Solen tehuelchus Hanley, 1842 is currently the only razor-clam reported from Brazilian waters. Although its shell is well known and similar to the other Solenoidea, their anatomical aspects are poorly studied. Recently some living specimens of S. tehuelchus were obtained from a Brazilian beach, allowing the removal of their testes for an ultrastructural analysis. In order to add a new anatomical feature for this species and provide a brief comparison between some related taxa, the shell and sperm ultrastructure were described in detail. The present study showed that characteristics of the spermatozoa of S. tehuelchus are similar to those of other solenids, although certain sperm ultrastructural characteristics such as a short acrosome with an electron-dense base and rounded nucleus are also similar to the species Tagelus plebeius (Lightfoot, 1786) (Solecurtidae). Herein, we have added new anatomic and taxonomic data hitherto unknown to science. The sperm morphology of S. tehuelchus, might in the near future bring new insights into the systematic of Solenidae.

Individuals can respond to predation risk by building morphological defenses or by altering their behavior. We tested whether freshwater Physa acuta (Draparnaud, 1805) snails with better morphological defenses against predation risk displayed lower or higher behavioral responses to predator cues compared to more poorly defended snails. We examined how the morphological traits of snails influence their risk of predation by crayfish, inferred by crush resistance, and how those same traits also influence their patch use in the absence and presence of predator cues. Using model selection, we found that a large shell width increased crush resistance. We also found that other morphological traits interacted with predator cues to influence the use of high resource patches, however shell width had almost no influence. Aperture length and aperture width both strongly interacted with cue: larger aperture length and larger aperture width snails decreased their use of the high resource patch substantially. Additionally we used a composite model to test whether estimated crush resistance, predator cue, or their interaction best predicted space use, and found no support that our estimate for crush resistance affected space use. Generally we found strong support that morphology effects crush resistance and also that morphology influences snail space use. However, crush resistance and space use are influenced by very different morphological traits.

We present evidence that the most recent redescription of Elysia patina Marcus, 1980, by Ortea et al. (2005) is incorrect. Instead, the redescribed characters used to classify E. patina exactly match those of Elysia papillosa Verrill, 1901. Therefore, Ortea et al.'s (2005) redescriptions of E. patina and E. papillosa should not be used.

Diphenhydramine HCl (DH) and caffeine are commonly detected contaminants in waterways and drinking water nationwide (U.S.A.) and yet little is known of their influence on the development of aquatic molluscs. The antihistamine diphenhydramine blocks the chemical effects of histamine by inhibiting the re-uptake of serotonin (5-HT). Caffeine can influence the regulation of calcium (Ca² ) and neurotransmitters, such as 5- HT, by inhibiting the re-uptake of adenosine. Serotonin receptor-mediated signaling is key during embryonic development in the freshwater snail Helisoma trivolvis (Say 1816). Embryonic development rates of H. trivolvis depend upon external conditions such as oxygen concentration and temperature. We examine the effects of diphenhydramine (DH) and caffeine on development and reproductive potential of this common aquatic snail. Concentrations of DH at 40.0, 50.0 and 60.0 µM affect the in-capsule embryonic development and hatching rate. Caffeine at 40.0, 50.0 and 60.0 µM show no influence to the hatching rates; however, these caffeine concentrations influence the in-capsule embryonic rotation rate. Eight-month observations of adult H. trivolvis reproductive activities show no influence in number of egg masses deposited when exposed to test concentrations of DH or caffeine.

A new species of Melanochlamys is described based on specimens collected in Russia and Korea. This new species is genetically and anatomically different from other North Pacific species. Phylogenetic analyses of two mitochondrial (COI, 16S) and a nuclear (H3) gene confirmed the results of previous analyses and recovered a clade including specimens of the new species. Although this clade is poorly supported, species delimitation analyses and anatomical differences confirmed it constitutes a distinct species. These results confirm the presence of two distinct species of Melanochlamys in Russia and Korea, bringing the total diversity of the genus in the North Pacific to five.

About 70% of freshwater mussel species in North America are threatened, endangered, or recently extinct. A large number of the surviving species are endemics. One hotspot for endemic diversity is the southeastern U.S.A. Lake Waccamaw in southeastern North Carolina contains two putative endemic unionids, Lampsilis fullerkati (Johnson, 1984) and Elliptio waccamawensis (Lea, 1863). We used multiple phylogenetic analyses to assess phylogenetic affinities and test the status of these named species. Mitochondrial 16S rRNA gene, cox1, and nad1 sequences were obtained from 109 individuals of the putative endemics and potentially related species from Lake Waccamaw, the Waccamaw River, and the Yadkin/Pee Dee, Little Pee Dee, and Lumber Rivers in the Pee Dee Drainage. In addition to the analysis of each individual gene region, a total evidence analysis, in which all three regions were combined, was conducted using Bayesian phylogenetic methods. All three genes were analyzed using both Bayesian and maximum likelihood methods to test the robustness of the phylogeny of the genus Elliptio (Rafinesque, 1819) and both methods produced consistent topologies with minor differences in the Elliptio “lance” clade. Results suggest that the status of the Lake Waccamaw putative endemics may need to be reconsidered. Lampsilis fullerkati is not phylogenetically distinct from L. radiata (Gmelin, 1791) from outside the lake, and Elliptio waccamawensis groups with and is not genetically distinguishable from E. congaraea (Lea, 1831) individuals from the Waccamaw River.

