American Malacological Bulletin

Online ISSN: 0740-2783
Publications
Article
Light sensitive rhabdoms in the octopus retina increase in cross-sectional area in the dark and shrink in the light. Growth in the dark is due to the formation of microvilli in an avillar region of the photoreceptor cell membrane and lengthening of rhabdomere microvilli already present. Diminution in the light is the result of the disassembly and shortening of the same microvilli. Each microvillus contains an actin filament core that must be assembled or disassembled in the dark or light, respectively. To understand the regulation of the construction and breakdown of rhabdomere microvilli in the light and dark, we used centrifugation to separate the rhabdom membranes followed by Western blotting and Rho pull-down assays to investigate the role of Rho GTPases in this process. Western blotting showed a difference in the distribution of Rho in rhabdom membrane and supernatant fractions. In the light, Rho was mostly present in the supernatant but in the dark it was found in the fraction enriched with rhabdom membranes. Complementing these results, pull-down assays showed that Rho is activated in the dark but in the light, Rho is mostly inactive. We believe that in the dark, activated Rho binds to the rhabdom membrane and initiates signaling pathways, leading to growth of rhabdomere microvilli. In the light, Rho is present in the soluble fraction, is inactivated, and is likely bound to a Rho GDI. Receptors involved in the activation of Rho in the dark are undetermined and may involve rhodopsin or another membrane protein.
 
Article
The physical structure and mechanisms of biomineralizatìon have been elucidated in the major lateral teeth of the chiton genus Acanthopleura with the aid of light and scanning electron microscopy and energy dispersive spectroscopy. Following its recent revision, this genus currently consists of 15 species, including three species suppressed as synonyms. Specimens representing all 18 (nominal) species have been examined. With two exceptions, the major laterals are typically discoid and unicuspid with only limited interspecific variation. The teeth of A. loochooana are also essentially discoid but have a small, distinct distal indentation, while those of A. rehderi possess four short rounded denticles. Biomineralization in all species of Acanlhopleura occurs in architecturally discrete compartments and, with the exception of A. rehderi, is consistent in all tooth regions except the cusp core, where A. curtisiana, A. miles, A. araucariana and A. loochooana differ in having substantial amounts of iron. The first three of these species were previously included in the genus Squamopleura and there is evidence to suggest that this genus should not have been suppressed. The substantial difference in tooth structure between A. rehderi, with its four denticles and total lack of a lepidocrocite region, and that of other members of the genus Acanthopleura suggest that this species may be more closely aligned with Onithochiton. The inclusion of additional characters, such as tooth biomineralization, is strongly recommended in future studies of chiton taxonomy.
 
Relationship between food consumption and egg production in snails reared under LD (Long Day, circles) and MD (Medium Day, squares) conditions with the three feeding cycles. White fill, regimen 3; intermediate fill, regimen 2; dark fill, regimen 1. The lines are fitted to all the data of the MD and LD groups, respectively.
Article
With the aim of integrating the physiology and evolutionary ecology of Lymnaea stagnalis (Linnaeus, 1758), we studied the effects of day length and food availability on the energy budget. Snails were assigned to two different photoperiods and three levels of food availability. The snails were kept individually, and food consumption, growth, and egg production were measured for about 2 months. Snails could nearly compensate for a one-day starvation period by increasing the rate of food-intake. However, food-intake rates did not increase further after a starvation period of 2 days. Growth was well described by the Von Bertalanffy growth equation. The ultimate size of snails kept under medium-day conditions (MD; light:dark = 12:12 h) was not affected by food availability. By contrast, the ultimate size of snails kept under long-day conditions (LD; light:dark = 16:8 h) depended on food availability; those fed the lowest quantities grow the least. Dry-weight densities (dry weight/wet weight) of MD snails were considerably above those of LD snails. In MD snails, food availability did not appreciably affect dry-weight density. By contrast, in LD snails, dry-weight density decreased with decreasing food availability. The reproductive output of LD snails declined with declining food availability, but was 2 to 4 times that of MD snails. The difference in reproductive output was largely accounted for by the difference in stored energy, i.e. dry-weight density. To gauge the extent to which the conclusions from our laboratory work applied to free-living snails, a field study was conducted. The wild-caught snails' dry-weight density was also lowest in long-day conditions when most eggs were laid. However, the dry-weight densities during medium and short days were lower than the dry-weight densities of laboratory animals under LD conditions. Thus, in the field, snails stored less energy than in the laboratory.
 
Article
In 2002, the U.S. Department of Agriculture requested assistance from the American Malacological Society in the development of a list of non-native snails and slugs of top national quarantine signifi cance. From a review of the major pest snail and slug literature, together with our own experience, we developed a preliminary list of gastropod species displaying signifi cant potential to damage natural ecosystems or agriculture, or human health or commerce, and either entirely absent from the United States to our knowledge or restricted to narrow areas of introduction. Comments on the list from the worldwide malacological community were then solicited and led us to modify the original list. We then evaluated the taxa on this list by ranking them according to 12 attributes - - -seven biological variables and fi ve aspects of human interaction - - -based on thorough review of the detailed literature. The ranked list that emerged from this risk assessment process included 46 taxa (species or species-groups) in 18 families. The highest ranked taxa were in the Ampullariidae, Hygromiidae, Cochlicellidae, Helicidae, Veronicellidae, Succineidae, Achatinidae, and Planorbidae. We validated the risk assessment model by scoring a suite of non-native snail and slug species already present in the United States. The list is not defi nitive but rather is offered as a framework for additional research. There remain important gaps in biological knowledge of many of the taxa evaluated, and rigorous reporting of economic impacts is extremely limited. We expect the prioritizing and listing of taxa to be dynamic, not only as these knowledge gaps are fi lled but also as environmental, agricultural, international trade, and societal factors change.
 
Article
Two egg masses of the ommastrephid squid Todarodes pacificus (Steenstrup, 1880) are described. Immature squid were collected from inshore waters of southern Hokkaido, Japan, and maintained in a raceway tank where they matured, mated, and spawned. Both gelatinous masses were spherical and nearly neutrally buoyant. The larger mass measured 80 cm in diameter and contained approximately 200,000 eggs. The egg-mass surface layer effectively prevented crustaceans, protozoans, and bacteria from infesting the masses. Paralarvae hatched after 4-6 days at 18-19°C and actively swam at once, with many individuals swimming at the surface. Both masses disintegrated soon after hatching. Paralarvae died approximately 6-7 days after hatching, presumably due to starvation.
 
Article
A glutaraldehyde fixative developed for preserving the radula superior epithelium of the adult chiton Acanthopleura hirtosa (Blainville, 1825), was used in conjunction with conventional and microwave-assisted sample processing to produce high quality tissue preservation for light and electron microscopy. In addition, high-pressure freezing (HPF) and cryo-substitution were used to fix the radula tissue of juvenile specimens. Microwave-assisted fixation was preferred to conventional bench-top techniques due to the superior preservation of fine cell structure together with reduced processing times and chemical exposure. Although restricted to very small (<200 μm) samples, the quality of juvenile radulae processed by HPF was excellent. The improvements in tissue preservation using microwave and cryo-preservation techniques are therefore critical for obtaining accurate ultrastructural information on the radula in marine molluscs. In particular, these findings highlight additional processing options available for the study of cellular structures in biomineralizing tissues.
 
