I am looking to promote molluscs to a younger community and write to seek help from Society Members.
I have written five children’s fiction books all based around a pet African Land Snail called Old McSlithers, with whom my children have grown up. The first of these books, Snail Trail was published in November last year and has been very successful (See books section). The second book, Snails Don’t Burp! is due out on April 26th.
Whilst the books contain some elements of pure fantasy, I have aimed to get my facts on African Land Snails as accurate as possible to ensure that children learn something new whilst enjoying a good read.
The purpose of this letter is to extend an open invitation to any member of The Society who might be prepared to read through the second book, Snails Don’t Burp!, to check for accuracy of snail facts, particularly details relating to the poisoning of a snail by pyrite, or Fool’s Gold.
If you are a Member of The Society and are reading this letter with some interest, then please do visit my website for further background information - www.madaboutsnailbooks.com. Do bear in mind that the books are suitable for reading by 7-11 year olds and for bed-time reading to 5-7 year olds, depending on academic progress. In fact these books were written to be read aloud and make fun reading in schools.
I am visiting schools to promote my book but also to share facts about snails, so any help your members can give would be gratefully received.
Giant Snails overrun
An article for National Geographic News by Sabrina Valle on October 19th 2007 (Check it out here) states that the giant African snail, introduced to Brazil as a delicacy in gourmet restaurants, has become a major nuisance, thriving in every state. The invasion was probably sparked by an agribusiness fair in the south where kits with snails and rearing instructions were sold. If not bred in captivity, the snail (along with the garden snail) is a potential vector for Angiostrongylus cantonensis which can cause meningitis. Two cases were diagnosed in Espirito Santo in 2007. The snail, which can lay clutches of 400 eggs and produce 1200 eggs per year lives for up to 10 years. It has also become part of the food chain with increases in rat and snake populations, and it has begun to compete with larger native snails.
The late Leslie
We were saddened to hear that Leslie Elmslie, a member of The Society for many years, died in Rome on 15th November 2007 after a brain haemorrhage. Leslie worked in Rome as a translator and snail farmer and many members will remember him at conferences, most recently at the WCM in Antwerp.
A short video of a L paradoxum larva pulsating in the swollen tentacle of a succineid, signalling its presence to a potential predator – the final host – appears on the web from Oldrich Nedved, University of South Bohemia, at http://zoo.bf.jcu.cz/kz/invertebrates/leucochloridium.htm
Not only for vertebrates!
Ultrasound imaging in invertebrates
Ultrasound imaging has proven to be a reliable method for examining various parts of the brain of Octopus vulgaris. Sonographic measurements of the brain masses in vivo were correlated with those determined postmortem, and were reproducible with no significant differences over consecutive days. Furthermore, when sonographic examinations were 30 days apart, changes in brain dimensions were detectable.
|Grimaldi AM et al., 2007. Using ultrasound to estimate brain size in the cephalopod Octopus vulgaris|
|Cuvier in vivo. Brain Res. 1183: 66-73|
The ciliated velar lobes that gastropod larvae use to swim are supported by a constant volume hydrostatic skeleton. In defense behaviour the velar lobes and foot are rapidly withdrawn into a protective biomineralized shell. Adding fluorescein dye to the internal fluid showed that the fluid supporting the extended velar lobes is expelled from discrete release sites during defensive withdrawals.
|Page LR, 2007. Shrinking to fit: fluid jettison from a haemocoelic hydrostatic skeleton during defensive|
|withdrawals of a gastropod larva. Proc Roy Soc B-Biol Sci 274 (1628): 2989-2994|
More than pearls
– antimicrobial peptide from oyster
A novel cysteine-rich antimicrobial peptide, CgPep33, exhibiting activity against Gram-positive and Gram-negative bacteria (E. coli, Pseudomonas aeruginosa, B.subtilis and S. aureus) and fungi (Botrytis cinerea and Penicillium expansum), was isolated from the enzymatic hydrolysates by digestion of oyster with alcalase and bromelin. Proteolysis may offer simple and cheap large-scale production of a safe antimicrobial peptide from marine bivalves.
|Liu ZY et al, 2008. Production of cysteine-rich antimicrobial peptide by digestion of oyster (Crassostrea|
|gigas) with alcalase and bromelin. Food Control 19 (3): 231-235|
The late Leslie Elmslie sent a newspaper cutting from Sofia, Bulgaria, in May, with this illustration of paintings by snails, part of an exhibition promoting unusual pets.
