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Octopus vulgaris type III preys upon molluscs by drilling a hole in the shell, through which it injects venom, weakening the muscles and allowing the octopus to remove and eat the mollusc flesh. In False Bay, South Africa, the abalone Haliotis midae, the kelp limpet Cymbula compressa and the helmet snail Semicassis zeylanica, are all common octopus prey, but each has a very different shell morphology and underlying anatomy. It is hypothesized that O. vulgaris type III targets the muscle attachment site of all three species and that the precision of drilling should correlate with the relative size of these muscle attachment sites. Measurements of the locations of drill holes from collected shells of each species showed that drilling locations were significantly non-random. In the abalone and limpet, the muscle attachment site was targeted two and 4.5 times more frequently than expected, respectively. Octopus vulgaris type III drilled helmet snails with extreme precision, with over half the holes drilled on the spire at an angle of 45° and 90° from the lip. Kernel density heat maps demonstrated that octopus drilled abalone with low precision, limpets with medium precision and helmet snails with high precision. The reason for the high precision in the helmet snail remains speculative, as the main drilling location did not align with the columellar muscle attachment and no target could be defined. This study is the first to assess octopus drilling in temperate southern Africa and to compare drilling precision across different prey species., Author(s): Gareth N. Fee [sup.1] [sup.2] , Jennifer Mather [sup.3] , Jannes Landschoff [sup.2] , Charles L. Griffiths [sup.1] Author Affiliations: (1) grid.7836.a, 0000 0004 1937 1151, Department of Biological [...]

A novel histological and ultrastructural study of the three ganglia types of Scrobicularia plana was made. Adults of both sexes and immature specimens were collected at Ria Formosa lagoon, Portugal. For light microscopy, animals fixed in formalin were processed for various staining, including serotonin and dopamine immunohistochemistry. For transmission electron microscopy, dissected ganglia were fixed in glutaraldehyde and routinely processed. Every ganglion reveals an outer cortex and inner medulla, with the cortex displaying large and small neurons. Their sizes decrease as they are located closer to the medulla. Almost all are unipolar, and only a few are bipolar. Glial cells appear around the neurons and amidst the axons. They usually have smaller sizes and greater nucleus-cytoplasm ratios. The glial morphologies (fusiform, roundish, and triangular) may correspond to glia subtypes and/or functional statuses. Ultrastructural differences from earlier studies were noted, mainly in the type of inclusions and vacuoles. Serotonergic and dopaminergic cell bodies and neuntes exist in all ganglia. There is an identical expression pattern in adults (both sexes) and in immature animals. Nevertheless, the extent/intensity of serotonin positivity in visceral ganglia supports that mature animals have a stronger expression, which may be connected the role of that amine in gonad maturation and spawning. KEY WORDS: Scrobicularia plana, bivalve, nervous system, glial cells, histology/ultrastructure, monoamines, neurons, INTRODUCTION The nervous system of invertebrates is composed of two main categories of cells, neurons and glial cells (Bullock & Horridge 1965, Coles & Abbott 1996, Harrison & Kohn 1997, [...]

ABSTRACT This study examined the scaling of the radula of the Atlantic slippersnail Crepidula fornicata with body size. As a suspension feeder, the prediction was that the radula may be [...]

Mollusks, and particularly gastropods, are one of the major taxonomic groups at vents. In these ecosystems, devoid of light, chemoautotrophic bacteria are at the base of the food web and symbiotic association between metazoa and these bacteria is numerous. Nevertheless, apart few 'large-size' well-known species, the 'small-size' gastropods (shell < 5 mm), although very abundant, remain poorly studied regarding symbioses. We investigated here Cyathermia naticoides (Waren and Bouchet in Zool Scr 18(1), 1989), a small coiled gastropod found in abundance on the East Pacific Rise among Riftia pachyptila tubes, and usually inferred to graze on tubeworm bacterial cover, and/or filter feeding. Among mollusks, symbioses are well known in large species and almost exclusively rely on sulfide or methane-oxidizing proteobacterial endosymbionts, occurring within the host tissues in gill epithelial bacteriocytes. Combining several approaches (molecular biology, microscopy, stable isotopes analyses), we described here an unusual symbiosis, where autotrophic filamentous Epsilonproteobacteria are located extracellularly, at the base of host gill filaments. Numerous endocytotic lysosome-like structures were observed in the gill epithelium of the animal suggesting bacteria may contribute to its nutrition through intracellular digestion by gill cells. Additional food source by non-symbiotic proteobacteria grazed on R. pachyptila tubes could complete the diet. The possible role of temperature in the selection of Epsilon- vs Gammaproteobacterial partners is discussed., Introduction To date, about 600 metazoan species have been reported at hydrothermal vents, belonging to 12 phyla. Among those, 150 species of molluska and more than 100 species of Gastropoda [...]