Article
We collected six species of freshwater snails from Dominica, including Biomphalaria kuhniana (Clessin, 1883), Gundlachia radiata (Guilding, 1828), Helisoma (=Planorbella) trivolvis (Say, 1817), Melanoides tuberculata (Müller, 1774), Neritina punctulata Lamarck, 1816, and Physa marmorata Guilding, 1828. Our collections indicate that un-reported species such as G. radiata and H. trivolvis are established on Dominica, West Indies. We tested a limited number of M. tuberculata for rickettsial pathogens, Neorickettsia spp., but did not identify this agent. Three species of snails previously reported from Dominica, Biomphalaria glabrata (Say, 1818), Biomphalaria straminea (Dunker, 1848), and Thiara granifera (Lamarck, 1822), were not collected. Our data suggest that B. glabrata has not re-emerged as a prominent component of the freshwater snail fauna since it disappeared or was locally eradicated. In addition, previous reports of B. straminea were probably misidentifications of B. kuhniana, and some abnormally large specimens of M. tuberculata from Freshwater Lake could be misidentified as T. granifera. Our sampling was not adequate to demonstrate that T. granifera was absent from Dominica. We determined that B. kuhniana was not eradicated by previous molluscan control regimes. Additional studies on the relationships of freshwater snails in Dominica to helminths of animals and humans are needed to understand the public and veterinary health significance of these snails.
 
Article
The present study establishes for the first time an atlas for the normal development of Todarodes pacificus Steenstrup, 1880, from fertilized egg to rhynchoteuthion paralarva. In the course of the study, observations on embryogenesis and histological differentiation in T. pacificus were made for consideration of the developmental mode of the Oegopsida, which is a specialized group with a reduced external yolk sac. It appears that differentiation of the respiratory and digestive organs is relatively delayed in the Oegopsida, with reduction of the yolk sac as well as the egg size. These characters could be related to a reproductive strategy for paralarval dispersion in the open ocean.
 
Article
Embryonic development and survival of paralarvae of the Japanese common squid, Todarodes pacificus (Steenstrup, 1880), were examined at 16 temperatures (3-29°C) to determine the optimum temperature range for development and survival. Normal embryonic development occurred at temperatures between 14.0° and 26.0°C, with highest embryonic survival rates occurring between 14.7° and 22.2°C. The relationship between temperature (T) and the number of days from artificial fertilization to hatching (D) is expressed by a polynomial function: In(D) = 4.73 - 0.227(T) + 0.00304(T2). A modified formula, based on observations of two egg masses spawned in captivity, was used to estimate the development rate of eggs within naturally spawned egg masses. It is suggested that T. pacificus spawns in waters warmer than 12.1°C, and egg masses maintain their structure for 4.0 - 9.5 days before disintegrating at temperatures between 14.7° and 22.2°C. Paralarvae survived up to 13 days after hatching, with the highest survival rates occurring at 15°C.
 
Article
There are few studies on pelagic mollusks from the California Current, despite their ecological importance and vulnerability to climate change (e.g., ocean acidification and hypoxia). We analyzed abundances of holoplanktonic mollusks during three years (2006-2008) along a transect-line parallel to the Baja California coast. The main differences in physical factors were increasing temperature and salinity from north to south, and lower dissolved oxygen concentration south of Punta Eugenia (28°N). The lowest oxygen concentrations occurred in summer, with hypoxic conditions (< 0.5 ml · L⁻¹) in the upper 100 m depth at some locations. Planktonic mollusk abundance did not differ along the latitudinal gradient, excepting Desmopterus pacificus Essenberg, 1919 and individuals from the genus Pterotrachea Forskal, 1775. In contrast, the temporal variability was high, mainly in a seasonal scale but also among years. The influence of El Niño 2006-2007 and La Niña 2007-2008 were evident by a sharp increase of Corolla spectabilis Dall, 1871 in April 2007 during the El Niño-La Niña transition. During 2008, pelagic mollusks remained with moderate abundance in winter-spring despite the high chlorophyll concentrations recorded (up to 3.26 mg · m⁻³). Subsequently, during the relaxation of a first pulse of La Niña in July 2008, there was a rebound in the abundance of the heteropod Atlanta Lesueur, 1817. and individuals in the Order Gymnosomata. The oxygen gradient inversely influenced mollusk abundance in most of the genera (Clio Linnaeus, 1767, Limacina Bosc, 1817, Atlanta, and Firoloida Lesueur, 1817) and the order Gymnosomata, but for Cavolinia Abildgaard, 1791, Creseis Rang, 1828, Desmopterus, and Pterotrachea, the salinity gradient was more influential. Therefore, holoplanktonic mollusks genera were useful indicators of climatic variability.
 
Collection localities for the fi ve Praticolella populations listed in Table 1. A-Praticolella candida, B-P. trimatris, C-P. taeniata, D-P. salina 2, E-P. salina 1. 
Unrooted neighbor-joining tree of fi ve Praticolella populations based on Nei's genetic distance. Population information is given in Table 1. 
Pairwise Fst values between Praticolella populations.
Article
We developed and characterized 13 polymorphic microsatellite loci in South Texas species of Praticolella von Martens, 1892 (Gastropoda: Polygyridae), some of which have restricted distributions and can be difficult to identify using traditional shell characters. To make this genomic tool more broadly useful in these species, instead of characterizing loci in many individuals of a single species, we tested them across five populations of four different species. Twelve loci amplified in all four species tested, and eleven loci showed deviations from Hardy-Weinberg equilibrium. These loci will be valuable in assessing species identity and population genetic connectivity among South Texas Praticolella.
 
The δ 13 C values of stomach contents for labeled (gray) and 
Gill tissue analyzed with and without δ 13 C label across 
Foot tissue analyzed with δ 13 C label across a range of 
Article
Bacteria are ingested by suspension feeding bivalves and can be an important component of their diet. This study evaluated whether a common bacterium of vertebrate enteric origin, Escherichia coli (Migula, 1895), is retained in the stomach or gill by two different freshwater bivalve species, Corbicula fluminea (Müller, 1974) and Elliptio complanata (Lightfoot, 1786). A series of diet treatment experiments were conducted comparing each anatomical section using a δ13C label and E. coli cells grown from stock cultures. A significant difference in δ13C values was related to anatomic structure among all treatment groups during a 7-day feeding experiment (24 jars, df = 140; F = 4.88; P < 0.001). A key finding was that in gill tissue, a significant difference was observed among <δ13C-labeled and unlabeled treatment combinations for both C. fluminea and E. complanata (F = 13.57; df = 31; P < 0.0001). The results suggest that water column E. coli are likely retained on gill tissue and to a lesser degree in the stomach in both E. complanata and C. fluminea. This study serves to validate the hypothesis that E. coli may be initially more abundant in gill tissue during sorting processes before being transferred to the stomach.
 
