Sexual differences in size and morphology are conspicuous features of dioecious organisms like octopuses. In this study, we analyze differences on body dimensions and the size and shape of Octopus hubbsorum Berry, 1953 stylets, using traditional and geometric morphometrics to ascertain if both methods can recognize differences between males and females. Traditional morphometrics revealed differences in body and stylet sizes because the females were bigger than the males, and the total body weight was the most related body measure with all the stylets measures. Due to the shape of the stylets we used two landmarks and 40 semilandmarks, and for the semilandmarks alignment we used two methods: minimization of bending energy (min BE) and minimization of Procrustes distance (min D), to test if the method to align semilandmarks influenced the analysis. Differences were found between the two methods, such as the mean shape, the percentage of predicted organisms to their corresponding sex in discriminant function analysis (DFA), and the relationships between stylet shape and body size as well as centroid size of the stylets; however, the deformation grids were similar between the two methods and their canonical variate analysis (CVA) found significant differences in mean shape of the stylets of males and females. These results demonstrated the morphometric sexual dimorphism in O. hubbsorum using body dimensions and the size and shape of the stylets.

Much is still unknown about why freshwater mussels (Unionidae) are particularly sensitive to environmental change. A better understanding of freshwater mussel metabolism is needed, and the field of environmental metabolomics holds the promise to inform these questions. A number of protocols exist for the extraction of metabolites for identification from animal tissues. As a first step in the application of environmental metabolomics to the study of freshwater mussels, we compared extraction protocols using an inorganic oxidizing acid (perchloric acid), an organic nitrile (acetonitrile), and a salt/water solution (Ringer's solution) to establish an uncomplicated, robust, repeatable and inexpensive tissue extraction protocol for freshwater mussel tissue. Perchloric acid resulted in notable extraction of energy-related nucleotides (AMP/ADP/ATP), yet had the lowest peak count of the three extraction methods and showed poor repeatability. Acetonitrile and Ringer's solution yielded metabolite extraction results similar to each other with Ringer's solution having the greatest number of peaks particularly in the 3.0–4.5 ppm sugar/amino acid range. Ringer's solution is simple to use, safe and consistent and bears consideration when selecting an extraction protocol for ¹H nuclear magnetic resonance experiments.

Although habitat alteration and degradation in riverine systems are the major threats to overall mussel assemblages to date, no or few studies have been able to document significant differences in habitat variables between species. The purpose of this study was to evaluate microhabitat associations of three federally threatened freshwater mussel species, Fusconaia burkei (Walker, 1922) (Tapered Pigtoe), Hamiota australis (Simpson, 1900) (Southern Sandshell), and Pleurobema strodeanum (Wright, 1898) (Fuzzy Pigtoe), and a common mussel species, Elliptio pullata (Lea, 1856) (Gulf Spike), at 3 localities in the Choctawhatchee River watershed in southeast Alabama and northwest Florida. Depth, current velocity, and compaction were measured, and a sediment core sample was collected for each individual mussel encountered. The Kruskal-Wallis H-test was performed to determine differences in each variable measured and each sediment size class among the mussel species at each site, followed by the Mann-Whitney U-test after applying Bonferroni's correction if significant. Six out of nine times, current velocity (3 times), depth (twice), and compaction (once) were significantly higher for the threatened species compared to E. pullata, whereas there were no differences in these variables between a set of any two threatened species within a site. This study suggests that E. pullata was associated with shallow and slow flowing water and loose sediment (usually stream banks), while the threatened species used deeper and relatively faster flowing water with more compact sediment. Anthropogenic disturbances are causing Coastal Plain streams to become more sand-bottomed and shallower, which is suited to species such as E. pullata and/or its host fishes, while the species in this study preferring deeper and faster flowing water and more compact sediments are in decline.

Morphological phylogenetic analysis of the mactrid subfamilies Mactrinae and Kymatoxinae, plus the mactroidean family, Anatinellidae, indicate that the Kymatoxinae shares closer common ancestry with the Anatinellidae than with the Mactridae. Kymatoxinae is, therefore, reassigned from Mactridae to subfamily rank within Anatinellidae. The lack of a pallial sinus in Anatinella G. B. Sowerby I, 1833 suggests that its family was derived from anatomically plesiomophic members of Mactroidea with at best only weakly developed siphons.