Daily rhythms of activity driven by circadian clocks are expressed by many organisms, including molluscs. We initiated this study, with the nudibranch Melibe leonina, with four goals in mind: (1) determine which behaviors are expressed with a daily rhythm; (2) investigate which of these rhythmic behaviors are controlled by a circadian clock; (3) determine if a circadian clock is associated with the eyes or optic ganglia of Melibe, as it is in several other gastropods; and (4) test the hypothesis that Melibe can use extraocular photoreceptors to synchronize its daily rhythms to natural light-dark cycles. To address these goals, we analyzed the behavior of 55 animals exposed to either artificial or natural light-dark cycles, followed by constant darkness. We also repeated this experiment using 10 animals that had their eyes removed. Individuals did not express daily rhythms of feeding, but they swam and crawled more at night. This pattern of locomotion persisted in constant darkness, indicating the presence of a circadian clock. Eyeless animals also expressed a daily rhythm of locomotion, with more locomotion at night. The fact that eyeless animals synchronized their locomotion to the light-dark cycle suggests that they can detect light using extraocular photoreceptors. However, in constant darkness, these rhythms deteriorated, suggesting that the clock neurons that influence locomotion may be located in, or near, the eyes. Thus, locomotion in Melibe appears to be influenced by both ocular and extraocular photoreceptors, although the former appear to have a greater influence on the expression of circadian rhythms., Introduction Most organisms are typically more active at certain times of the day or night, and this tendency is controlled, in part, by endogenous circadian clocks. When these organisms are [...]

ABSTRACT The nuclear factor-κB (NF-κB) signaling pathway has been studied extensively in mammalians and insects but has been less well investigated in marine molluscs. Inhibitor of κB (IκB), an important [...]

ABSTRACT The diet of the keyhole limpet Megathura crenulata was determined from stomach contents of 119 specimens collected from 3 rocky reefs on the west coast of the Baja California [...]

In nature, mollusk shells have a role in protecting the soft body of the mollusk from predators and from the external environment, and the shells consist mainly of calcium carbonate and small amounts of organic matrices. Organic matrices in mollusk shells are thought to play key roles in shell formation. However, enough information has not been accumulated so far. High toughness and stiffness have been focused on as being adaptable to the development of organic-inorganic hybrid materials. Because mollusks can produce elaborate microstructures containing organic matrices under ambient conditions, the investigation of shell formation is expected to lead to the development of new inorganic-organic hybrid materials for various applications. In this review paper, we summarize the structures of mollusk shells and their process of formation, together with the analysis of various organic matrices related to shell calcification. Key words: mollusk shell, shell matrix protein, shell microstructure. Dans la nature, la coquille du mollusque joue un role de protection du corps mou de l'animal contre les predateurs et le milieu exterieur, et cette coquille est principalement composee de carbonate de calcium et de petites quantites de matrices organiques. Ces matrices organiques joueraient un role cle dans la formation des coquilles de mollusques, mais l'information a ce sujet demeure insuffisante. L'attention a porte sur la grande tenacite et la forte rigidite de telles matrices, qui pourraient se preter a la mise au point de materiaux hydrides organiques-inorganiques. Puisque les mollusques peuvent produire des microstructures complexes renfermant des matrices organiques dans des conditions ambiantes, l etude de la formation des coquilles devrait mener a la mise au point de nouveaux materiaux hybrides organiques-inorganiques se pretant a des applications variees. Dans la presente synthese, nous fournissons une description sommaire des structures des coquilles de mollusques et de leur processus de formation, ainsi qu'une analyse de differentes matrices organiques associees a la calcification des coquilles. [Traduit par la Redaction] Mots-cles : coquille de mollusque, proteine de la matrice de la coquille, microstructure de la coquille., Introduction The mollusk organism is eaten as seafood, and the various mollusk shells with their beautiful shapes and colors can often be seen on beaches and in artwork and jewelry. [...]