Article
Anthropogenic impacts on marine environments can be far-reaching and variable, and in an effort to mitigate these impacts, marine protected areas (MPAs) have been established globally. Indirect effects of MPAs on marine food webs and consumer behavior can be revealed through the diet of generalist predators, like octopuses, since their diet is a reflection of both preference and prey availability. Octopuses (Octopus bimaculatus Verrill, 1883) and invertebrate prey species were collected around Santa Catalina Island, CA in the summer of 2012, 2013, and 2014, and muscle tissues were analyzed for δ¹³C and δ¹⁵N. The δ¹³C and δ¹⁵N signature of octopuses caught within the MPA area and the non-MPA area were compared within diet space. Estimated contribution of prey species to octopus diet was calculated using a Bayesian mixing model. Octopuses caught in MPA areas had significantly different isotopic signatures than octopuses caught outside MPA areas in 2012 and 2013, but not 2014. Prey contributions to diet were highly variable between areas and years. Bivalves were a consistent contributor to MPA octopus diet, and the large snail Megastrea undosa (W. Wood, 1828) made up a relatively large proportion of the diet of octopuses from all areas and years. Additionally, there were more moray eels, a nocturnal predator outside MPA areas but more diurnal predators inside MPA areas. These results suggest octopus foraging behavior could be influenced by variation in predation risk reveal an indirect impact of diurnal predator recovery in the MPA. To fully understand the impact of anthropogenic change on marine environments, we must assess changes in the entire community and the interactions that drive community function.
 
Article
Phylogenetic relationships for extant cephalopods have been based, so far, mainly on morphology and paleontology. Nucleotide sequence data are still rare. Sequence analyses from the 3' end of the 16S rDNA gene of cephalopods have shown that this portion of gene can provide valuable information on taxonomic relationships at the infrafamilial level. Another mitochondrial gene, cytochrome oxidase III, is investigated to analyze higher (i. e. ordinal) taxonomic levels. The results obtained by the two gene portions are compared, but the low number of species does not allow a definitive answer on interfamilial relationships. The low divergence between nucleotide sequences of two populations of Loligo vulgaris Lamarck, 1798, and of L. reynaudii Orbigny, 1845, suggests that the latter is not a clearly distinct species. The grouping of the three families of Sepioidea (Sepiidae, Spirulidae, and Sepiolidae) is not supported. Idiosepiidae groups with the oegopsid squid Enoploteuthis irregardless of the analysis (parsimony or distance).
 
Article
The gametogenic cycle of a population of Brachidontes exustus (Linné, 1758) was studied from January to December 1993 at the northern beach of Wassaw Island, Georgia. Staging values were assigned for Gonadal Indexing (GI) of histologically prepared gonadal tissue: 1 = spent; 2 = partially spawned; 3 = early active; 4 = late active; 5 = ripe. From January to March and September to December, males had significantly higher (ANOVA, p = 0.0249) GI values when compared to females. Because male and female GI showed no significant difference (ANOVA, p = 0.1244) over the major reproductive period (April to August), they were averaged per sample period. Rapid gonadal development occurred from March to mid-May and follicles were ripe by mid-July. A minor spawn might have occurred in late July. A major spawn occurred from September to November. Of 261 animals sampled, the sex ratio was significantly different (Chi-square = 7.48; p < 0.05) from parity (1.00 female:1.43 male) and 9.6% were sexually undifferentiated. The greatest percentage of sexually undifferentiated individuals occurred in March (66.7%) with fewer from January to April. No hermaphrodites were observed.
 
Article
In order to aid identification of larval and post-larval stages of mytilid species, the green mussel Perna viridis, we describe morphological features of larval and post-larval shells of P. viridis using both an optical microscope and SEM. The features are based on specimens obtained by artificial rearing in laboratory. Umbo and post-larval stages of P. viridis are clearly distinguished from the other mytilids that have been described by past studies, except P. canaliculus and P. perna.
 
Article
Rumina decollata (Linnaeus 1758) is native to the Mediterranean region of Europe and north Africa. The first report in Argentina was in 1988 in Buenos Aires. In 2007, it was found in La Pampa and Mendoza. Here, we report its presence in Córdoba, extending its distributional range northwards more than 600 km. This finding is significant given that Rumina decollata is a facilitative predator and can deleteriously impact mollusk assembles causing ecological imbalances.
 
Map indicating the locality of collection of Perna viridis in La Restinga Lagoon, Isla Margarita, Venezuela.  
Fignre 2. Red mangrove roots in La Restinga Lagoon, from where the material was collected.  
Article
The Asian green mussel Perna viridis was first recorded in the Americas in 1992 at Trinidad Island. In 1995 it was observed in the mainland coast of South America at Sucre State (Venezuela) and in 1998 at La Restinga Lagoon, Margarita Island, Venezuela. We studied the size at sexual differentiation, size at first maturity, and gametogenesis of P. viridis from La Restinga Lagoon using histological sections. One hundred specimens of P. viridis between 8 and 91.2 mm in total shell length were examined. No gonadal development was observed in individuals smaller than 18 mm. Sexual differentiation began at 20 mm with incipient follicular formation. Specimens larger than 25.0 mm had well-developed gonads at different stages of maturation. Size at first maturity was larger than previously reported at other localities. Because the lagunar mangrove system is permanently open to the sea, larval supply could come either from outside or inside the Lagoon, assuring the recruitment of new spat and the dispersal of the species. The introduction of this invasive species into the Lagoon has increased the available hard substrata for settlement of sessile invertebrates.
 
Map showing locations where Nautilus pompilius pompilius was live-caught in 1987 and 2011. A, illustrated specimens were trapped at ~150-300m depth off village of Eri, 6km S of Ambon City, Ambon (WBS, LCH; 1987). Ambon, (Molucca Islands), should be regarded as the type area for the genus, species and subspecies (See Beekman 1999 and Nikolaeva et al. 2015 for historical accounts.). B, a second population of Indonesian Nautilus pompilius was live-caught in 2011 in the Sumbawa-Lombok regions at ~200-250m depth (RHM).
Species, sample locations, voucher 1 numbers, and Genbank accession numbers for samples of Nautilus and Allonautilus.
The 50% condensed tree of the Maximum Likelihood analysis of the combined COI and 16SrRNA sequence data for haplotypes of Allonautilus scrobiculatus (Manus, PNG); Nautilus macromphalus (New Caledonia-Loyalty Is.); Nautilus pompilius s.l. (Vanuatu); N. pompilius s.l. (Carter Reef, GBR, Australia) N. belauensis (all specimens labeled Palau); and N. pompilius s.s. (Ambon, Molucca Is.; Moyo Island, Salah Bay, Sumbawa-Lombok (southcentral Indonesia). All individuals labeled "Ambon" are topotypes of N. pompilius pompilius and USNM 816877 is the proposed neotype. (Nikolaeva et al. 2015).
Article
The taxonomic history of Nautilus pompilius Linnaeus, 1758, the most widely distributed species of Nautilus Linnaeus, 1758, is complex, mostly owing to the antiquity of the earliest description by the naturalist Rumphius (Rumpf) in 1705. His account of its habits and illustrations of soft anatomy of specimens from Ambon, Molucca Islands, Indonesia were cited by Linnaeus in his description of N. pompilius. Nevertheless, there is almost no information on Nautilus in Indonesia. Live-caught animals (n = 44) from 150-400 m depth off Ambon provide the first morphologic and genetic details on Nautilus pompilius from the type region, including a recently proposed neotype for the type species. An additional sample (n = 62) obtained from the Sumbawa-Lombok Islands area, Indonesia, 1,500km to the southeast appears identical to those from Ambon. These populations have the largest known mature shells (mean ∼198mm diameter, ∼1,160 g shell plus body weight) of any of the numerous Indo-Pacific occurrences of Nautilus pompilius s.l. presently assigned to this species. Aside from size, few major phenotypic aspects differ from other populations of the species throughout its broad Indo-Pacific range. Data from two mitochondrial DNA gene regions identified a strongly supported clade comprising Ambon, Sumbawa, and Philippines N. pompilius s.s. These new data provide a baseline for evaluating genetic, phenotypic and geographic variation in the broadly distributed species N. pompilius s.l., as well as for establishing taxonomic relationships in populations of living Nautilus, including N. pompilius pompilius Linnaeus, 1758.
 
