1997, inhabiting reef systems throughout the Indo-Pacific region. Some individual populations of Nautilus show subtle differences in shell morphologies, and these morphological differences may be used to diagnose different species. An alternative view is that these differences are simply geographically localized, morphological variants within the broadly distributed taxon generally referred to as Nautilus pompilius Linnaeus, 1758. Here we present a hypothesis for the phylogeny of present-day Nautilus and Allonautilus using molecular characters from two mitochondrial gene regions, 16S rDNA and Cytochrome Oxidase c subunit I. Populations of N. pompilius in Indonesia (Ambon Strait), the Philippines, Vanuatu (New Hebrides Islands), Papua New Guinea, Carter Reef and Osprey Reef (Great Barrier Reef, Queensland, Australia) and N. macromphalus (Sowerby, 1849) in New Caledonia were surveyed as well as samples of N. repertus (Sowerby, 1849) (Rowley Shoals, Western Australia), N. belauensis (Saunders, 1981) (Palau), and N. stenomphalus (Sowerby, 1849) (Queensland, Australia). The gastropod Crepidula striolata (Menke, 1851) was included as an outgroup. Our results indicate that Nautilus is currently undergoing a period of evolutionary radiation throughout the Indo-Pacific region. The topology of the strict consensus tree suggests that the basal divergence between Nautilus and Allonautilus occurred in the waters surrounding the present-day island of New Guinea and the northern part of the Great Barrier Reef in northeast Australia. This was followed by a migration to the east by the common ancestor of N. macromphalus and the N. pompilius populations in Vanuatu, Fiji, and American Samoa. A subsequent migration to the west led to the founding of populations off the west coast of Australia, the Philippines, Palau, and Indonesia. Our results also indicate that N. macromphalus and A. scrobiculatus are phylogenetic species. However, N. pompilius is a paraphyletic assemblage of populations and does not represent a true phylogenetic species. Divergences within the genus Nautilus appear to be driven by geographic isolation, and we discuss how this may be a result of constraints on dispersal imposed by the ecology of the animals.

In Argentina the exotic snail Physa acuta Draparnaud, 1805 is predominant in environments previously inhabited by the native species Stenophysa marmorata Guilding, 1828, raising the question of whether this could have occurred because of differences in survival or reproductive strategies. To analyze the life cycle of these two species, I used the horizontal—life-table method and considered the number and proportion of viable of eggs per oviposition. Although both species suffered a high degree of mortality during the first weeks after oviposition, both the rate and the force of mortality was much greater during the reproductive period, so that the survival curve was not as markedly concave as with other gastropods. Physa acuta survived longer than S. marmorata, began its reproductive period earlier, and had a longer and more continuous reproductive stage. The number of ovipositions per snail was not different between the two species; but since the mean number of eggs per oviposition was higher in P. acuta, fecundity was likewise higher. The increase in fecundity was accompanied by an enhancement of the mortality rate in S. marmorata. The percentage of viable eggs was higher in P. acuta than in S. marmorata, but fecundity increased with age in both species. Life expectancy, reproductive value, and net reproductive rate were higher in P. acuta. The success of the exotic species P. acuta in the native habitat of S. marmorata could be explained in part by the former's earlier sexual maturation, higher reproductive potential, and greater longevity. Further field and laboratory studies are needed to demonstrate the existence of interspecific competition between these two gastropods.

The distribution of the slipper limpet Crepidula fornicata (Linnaeus, 1758) in the northwestern Atlantic is generally understood to extend only as far north as Baie des Chaleurs (∼48°N, 66^°W) in the southwestern Gulf of St. Lawrence and only as far east as Cape Breton Island, Nova Scotia (-46^°N, 60^°W). Here we present evidence that this species is found considerably further north (to 51°N) and east (to 55^°W) than previously recognized. More specifically, its distribution is now known to include the Quebec “Lower North Shore” of the Gulf of St. Lawrence as well as the southern and western coasts of Newfoundland. Our evidence is based upon (1) shell collections from 12 museums in Canada and the U.S., (2) reports from both the primary and the secondary literature dating back to 1841, and (3) collections of C. fornicata in Newfoundland in 2009. While our investigations suggest that C. fornicata is expanding its geographic range in eastern Canada, we cannot be certain of this since the northern Gulf of St. Lawrence, Newfoundland, and Labrador have not been extensively sampled in the past for non-commercial benthic marine molluscs. Factors such as larval drift in known surface currents may be sufficient to explain such supposed range extensions. Clarification of current geographic ranges of marine species, particularly of well-studied and easily recognizable taxa such as C. fornicata, remains an important task for establishing temporal benchmarks against which to assess the effect of climate change on the marine environment.