In the present study, the hypothesis that marine nudibranch mollusks harbor symbiotic bacteria was tested using analyses of fatty acids as biochemical markers and transmission electron microscopy of the tissues of Dendrodoris nigra (Gastropoda/Opisthobranchia/Nudibranchia). An aberrant level of the odd-numbered carbon chain and branched fatty acids, iso- and anteiso- that are specific for bacteria, was detected in the nudibranch tissues. Their amounts in the notum exceeded significantly that in the viscera. Rod-shaped gram-negative bacteria were revealed in the epithelial cells of the notum and the mantle edge as well as in the adjoining glycocalix. These bacteria were enclosed in secondary vacuoles in the epithelial cells. The consequent stages of inoculation of the bacteria into the cytoplasm of epithelial cells, from adhesion to the apical surface to invagination of the cell membrane and formation of the vacuole with an enclosed bacterium, were observed. The presence of dividing bacteria suggests that the epithelium includes a renewable, dividing population of symbiotic bacteria. No bacteria were detected in the gonads and the digestive system. Probable functions of these symbiotic bacteria such as involvement in protection or defense from predators and environmental impacts as well as their nutritional role in the nudibranch are discussed., Introduction Dendrodoris nigra (Stimpson 1855) is a common Indo-West Pacific nudibranch species (Brodie et al. 1997). It occurs at moderately protected to moderately exposed rocky sites, where it is usually [...]

Certain mRNAs have been shown to be segregated in different cells in various metazoan embryos. These events represent aspects of autonomous mechanisms that establish particular embryonic cell fates and axial properties associated with asymmetric cell divisions. The spiralian lophotrochozoans (which include molluscs, annelids, nemerteans, gnathostomulids, dicyemid mesozoans, entoprocts, and platyhelminthes) exhibit a highly conserved pattern of early development that involves stereotypical, asymmetric cell divisions (termed 'spiral cleavage'). Recently, it was demonstrated that various mRNAs are dynamically localized to the centrosomes in specific cells during early development in the gastropod mollusc, Ilyanassa obsoleta. During subsequent cell divisions, these messages become segregated in particular daughter cells, and it has been proposed that these events distinguish the developmental potential of these cells within the early embryo of I. obsoleta. The molecular mechanisms underlying these events, however, are still unknown. Here we show for the first time in another spiralian lophotrochozoan (the gastropod Crepidula fornicata) that similar patterns of mRNA localization take place during early development. To characterize the transcriptome of early development, and identify candidate genes for the expression analyses, high-throughput sequencing was carried out, via GS FLX Titanium 454 pyrosequencing. The annotated sequences have been made available as a resource for the scientific community (www.life.illinoi.edu/henry/crepidula_databases.html). Presumably, specific proteins associated with centrosomes may be important for these mRNA localization events. In silico sequence comparisons with known centriolar/centrosomal, ciliary/basal body proteomes shows that a large number of those proteins are represented in the collection of expressed sequence tags of C. fornicata annotated in this study. These data should be useful for future studies of the role of specific mRNAs in controlling cell fate and axial specification in the spiralian Lophotrochozoa, and for dissecting the underlying molecular mechanisms that accomplish these events. doi: 10.1093/icb/icq088

