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Cambrian Pelecypoda (Mollusca)

The record of Cambrian bivalved organisms that have been placed in the Mollusca includes undoubted pelecypods and other bivalved shells. This record is reviewed herein. Additional topotype material of Delgado's (1904, Communicacoes da Commissao do Servico Geologico de Portugal 5:307-374) Lower Cambrian specimens from Portugal shows that they are distorted brachiopods. Restudy of Zhang's (1980a, Bulletin Chinese Academy of Geological Sciences, Series 8, 1:1-19; 1980b, 26th International Geological Congress 4:121-129) type specimens from the Lower Cambrian of China shows that most of them are also brachiopods. New specimens of Tuarangia MacKinnon indicate that this genus is a Middle-Upper Cambrian pelecypod.

American Malacological Bulletin

Survival and growth of newly transformed Lampsilis cardium and Lampsilis siliquoidea in a flow-through, continuous feeding test system

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

American Malacological Bulletin

Use of swabs for sampling epithelial cells for molecular genetics analyses in Enteroctopus

We evaluated the efficacy of using swabs to collect cells from the epidermis of octopus as a non-invasive DNA source for classical genetic studies, and demonstrated value of the technique by incorporating it into an effort to determine, within a day, the lineage of captured, live Enteroctopus ( E. dofleini or a cryptic lineage). The cryptic lineage was targeted for captive behavioral and morphological studies, while once genetically identified, the non-target lineage could be more rapidly released back to the wild. We used commercially available sterile foamtipped swabs and a high-salt preservation buffer to collect and store paired swab and muscle (arm tip) tissue sampled from live Enteroctopus collected from Prince William Sound, Alaska. We performed a one-day extraction of DNA from epithelial swab samples and amplification of two diagnostic microsatellite loci to determine the lineage of each of the 21 individuals. Following this rapid lineage assessment, which allowed us to release non-target individuals within a day of laboratory work, we compared paired swab and muscle tissue samples from each individual to assess quantity of DNA yields and consistency of genotyping results, followed by assessment of locus-by-locus reliability of DNA extracts from swabs. Epithelial swabs yielded, on average, lower quantities of DNA (170.32 ± 74.72 (SD) ng/μL) relative to DNA obtained from tissues collected using invasive or destructive techniques (310.95 ± 147.37 (SD) ng/μL. We observed some decrease in yields of DNA from extractions of swab samples conducted 19 and 31 months after initial extractions when samples were stored at room temperature in lysis buffer. All extractions yielded quantities of DNA sufficient to amplify and score all loci, which included fragment data from 10 microsatellite loci (nine polymorphic loci and monomorphic locus EdoμA106), and nucleotide sequence data from a 528 base pair portion of the nuclear octopine dehydrogenase gene. All results from genotyping and sequencing using paired swab and muscle tissue extracts were concordant, and experimental reliability levels for multilocus genotypes generated from swab samples exceeded 97%. This technique is useful for studies in which invasive sampling is not optimal, and in remote field situations since samples can be stored at ambient temperatures for at least 31 months. The use of epithelial swabs is thus a noninvasive technique appropriate for sampling genetic material from live octopuses for use in classical genetic studies as well as supporting experimental and behavioral studies.

American Malacological Bulletin

Thermal tolerance limits of the Chinese mystery snail (Bellamya chinensis): Implications for management

The Chinese mystery snail, Bellamya chinensis (Gray, 1834) is a gastropod native to East Asia and is considered an invasive species in North America where its impacts on native species and ecosystems are not well understood. Scientific literature describing its biology and life history are sparse. Thermal tolerance limits, or the maximum and minimum temperature under which a species can survive, are key to identifying the potential geographical range of a species. The ability of managers to control invasive species is directly impacted by the thermal tolerance limits of a species. We attempted to identify the thermal tolerance limits of B. chinensis in a laboratory setting. Using a random sampling design, we exposed groups of wild-caught B. chinensis to either extreme high or low temperature treatments. We identified the upper temperature tolerance limit as between 40 and 45 °C. This result indicates some hot water management techniques may successfully prevent spread of B. chinensis among waterways. Despite exposing B. chinensis to freezing temperatures for extended periods of time we did not identify a lower temperature limit. Identifying the thermal tolerance limits of this and other invasive species informs predictions of range expansion and identification of potential prevention efforts.

American Malacological Bulletin

Abundance and distribution of large thecosome pteropods in the northern Gulf of Mexico

The ecological role of large thecosome pteropods in the pelagic ecosystem of the northern Gulf of Mexico (GoM) may be substantial, both in the food web and biogeochemical cycling. We analyzed species abundances, vertical and horizontal distributions of large species with calcareous shells (those collected in 3-mm mesh nets). Pteropod samples were collected following the 2010 Deepwater Horizon oil (DWH) spill by two midwater sampling programs: the Offshore Nekton Sampling and Analysis Program (ONSAP 2011) and the Deep Pelagic Nekton Dynamics of the Gulf of Mexico ( DEEPEND 2015 ) projects. All samples were collected using a 10-m 2 Multiple Opening/Closing Net and Environmental Sensing System (MOC10) midwater trawl, with 3-mm mesh. This gear sampled five discrete depths between 0–1500 m. Over 13,000 pteropod specimens were examined, with 25 species identified. Clio pyramidata Linnaeus 1767 was the most abundant species during both collection periods. Five genera ( Diacria, Clio, Styliola, Cuvierina, Cavolinia ) demonstrated diel vertical migration from the mesoto epipelagic zone.