The Spheniopsidae Gardner, 1928 comprises four living species of Spheniopsis Sandberger, 1861 and eight of Grippina Dall, 1912, the latter restricted to the Pacific Ocean, the former also occurring in the Atlantic. Spheniopsis brasiliensis new species and Grippina coronata new species are described from the Brazilian southeastern coast, based on a detailed study of their shells. They are distinguished from already described species mainly by differences in the outline of the valves, external sculpture and right hinge dentition. Shallow micro-pits present all over the outer surface of the dissoconch are viewed as similar to those already described for cuspidariids. They may, thus, represent further evidence for the relatedness of spheniopsids and cuspidarioideans. The new species from Brazil represent the first finding of these rare minute bivalves of this family from the southwestern Atlantic.

The freshwater gastropod family Pleuroceridae suffers from a disproportionately high number of imperiled species and recent extinctions. As pleurocerid diversity has been lost, so too has our ability to study the biology of these animals. However, many extinct species were deposited in natural history collections before their demise. I extracted radulae from dried tissue left in shells of seven extinct species in three genera (Leptoxis Rafinesque, 1819, Gyrotoma Shuttleworth, 1845, Lithasia Haldeman, 1840) to gain insights into the morphological differences separating species and provide data for future researchers. There were notable intergeneric and interspecific differences in radular morphology such as shape of cusps (e.g., dagger-like vs. blunt) and number of denticles on the rachidian, lateral, and marginal teeth. Interestingly, the degree of radular differences among Leptoxis spp. likely corroborates previous hypotheses that the genus is not a natural group. These data are a resource for future studies and should aid in determining the feeding habits and relationships of extinct pleurocerids.

An introduced slug, Boettgerilla pallens Simroth, 1912, was found both in the Pedregal de San Angel Ecological Reserve, Ciudad Universitaria, Mexico City and Teopancingo, Puebla. Although this slug is native to Europe, it has been recently recorded from various locations around the world. Through dissection, the diagnostic characters were identified as the spindle shaped swelling along the vas deferens characteristic of the genus, and the elongate shape of the bursa copulatrix typical of this species. In addition, cytochrome oxidase I mtDNA, and 16S and 28S ribosomal RNA genes were sequenced and used in a phylogenetic analysis to confirm its identity.

The Chilean Fjords Region has been regarded as one of the most complex coastal systems of the world, with a high level of mollusk diversity. Contradictorily, bivalves from this region have been recently considered both well and insufficiently known. This study critically evaluates the current state of knowledge on bivalves from the Chilean Fjords Region, by combining information coming from previously published literature, the study of material housed at museum collections, and new data coming from recently collected material. Although a total of 223 species appear listed in the literature for the area, only 81 valid species have documented records, the remaining corresponding to nomina dubia/nuda, synonyms, misidentifications, species complexes or species which were listed for the area, but based on unknown sources. The present study makes evident that, after more than two centuries the knowledge on bivalve diversity from the Chilean Fjords Region still remains at its first stages.

Bivalves are one of the most abundant groups of invertebrates in many benthic communities. From 1817 to date, numerous contributions have dealt with the Argentine fauna of marine bivalves. Despite this, at present, there is no a text summarizing the currently available information on this group in Argentine waters. The present contribution aims to provide a synthesis of the current state of knowledge of systematics, geographic distribution, biology, and ecology of the living marine and estuarine species of bivalves from the Argentine coast and its shelf and, based on this information, to analyze the species diversity of these areas. For that, 225 publications, including results of scientific expeditions, systematic revisions, description of new species, new distributional records, checklists, compilations on the diversity for particular areas, and contributions dealing with biological and ecological information, were surveyed. As part of this study, 277 nominal species of bivalves were found reported for the study area, although only 169 of them are currently regarded as valid. The analysis of the available bibliography makes evident that the Argentine bivalves have been overlooked throughout the years. This fact results in several limitations and gaps in the current knowledge of this fauna, which are highlighted in the present revision.

The Olympia oyster, Ostrea lurida Carpenter, 1864, is the only native oyster on the west coast of temperate western North America and a conservation target for native species restoration throughout much of its known range, from British Columbia, Canada to Baja California, Mexico. This species was recently demonstrated to be genetically distinct from its southern congener, O. conchaphila Carpenter, 1857, but our new sampling, combined with previously published data, supports a tentative allopatric pattern, with the southern and northern species restricted to either side of Punta Eugenia in Baja California, Mexico, a known biogeographic boundary. We collected O. conchaphila and multiple co-occurring oyster species at 11 sites along the Pacific coast of Baja California Sur or within the Gulf of California, Mexico. Oyster surveys revealed at least six other co-occurring species, including two exotics, of Ostreidae Rafinesque, 1815 that were identified by sequencing 16S ribosomal DNA (16S) and cytochrome oxidase subunit I (COI) mitochondrial markers. In addition to our newly collected material, our phylogenetic analyses included Ostreidae from worldwide localities available in GenBank.