[delta][sup.18]O values of mollusks recovered from near-shore marine cores in northwest Iceland quantify significant variation in seasonal temperature over the period from ~360 B:C: to ~A:D: 1660. Twenty-six aragonitic bivalve specimens were selected to represent intervals of climatic interest by using core sedimentological characteristics. Carbonate powder was sequentially micromilled from shell surfaces concordant with growth banding and analyzed for stable oxygen ([delta][sup.18]O) and carbon ([delta][sup.13]C) isotope values. Because [delta][sup.18]O values record subseasonal temperature variation over the lifetime of the bivalves, these data provide the first 2,000-year secular record of North Atlantic seasonality from ca. 360 cal yr B.C. to cal yr A.D. 1660. Notable cold periods (360 B.C. to 240 B.C.; A.D. 410; and A.D. 1380 to 1420) and warm periods (230 B.C. to A.D. 140 and A.D. 640 to 760) are resolved in terms of contrast between summer and winter temperatures and seasonal temperature variability. Literature from the Viking Age (ca. 790 to 1070) during the establishment of Norse colonies (and later) in Iceland and Greenland permits comparisons between the [delta][sup.18]O temperature record and historical records, thereby demonstrating the impact of seasonal climatic extremes on the establishment, development, and, in some cases, collapse of societies in the North Atlantic. climate change | stable isotopes | Vikings | micromilling www.pnas.org/cgi/doi/10.1073/pnas.0902522107

We present a model to explain how the neurosecretory system of aquatic mollusks generates their diversity of shell structures and pigmentation patterns. The anatomical and physiological basis of this model sets it apart from other models used to explain shape and pattern. The model reproduces most known shell shapes and patterns and accurately predicts how the pattern alters in response to environmental disruption and subsequent repair. Finally, we connect the model to a larger class of neural models. neurosecretory | mathematical model | bifurcation

Chitin is usually found in stiff extracellular coatings typified by the arthropod exoskeleton, and is not associated with the soft, flexible mollusc skin. Here, we show, however, that chitin in nudibranch gastropods (Opisthobranchia, Mollusca) occurs as intracellular granules that fill the epidermal cells of the skin and the epithelial cells of the stomach. In response to nematocysts fired by tentacles of prey Cnidaria, the epidermal cells of eolid nudibranchs (Aeolidacea) release masses of chitin granules, which then form aggregates with the nematocyst tubules, having the effect of insulating the animal from the deleterious action of the Cnidaria tentacles. Granular chitin, while protecting the animal, does not interfere with the suppleness and flexibility of the skin, in contrast to the stiffness of chitin armor. The specialized epidermis enables nudibranchs to live with and feed on Cnidaria., Introduction Chitin, a homopolymer of N-acetyl-D-glucosamine, is probably the most abundant biological material in the animal kingdom. The stiff chitin exoskeleton of arthropods may have been a decisive factor in [...]

A PCR-based method was developed to detect Angiostrongylus cantonensis directly from molluscan tissue to control the outbreak of human eosinophilic meningitis.

The goal of this study was to further investigate the role of endogenous APGWamide levels in imposex induction in snails. APGWamide is a common neurotransmittor/neuromodulator peptide found in many species of molluscs, and is often related to sex organ growth or reproductive behavior. Mud snails (Ilyanassa obsoleta) were collected from the Rachel Carson Estuarine Reserve near Beaufort, NC, and were dosed with the environmental contaminant tributyltin (TBT), testosterone (T), or solvent vehicle (EtOH/ saline) controls. Both TBT and T have been shown previously to induce female snails to grow penises (a condition termed imposex), and to increase male penis size. Male normalized penis length was correlated to endogenous APGWamide levels (as measured by Western blotting of whole animal homogenates, [r.sup.2] = 0.475), and control males had significantly higher APGWamide levels than control females. All TBT-treated animals, (male, female, and imposex) had levels of APGWamide similar to control males and significantly higher than control females. In testosterone treated animals, APGWamide levels were the same as controls and it is likely that testosterone interferes with a downstream signaling event to induce imposex. In addition, immunohistochemistry for APGWamide expression in abdominal areas was done on female, male and imposex snails collected from the wild. The pattern of APGWamide in imposex snails was similar to male snails, showing large patches of immuno-reactive areas in the top portion of the visceral mass. In female snails, no areas of cross-reactivity were found.