Article
The Verdigris River in Kansas and Oklahoma, USA once held a diverse native unionid mussel fauna although a number of these populations have declined in richness and abundance. There is recent evidence that populations of some species of unionid mussels are increasing in parts of the Verdigris River in Kansas, but no current data exist for Oklahoma. In addition, zebra mussels (Dreissena polymorpha Pallas, 1771) have been introduced into a major impoundment on the Verdigris River, Oologah Lake, and may further threaten mussel populations downstream from this reservoir. This study updates the distribution and abundance of native mussels in the Oklahoma portion of the Verdigris River upstream and downstream of Oologah Lake, and documents the current distribution of zebra mussels in this region. Thirty-one sites were sampled and a significant increase in species richness and abundance of native mussels was observed as compared to a 1997 study. Two species of special interest, Cyprogenia aberti (Conrad, 1850) and Quadrilla cylindrica (Say, 1817), were found. Zebra mussels were not found at sites upstream of Oologah Lake but were present at every downstream site. In September 2006, zebra mussel byssal threads were observed on shells of a number of native mussels downstream from Oologah Lake, but unionid richness and abundance were not significantly different between sites above and below the reservoir.
 
Mínimum and Máximum valúes of shell length in European Cor bicula populations.
Article
Two populations of Corbicula fluminea were found in the Iberian Península; one in Spain and the other in Portugal. A detailed description in terms of ecology shell morphology and microstructure, morphometrics and anatomy is given for the Spanish population from the Mino River. Lectotypes for Tellina fluminea and T. fluminalis, and a neotype for T. fluviatilis are designated and illustrated. Distribuüon and spread of C. fluminea in Europe are revised. Comparisons among some European populations and the populations from Cantón, China, and the Mino River are made. Results suggest that, except for one doubtful population, all records of Corbicula in Europe are attributable to C. fluminea. Corbicula taxonomy begins in 1774 with Müller who described three species in the genus Tellina Linne, 1758: T. fluminalis "in fluvio Asiae Euphrat"; T. fluminea "in arena fluviali Chinae"; T. fluviatilis "in ilumine emporium Can tón Chinae praeterlabente". Since then, many living species of Corbicula Mühlfeldt, 1811, have been described in freshwater and estuarine habitáis from Southeast Asia, the Indian subcontinent, the Pacific islands, and the easternmost part of Europe and África (McMahon, 1983). The fossil record of Corbicula includes Europe, North América and Japan (see Linstow, 1922; Zhadin, 1952; Ellis, 1978; and Britton and Morton, 1979 for a review). The first published record of Corbicula in North América is that of Burch (1944) in 1938. Counts (1981, 1985) cites the presence of the species in 1924 and 1937 in Nanaimo, Vancouver Island, British Columbia, Canadá, and in Ray-mond, Pacific County, Washington, respectively. Since then, it spread widely in most lotic and lentic habitáis, being a pest with very important economic and ecological effects (Sinclair and Isom, 1963; McMahon, 1983). Many papers have been published with records of new localities and biological data using different species ñames, mainly C. fluminea, C. manilensis and C. leana (McMahon, 1983 and references therein). Several hypotheses about the importance of the role of human activities in the spread of Corbicula have been treated (e.g. Thompson and Sparks, 1977; McMahon, 1982). The wide geographical and ecological range of Cor bicula seems to be related to the great variation in shell form and colour. These two features are the most common tax-onomic characters and the only ones used by the early conchologists, suggesting that Corbicula taxonomy probably involves more species ñames than needed. Thus, Talavera and Faustino (1933) {In: Britton and Morton, 1979) placed Corbicula manilensis (Philippi, 1844) into synonymy with C. fluminea, Morton (1977) considered C. leana to be a júnior synonym of C. fluminea, while C. fluviatilis was previously placed into synonymy with C. fluminea by Prashad (1929). Moreover, a thorough review by Britton and Morton (1979) lead the authors to consider that most Asiatic species previously described could be attributed to two taxa: the freshwater species C. fluminea (Müller, 1774) and the estuarine species C. fluminalis (Müller, 1774). Studying North American populations of Corbicula on the basis of ecology, functional morphology and reproduc-tive biology, Britton and Morton (1979) concluded that all belonged to the single species, C. fluminea. The results of this paper, and the conclusions of Morton (1982), seem to provide a good discrimination between C. fluminea and C. fluminalis. In the last decade, Corbicula was also introduced into South América (Ituarte, 1981) and Europe. Mouthon (1981) reports the presence of C. fluminalis in France (La Dordogne) and in Portugal (Tajo River estuary). Nagel (1989) cites the species from the Duero River near Oporto (Portugal) and Girardi (1989-1990) indicates the occurrence of C. fluminalis also in France at the Canal du Midi at Grisolles (Tarn and Garonne). We found two Corbicula populations in the Iberian Península, one in Spain and the other in Portugal, apparent-ly corresponding to C. fluminea. These facts suggest that, as occurred in North América, Europe is being currently invaded by this bivalve and that species discrimination is probably not as clear as previously thought (Morton, 1982), because it still seems to allow the use of various species ñames for morphological variants of the same species concept.
 
Article
The mussel Choromytilus chorus (Molina, 1782) is a commercially and ecologically important bivalve, which is extensively distributed along the Chilean coast (20°S-54°S). However, there are no previous studies regarding the reproductive aspects of this species in the northern part of its range. Mussels were collected at Caleta Errázuriz, along the Antofagasta coast (ca. 24°S), between December 2014 and June 2015. A total of 1620 individuals were examined using histological techniques and macroscopic visual inspection. Seventeen size categories, which included individuals from 5 mm to 100 mm in length, were analyzed. The size at the onset of sexual differentiation and the size at first sexual maturity (50% mature individuals) were determined. Males comprised 49% of the total sample, and 51% were females. Mussels from 5-22 mm in valve length were undifferentiated and from 22-24 mm were sexually differentiated. The size at first sexual maturity was recorded as 38-40 mm. In vitro fertilization trials demonstrated that sexually differentiated individuals were able to produce viable gametes. The biological parameters analyzed for C. chorus were similar to those recorded for populations of this bivalve from the southern latitudes. However, the lower number of eggs per female and the smaller egg size suggests that the population parameters may be different for C. chorus between the northern and southern latitudes.
 