American Malacological Bulletin

New information about Echinochiton dufoei, the Ordovician spiny chiton

Echinochiton dufoei Pojeta et al ., 2003 is now known from seven specimens. The new material shows the anterior end and allows for a full reconstruction of the animal. The hollow spines are circumsomal; they were flexible and perhaps moveable in rotary anterior-posterior directions. Possible functions for the hollow spines are discussed. The relationships of E. dufoei to other chitons and to other molluscs and mollusc-like organisms are presented.

American Malacological Bulletin

Zebra mussel induced mortality of unionids in firm substrata of western Lake Erie and a habitat for survival

The present study was conducted to determine impacts of zebra mussel [Dreissena polymorpha (Pallas, 1771); Dreissenidae] infestation on unionids in firm substrata in western Lake Erie. Unionid mollusks were collected at a total of 15 stations on three offshore depth contours (2, 3, and 4 m) in 1983 (before zebra mussel infestation), in 1990 and 1993 (after zebra mussel infestation), and at one station on a nearshore 2-m depth contour and along one transect on a nearshore 1-m depth contour in 1993. Numbers of living unionids on substrata along offshore contours remained similar between 1983 and 1990 and then decreased from 97 individuals in 1990 to only five individuals in 1993. In addition, the number of species decreased from nine to four between 1990 and 1993. In contrast, on nearshore contours 85 living individuals representing nine species were found in 1993. About 48% of the living and 79% of the dead unionids at the two nearshore locations were covered with byssal threads of dreissenid mussels, but were not actively infested by mussels. The presence of living unionids on nearshore contours of western Lake Erie in 1993 indicates that survival of unionids in the presence of abundant zebra mussel populations can be possible in firm substrata and that these habitats can provide natural ''refugia'' for unionid populations. At present, we do not know what allows unionids to survive in the presence of zebra mussel colonization, but believe that water-level fluctuations and waves could contribute to the removal of mussels from unionids. This information could be of major concern in the mitigation of impacts of infestation on unionids in waters throughout North America.

American Malacological Bulletin

Variation in glycogen concentrations within mantle and foot tissue in Amblema plicata plicata: Implications for tissue biopsy sampling

With the development of techniques to non-lethally biopsy tissue from unionids, a new method is available to measure changes in biochemical, contaminant, and genetic constituents in this imperiled faunal group. However, before its widespread application, information on the variability of biochemical components within and among tissues needs to be evaluated. We measured glycogen concentrations in foot and mantle tissue in Amblema plicata plicata (Say, 1817) to determine if glycogen was evenly distributed within and between tissues and to determine which tissue might be more responsive to the stress associated with relocating mussels. Glycogen was measured in two groups of mussels: those sampled from their native environment (undisturbed mussels) and quickly frozen for analysis and those relocated into an artificial pond (relocated mussels) for 24 months before analysis. In both undisturbed and relocated mussels, glycogen concentrations were evenly distributed within foot, but not within mantle tissue. In mantle tissue, concentrations of glycogen varied about 2-fold among sections. In addition, glycogen varied significantly between tissues in undisturbed mussels, but not in relocated mussels. Twenty-four months after relocation, glycogen concentrations had declined by 80% in mantle tissue and by 56% in foot tissue relative to the undisturbed mussels. These data indicate that representative biopsy samples can be obtained from foot tissue, but not mantle tissue. We hypothesize that mantle tissue could be more responsive to the stress of relocation due to its high metabolic activity associated with shell formation.

American Malacological Bulletin

Morphology of glochidia of Lampsilis higginsi (Bivalvia: Unionidae) compared with three related species

Glochidia of the endangered unionid mussel Lampsilis higginsi (Lea) are morphologically similar to those of several other species in the upper Mississippi River. Life history details, such as the timing of reproduction and identity of host fish, can be readily studied if the glochidia of L. higginsi can be distinguished from those of related species. Authors used light and scanning electron microscopy and statistical analyses of three shell measurements, shell length, shell height, and hinge length, to compare the glochidia of L. higginsi with those of L. radiata siliquoidea (Barnes), L. ventricosa (Barnes), and Ligumia recta (Lamarck). Glochidia of L. higginsi were differentiated by scanning electron microscopy on the basis of a combined examination of the position of the hinge ligament and the width of dorsal ridges, but were indistinguishable by light microscope examination or by statistical analyses of measurements.