Bivalve molluscs have a highly plastic feeding and growth physiology. The increasing availability of families artificially selected for faster growth has enabled physiological experiments to investigate the genetic basis for variable rates of growth. Fast growth is achieved by a combination of increased rates of feeding, reduced metabolic rates and lower metabolic costs of growth. In at least one species there is a tradeoff between growth in protein and the storage of lipids that are utilized in gametogenesis. Energy requirements for maintenance are also higher in slow-growing individuals. Reduced costs of growth are due in part to increased efficiencies of protein turnover. Nevertheless, high protein turnover (and therefore high metabolic cost) may benefit fitness in the later stages of gametogenesis. Faster feeding rates do not impair flexibility in feeding behavior which compensates for changes in the food environment. Both inter- and intraspecies differences in feeding behavior are evident and suggest possible constraints imposed by faster feeding on the efficiency of selection between food particles of different nutritional value.

The relationship between the [[delta].sup.13] C of dissolved inorganic carbon (DIC) and modern mollusk aragonite from rivers was calibrated for the purpose of reconstructing DIC paleochemistry from the shell record. The [[delta].sup.13]C values of aragonitic bivalves (Dreissena polymorpha, Corbicula fluminea), prosobranch gastropods (Bithynia tentaculata, Theodoxus fluviatilis, Viviparus viviparus), and an air-breathing pulmonate gastropod (Limnea auricularia) were analyzed from several locations on the Rhone River (-13.7% to -6.0%) and its major tributary, the Saone River (-11.4% to--10.2%). The [[delta].sup.13][C.sub.DIC] varied from -11.5% to -7.5%, and the [[delta].sup.13]C of particulate inorganic matter (POM) varied from -31.7% to -25.4%. At a given site, the [[delta].sup.13]C of all species except the pulmonate were within 1% of each other. Whole-shell [[delta].sup.13]C correlated positively with [[delta].sup.13][C.sub.DIC], with a slope close to unity. Bioaragonite-DIC fractionations were 0-1.5% for bivalves and 0-2.7% for gastropods (excluding the pulmonates). Applying these fractionations, bivalves that live in open water are a reliable proxy, monitoring the average [[delta].sup.13][C.sub.DIC] value to within its natural ~2% temporal variation within the growth period. For the suspension feeders (bivalves) using POM as a food source, the [[delta].sup.13]C of whole shells and bulk POM indicated that the incorporation of carbon derived from respiratory sources lay in the range 10-30%. Fine-scale analyses of growth increments of C. fluminea could not be related simply to [[delta].sup.13]C DIC because metabolic and seasonal variations in [[delta].sup.13][C.sub.DIC] produced similar isotopic fluctuations ([less than or equal to] 2.5%).

Byline: O. V. Zaitseva (1) Keywords: visceral nervous system; afferent system; osphradia; gills; structural organization; gastropod mollusks Abstract: A variety of common histological stains was used, along with the Golgi and Colognier silver impregnation methods and electron microscopy, to perform a comparative study of the morphological characteristics of receptor and nerve cells and their interactions in the nervous system of the wall of the mantle cavity and mantle derivatives -- gills, siphon, and osphradia -- of the marine prosobranch gastropod mollusks Buccinum undatum and Littorina littorea. The results are discussed along with our own previously obtained data on the organization of the osphradial sensory organs and the afferent elements of the mantle cavity wall in other prosobranch mollusks -- the terrestrial Pomatia elegans and the freshwater Viviparus contectus and Pomacea paludosa. Using the nervous system of the complex of mantle organs of prosobranch mollusks as examples, the structural features and evolutionary trends of the afferent part of the visceral nervous system of gastropods are discussed. Author Affiliation: (1) A. A. Ukhtomskii Science Research Institute of Physiology and Department of General Physiology, St. Petersburg State University, 7/0 Universitetskaya Bank, 199034, St. Petersburg, Russia Article History: Registration Date: 12/10/2004