When bivalves took
over the world
The end-Permian mass extinction is commonly portrayed not only as a massive biodiversitv crisis but also as the time when marine benthic faunas changed from the Paleozoic Fauna, dominated by brachiopods, to the Modern Fauna, dominated by gastropod and bivalve taxa. Scenarios involving the Mesozoic Marine Revolution portray a steady increase in numerical dominance by these benthic molluscs as largely due to the evolutionary effects of an "arms race." A new global paleoecological database from shell beds shows a dramatic and sudden takeover by bivalves in level-bottom benthic marine communities, starting in the earliest Triassic and continuing through the Early Triassic. Three bivalve genera were responsible for this switch, none of which has any particular morphological features to distinguish it from many typical Paleozoic bivalve genera. The numerical success of these Early Triassic bivalves cannot be attributed to any of the well-known morphological evolutionary innovations of post-Paleozoic bivalves that characterize the Mesozoic Marine Revolution. Rather, their ability to mount this takeover most likely was due to the large extinction of rhynchonelliform brachiopods during the end-Permian mass extinction, aided by their environmental distribution and physiological characteristics that enabled them to thrive during periods of oceanic and atmospheric stress during the Permian/ Triassic transition.
Fraiser ML and Bottjer DJ, 2007. When bivalves took over the world. Paleobiology 33 (3): 397-413
Rare or scattered?
Antarctic deep-sea gastropods
The abyssal depths of the polar oceans are thought to be low in diversity, but a recent study on the gastropod fauna of the deep Southern Ocean has revealed a rich gastropod assemblage at abyssal depths. 37 deep-sea species (44%) were represented by a single specimen, and another 20 species (24%) were found at a single station, suggesting that more than two thirds of Antarctic deep-sea gastropod species are very rare or have a very scattered distribution.
|Schwabe E et al., 2007. Rich and rare - First insights into species diversity and abundance of Antarctic|
|abyssal Gastropoda (Mollusca). Deep-Sea Research Part II-Topical Studies in Oceanography 54 (16-17): 1831-1847|
Temptin – one more needed component for finding love in the sea
Temptin, a component in the complex of protein pheromones that stimulate attraction and mating behavior in Aplysia, has a sequence homologous to the EGF-like domains of higher organisms that mediate protein-cell surface contact during fertilization and blood coagulation. Recombinant temptin was produced in Escherichia coli. Docking results with Aplysia model and the NMR structure of attractin suggest that one face of temptin interacts with the pheromone, perhaps controlling its access to the cellular receptors. Gel shifts confirmed that temptin complexes with wild-type attractin. These results indicate that temptin, analogous to the role of fibrillin in controlling transforming growth factor-beta concentration, modulates pheromone signaling by direct binding to attractin.
|Cummins SF et al., 2007. Aplysia temptin - the 'glue' in the water-borne attractin pheromone complex.|
|FEBS Journal 274 (20): 5425-5437|
Shell genes suggest
shared metazoan ancestor
This overview of evolution of Mollusca emphasizes how the evolvability of the external shell has in part contributed to the evolutionary success of the molluscs. Major developmental transitions in shell morphology often correlate with ecological transitions (e. g. from a planktonic to benthic existence at metamorphosis). The authors relate the developmental expression of nine genes in the tissue responsible for shell production - the mantle - to ecological transitions during the life of the tropical abalone Haliotis asinina. All nine genes display dynamic spatial and temporal expression profiles within the larval shell field and juvenile mantle. The use of both ancient and novel genes in all stages of shell construction suggests that a core set of shell-making genes was provided by a shared metazoan ancestor.
|Jackson DJ et al., 2007. Dynamic expression of ancient and novel molluscan shell genes during|
|ecological transitions. BMC Evolutionary Biol. 7: Art. No. 160|
Hidden “values” in seafood – but safe?
This article compiles available data and presents an approach for predicting human intakes of inorganic arsenic, monomethylarsonic acid and dimethylarsinic acid (DMA) from marine, estuarine, and freshwater seafood when only total arsenic concentrations are reported. Due to the nonlinearity and low carcinogenic potency of DMA, reported DMA concentrations should not contribute substantially to potential health risks from arsenic in seafood.
|Schoof RA and Yager JW, 2007. Variation of total and speciated arsenic in commonly consumed fish|
|and seafood. Human and Ecological Risk Assessment 13 (5): 946-965|
Scallops are often consumed in Tenerife (Canary Islands). The concentrations of lead and mercury in preserved scallops were far below the maximum limit permitted for human consumption by the European Communities Commission regulation (1 and 0.5 mg kg-1) wet weight for Pb and Hg, respectively), but concentrations of cadmium were close to the maximum limit (1 mg kg-1 wet weight).
|Gutierrez AJ et al., 2007. Content of toxic heavy metals (mercury, lead, and cadmium) in canned|
|variegated scallops (Chlamys varia). J. Food Protection 70 (12): 2911-2915|
– does it drive mating system evolution?
