The late Dr Albert Mead Dr Albert Mead, the expert on Achatinid snails, died on 13th March at the age of 93. He taught at the University of Arizona and was president of the American Malacological Union (now AMS) in 1963. He was greatly appreciated for his lecturing style and sense of humour. His book ‘The Giant African Snail: A Problem in Economic Malacology’ published in 1961 by University of Chicago Press recently became available online from the Hawaiian Ecosystems at Risk project at http://www.hear.org/books/tgas1961/
The late Martin Wells Dr Martin John Wells, the distinguished researcher on cephalopods, died on 1 st January 2009 aged 80. He started his research career on insects under Professor Wigglesworth at Cambridge but abandoned his PhD to work at Statione Zoologica di Napoli on tactile discrimination in octopuses with his wife Joyce, a fellow graduate. He also investigated these cephalopods’ ability to ‘taste by touching’. In 1959 in J. exp. Biol., Martin and Joyce Wells also described the close association of the optic gland with sexual maturation. In the 1970s, his work switched to cardiovascular and respiratory physiology of cephalopods, and the physiology of the pearly nautilus. His contribution to the Cambridge zoology department was enormous and he received a D.Sc in 1966.
The late James Nubakken Professor Nybakken, a past president of AMS in Monterey, died on 20 June. His work focussed on conids and opisthobranchs, and he was the author of a popular text, Marine Biology: an Ecological Approach.
Iberian Land Snail Diversity Alex Menez from Gibraltar has been awarded the degree of Doctor of Philosophy by Cardiff University. His thesis is entitled Pattern and process in southern Iberian land mollusc diversity.
|‘Alien’ snail search for kids Cardiff Museum is recruiting budding naturalists in searching for an ‘alien’ snail Hygromia cinctella. Copies of the snail guide and key are available at www.museumwales.ac.uk/scan , along with a current distribution map. The species was first recorded from Britain at Paignton, Devon, in 1950, and first recorded in Wales in Cardiff in 2000.|
Humboldt squid invades Californian coast An influx of Humboldt squid into Californian coastal waters from more tropical waters appears to be reducing local populations of hake. Examination of videos from submersibles in Monterey Bay show the squid have been abundant in the area since 2002. The expansion may be linked to overfishing of tuna which compete with squid for food. Although the squid hunt in schools they stay too deep to bother swimmers and surfers, but divers have reported being attacked, with tentacles pulling at their masks and gear.
How radula sensors modify feeding pattern To interact successfully with its environment, an animal must take in and process information and then modify its behaviour appropriately in keeping with changing stimuli. Many rhythmic behaviours, from locomotion to feeding, are controlled by central pattern generators in the nervous system, but modified according to external events. A set of motor neurons underlying feeding patterns in the planorbid Helisoma has been identified and characterised, along with some of the mechanosensory neurons which subtly modulate the feeding central pattern generator in myriad ways. The modulations are characterised at the level of individual neurones and synapses.
Delfeld, M M. 2008. Dissertation Abstracts International. 69(6), suppl. B, 116 p. 2008.
Parasites make sex worthwhile for snails This study provides experimental evidence for the ‘Red Queen’ hypothesis and for the geographic mosaic theory, namely that natural selection can be intense in ‘hot spots’ of a population but absent elsewhere. Females of the New Zealand Potamopyrgus antipodarum favour asexual reproduction, which lets them produce offspring directly, in the absence of the parasitic trematode Microphallus, but sexual reproduction lets the snail hosts produce genetically diverse offspring which can ward off infection. The parasites need both the snail and ducks to complete their life cycle. Snails were more likely to reproduce sexually in the shallows, where ducks can feed and parasites are more common than in deep water. To see if sexual reproduction was linked to parasites, the researchers exposed snails from one isolated lake to parasites from another. Snails from the shallows were susceptible to worms from their own lake but resistant to worms from the other lake.
King KC, Delph LF, Jokela J and Lively CM. 2009. The geographic mosaic of sex and the red queen. Current Biology.