Byline: T. P. Norekyan (1), E. S. Nikitin (1), N. I. Bravarenko (1), A. Yu. Malyshev (1), P. M. Balaban (1) Abstract: Rhythmic activity in two independent structures of the digestive apparatus of Clione limacina -- the radula and the hooks -- is coordinated by neural networks in the buccal ganglion during feeding behavior. Optical recording of neuron activity in the buccal ganglion, which allows simultaneous recording of large numbers of neurons, showed that the activity of all neurons producing volley discharges can be assigned to only two phases of a single rhythm. Instead of the four theoretically possible phases of rhythmic neural activity, all experiments yielded recordings of biphasic activity, even in conditions of electrical stimululation of the cerebrobuccal connectives, which triggers rhythmic movements of this apparatus in preparations. These data demonstrate the phase-dependent coordination of two independent rhythmic food-procuring movements in Clione. Author Affiliation: (1) Institute of Higher Nervous Activity and Neurophysiology, Russian Academy of Sciences, Moscow Article History: Registration Date: 12/10/2004

Laboratory experiments tested whether the cardiac activity of two species of limpets (Cellana spp.), co-occurring on the rocky shores of Hong Kong but having different zonal distributions, was differently affected by variations in physical environmental characteristics. Experiments reproduced exposure of limpets to dehydration, high water temperature and reduced salinity, all conditions that can occasionally be faced by animals during low tides. Cardiographic traces were obtained using a non-invasive method based on infrared light sensors glued onto the limpet shell in a position directly over the heart. The signals were filtered and amplified, viewed on portable oscilloscopes and automatically transferred to computer. When tested under acclimation temperatures, the lower shore C. toreuma had faster heart rates than the upper shore C. grata, both in air and when submerged in seawater. Regular alternation of heartbeating and acardia were observed in C. grata exposed to both dry and saturated air, whilst C. toreuma showed transient acardia only during exposure to dry air. Both species showed a similar increase in heart rate with increasing temperature ([Q.sub.10]~l.8 in the range 25-34 [degrees] C). When submerged in freshwater, C. grata regularly alternated acardia with beating at a rate slightly lower than in seawater, whilst C. toreuma showed strong bradycardia with reduction of beat amplitude, followed by steady acardia. Recovery of heartbeating after return to initial salinity was faster in C. grata, whilst C. toreuma, initially bradycardic, showed a consistent return to tachycardia. Overall, this study shows that the two congeneric species exhibit different cardiac responses to variations in environmental characteristics, which may be related to their differing vertical distribution.

Postinhibitory rebound (PIR) is an intrinsic property of many neurons but the underlying mechanism is not well understood. We studied PIR and its relationship to spike adaptation in B-cells isolated from the buccal ganglia of Aplysia. These neurons exhibit PIR following inhibitory synaptic input and following direct membrane hyperpolarization. Hyperpolarizing and depolarizing voltage clamp pulses from the resting potential evoke slow changes in membrane current that persist in the form of tail currents following the pulses. A subtraction method was used to isolate slow tail currents for study. Current-voltage measurements indicate that slow outward tail currents following depolarizing pulses result from increases in membrane conductance, while inward tail currents following hyperpolarizations to -50 and -60 mV result from conductance decreases. The reversal potential of both outward and inward tail current is between -60 and -70 mV. Tail currents activated by pulses more positive than -60 mV are sensitive to the external [K.sup.+] concentration and blocked by injection of [Cs.sup.+] and TEA. When [Ca.sup.2+] influx is prevented by bathing cells in [Ca.sup.2+] free saline or by adding [Co.sup.+] or [Ni.sup.2+], the tail currents are reduced but a significant fraction of the current is insensitive to these treatments. More negative conditioning pulses activate a second component of inward tail current that is weakly sensitive to [K.sup.+] but more strongly effected by substitution of N-methyl glucamine or [Li.sup.+] for external [Na.sup.+]. We conclude that both PIR and adaptation result from slow changes in a voltage dependent, non-inactivating [K.sup.+] conductance that is active at voltages near the resting potential and is not tightly coupled to [Ca.sup.2+] influx. In addition, a second inward current is activated by large hyperpolarizing pulses that results from an increase in [Na.sup.+] and [K.sup.+] conductance. This second process is likely to contribute to PIR under particular circumstances.

