Effects of shell shape,size, and sculpture in burrowing and anchoring abilities in the freshwater mussel Potamilus alatus (Unionidae)

Because of the sedentary lifestyle of freshwater mussels, studies examining their movement capabilities are scarce. However, the ability to burrow into the substrate and the ability to remain stationary are likely crucial components of their behavioural repertoire. The performance of these different tasks is likely to be affected by the presence of the shell ornamentation characteristic of many mussel species. Previous studies have suggested that shell ornamentation results in a trade‐off between burrowing ability and remaining stationary when an extrinsic force attempts to dislodge it from the substrate once buried. We examined the effect of morphology and shell ornamentation on burrowing performance and anchoring ability by artificially creating shell ornamentation on a relatively smooth‐shelled species (Potamilus alatus). Burrowing behaviours and performance and the force required to dislodge mussels (anchoring ability) were quantified with and without ornamentation. Interestingly, we found that the artificial shell ornamentation had no significant effect on burrowing behaviours and performance or dislodgement force. Burrowing and dislodgement, however, were both highly influenced by shell size and shape. All of the available information suggests that shell size, shape, and sculpture influence burrowing and anchoring in complex ways that needs further examination. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 111 , 136–144.     

Effects of light-emitting diodes on thermally-induced oxidative stress in the bay scallop Argopecten irradians

ABSTRACT

Water temperature is an important stressor that affects the physiological and biochemical responses of scallops. In this study, we investigated the effect of different light-emitting diodes (LEDs; red, green and blue) on oxidative stress in Argopecten irradians. PCR revealed MnSOD mRNA expression in the digestive diverticula, gill, adductor muscle and eye. CAT and HSP70 mRNA were expressed in the digestive diverticula, gill and adductor muscle. Additionally, we measured the changes in the expression of HSP70, MnSOD and CAT as well as H₂O₂ levels during thermal/laboratory stress. In the digestive diverticula, gill and adductor muscle, the mRNA expressions and activities and H₂O₂ levels significantly increased in response to thermal changes. The gene expressions and activities and H₂O₂ levels were significantly lower in scallops that received green LED light than in those that received no mitigating treatment. A comet assay revealed that thermal change groups had increased rates of nuclear DNA damage; however, treatment with green LED reduced the frequency of damage. The results indicated that low or high water temperature conditions induced oxidative stress in A. irradians but that green LED significantly reduced this stress.     

Evolutionary trends within bivalve prey of chesapeake group naticid gastropods

Five genera of Miocene bivalves evolved antipredatory adaptations in response to predation by drilling naticid gastropods. I examined the evolution of two traits affecting predator‐prey interaction, prey shell thickness (TH) and internal volume (IV). Thickness controls predation costs by determining drilling time, and internal volume influences the benefit derived by the predator.

Internal volume showed no consistent pattern of temporal change among the taxa studied. IV fluctuated nondirectionally during the history of most genera, though both increasing and decreasing trends occurred within species ofAstarte. In contrast, all five genera exhibited significant thickness increases (from 8–157%) during the three‐million‐year interval. Both gradual intraspecific and interspecific directional changes occurred. Taxa with the greatest predation intensities displayed the most change, suggesting that predation selected for the thickness increases. Increased thickness apparently reduced predation; a significant negative correlation between TH and predation intensity occurred within four of the bivalve genera. Improvement of predator capabilities apparently did not keep pace with increased antipredatory morphologic adaptations over the interval studied.     

High connectivity across the fragmented chemosynthetic ecosystems of the deep Atlantic Equatorial Belt: efficient dispersal mechanisms or questionable endemism?

Chemosynthetic ecosystems are distributed worldwide in fragmented habitats harbouring seemingly highly specialized communities. Yet, shared taxa have been reported from highly distant chemosynthetic communities. These habitats are distributed in distinct biogeographical regions, one of these being the so‐called Atlantic Equatorial Belt (AEB). Here, we combined genetic data (COI) from several taxa to assess the possible existence of cryptic or synonymous species and to detect the possible occurrence of contemporary gene flow among populations of chemosynthetic species located on both sides of the Atlantic. Several Evolutionary Significant Units (ESUs) of Alvinocarididae shrimp and Vesicomyidae bivalves were found to be shared across seeps of the AEB. Some were also common to hydrothermal vent communities of the Mid‐Atlantic Ridge (MAR), encompassing taxa morphologically described as distinct species or even genera. The hypothesis of current or very recent large‐scale gene flow among seeps and vents was supported by microsatellite analysis of the shrimp species Alvinocaris muricola/Alvinocaris markensis across the AEB and MAR. Two nonmutually exclusive hypotheses may explain these findings. The dispersion of larvae or adults following strong deep‐sea currents, possibly combined with biochemical cues influencing the duration of larval development and timing of metamorphosis, may result in large‐scale effective migration among distant spots scattered on the oceanic seafloor. Alternatively, these results may arise from the prevailing lack of knowledge on the ocean seabed, apart from emblematic ecosystems (chemosynthetic ecosystems, coral reefs or seamounts), where the widespread classification of endemism associated with many chemosynthetic taxa might hide wider distributions in overlooked parts of the deep sea.     