The Tallahatchie River, Mississippi, southeastern U.S.A., is a medium-sized waterway originating in the North Central Hills and flowing into the Mississippi Alluvial Plain physiographic province. Although the river's molluscan fauna remains relatively poorly studied, a survey by Haag and Warren (2007) of Lower Lake, an impounded, regulated segment of the Little Tallahatchie River high in the drainage, revealed a freshwater mussel assemblage that was surprisingly diverse and healthy given current stream management practices. Mussel assemblages from three prehistoric sites in Leflore County, Mississippi, further downstream on the main Tallahatchie River, yielded 32,303 valves representing 41 taxa, including 24 new river records, one of which, Quadrula fragosa (Conrad, 1835), represents a new state record and a notable range extension for this species. Comparison with modern data shows that about twice as many species existed in the waterway prior to Historic-era impacts, including five currently listed as threatened or endangered. These results highlight the importance of applied zooarchaeology for establishing conservation baselines.

One way that archaeologists provide unique conservation datasets is through the establishment of pre-Euroamerican baselines for animal communities that were part of human-environment interactions during the last few millennia. Freshwater mussel remains from archaeological sites offer a rich data source for establishing this type of baseline. We establish a conservation baseline for the late Holocene sandbank pocketbook (Lampsilis satura, Lea 1852) in the upper Trinity River of central and north Texas. These data may 1) lead to greater confidence in existing contemporary data for unoinid biogeography; 2) lead to information on whether or not community composition differs between the late Holocene and today; and/or 3) provide a justification for more intensive contemporary surveys. Such data are relatively easily acquired, inexpensive to generate, and highly informative for environmental management.

Deep-sea wood-boring bivalves of the genus Xylopholas Turner, 1972 are unified by a plate-like elaboration lateral to the siphon tips; this genus, known only from specimens under 4 mm in shell length, may provide essential clues to the group's phylogeny. Here three aspects of their biology are treated. A new species, Xylopholas dostwous sp. nov., is distinguished by the absence of a siphonal collar, gills that extend into the incurrent siphon, a curved posterior valve margin and a fleshy cover over the anterior adductors. Second, specimens nearly eight times larger than any in the type series of X. crooki Voight, 2007 show strong positive allometry of the fleshy Anterior Adductor Cover, forcing a reconsideration of the mesoplax (calcified plates over the anterior adductor muscle). Third, apparent dwarf males of Xylopholas may fuse with the female's mantle, allowing sperm to be released inside the mantle near the oviducts. Dramatic differences among hypothesized dwarf xylophagaid males suggest male dwarfism evolved repeatedly. A photomicrograph of the prodissoconch of a suspected dwarf male indicates larvae feed in the plankton. Combined, the unique and potentially plesiomorphic characters discussed here highlight how little we know of wood-borer evolution. Both Xylopholas crooki and X. dostwous sp. nov. are known only from artificial deployments that spent at least 22 months on the seafloor; additional collections are required to determine if the genus is restricted to long-sunken wood.

The bivalve mantle margin comprises the free portion of the pallial lobes, and often bears muscular, sensory or secretory structures located on extensions of the mantle, called mantle folds. In the bivalve Infraclass Pteriomorphia, which underwent an extensive adaptive radiation in epifaunal habitats, the mantle margin exhibits an enormous diversity in mantle fold organization and associated structures. The present work reviews the current knowledge of the mantle margin in Pteriomorphia and discusses how the mantle margin can be used as a model for investigating the evolution of the marine epifaunal benthos as many species in this community have undergone similar selective pressures and developed comparable morphological adaptations, such as ciliated tentacular organs. Herein, we stress how additional investigations are necessary to cover the huge diversity seen in this taxonomic group. Given the scarcity of broad comparative studies of bivalves, including Pteriomorphia, the homology of their pallial features is still not clear. Moreover, although it is suspected that mantle margin diversification is correlated with transitions in pteriomorphian life habits, no hypotheses have been tested within a phylogenetic framework. To address these questions requires extensive comparative analyses of mantle margin diversity in Pteriomorphia that focuses on: 1) genetic expression and molecular dynamics in the mantle margin; 2) mantle margin morphogenesis, 3) assessment and test of hypotheses on homology, convergent and parallel evolution of mantle margin characters, and 4) testing possible correlations between mantle margin morphological diversity and lifestyle transitions. In a broader sense, by using Pteriomorphia as a model clade, we will gain insight into the macroecology of the marine epifauna.

The ‘disco’ clam Ctenoides ales (Finlay, 1927) is an Indo-Pacific bivalve with an unusual reflective flashing display. The function of the flashing is unknown. Ctenoides ales is a suspension-feeder, so experiments were conducted to test the hypothesis that the flashing acts as a lure for planktonic prey items that are phototactic. First, the reaction of C. ales to a plankton stimulus was analyzed. Exposure to a concentrated plankton mix was followed by a significant increase in flash rate (Hz) for 5s, after which the rate returned to pre-stimulus levels. Next, two experiments were conducted to determine if potential prey (mixed phototactic plankton species <500µm, which were collected from the bivalves' habitat) were attracted to a simulation of C. ales flashing. The first experiment tested whether there was higher phototactic plankton density inside artificial clams with flashing lights than inside artificial clams that had constant lights, or lights that were turned off, but there were no significant differences between the three treatments. In the second experiment, a program played two illuminated lines on an electronic tablet screen that was exposed to experimental plankton. This second plankton experiment tested whether there was a higher phototactic plankton density collected over the line that flashed, mimicking the light spectra and frequency of C. ales, compared to the line that was constant. There was no significant difference in recorded densities between the two treatments. Plankton density was then measured inside the mantle cavity of C. ales in situ using SCUBA in Pemuteran, Indonesia (lat 8°17′ S, long 114°65′ E). Samples were taken twice daily to determine if phototactic plankton density was higher inside the clam when the flashing was visible (day) than when the flashing was not visible (dusk). Again there was no significant difference in the recorded plankton densities. Overall, the results from this study did not support the hypothesis that the flashing display of C. ales induced positive phototaxis in their planktonic prey.