Three primary factors contribute to locomotory speed changes in the pteropod mollusk Clione limacina. (1) An increase in cycle frequency of locomotory appendages is associated with a baseline depolarization and enhancement of postinhibitory rebound in central pattern generator (CPG) interneurons, and a reorganization of the CPG through recruitment of additional interneurons. (2) An increase in the force of appendage movements is generated through enhancement of activity of active motoneurons, recruitment of additional motoneurons and peripheral modulation of swim musculature. (3) Changes in biomechanical aspects of appendage movements are presumably achieved, at least in part, through changes in the activity of motoneurons and swim muscle. All changes associated with non-startle swim acceleration are produced by a serotonergic arousal system that acts at all three levels of the swimming system: CPG interneurons, motoneurons and swim musculature.

Research has been conducted on the nudibranch genus Phyllidiopsis distributed throughout the tropical indo-Pacific, eastern Pacific, Northwest Atlantic and Caribbean Sea. The phylogeny and the evolution of these species characterized by having geographic and bathymetric distribution among dorid nudibranches have been investigated and discussed.

Byline: N. N. Kamardin (1), Ya. Shalanki (2), K. Sh.-Rozha (2), A. D. Nozdrachev (1) Keywords: mollusks; electrophysiology; membrane currents; chemoreception Abstract: The formation and operation of the peripheral nervous system can be observed and studied in mollusks using as an example the primitive chemoreceptor organ, the osphradium, which is connected to the visceral arch of the CNS and analyzes the physicochemical properties of water in the mantle cavity. Nerve recordings showed that the osphradium is sensitive to excess osmotic pressure, sodium chloride, and amino acids. In addition, the osphradium responds to the quality of the water in which the animal is living. The osphradium of the pond snail retains its ancient multisensory function, uniting the perception of various chemical and physical stimuli. Patch clamp recordings at fixed potential or current were used to study membrane currents in identified ganglion and receptor cells, associated with increases in the concentrations of Na.sup.+ and L-aspartate in the solution bathing the osphradium. The influx current appears to be a sodium and/or calcium current, and is not blocked by tetraethylammonium, while the efflux current is a potassium current, as has been shown for the taste cells of vertebrates. Author Affiliation: (1) Department of General Physiology, St. Petersburg State University, 7/9 Universitetskaya Bank, 199034, St. Petersburg, Russia (2) Hungarian Academy of Sciences, Balaton Limnological Science Research Institute, Tihany, Hungary Article History: Registration Date: 08/10/2004

Byline: E. S. Nikitin (1), P. M. Balaban (1) Abstract: Electrophysiological methods and optical methods based on the use of potential-sensitive dyes were used to record stable rhythmic oscillations of local potentials in the olfactory structure (procerebrum) of the pulmonate mollusk Helix these oscillations were generally similar to those previously observed in slugs. Odor had the effect of transiently altering rhythmic oscillations to generate an individual pattern. This is the first study describing the recording of procerebrum potentials evoked by presentation of odor, with mapping of the areas of propagation of these potentials relative to the areas of propagation of rhythmic oscillations. The boundary of the propagation of the evoked potential was essentially similar to the projection of the neuropil, and rhythmic oscillations were recorded in the projection layer of procerebrum cell bodies. Evoked potential waves appeared in areas corresponding to the site at which the olfactory nerve enters the cerebral ganglion (of which the procerebrum forms a part) and were propagated in the procerebrum neuropil towards the cell body layer. Evoked potentials did not provoke out-of-phase waves of rhythmic oscillations. Author Affiliation: (1) Russian Academy of Sciences, Institute of Higher Nervous Activity and Neurophysiology, Moscow Article History: Registration Date: 08/10/2004

Byline: O. V. Zaitseva (1,2) Author Affiliation: (1) A. A. Ukhtomskii Physiological Science Research Institute, USA (2) Department of General Physiology, St. Petersburg State University, St. Petersburg Article History: Registration Date: 08/10/2004