American Malacological Bulletin

The bellerophont controversy revisited

An old controversy reestablished itself in the late 1970s and early 1980s that focused on the systematic placement of the enigmatic Bellerophontoidea (informally, "bellerophonts"), a group of planispirally coiled, wholly fossil molluscs. The controversy embraced three fundamental concepts that are based on different philosophical interpretations of shell form, muscle scar patterns, and other preserved shell features: 1) all bellerophonts were monoplacophorans; 2) all bellerophonts were gastropods; and 3) some bellerophonts were monoplacophorans and some were gastropods. A review of the main issues appearing in the literature since the early 1980s indicates that these three philosophical divisions still exist and, indeed, have become entrenched. An examination of the relevant anatomical and shell features of recent gastropods and monoplacophorans, and comparison with preserved features in enigmatic fossil forms, convinces us that the bellerophontoideans and the coiled and high-domed "monoplacophorans" (Cyclomya) were gastropods. Only the flattened, spoon-and cap-shaped monoplacophorans (Tergomya) were true monoplacophorans. We present a hypothetical scheme for the morphological diversification of gastropods from early monoplacophorans that could account for Cyclomya, Bellerophontoidea, Patellogastropoda, and Prosobranchia.

American Malacological Bulletin

Reproductive biology of four freshwater mussels (Bivalvia: Unionidae) endemic to eastern Gulf Coastal Plain drainages of Alabama, Florida, and Georgia

The reproductive biology and glochidial shell morphology of three federally endangered freshwater mussels, the fat threeridge, Amblema neislerii; Gulf moccasinshell, Medionidus penicillatus; and oval pigtoe, Pleurobema pyriforme; and one federally threatened mussel, the purple bankclimber, Elliptoideus sloatianus, were studied from May 1995 to June 1997 in the Apalachicola, Flint, and Ochlockonee river drainages of Florida and Georgia. Gravid A. neislerii were found in early June. Laboratory experiments indicated that five fish species served as hosts: weed shiner, Notropis texanus; bluegill, Lepomis macrochirus; redear sunfish, L. microlophus; largemouth bass, Micropterus salmoides; and blackbanded darter, Percina nigrofasciata. Elliptoideus sloatianus were found gravid from late February through mid-April. None of the 14 fish species exposed to E. sloatianus glochidia resulted in the identification of a primary host fish. Medionidus penicillatus were found gravid during September, November, March, and April. The brown darter, Etheostoma edwini, and blackbanded darter, Percina nigrofasciata, were identified as primary host fishes for M. penicillatus. Pleurobema pyriforme were found gravid from March through July. Only the sailfin shiner, Pleronotropis hypsehpterus, was identified as a primary host fish for P. pyriforme. Glochidial shell morphology of A. neislerii, M. penicillatus, and P. pyriforme were similar to other species in their respective genera. The glochidia of the monotypic species E. sloatianus were morphologically most similar to Epioblasma brevidens and E. capsaeformis.

American Malacological Bulletin

Seasonal growth and mortality of juveniles of Lampsilis fasciola (Bivalvia: Unionidae) released to a fish hatchery raceway

Recent efforts to restore remnant or extirpated populations of freshwater mussels have focused on artificial propagation as an effective and practical conservation strategy. Although artificially cultured juveniles have been produced and released to the wild at various times of the year, no study has investigated the best time of year to release these juveniles. Newly metamorphosed juveniles of the wavyrayed lampmussel (Lampsilis fasciola) were released into a stream-fed fish hatchery raceway during March, June, and September. Growth and survival rates were measured 32, 52, 72, and 92 days post-metamorphosis. Juveniles released in June experienced the greatest growth and survival rates. Juveniles released in September and March experienced high mortality within the first month of release and exhibited poor growth in the cool water conditions typical of those seasons. Overwinter survival exhibited a size-dependent relationship.

American Malacological Bulletin

A quantitative analysis of naiad mollusks from the Prairie du Chien, Wisconsin dredge material site on the Mississippi River

The Prairie du Chien dredge material site contains about 100,000 cubic meters of material dredged from the East Channel of the Mississippi Riverin1976. Previous studies in that area suggested a rich molluscan fauna, but most studies were only qualitative or simply observations. Our study of this material was designed to determine the density and diversity of molluscan fauna, to assess changes in the fauna, to identify endemic species previously unreported, and to evaluate the status of the endangered Lampsilis higginsi. Ten cubic meters of dredge material were sieved to recover shells. Molluscan fauna at the site contained38 species of naiades and up to 1,737 identifiable valves per cubic meter. The endangered L. higginsi ranked18th In occurrence, accounted for only 0.52% of the identifiable shells, and averaged about three valves per cubic meter. From a total of 813 kg of naiades and gastropods, 6,339 naiad valves were identified. Five naiad species were collected at the site for the first time, and Eploblasma triquetra had not been reported previously in the Prairie du Chien area. Although the molluscan fauna has changed, the East Channel at Prairie du Chien is obviously suitable for L. higginsi.

Bulletin of American Malacological Union