Article
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.
 
Article
Predation indices commonly calculated to quantify the interaction between drilling naticid gastropods and their bivalve prey include boreholesite stereotypy, predator-prey size selectivity, preysize class preference, size refuge from predation, prey effectiveness (PE) and predation intensity (PI; synonymous with drilling frequency or incidence of drilling in the literature). The indices were calculated for samples of the blood ark Anadara ovalis (Bruguière, 1789) (six sites; n = 2023, collectively) and the cross-hatched Iucine Divalinga quadrisulcata (Orbigny, 1842) (five sites; n = 2597, collectively) from New Jersey (Virginian molluscan subprovince) to the Florida Keys (Caribbean molluscan province). Borehole sites are concentrated on the ventral margin in New Jersey and the dorsal margin in South Carolina and Florida on valves of D. quadrisulcata, with a North Carolina site showing a bimodal distribution for the umbos and the ventral margin. This latitiudinal shift in borehole-site stereotypy is attributed to a different suite of naticid species drilling D. quadrisulcata in the northern vs. southern populations. Euspira heros, (Say, 1822) and Neverita duplicata (Say, 1822) drill the cross-hatched Iucine north of the Chesapeake Bay, whereas Sinum perspectivum (Say, 1831), Polinices lacteus (Guilding, 1834), and Naticarius canrena (Linnaeus, 1758) and other naticid species drill populations of the cross-hatched Iucine in the Outerbanks and further south. No such latitudinal shift in stereotypy is evident for A. ovalis; complete boreholes are invariably concentrated on the exposed umbos of the hairy periostracum-veneered, semi-infaunal blood ark at all sampled latitudes. No size refuge from predation is evident for D, quadrisulcata at any latitude as the largest size classes are bored at each sample site. In contrast, A. ovalis has a size refuge at each locality, with the largest unbored specimens at least 10 mm greater than the largest bored specimen. Nevertheless, maximum size of a bored valve does not increase or decrease across the latitudes. Prey size selectivity by naticids shows no pattern from New Jersey to Florida for either bivalve species. Correlations between predator size, indexed by the outer borehole diameter (OBD) in the valve, and prey size (length or width) are significant for only three of 11 samples combined for both species. Prey effectiveness increases for D. quadrisulcata from north to south, suggesting that this bivalve prey more frequently escaped from foot-envelopment by the smaller southern naticids (< mean OBD). In contrast, incomplete boreholes are very infrequent on A. ovalis, which is a sluggish, semi-infaunal burrower that cannot elude the enveloping naticid foot. Although possibly complicated by taphonomic biases, as is PE, predation intensity increases for both species from the Virginian Subprovince to the Caribbean Province. In northern latitudes, the copious, large surfclam Spisula solidissima (Dillwyn, 1822) is the preferred naticid prey. But south of the Chesapeake, naticids increasingly drill D. quadrisulcata and A. ovalis as part of the alternative bivalve prey to the vanishing surfclams.
 
Temperature induced changes in relative abundances of two key fatty acids (cis-11-Eicosenoic acid, Palmitic acid, white bars) and an organic acid (Fumaric acid, grey bars) identifi ed by the DFA stepwise variable selection. Values are presented as fold change increase/decrease as compared to ambient control values (0 value on x axis). Signifi cant differences occur where 95% confi dence intervals do not overlap. 
Metabolites extracted from mussel gill after experiencing an acute thermal challenge. 
Results of stepwise variable selection of Discriminant Func- tion Analysis model for comparing metabolites of adult green- lipped mussel, Perna canaliculus, after an acute thermal challenge. 
Article
The green-lipped mussel (Perna canaliculus Gmelin, 1791) is an economically and ecologically important marine species within New Zealand, yet the ability of adult mussels to cope with acute temperature change remains unknown. To address this, we sought to characterize the thermotolerance capacity of P. canaliculus adults and, using metabolomics, identify any metabolic biomarkers of thermal stress in this species. To achieve this, mussels were exposed to a 3 h acute temperature challenge using temperatures of 20 °C (Ambient), 25 °C, 29 °C, 31 °C, 33 °C, and 35 °C. No mortality was observed in mussels exposed to 31 °C or less, even after 30 days recovery. However, mussels exposed to 33 and 35 °C exhibited 100% mortality within 48 h of the challenge. Gill tissues were harvested from mussels for metabolomic analysis of thermal stress biomarkers via Gas Chromatography-Mass Spectrometry (GC-MS). Discriminant Function Analysis (DFA) of 52 metabolites identified eight key biomarkers indicative of thermal stress in this species (i.e., cis-11-Eicosenoic acid, Palmitic acid, Proline, GABA, Aspartic acid, Fumaric acid, beta-Alanine and Asparagine). These metabolites were entirely consistent in their ability to classify the exposure temperature that mussels experienced, indicating that the discriminatory capacity of these biomarkers was strong. Therefore, our results reveal that mortality in thermally-stressed adult P. canaliculus seems assured once temperatures reach 33 °C. Additionally, metabolite biomarkers can discriminate those mussels exhibiting varying levels of thermal stress; thus, metabolomics offers a new tool for physiologists seeking to gain greater mechanistic understanding of the effects of acute thermal stresses on invertebrate species.
 
Article
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.
 
Article
The European land snail, Aegopinella nitidula (Drapamaud, 1805), is reported for the first time from British Columbia, from three sites in the city of Vancouver. These new records are the only documentation of the species in North America, except for two old records that are probably erroneous and have been ignored in recent literature. Comparisons are made between A. nitidula and similar native and introduced species. Information about its ecology in Europe is summarized.
 
Article
Four species of lined chitons from the Pacific coast of North America (two of them new) formerly regarded as Tonicella lineata (Wood, 1815) are described and discussed. Tonicella lineata; T. undocaerulea Sirenko, 1973; T. lokii Clark, spec. nov.; and T. venusta Clark, spec. nov. are differentiated by characteristics of their shells, girdle elements and radulae.
 