Phylogenetic estimates, using maximum likelihood, supported the sister species relationship between Ostrea lurida Carpenter, 1864 and O. conchaphila Carpenter, 1857. Together, they group as the sister lineage of Myrakeena angelica (Rochebrune, 1895), nested within a grouping of species currently assigned to Ostrea Linnaeus, 1758. Thus, we have revived the original name Ostrea angelica Rochebrune, 1895 and consider the monotypic genus, Myrakeena Harry, 1985 a junior synonym of Ostrea. We also collected O. equestris Say, 1834, native to the Caribbean and not previously reported in the Eastern Pacific. Our results are consistent with the recognition of only four subfamilies within Ostreidae: Ostreinae Rafinesque, 1815, Crassostreinae Scarlato and Starobogatov, 1979, Saccostreinae Salvi et al., 2014, and Striostreinae new subfamily. Another subfamily, Lophinae Vialov, 1936, is best synonymized with Ostreinae because it would otherwise be paraphyletic to that taxon. Sequences of Saccostrea palmula (Carpenter, 1857) revealed a striking lack of genetic variation that contrasted with their substantial phenotypic plasticity. Surprisingly, the morphologically distinctive species, Ostrea tubulifera Dall, 1914, was revealed as an ecotype of S. palmula, and so is herein considered a junior synonym of the latter species.

The temperate zone of the southwestern Atlantic Ocean (23–42°S), which includes the Patagonian Shelf Large Marine Ecosystem and the Subtropical Convergence Zone, is one of the most productive areas of the Southern Hemisphere. Key features of this region are a wide continental shelf, the convergence of cold and warm currents, and continental freshwater input of the La Plata River. The Uruguayan marine and estuarine waters are at the core of this zone. The marine and estuarine bivalve fauna of Uruguay has received good attention since the publication of the Voyage of Alcide d'Orbigny (1834–1846). Here we provide an overview of taxonomic, faunistic and biogeographic issues, identifying knowledge gaps and highlighting priorities for future research. The main threats for that fauna are discussed, with emphasis on species of current or potential socioeconomic interest. Of the 231 species reported from the area, only four species are strictly estuarine: Erodona mactroides Bosc, 1801, Tagelus plebeius (Lightfoot, 1786), Brachidontes darwinianus (d'Orbigny, 1842) and Mytella charruana (d'Orbigny, 1842). All of these have large biomasses, as is also the case for the marine eurihaline Mactra isabelleana d'Orbigny, 1846. A total of 112 deep-sea species (i.e., living deeper than 200 m) are recorded for the region, including almost every known group occurring elsewhere in deep-sea basins, with the exception of sunken wood associated species. Of these, 38 have been recorded only from the Argentine Basin. Some new records are preliminarily reported and discussed, including Acharax Dall, 1908 (Solemyidae), Lucinoma Dall, 1901, Graecina Cosel, 2006 (Lucinidae), and Callogonia Dall, 1889 (Vesicomyidae), all from the continental slope. A total of 19 warm and warm/temperate bivalve species have their southern distribution boundary in Uruguayan waters associated to warm waters of/or derived from the Brazil Current, including species distributed from the U.S.A. to Uruguay or from southeast Brazil to Uruguay. On the other hand, at least eight exclusively cold-water bivalves exhibit their northernmost distribution boundary off La Plata River; their occurrence there is associated with offshore sub-Antarctic waters. Uruguayan waters represent a critical biogeographical and ecological crossroads because of the complex interaction of currents and water masses. This region is thus particularly well suited as a system for the study of processes underlying biodiversity patterns. Pending challenges in taxonomic and biogeographic research will be successfully addressed only if multinational collaborative initiatives are undertaken in a framework of integrative taxonomy.

Many marine invertebrate clades exhibit diverse developmental modes, including planktotrophic, lecithotrophic and direct development. Evolutionary transitions among the developmental modes can be common and may have macroevolutionay consequences. The marine bivalve genus Lasaea (Brown, 1827) is composed of almost exclusively direct developing species, except for one planktotrophic species — Lasaea australis (Lamarck, 1818). To test whether L. australis represents an independent evolution of planktotrophic development or the retention of an ancestral trait, we estimated the ancestral developmental mode for Lasaea using phylogenetic comparative approaches. Our results show that the ancestral developmental mode of Lasaea is likely planktotrophic and multiple independent evolution of direct development has occurred in this genus. The repeated loss of planktotrophic development may be linked to the unusual asexual reproductive mode in Lasaea, but this hypothesis needs to be further corroborated. Our analyses also highlight the importance of using biologically realistic models for ancestral state reconstructions.