Conservation status of freshwater mussels in Europe: state of the art and future challenges

Freshwater mussels of the Order Unionida provide important ecosystem functions and services, yet many of their populations are in decline. We comprehensively review the status of the 16 currently recognized species in Europe, collating for the first time their life‐history traits, distribution, conservation status, habitat preferences, and main threats in order to suggest future management actions. In northern, central, and eastern Europe, a relatively homogeneous species composition is found in most basins. In southern Europe, despite the lower species richness, spatially restricted species make these basins a high conservation priority. Information on freshwater mussels in Europe is unevenly distributed with considerable differences in data quality and quantity among countries and species. To make conservation more effective in the future, we suggest greater international cooperation using standardized protocols and methods to monitor and manage European freshwater mussel diversity. Such an approach will not only help conserve this vulnerable group but also, through the protection of these important organisms, will offer wider benefits to freshwater ecosystems.     

Detection of oxidative DNA damage in isolated marine bivalve hemocytes using the comet assay and formamidopyrimidine glycosylase (Fpg)

Organisms in polluted areas can be exposed to complex mixtures of chemicals; however, exposure to genotoxic contaminants can be particularly devastating. DNA damage can lead to necrosis, apoptosis, or heritable mutations, and therefore has the potential to impact populations as well as individuals. Single cell gel electrophoresis (the comet assay) is a simple and sensitive technique used to examine DNA damage in single cells. The lesion-specific DNA repair enzyme formamidopyrimidine glycoslyase (Fpg) can be used in conjunction with the comet assay to detect 8-oxoguanine and other damaged bases, which are products of oxidative damage. Fpg was used to detect oxidative DNA damage in experiments where isolated oyster (Crassostrea virginica) and clam (Mercenaria mercenaria) hemocytes were exposed to hydrogen peroxide. Standard enzyme buffers used with Fpg and the comet assay produced unacceptably high amounts of DNA damage in the marine bivalve hemocytes used in this study necessitating a modification of existing methods. A sodium chloride based reaction buffer was successfully used. Oxidative DNA damage can be detected in isolated oyster and clam hemocytes using Fpg and the comet assay when the sodium chloride reaction buffer and protocols outlined here are employed. The use of DNA repair enzymes, such as Fpg, in conjunction with the comet assay expands the usefulness and sensitivity of this assay, and provides important insights into the mechanisms of DNA damage.     

Abundance and Distribution of Pelagic Larvae of Bivalves and Echinoderms in Busse Lagoon (Aniva Bay,Sakhalin Island)

The taxonomic composition and numbers of pelagic larvae of bivalves in Busse Lagoon and the contiguous areas of Aniva Bay (southern Sakhalin) were studied in 2000–2001. In comparison with 1973–1974, the total density of larvae increased 2–3 times, but their taxonomic composition changed and a redistribution of dominant species occurred. Numbers of bivalve larvae increased at the expense of larvae of Musculista senhousia, Crassostrea gigas, and species of the Tellinidae. In 2000–2001, larvae of Ruditapes philippinarum, Mya arenaria, Swiftopecten swifti, and some other species were encountered in plankton very rarely or were not found at all. The drastic decrease in the larval density of some bivalve species was caused by uncontrolled and nearly total harvesting of mollusks. Larval echinoderm numbers in the lagoon were not high in 2000–2001; larvae of the sea cucumber Apostichopus japonicus and the sea urchin Strongylocentrotus intermedius predominated.     

Morphological Variability and Levels of Nuclear Ploidy in Neurons of the Central Nervous System of Bivalves Relative to the Problem of Somatic Polyploidy

Ploidy of neurons was assessed by the method of nuclear DNA cytophotometry in ganglia of the central nervous system (CNS) in 28 species of Bivalvia belonging to 5 existing subclasses and having various bio-ecological characteristics. A significant variation in the nucleus size and chromatin structure was revealed on crush preparations and slides; however, almost all nuclei were diploid. Some species had nuclei with tetraploid DNA value (from 0.2 up to 1%) and with condensed chromosomes, the probable mitotic fraction of cells. It was concluded that variation in the sizes of neurons and of their nuclei in the given instance was of a functional character, and polyploidy was untypical for the nervous system of bivalves. Apparently, the polyploidy, as an evolutionary strategy of neuron growth, had no anatomical prerequisites in bivalves, which is similar to CNS oligomerization in higher gastropods, as they are devoid of any functional adaptive sense.     

New ideas on the system of the Permian <Emphasis Type="Italic">Inoceramus</Emphasis>-like bivalves of the eastern Boreal zone

New concepts of systematics and phylogeny of the Permian Inoceramus-like bivalve mollusks of the eastern part of the Boreal zone are discussed based on analysis of the group’s historical development. All taxa studied are referred to the family Kolymiidae Kusnezov, which is divided into two subfamilies, Kolymiinae and Atomodesmatinae. In the subfamily Kolymiinae, two new genera are described: Praekolymia with the type species P. archboldi sp. nov. and P. urbajtisae sp. nov., and Taimyrokolymia with the type species T. ustritskyi sp. nov. In the subfamily Atomodesmatinae, two new genera, Costatoaphanaia and Okhotodesma, are described. The development of the group is shown to be generally autochthonous with some invasions (genus Atomodesma and, probably, Trabeculatia) from extraboreal regions.