We investigated brooding patterns and timing of reproduction in three species of freshwater mussels, Elliptio complanata (Lightfoot, 1786), Elliptio roanokensis (Lea, 1839), and Elliptio angustata (Lea, 1831) in the lower Broad River near Columbia, South Carolina. Through repeatedly marking and recapturing individuals from late March through late lune 2008, we determined that E. complanata and E. roanokensis can complete at least two broods during this season, and that E. angustata can complete at least three broods with very little time between broods. The lengths of brooding periods were difficult to estimate and subject to a wide margin of error. However, the brooding period was estimated to be 20 to 36 days in most broods of E. angustata, and could be as short as 18 days in E. roanokensis and 25 days in E. complanata. Mark and recapture of gravid mussels provided a much more detailed picture of brooding strategies than the collection and preservation of different individuals throughout the year.

Effective conservation requires that natural resource managers understand the diversity of organisms within a jurisdictional unit. Too frequently, conservation priorities are determined without adequate biological information, leading to inefficient use of very limited resources. We investigated molluscan community composition and richness within the eastern portion of the Sawtooth National Recreation Area (i.e., management unit) in Custer County, Idaho, USA to (1) identify populations of non-native species, if present, (2) acquire baseline information on the distribution, relative abundance, and diversity of molluscs in this high-elevation ecosystem, and (3) provide resource managers with useful information with which to inform conservation priority-setting. We found a rich molluscan community comprised of 19 species from 11 genera and 7 families. We also documented a single population of the non-native species Radix auricularia Linnaeus, 1758 from samples at Alturas Lake. Management of the very popular, eastern portion of the Sawtooth National Recreation Area should include public outreach regarding invasive species, importance of proper cleaning of boats and fishing gear, and importance of native invertebrates to healthy, functioning ecosystems.

The tropical land snail Achatina fulica Bowdich, 1822, native to Africa, is reported for the first time in Argentina, in Puerto Iguazú City, Misiones Province. This city is surrounded by protected areas. Three randomly selected 1-m2 plots were marked off in private gardens and in the area surrounding an urban stream for snail sampling. The high snail density detected could have ecological, sanitary, and economic consequences which have already been documented in other countries.

Geographical separation is arguably fundamental to speciation. John Thomas Gulick (13 March 1832 – 14 April 1923), a missionary from the Hawaiian Islands and one of the earliest evolutionary biologists, was among the first to recognize the critical role for geographical separation in the diversification of ecologically similar Hawaiian land snails. Although Gulick's work is not well-known today, his ideas were discussed by Darwin and Wallace as well as leaders in the Modern Evolutionary Synthesis (e.g., Wright and Mayr) who saw an important role for geographical isolation in speciation. It was perhaps no accident that organisms with low vagility, such as land snails of the Hawaiian Islands (i.e., achatinelline tree snails and ground-dwelling amastrid snails) exemplified the importance of geographical separation in speciation. Here I provide context for Gulick's snail research, showing that the natural setting of the Hawaiian Islands, combined with Gulick's development as a naturalist and evolutionary thinker lead to important insights on speciation, resulting from observations of substantial species richness in achatinelline and amastrid land snails, among the ridges and valleys of the Hawaiian Islands. Gulick's research on lesser-known organisms, island land snails, illustrates key areas for future inquiry, particularly in understanding “nonadaptive” contributions to evolutionary radiations.