Potamopyrgus impacts Great Lakes Although in its native New Zealand, P. antipodarum is kept in control by native trematodes, in the Great Lakes, it occupies water that is too deep for diving ducks in which the trematodes can complete their life cycle. In the western states, the snail can modify nitrogen and carbon cycling and occurs in high densities. Densities in eastern states, including the great lakes are lower, but anglers in New York are being urged to clean their gear to avoid moving the snails to new areas.
Papillifera papillaris found in National Trust estate A colony of Italian snails has been discovered at Cliveden estate in Buckinghamshire. The Cliveden snail colony must originate from the shipping of a large marble balustrade from the Villa Borghese in Rome in 1896.
The chemistry of marine invasions The Mediterranean, like other seas, is losing its biological distinctiveness. Researchers in Naples, focussing on the secondary metabolite composition of three exotic sea slugs in Greece that have most probably entered the Mediterranean basin by Lessepsian migration found feeding deterrents in the cephalaspidean Haminoea cyanomarginata and in the nudibranch Melibe viridis. These findings lead to a proposal that aposematism and dietary autonomy are predisposing factors to the migration. In the anaspidean Syphonota geographica, the same compounds were found in the viscera and their seagrass food, implying a dietary dependency.
Mollo, Ernesto et al. 2008. Proc. Natl. Acad. Sci. USA. 105(12), 4582-4586.
Key Arctic pteropod threatened by ocean acidification Limacina helicina is an important pteropod in Arctic food webs and plays a key role in cycling carbon and carbonate. Theirs shells leave them sensitive to ocean acidification caused an increase in anthropogenic CO 2 emissions. Pteropods kept under different controlled levels of pH showed 28% decrease in calcification at the pH level expected for 2100 compared to present values.
Comeau S et al. (2009) Biogeosci. Disc. 6(1), 2523-2537.
Caffeine and Conditioned Defensive Reflex in a Snail When daily caffeine injections were given to snails immediately after a training procedure, the conditioned defensive reflex was acquired more quickly than when caffeine injections were given before the training procedure started. Comparative studies showed that addition of caffeine to the solution bathing the mollusk nervous system resulted in decreases in the threshold potential of command neurons in both intact and trained snails; there was, however, no change in the membrane resting potential.
Silant'eva, DI et al. 2009. Neurosci. Behav. Physiol. 39(4), 403-407.
Polyandry and larval diversity in slipper limpet The invasive sessile marine gastropod Crepidula fornicata exhibits polyandry and extreme larval growth variation. Using microsatellite markers, to assign fast- and slow-growing larvae to a particular father, this study showed that the range of larval growth rates within a brood was significantly correlated to sire diversity and larval relatedness within broods. Multiple paternity could thus play an important role in determining the extent of pelagic larval duration and consequently the range of dispersal distances achieved during larval life.
Le Cam, S et al. 2009 J. Hered. 100(4), 455-464.
The nervous system of the basal mollusk Wirenia argentea (Solenogastres) The nervous system of Wirenia argentea displays a distinct tetraneury with fused cerebral ganglia, large pedal ganglia, and longitudinal nerve cords connected by regularly spaced connectives and commissures resulting in an orthogon-like arrangement. There is no indication of metamery.
Todt, C; Buechinger, T; Wanninger, A. 2008. Mar. Biol. Res. 4(4), 290-303.
Lophotrochozoan neurogenesis and larval neuroanatomy Neurodevelopmental studies contribute to questions about the evolution of the nervous system of Lophotrochozoa (Spiralia + Lophophorata). For example, echiurans, spiralians which are unsegmented as adults, do have segmentally arranged perikarya and commissures during ontogeny. Similarly, sipunculans develop their adult single ventral nerve cord by fusion of a paired larval nerve, and show transitional stages of segmentation. These findings indicate that echiurans, annelids and sipunculans stem from a segmented ancestor. By contrast, no traces of body segmentation are present during neurogenesis of basal molluscs. However, larval entoprocts possess a tetraneurous condition (paired ventral and lateral nerve cords), like Mollusca, and a serotonergic larval apical organ like that of polyplacophora, thus strongly supporting a mollusc-entoproct clade. The recent advances in molecular phylogenetics and developmental neurobiology suggest a clade comprising Sipuncula + Annelida (including Echiura) on the one hand and a monophyletic assemblage of Entoprocta + Mollusca on the other.