Scanning electron micrographs showing the shapes of the valves of the glochidia of A, Cristaria herculea, scale bar = 35 μm and B, Sinanodonta amurensis, scale bar = 40 μm. 
Scanning electron micrographs illustrating the hinge lengths of the glochidia of A, Cristaria herculea (internal view); B, Cristaria tuberculata (external view); and C, Sinanodonta amurensis (internal view). All scale bars = 50 μm. 
Scanning electron micrographs showing the hooks of the glochidia of A-B, Cristaria herculea; C-D, Cristaria tuberculata; E-F, Sinanodonta amurensis . Figures A, C, and E show the hook viewed perpendicular to the plane of the valve commissure. Figures B, D, and F show the hook in side view. All scale bars = 10 μm. 
Scanning electron micrographs showing pits on the surfaces of the glochidial valves of A-B, Cristaria herculea; C-D, Cristaria tuberculata; E-F, Sinanodonta amurensis . Figures A, C, and E (top row) are of the internal valve surfaces. Figures B, D, and F (bottom row) are of the external valve surfaces. All scale bars = 5μm. 
Mean values of seven characters of glochidia of Cristaria herculea (Ch), Cristaria tuberculata (Ct), Sinanodonta amurensis (Sa), and Sinanodonta likharevi (Sl) (five characters). Length is measured parallel to the hinge. Error bars are standard deviation. Different letters indicate values that differ significantly at p < 0.05. 
Article
Light and scanning electron microscopy (SEM) revealed similarities and differences in the glochidia of four species belonging to two unionid genera from Primorye Territory in Far Eastern Russia: Cristaria herculea, Cristaria tuberculata, Sinanodonta amurensis, and Sinanodonta likharevi. Glochidia of the two species of Cristaria Schumacher, 1817 differed from each other in morphological details of the hook (hook length, maximum height of hook microstylets) and hinge, but not in shape (height/length ratio) or size. Glochidia of the two species of Sinanodonta Modell, 1945 differed from each other in quantitative features such as height, length of hinge, and shape (height/ length ratio). Glochidia of these two species of Sinanodonta lacked some characters possessed by other genera in the tribe Anodontini, in which Sinanodonta has been classified, and shared some characters with the two species of Cristaria, which are classified in the tribe Limnoscaphini, raising uncertainty about the correct classification of Sinanodonta.
 
Article
The systellommatophoran slug Veronicella sloanii (Cuvier, 1817), is a simultaneous hermaphrodite. This slug is an agricultural and horticultural pest in Barbados and several islands of the Lesser Antilles. Over the period January-July 2006 and June-August 2010, the mating behavior of this species was determined by ad libitum and focal animal sampling of captive slugs collected from six sites on the island of Barbados, supplemented by observations and length measurements of slugs seen mating in the field. Individuals of Veronicella sloanii mated reciprocally in pairs, but also in a multi-partner ring formation involving three individuals. Two stages in the mating process were identified, courtship and copulation. Courtship was short, less than two minutes in mating events that led directly to copulation (mean 1.87 minutes, range 0.25–2, N = 53). Copulation in contrast was long, lasting on average 1.03 hours (range 0.4–2, N = 40). During mating the penial gland of each partner made contact with the foot or the hyponotum of the other partner. Aggressive behavior during mating in this slug was manifested by non-mating individuals pushing themselves between mating pairs resulting in the withdrawal of the penis of the mating pairs and cessation of copulation. A strong size-assortative mating pattern was observed; individuals in mating pairs were of similar size.
 
Article
Behavioral tendencies during mating interactions can have important effects on mating patterns. Factors hypothesized to influence mating behavior include the degree of genetic similarity between mates and sexual motivation. This study tested for effects of these factors on mating interactions of the aquatic snail Physa gyrina. Three types of pairs were created from two populations of snails (i.e., two types of intrapopulation pairs and one type of interpopulation pair) and individuals experienced one of three isolation treatments. I recorded behavioral dynamics during mating interactions, including: escalations of mating behaviors, error frequencies, rejection behaviors, and mating frequency. Mating interactions were influenced by both the pairing treatments and isolation treatments. Additionally, there were significant interaction effects between the experimental factors on the behavioral dynamics between individuals during mating interactions. Interpopulation pairs had greater avoidance rates than intrapopulation pairs and differed from control pairs in a variety of ways. Altering the amount of isolation time individuals experienced also significantly affected the behavioral dynamics. Isolation resulted in decreased avoidance responses, with concomitant increases in the escalations of interactions and numbers of copulations. Matings occurred sooner after longer isolation periods, but also experienced higher error frequencies, e.g. misalignment during copulation attempts. These results indicate that the type of potential mate and the context in which interactions occur are important considerations when interpreting observations of mating interactions.
 
Article
Although gastropods are important members of freshwater communities, the geographic range, ecological requirements, and conservation status of most species are poorly known. To advance this understanding, I used survey data from museums and peer-reviewed literature to summarize knowledge of the taxonomic composition and geographic distributions of freshwater gastropods in Iowa, U.S.A. Excluding records likely based on erroneous reports, 49 freshwater gastropod taxa (47 species and 2 genera with unknown numbers of species) inhabited Iowa during all or part of the period when records were collected (1821-1998). The Mississippi River and nearby tributaries of eastern Iowa and the prairie pothole and kettlehole regions of northern Iowa historically supported a large number of taxa. In contrast, few gastropods have been reported from the loess soils ecoregion of southwestern Iowa. Although recent improvements in water quality and increases in wetland habitat have likely benefited many gastropod taxa, it appears that as many as 18 species are now imperiled or extirpated from Iowa, and an additional 7 species were much less widespread at the end of the 20th century than formerly. These 25 species of conservation concern were identified on the basis of rarity or absence of recent records and on evidence of local extinctions that were associated with pollution and habitat loss. By comparing data summarized in this review with future data from field surveys, evidence of restricted or shrinking geographic ranges can be provided, and the true conservation status of lowan gastropods will be determined. This information is of critical importance in establishing legal protection and action plans for the recovery of endangered species.
 
Map of the Mariana Islands, Micronesia (after Bauman 1996), identifying islands mentioned in the text.  
Sinistrally coiling Partula gibba Férussac, 1821 from Guam, Mariana Islands. A, Undoubted lot (NMHN unnumbered) of A. Marche's specimens, showing early label. B, Sinistral specimens and a co-collected dextral example from Marche's undoubted lot. C, Sinistral specimens with a co-collected dextral example from the lot putatively collected by Marche. D, Single sinistral partial shell discovered in 2013 in northern Guam (BPBM 278616). Scale bars: B, C, D = 5 mm. (Color shown in electronic version only).  
Article
Based on museum specimens and zooarchaeological material recovered by us, we note the historic presence of a population of sinistrally coiling Partula gibba Férussac, 1821 on the island of Guam. A single extinct population of this species is also known on an island > 150 km to the north. Hence, given the absence of sinistral populations on intervening islands and lack of indigenous cultural transport, we suggest that sinistrality independently evolved at least twice in P. gibba, the only species of Partula Férussac, 1821 outside of Polynesia to regularly display reverse coiling.
 
Article
The growth rate and reproductive cycle were determined for the transverse ark, Anadara transversa held in pearl nets in the Skidaway River, Georgia during 1996 and 1997. The arks grew from an initial mean shell length of 10.3 ± 0.2 mm in June 1996 to 25.2 ± 0.34 mm in September 1997. Growth was well described by the von Bertalanffy growth model: K = -0.52, L∞ = 24.93, t0 = -0.02. Arks were noted to reach sexual maturity early, with 80% of individuals (n = 30) examined in October 1996 achieving the ripe stage. Some spawning was observed in December 1996 and January 1997; however, major spawning occurred between May 1997 and July 1997. By August 1997, arks were either spent or inactive and all were dead by October 1997. The overall female-to-male sex ratio was 1.00:0.53. When cultured in pearl nets in Georgia, transverse arks are short lived (< two years), grow rapidly, reach sexual maturity at an approximate size of 10 mm, spawn in May-June, are a semelparous species, and obtain a maximum size of approximately 30 mm.
 