Inbreeding depression, a major factor driving mating system evolution, can itself evolve as a function of the mating system (the genetic purging hypothesis). Classical models of coevolution between mating system and inbreeding depression predict negative associations between inbreeding depression and selfing rate, but more recent approaches suggest that negative correlations should usually be too weak or transient to be detected within populations. Empirical results remain unclear and restricted to plants. The authors evaluated the within-population genetic correlation between inbreeding depression and a trait that controls the amount of self-fertilization (the waiting time) in a self-fertile hermaphrode, the freshwater snail Physa acuta. In agreement with recent models, this result shows that mutational variance rather than differential purging accounts for most of the genetic variance in inbreeding depression within a population.
|Escobar JS et al., 2007. No correlation between inbreeding depression and delayed selfing in the|
|freshwater snail Physa acuta. Evolution 61 (11): 2655-2670|
Fiber optics and
feeding in bivalves
A novel sensor based on fiber optic technology for fine scale (similar to 0.1 mm laboratory) measurement of valve gape in bivalve molluscs is capable of accurate and repeatable measurements with few of the drawbacks of other valve gape sensing methods (e.g., levers, strain gauges, electromagnetic sensors). This sensor can be applied to other systems requiring the measurement of axial distances while immersed in seawater or other harsh environments.
|Frank DN et al., 2007. A fiber optic sensor for high resolution measurement and continuous monitoring of|
|valve gape in bivalve mollusks. J. Shellfish Res.26 (2): 575-580.|
A use for clapped
In marine invertebrate populations, natural mortality events tend to be episodic. The intensity of these events can be estimated from the decline in catch rate of live animals over successive sampling periods. However, the high variability of catch rates makes them relatively insensitive indicators of mortality. Mortality of bivalves can be estimated with greater precision by the change in abundance of ‘clappers’, which are gaping shells of recently dead bivalves still hinged together. The authors present a change in ratio estimator and its associated variance of the proportion of animals dying due to an episodic mortality event.
|Walter J et al., 2007. An estimator of episodic mortality in bivalves with an application to sea scallops|
|(Placopecten magellanicus). Fisheries Research 86 (2-3): 85-91|
and extinction of Aldabra banded snail
The only known population of the Aldabra banded snail Rhachistia aldabrae declined through the late twentieth century, becoming extinct in the late 1990s. This occurred within a stable habitat and its extinction is attributable directly to decreasing rainfall leading to increased mortality of juvenile snails.
|Gerlach J, 2007. Short-term climate change and the extinction of the snail Rhachistia aldabrae|
|(Gastropoda : Pulmonata). Biology Letters 3 (5): 581-584|
Heading for 0 – are pesticides responsible?
Elevated levels of DDT and its metabolite DDE, as well as of cadmium and some other heavy metals, has been detected in pearl mussels (Margaritifera margaritifera) which are in decline throughout Europe. Both classes of pollutants are known to potentially interfere with calcium homeostasis. Pollutants of various kinds are listed among the factors that are possibly contributing to the extinction of aquatic molluscs.
|Frank H and Gerstmann S, 2007. Declining populations of freshwater pearl mussels (Margaritifera|
|margaritifera) are burdened with heavy metals and DDT/DDE. Ambio 36 (7): 571-574|
Pesticidal effects – more than previously thought?
The impact of pesticides on the health of Pacific oysters was assessed by monitoring the effects of pesticide exposure combined with a bacterial challenge on cell activities and gene expression in hemocytes. The bacterial challenge was intramuscular injection of two Vibrio splendidus-related pathogenic strains. Oyster mortality and expression of 10 of the 19 selected genes were followed 4 and 24 h post-injection. After the bacterial challenge, oyster mortality was higher and gene expression was up-regulated, in pesticide-treated oysters. The authors hypothesize that gene over-expression due to an interaction between pesticides and bacteria resulted in injury of host tissues. This study is the first to show effects of pesticides at environmentally relevant concentrations on C. gigas hemocytes and to hypothesize that pesticides modulate the immune response to a bacterial challenge in oysters.
|Gagnaire B et al., 2007. Combination of a pesticide exposure and a bacterial challenge: In vivo effects on|
|immune response of Pacific oyster, Crassostrea gigas (Thunberg). Aquatic Toxicology 84 (1): 92-102|