Wanninger, A. 2008. Acta Biol. Hung. 59,127-136.
How mussel physiology affects bioaccumulation Because mussels bioaccumulate up to 100,000-fold toxic pollutants such as metals in their soft tissues, they have been used as proxies for contamination in coastal waters. However, to accurately quantify water pollution using molluscan tissue contaminant levels, the biodynamics of bioaccumulation must be well-characterized. Metal bioaccumulation is determined by the metal's bioavailability, the exposure route, and the mussel's physiology. When mussels, Mytilus galloprovincialis, from an uncontaminated Mediterranean site were transferred into waters polluted by Pb, Cd, Cu or Hg, uptake of metals into the soft tissue was rapid. Accumulation follows an asymptotic form for all metals. Bioaccumulation then reaches a plateau that represents a sort of equilibrium with the contaminant concentrations in the organism's environment. Weight increase during growth or decrease during spawning, strongly affect the metal content in the tissues.
Casas, S et al. 2008. Environ. Toxicol. Chem. 27(7), 1543-1552.
Sea Ranching Manila Clams (Venerupis philippinarum) Little Skookum Shellfish Growers has operated under economically and environmentally sustainable sea ranching guidelines for Manila clams (Venerupis philippinarum) since 1977 near Shelton, Washington, USA. Its system of benthic surveys and seeding is a rational approach for establishing and monitoring standing stocks and biomass dynamics of infaunal mollusk populations, allowing it to sea ranch in excess of 60,000 kg Manila clams/ha/y sustainably. Until successful acoustical methods for infaunal biomass analysis are established, this approach may be the only cost effective way of achieving economical and sustainable results with a full working knowledge of the impacts involved in either intertidal sea ranching or stock enhancement for infaunal mollusks.
Becker P, Barringer C, Marelli DC. 2008. Rev. Fish. Sci.16(1),44-50.
Opioids and Mollusc Innate Immune Response The nervous and immune systems exchange information through opioid peptides, some of which are endogenous messengers of the immune system, and participate in the regulation of the immune response. The capacity of immunocytes to release and respond to opioid neuropeptide messengers is not restricted to mammalian organisms. The immunocytes of molluscs resemble cells of the vertebrate monocyte/macrophage lineage and are activated by similar substances to control phagocytosis, chemotaxis, and cytotoxicity. Recently, Mytilus edulis has been the subject of studies to determine whether the relationship between the immune and nervous systems seen in vertebrates also exists in invertebrates.
Liu, Dong-Wu 2008. Protein Peptide Lett.15(7), 683-686.
Partial sterility of triploid oysters Triploidy has become increasingly important for aquaculture of C. gigas as it provides quicker growth and, most of the time, better survival over their diploid counterparts. This is probably due to the high level of infertility. Additionally, triploidy provides a beneficial taste profile for human consumption during the active gametogenesis period. Both diploids and triploids show active gametogenesis, but in triploids, the gonad occupation rate was 50% less than in diploids. Only 30% of triploids showed complete gonadal maturation. Using two genes (oyster vasa-like gene and oyster-gonadal-TGFβ –like) to compare reproduction at the molecular level the Brest researchers found that most triploids do not go past the gonial proliferation step. As a result, the reduced fecundity of most triploids is not found in the first stages of gametogenesis but rather at the point when spermatogonia/oogonia differentiate into spermatocytes/oocytes.
Fabioux C et al. 2008. Physiomar 08. 'Marine molluscs in a changing environment', 2nd marine mollusc physiology conference. Book of abstracts. p. 27.
Mussel spat evidence of turtle brunation Mussels up to 3 months old along with barnacles and green algae have been found on green turtles off the Atlantic coast of Uruguay. They provide evidence that the turtles are resting there in a state of lethargy during winter months – a process called brunation.
Prieto JC et al. 2008. NOAA Tech. Memo. NMFS SEFSC 567, 118.