Article
An infestation of the giant African snail, Achatina fulica, was established in North Miami Beach, Florida, in the 1960s as a result of the actions of a boy returning from Hawaii with three juvenile snails in his pocket. Seven years' efforts and $700,000 were required to eradicate the snails. More recently, A. fulica and two other achatinid species have become established on some of the Caribbean islands that trade with the United States, resulting in potential new pathways for introduction of these species. The Plant Epidemiology and Risk Analysis Laboratory (PERAL) of the United States Department of Agriculture (USDA) has prepared a pathway risk assessment to determine where resources should be allocated to prevent another infestation in the U.S. or its territories in conjunction with the recognition of these new risks. In the past, the number one pathway for importing achatinid snails into the U.S. had been considered to be deliberate smuggling of live snails in personal baggage from several countries in Africa and from Hawaii (based on data from internal USDA databases that track passengers and their possessions), but these newly recognized potential pathways from the Lesser Antillean islands of the Caribbean demonstrated a need for this new pathway and risk assessment, which is currently undergoing review, with appropriate mitigations for those pathways.
 
Article
To test for sexual dimorphism in Lampsilis siliquoidea, we collected data on total length, height, width, anterior-to-beak length, thickness of the right valve, presence of color rays, and sex from shells of specimens collected across Wisconsin, between 1973 and 1977. Based on the means of these measurements, females were smaller than males. However, detailed statistical analysis of female/male differences in size and shape revealed a more complex relationship between these factors and provided an in-depth view of sexual dimorphism in this species, in contrast to prior simplified generalizations in the literature on this topic.
 
Article
The reproductive biology of the freshwater bivalve Diplodon rotundus gratus (Wagner, 1827) was studied in specimens collected from the Pardo River, in the northeastern region of the State of São Paulo, Brazil. Analysis of the gametogenic cycle revealed that the species is a functional hermaphrodite. The gametogenic cycle began at the end of spring (November) and continued until the beginning of winter (June). In spring and summer the population was found to consist of pure females with only a small proportion of hermaphroditic individuals. Active gametogenesis occurred between February and June. Mature oocytes and sperm occurred simultaneously in the fall. Spawning is probably affected by exogenous factors such as temperature and prolonged droughts associated with host biology. In winter, spring, and summer, no fish with glochidia were found, although glochidial release occurred from February to August.
 
Article
To develop a suitable diet for rearing recently metamorphosed freshwater mussels, nine species of algae and one live bacterium were tested in various trialgal or bialgal and bacterium combinations. A substratum was included in the culture chambers with each treatment to facilitate pedal-feeding by juvenile mussels. Kaolin, an artificial substratum, and fine sediment were tested in combination with algae and without algae. An unfed (no algae or substratum) control treatment also was tested. Juveniles fed a freshwater trialgal diet consisting of Neochloris oleoabundans Chantanachat and Bold, 1962, Bracteacoccus grandis Bischoff and Bold, 1963, Phaeodactylum tricornutum Bohlin, 1897, with fine sediment showed the best growth over time (140 d). These individuals achieved a mean shell length of 1747 μm, and had 30.0% survival after 140 d. Other trialgal mixtures containing N. oleoabundans, Nitzschia acicularis (Kützing) Wm. Smith, 1853, and Cyclotella meneghiniana Kützing, 1844, enhanced growth more than a green trialgal mixture of Chlorella vulgaris Beyernik, 1890, Ankistrodesmus falcatus (Corda) Ralfs, 1848, and Chlamydomonas reinhardtii Dangeard, 1888. A diet of fine sediment alone sustained juveniles through 140 d; however, an additional food source such as algae was necessary to increase survival. Bacteria did not contribute appreciably to juvenile growth and survival. Juvenile mussels reared on commercial yeast diets survived only 8 d; juveniles reared on kaolin and algae survived 60 d.
 
Article
The rostroconch Conocardium formosum n. sp. is described from the Mississippian (Chesterian) of Missouri. The narrow, elongate shape of the shell is different from all other known North American species of the genus.
 
Article
Dosidicus gigas (d'Orbigny, 1835) is a large, active squid that undergoes a diel vertical migration in the Eastern Tropical and Temperate Pacific. It is a voracious predator on zooplankton and micronekton and supports a large fishery. It is further preyed upon by large vertebrate predators, including whales. Its horizontal distribution is closely tied to productive upwelling regions that are characterized by strong oxygen minimum zones (OMZs). The apparent association with extreme hypoxia is surprising given its large size and high oxygen demand. As part of its daily vertical migration, D. gigas experiences daily temperature changes of 15-20°C, oxygen partial pressures ranging from near anoxia (< 0.8 kPa) to air-saturation (21 kPa) and pH changes from ∼8.1 to < 7.6 at depth. Oxygen minimum zones are believed to be expanding due to climate change, with minimum oxygen levels in the core of the OMZ declining and the low oxygen horizon shoaling. Simultaneously, surface waters are becoming more acidic and temperatures are rising. Here I review the extensive studies of this species that have been conducted over the past decade. D. gigas has a high affinity respiratory protein in the blood that supports a low critical oxygen partial pressure (3.8 kPa at 20 °C) and aerobic survival at night in the upper 200 meters of the water column. A pronounced pH- and temperature sensitivity of oxygen binding promotes oxygen transport across a depth range and in support of high rates of oxygen utilization but may impose constraints on high-temperature and CO2 tolerance. At its deeper, colder daytime habitat depth, D. gigas undergoes a pronounced metabolic suppression. Reduced activity levels and an apparent suspension of transcription and translation contribute to a ∼80% reduction in oxygen demand under 1% oxygen (0.8 kPa at 10 °C). Anaerobic metabolic pathways contribute some energy under these conditions. This metabolic suppression likely limits feeding at depth. Sub-critical oxygen levels, rather than temperature, predator avoidance or prey availability, appear to set the daytime depth distribution. Thus, expanding oxygen minimum zones will alter the daytime depth of peak abundance for these squids while ocean acidification and warming may impose a shallow ceiling above which squid performance is limited. The role of climate change in setting the vertical and horizontal distribution of the species is discussed.
 
Article
A new occurrence of Anodontites soleniformis Orbigny 1835 is recorded for the first time in the Pardo River drainage. Thirty specimens were collected and the shell was compared with published figures. By the configurations and the layout of the shell we consider A. soleniformis as subgenus Ruganodontites. We note the presence of A. soleniformis in the Northeastern part of São Paulo State, Brazil.
 
Columella simplex (Gould, 1841) as found inside the dissected stem of a soybean plant harvested from a no-till fi eld in Crittenden County, Arkansas. Note position above the frass plug of the overwintering chamber of Dectes texanus . 
Columella simplex (Gould, 1841) same specimen as Figure 1 viewed through a dissection microscope. Length of specimen is < 3 mm. 
Article
An individual snail shell of Columella simplex (Gould, 1841) was discovered inside of a soybean stem from no-till field in Crittenden County, Arkansas. The shell was found on top of the frass plug of an overwintering chamber of the cerambycid beetle, Dectes texanus.
 