The ranges of Pleurocera (formerly Goniobasis or Elimia) catenaria (Say, 1822) and P. proxima (Say, 1825) extend from Virginia south through the Carolinas into the piedmont and upper coastal plain of Georgia, where they intersect with populations of P. floridensis (Reeve, 1860). In contrast to the situation in surrounding states, however, Georgia populations of P. catenaria have been taxonomically subdivided and re-described under at least ten specific nomina, over a complex monographic history extending 150 years. To see if this increased nomenclatural diversity might signal higher levels of population divergence, we compared gene frequencies at 11 polymorphic allozyme-encoding loci among eight populations of P. catenaria and three populations of P. floridensis sampled from central Georgia region to three populations of P. proxima, which have never been taxonomically subdivided. Genetic variation was moderate within our 14 populations and high among them, as has been reported in many prior surveys of pleurocerid allozyme divergence conducted elsewhere. The pairwise genetic distances demonstrated among our populations of P. catenaria from Georgia were lower than those observed among control P. proxima populations, or among a comparable sample of P. catenaria populations from the Carolinas previously published. Central Georgia does not appear to be a region of pleurocerid endemicity, but rather of faunal suturing, the proliferation of specific nomina attributable to qualitatively higher levels of shell morphological variation, possibly ecophenotypic in origin. Junior synonyms of P. catenaria include albanyensis, boykiniana, caelatura, darwini, mutabilis, postelli, suturalis and viennaensis. Junior synonyms of P. floridensis include inclinans, induta, exul, and nymphaea. The Goodrich nomen timidus is retained as a subspecies of P. floridensis (new combination). We suggest that faunas demonstrating great evolutionary stasis, such as the pleurocerid populations of central Georgia, might profitably serve as the next “laboratories of speciation.”

Modern speciation theory is heavily influenced by Mayr's postulate that prolonged geographical isolation is necessary for differentiated populations to evolve reproductive isolation. Present-day distributions of sister species are consistent with allopatric or peripatric speciation in many terrestrial and freshwater animal groups. However, the oceans present few obstacles to dispersal for marine taxa with planktonic larvae, and sister species are not often split at biogeographical breakpoints in the sea. Theory predicts that disruptive selection on habitat choice or resource use can split a population into divergent ecotypes without physical separation, yet sympatric speciation is still often viewed as improbable. Here, I review phylogenetic evidence from diverse marine gastropods to test Mayr's prediction that recently diverged sister species should not be sympatric over most of their ranges. In contrast to expectations, young sister species are often broadly sympatric in many gastropod groups, suggesting that classical models of allopatric divergence are insufficient to explain marine speciation. I discuss four mechanisms that may contribute to this deviation from predicted biogeographical patterns: transient allopatry along continuous coastlines, rapid evolution of gamete recognition proteins, shifts to non-planktonic development, and ecological divergence. The available evidence argues that patterns of marine speciation depend on complex interactions between geography, life history, and ecology, often resulting in local radiations within a basin or endemic to an island group. Whether selection acts on ecotypes in sympatry or on populations during secondary contact, ecological factors may promote speciation in the sea at smaller spatial scales than expected. I highlight areas for future study to improve our understanding of the forces generating marine biodiversity, and why the geography of speciation may be fundamentally different for shallow-water animals.

As much as the century-long debate on what species are has created confusion and controversy, not less has speciation been discussed, i.e., the process of how new forms and taxa evolve, ultimately resulting in the multiplication of species. Darwin's often cited “mystery of the mysteries”, i.e., the origin of species and, as a consequence, of biological diversity in general, remains at the forefront of current evolutionary biology. While allopatric speciation by geographical separation is still considered an important mechanism in most cases, recently it became evident (as a slow and quiet revolution) that alternative explanations may account for how new species come into being. Among the most prominent factors, particularly in the context of adaptive radiation, is ecology in concert with specialization, albeit not necessarily in a sympatric setting. Unfortunately, for freshwater gastropods we are far away from really understanding the details of the various speciation processes (allopatric versus sympatric) and the role of natural selection, adaptation and ecology that have lead to the array of radiations described recently for several taxa and cases. Contrasting lacustrine and riverine settings, I will discuss these issues for limnic Cerithioidean gastropods, in particular for (1) paludomids from East Africa (i.e., the thalassoid species from Lake Tanganyika and Potadomoides Leloup, 1953 in the Congo River system), (2) pachychilids Tylomelania Sarasin and Sarasin, 1897 endemic to lakes on Sulawesi in Indonesia, (3) Brotia H. Adams, 1866 in the Kaek River drainage in Thailand, and (4) Madagasikara Köhler and Glaubrecht, 2010 on Madagascar. With an increasing armamentarium of molecular genetic techniques for exploring the genetic structure of populations and species, the one mystery has become many, and possible solutions multiplied, as we uncover further complexities in what species really are and how they multiply.