Mollusks are among the most diverse and abundant animal groups, inhabiting many aquatic and terrestrial environments. They are important ecosystem engineers, helping to structure aquatic bottom environments and providing habitat, protection, and food to a wide array of other taxa. Mollusks have been historically important to humans in many ways, and are today an economically important group worldwide. As major calcareous organisms with an extensive fossil record, they can provide important information on past climate events and oceanic changes, thus, increasing our understanding of predicted future changes. This paper presents an overview of the use of mollusks in environmental and impact studies, to provide a baseline towards a wider use of this diverse group ( and the valuable collections housed in many museums) as proxies in environmental reconstruction, climate change, ocean warming, and acidification research.

Around the year 2000, populations of inconspicuous, 5-mm hydrobiid snails were discovered at several semi-isolated marshes around San Francisco Bay, California, where freshwater meets salt water. Coring indicated these are native species, including Tryonia porrecta (Mighels, 1845). The present, long-term monitoring at some of these sites with and without these small snails suggested that these abundances tend to be quite stable, through present 2014 sampling. But the recent, record drought since 2012 risked high salinities in these vulnerable brackish areas, including a site with the normally rare California Brackish Water Snail, Tryonia imitator (Pilsbry, 1899). Sites in presently 100% seawater at Elkhorn Slough on nearby Monterey Bay, once with frequent T. imitator brackish water snails yielded only dead shells during this past 15 years, among large, introduced predatory snails. Yet a more isolated site nearby at 50% seawater yielded small (3 mm) T. imitator brackish water snails observed (live) on green algae among pickleweed, at warm (30 °C) water temperatures, with no other gastropod species, soon after rare rains during the drought, in April, 2014. Isolated marshes may have advantages in slowing colonization of invasive species. Despite vulnerability of semi-isolated brackish-water sites to elevated salt during drought, some sites maintained these native snails (without invasive snails) even after drought.

Despite the mollusks being the second largest group in Kingdom Animalia, they have not been considered in environmental risk assessment so far, mainly due to the lack of standardized protocols. In this sense, the gastropods, with abundant species widely distributed in aquatic environments, have been employed in water and sediment quality assessments due their clear sensitivity to chemical compounds, as pollution indicators for different substances. Acute and chronic toxicity tests have been mostly used in ecotoxicological protocols to evaluate potential effects of contaminants on natural populations. However, with the need to assess potential sublethal hazards to ecosystems of pollutants at low concentrations, environmental monitoring programs have encouraged analyzing effects on gametes, fertilization, reproduction and embryo-larval development. Furthermore, among the myriad of chemicals reaching the environment, some compounds can directly affect the reproductive potential through induction of mutations in germ cells and vulnerable embryos. This work discusses some case studies of standardization assays with freshwater snails, especially good organisms for laboratory and in situ monitoring studies, to be considered for regulatory environmental agencies. In that context, this work also shows the prospects for using gastropods in monitoring freshwater environments in Latin America.

In this work, the toxicity of 11 products (three brands of mouthwash, three toothpastes, three detergents and two analgesics) was evaluated in relation to juvenile snails Physa acuta (Draparnaud, 1805). Bioassays of toxicity were conducted and the organisms exposed to six concentrations of each product, along with a control group, to determine the 96-hour LC₅₀ (Lethal Concentration 50). The sensitivity of the gastropods to the different products was determined by comparing their LC₅₀ values to that of acute toxicity values. In addition, the degree of lipoperoxidation in the gastropod tissue was evaluated by measuring the concentration of MDA (malondialdehyde) in sublethal tests (LC₁₀) for chronic toxicity (during 30-day exposure). The toxicity of the products tested varied from highly toxic and harmful (mouthwashes) through harmful (detergents), potentially harmful (analgesics), and non-toxic (toothpastes). The degree of lipoperoxidation observed in the sublethal tests was (from most to least toxic): Analgesics > Mouthwashes > Detergents > Toothpastes. These results indicate that a certain risk exists resulting from the presence in wastewater dumped into aquatic systems of components of these products which may cause adverse effects on populations of P. acuta and other aquatic organisms.