Map of the sampling area, Argentina. The dots () represent the trawling sites.
Aequipecten tehuelchus epibionts in the study site. A, diagram showing the division of each valve into 7 arbitrary regions. B, one individual of Ostrea puelchana (Op) and some Serpula sp. tubes (Ser). C, Microcionidae (Mic). D, Ascidiacea (As). E, several individuals of Ascidiella aspersa (Aa). F, several tubes of Spirorbinae (Spi). G, Balanus cf. amphitrite and Ascidiacea. H, Ostrea puelchana and Serpula sp. tubes. I, Paramolgula gregaria (Pg).
Frequency of occurrence of epibionts on each region of the valves of Aequipecten tehuelchus, Buenos Aires, Argentina.
Article
Aequipecten tehuelchus (d'Orbigny, 1846) is a commercial resource, distributed from Rio de Janeiro (Brazil) to Golfo Nuevo (Argentina), on sandy and muddy bottoms. In Argentina, the major banks of exploitation are located in the gulfs of San José and San Matías. This study represents the first ecological study of A. tehuelchus in shelf waters off Buenos Aires, Argentina. Eighteen epibiont taxa were registered on the individuals analyzed. Polychaetes were the most frequent epibiotic organisms (82%), including Serpulidae (Rafinesque, 1815), Phyllochaetopterus socialis (Claparède, 1869), Idanthyrsus armatus (Kingberg, 1807) and Chaetopterus antarcticus (Kingberg, 1866). Ostrea puelcheana (d'Orbigny, 1842), Balanus cf. amphitrite (Darwin, 1854) and solitary ascidians were found on less than 30% of the sampled individuals. Bryozoa and Porifera were scarcely represented. Phyllochaetopterus socialis, I. armatus and Balanus cf. amphitrite were most frequent on the upper (left) valve. This study nearly doubles the number of epibionts identified and mentioned on A. tehuelchus in Patagonian Gulfs. Three individuals of the commensal pea crab Tumidotheres maculatus (Say, 1818) were found inside three different specimens of A. tehuelchus. One left scallop valve was burrowed into by the parasitic polychaete Polydora (Bosc, 1802).
 
Article
The clonal, invasive New Zealand mudsnail Potamopyrgus antipodarum is rapidly spreading throughout rivers and estuaries of the western USA, where its densities can exceed 300,000/m2. Although very little is known about its ecology in the western USA, P. antipodarum can compete with native invertebrates and appears to have altered primary and secondary production in several western aquatic systems. There are no data published on intraspecific competition and density dependence for this species in the western USA. Populations contain a wide range of sizes; mechanisms responsible for this size distribution are unknown. We conducted laboratory growth experiments on P. antipodarum to determine if intraspecific competition would cause shifts in size hierarchy and decrease growth rates. We used the Gini coefficient (G) to evaluate size hierarchy shifts. Our results showed that asymmetric competition resulted in a strong size hierarchy and that an increase in snail densities caused a decrease in growth. These results suggest that size hierarchies of populations of P. antipodarum might not be entirely based on age class and that asymmetric competition may affect its ecology.
 
Article
The purple conch, Plicopurpura pansa, occurs on rocky shores of the tropical eastern Pacific of North and Central America, ranging from Magdalena Bay, Baja California to Colombia. When disturbed, it exudes a secretion that photo-oxidizes to an intense purple hue. This product has been used as a dye for ceremonial dresses. Unlike the case in other dye-producing molluscs, it is not necessary to sacrifice individuals to obtain the dye, allowing repetitive "milking" of the same animal without causing mortality. Evaluation of population parameters, rates of dye produced as a function of age at first milking, and milking frequency allowed us to simulate different exploitation scenarios and to evaluate strategies to determine the most profitable exploitation intensity and optimum milking frequencies. Laboratory experiments and field data showed that mortality occurs when the interval between milking is lower than 21 days. The most profitable exploitation strategies suggest that up to 310 L of dye in 50 km of shoreline length can be harvested during the three-month milking season. This volume of dye is sufficient to stain up to 260 skeins of cotton thread. Simulations showed that the stocks can withstand sustainable exploitation along their distribution range, allowing commercial exploitation of the dye produced by stocks of purple conch in other areas apart from those where it currently takes place, benefiting other groups of fishers elsewhere and ensuring the conservation of this tradition.
 
Article
Species of North American freshwater snails within the genus Physa are distinguished primarily on differences in shell shape. However, shell shape in this genus is ecophenotypically influenced by environmental factors. The present study examined the degree to which genes and environment influenced spire angle in specimens of Physa virgata collected from a single population in Arlington, Texas. Five separate genetic lines were inbred for five generations, after which progeny were reared under one of three temperature regimes (20°, 25°, or 30°C) until reaching adult size (approximately 5 mm in shell length). The spire angle of each individual was then measured and comparisons made across thermal regimes and genetic lines. Genetic line and temperature both significantly influenced spire angle. In general, snails reared at warmer temperatures had wider spire angles than snails reared at cooler temperatures. Some genetic lines had wider mean spire angles than others, regardless of temperature. Individual spire angles differed by as much as 23.8° under controlled conditions. These results suggest that shell shape is neither a consistent character nor taxonomically diagnostic. Thus, the number of currently recognized species of Physa is problematic.
 
Article
The Indo-West Pacific montacutid Curvemysella paula(A. Adams, 1856) is the sole representative of its genus and the only known bivalve that is an obligate commensal of hermit crabs. As such, studies on it are accordingly very few. It lives in small groups byssally attached to the internal columella of the host's adopted shell. This paper describes the species from a wave-exposed beach in central Vietnam at Danang. Here, it was living with Diogenes goniochirus, but elsewhere in Hong Kong and Japan other taxa serve as hosts. The adult shell of C. paula is antero-ventrally long, deeply concave ventrally and so inequivalve as to appear twisted. Smaller individuals are more equivalve and equilateral and become deformed with age and growth. The hinge plate has a structure typical of the Montacutidae with the ligament ventrally formed into a lithodesma. Anatomically, C. paula is also unremarkable and interest in it focuses on reproduction. The species lives in small groups, the oldest and largest being a female, the smallest and youngest males. Intermediate sized individuals are hermaphroditic. Curvemysella paula is thus a protandric consecutive hermaphrodite. Prodissoconch morphology suggests that C. paula does not ctenidially brood fertilised eggs or, if so, only briefly. Further, it seems likely that there is subsequently an abbreviated lecithotrophic period of development perhaps undertaken close to the sea bed - thereby keeping the larvae close to established hermit crab and parental bivalve populations.
 
Top-cited authors
Robert H Cowie
  • University of Hawaiʻi at Mānoa
Gary Rosenberg
  • Academy of Natural Sciences of Drexel University
Christian Albrecht
  • Justus-Liebig-Universität Gießen
Roland Schultheiß
  • University of Turku
Robert T. Dillon Jr
  • Freshwater Gastropods of North America Project