What can living marine bivalves tell us about speciation in the marine environment? Three sets of literature data on Recent marine bivalves are analyzed for insight into the mechanisms behind bivalve speciation processes. (1) A dataset of all marine bivalves described as new to science during the years 2000–2009 (381 species in 135 published papers) reveals that malacologists are still describing undiscovered biodiversity, based largely upon newly collected expedition material. New species include those of both large and small body size (0.86-500 mm, mean 28 mm), from 51 bivalve families, all oceanic basins, and a wide range of water depths (intertidal to 7,333 m, mean 444 m). External shell characters dominate the diagnoses but are increasingly supplemented by anatomical, molecular, and phylogenetic evidence. Endemism is low (2.6%) when stated as such although another 57% of species were described as (thus far) restricted to a particular geographic region, habitat, or both. High percentages of deep-water and otherwise (geographically or ecologically) restricted species, plus several case studies, suggest that physiological specialization, in the form of bathymetrie limits, unique dietary adaptations, or host/symbiont associations, plays an important role in setting up barriers to gene flow in marine bivalves. (2) Bivalve species complexes [i.e., closely related, cryptic (possibly sibling) species with obscure morphological boundaries, or highly variable single species] also imply factors involved in ongoing speciation. Seven recently studied marine taxa are presented in which species complexes are either revealed or resolved by molecular data. Apparent barriers to gene flow are in most cases physiological (sympatric), or (in two cases) physical (allopatric), and in one case can be readily broken down by anthropogenic transport. (3) Two recent published phylogenetic analyses are discussed that show (a) disparately sized sister taxa with their synapomorphies (glochidia in Unionoidea; chemosymbiotic bacteria and mucus-tube feeding in Lucinoidea; cruciform muscle and long siphons in Tellinoidea; aortic bulb in Veneroidea) as recognized innovations that facilitated radiation of the more species-rich sister, and (b) polytomies in Lucinoidea that suggest rapid ongoing evolutionary change in several clades. Together these three sets of published data defeat the concept of a Marine Speciation Paradox in bivalves—speciation clues are merely subtler in marine bivalves and most often act at the physiological, rather than physical, level.

Using fossils to study speciation requires careful analysis of the potential and limits of both biological and geological data. The most important biological data for a particular taxon includes to what degree species can be distinguished based only on hard-part morphology, what processes lead to speciation in that group today, and at what rates speciation occurs. Among the most important geological considerations is whether the incompleteness of the fossil record makes it possible to specify to within a reasonable degree of confidence when and where a putative speciation event took place. In benthic marine macroinvertebrates, the latter analysis is complicated by the “Common Cause” phenomenon: sea level change is both a major potential cause of gaps in the record and an important potential cause of evolutionary change. We consider the potential and limitations of fossil data for providing unique insight into the patterns and processes of speciation in marine shelled gastropods. A review of biological data shows considerable variation in mode of speciation and correlation between shell morphology and genetic divergence (cryptic species). Through examination of the fossil records of turritelline gastropods (Cerithioidea, Turritellidae) from Cenozoic deposits of the U.S. Gulf and Atlantic Coastal Plains and New Zealand, we propose simple tests for judging whether a particular fossil record is adequate for drawing conclusions about pattern and process of speciation. We conclude that the fossil record of marine gastropods can provide valuable information for studying species and speciation, but only if great care is used in evaluation of the data.