Possible biosentinels of human waste Monitoring viral pathogens in coastal waters requires initial viral recovery and concentration. The indigenous bivalve, Isognomon sp., ubiquitous in the Indo-Pacific area, has been used successfully in virus recovery to bioaccumulate human enteropathogenic viruses from seawater seeded experimentally with either raw sewage or human norovirus-positive stool samples. Human noroviruses and enteroviruses were detected by reverse transcription polymerase chain reaction employing specific primers.
Asahina AY et al. 2009. J. Virol. Methods 158(1-2), 46-50.
Responses of Manila clam to a toxic dinoflagellate The toxic dinoflagellate Heterocapsa circularisquama forms massive outbreaks along western Japanese coasts, associated with mass mortalities of at least 14 species of marine bivalves. Feeding, respiration and growth of adult Ruditapes philippinarum, from Tokyo Bay were studied while exposed to relatively low concentrations of H. circularisquama, at three different temperatures., and under exposure to H. circularisquama at different concentrations mixed with Isochrysis galbana. At 15°, feeding, respiration and food absorption were not affected by the presence of the toxic alga. However, the scope for growth (SFG) was significantly decreased for cell concentrations of 250 cells ml -1 and above. For 20° and 25°, the clearance and respiration rates significantly decreased, from a cell density of 5 cells ml -1. At both temperatures, the absorption efficiency became null starting from 250 cells ml-1. The SFG was significantly reduced at 20° for all toxic alga concentrations. The SFG was negative for exposure at 25°. Decreased feeding and respiration imply gill damage. The cessation of food absorption at temperature exceeding 15° could be due to poor food processing by the damaged gills. Decreased feeding, respiration and food absorption may lead to a decrease in the energy reserves and thus a general weakening of the clams with possible death.
Basti , L; Tsuchiya, K; Segawa, S. 2008. Physiomar 08. 'Marine molluscs in a changing environment', 2nd marine mollusc physiology conference. Book of abstracts. p. 19.
Effects of nutrient and insecticide treatments on predation on slugs in an upland grassland Slugs can have profound effects upon plant community structure and, by selective grazing, act as ecosystem engineers. Experimental treatments on upland grasslands significantly affected invertebrate communities, including potential slug predators. Nitrogen and lime enhancement significantly increased the depth of soil surface thatch, but this did not affect slug numbers or biomass. However, it did increase numbers of some slug predators - species of carabid and staphylinid beetle – as verified by testing for slug remains in their guts using a mollusc-specific monoclonal antibody and enzyme-linked immunosorbent assays. Other slug predators included Silphidae, Araneae and Opiliones. When time was included as a factor, there was no relationship between slug predator numbers and slug numbers. It was predicted that slug numbers should be greatest where there was more surface organic matter (nutrient enhancement treatment), and lowest where slug predators were reduced (insecticide treatment). The lack of an overall effect of treatment on slug numbers suggests that the greater numbers of potential slug predators in the nutrient enhancement treatment suppressed any increase in the slug population.
Fountain MT et al. 2009. Agric., Ecosyst. Environ.131(3-4), 145-153.
Survival of soft-bottom marine invertebrates with planktonic larvae A survey of marine benthic invertebrates in inner Danish waters looked at loss ratios of marine invertebrates from one development stage to the next in Bivalvia, Gastropoda, Polychaeta and Echinodermata. Loss ratios between post-larvae stage and adult stage (post-larval mortality) varies from 71.2-84.9% and loss ratios between larvae and post-larvae (larval mortality) and between larvae and adult, ranged from 85.2-97.6% and 97.8-99.5%, respectively. The results confirm that the larval stage, metamorphosis and settlement are the critical phase in terms of mortality in the life cycle for Bivalvia. The adult turnover time for Bivalvia is estimated to be 1.5 years and 2.1 years for Polychaeta. This exemplifies that species with short generation times may dominate in very dynamic transitional zones with a high frequency of catastrophic events like the frequent incidents of hypoxia in the inner Danish waters.
Pedersen, TM et al. 2008. J. Mar. Syst. 73(1-2),185-207.