The upper critical thermal limits were measured as heat-coma temperatures in Littorina species as a tool for examining physiological diversity. Thermal tolerance was found to be stable within a population, but extensive variation occurred between populations and species. All species examined displayed heat-coma values of ~30 [degrees] C and did not show a positive correlation with shore height. Eulittoral-fringe species tended to have higher coma temperatures than eulittoral species. Coma temperatures varied both seasonally and geographically. Lethal thermal limits were also investigated; these were ~10 C [degrees] higher than coma temperatures.

The form, anatomy and cytology of the water-passages in siphon-possessing and siphon-lacking species of a selected group of bivalve molluscs from the Red Sea (Callista florida, Circe currogata, C. crocea, Lucinia dentifera, Dosinia histrio, Pitar hebraea, Tridacna maxima, Pteria aegyptica), and from the Mediterranean Sea (Spondylus spinosus, Pinctada radiata, Pinna nobilis, Donax trunculus, D. semistriatus, Mactra stultorum, Tapes decussatus, Petricola lithophaga, Brachidontes pharaonis) were studied by means of light and electron microscopy. In the mytiloids, ostreoids and ptrioids studied, the water-passages are covered by a ciliated epithelium and the few tentacles around their openings are identical to those found on the mantle edges. Contrary to this, in the veneroids studied, the siphons are covered by a microvillar epithelium and their tentacles, especially of the inhalant siphon, reveal characteristic branching. The so-called Type I, Type II and Type III ciliated sensory organs on and within the siphons are similar to those observed in other bivalves, differing from each other in the dimension, number and form of cilia. In the studied mytiloid species only Type I and Type II organs were found. The form and structure of the siphons and the distribution of sensors on them can be used as markers for ecological as well as phylogenetic considerations.

The nature of heat coma was examined in the edible periwinkle Littorina littorea (L.). Duration of acclimation did not influence heat-coma temperature at 12 [degrees] C, although other acclimation temperatures were important in influencing thermal tolerance, with positive shifts in coma temperature observed in response to elevated temperatures. Previous thermal history also influenced heat-coma temperatures. Individuals subjected to repeat heat-coma events on a daily basis showed significant declines (P < 0.05) in coma-temperature; in contrast individuals exposed to repeat heat-coma events on a weekly basis showed no decline in thermal tolerance. Size-effects occurred at selected sites, where decreased heat-coma temperatures were recorded in large individuals. Thermal tolerance in intertidal gastropods is known to vary according to factors such as geography, season, and shore position. However, the effects of acclimation, previous thermal history and size have undergone relatively little investigation. Such factors may well influence the thermal capacity of an animal. This study examines the nature of heat coma in the edible periwinkle Littorina littorea.

The poorly known type species of Lingulella, Lingula davisii M'Coy, 185 lb, is redefined from new material collected from the type locality and horizon (Upper Cambrian, North Wales). Lingulella is similar to Obolus and to Ungula in its musculature, mantle canals, and pseudointerareas, but has a thinner shell and irregular pits over its internal surface, concentrated in the visceral areas. A dissolution method that can facilitate the study of lingulate brachiopods preserved in clastic lithologies is described, and its wider adoption is recommended in order to reveal diagnostic morphological characters.

Data is presented on the physiology of the Arctic freshwater pearl shell mollusk in relation to its longevity, which can reach 200 years. Contributing factors include the cold climate, which lowers metabolic rates, coupled with the species' ability to speed up the metabolic rate to repair damaged tissue or shell.

Copper dioxygen complexes derived from molecular receptor ligands are discussed relative to structure, synthesis and reactivity. The objective of realizing substrate-selective oxidation using a given complex, (2(Cu(II)(sub.2)O(sub.2))) was not realized. The complex was reactive toward phenols, but undesired radical coupling reactions were seen for the most part.

Research was conducted on ammonia effluxes in Mytillus edulis as influenced by starvation and emersion. Results demonstrate that similar patterns of ammonia efflux were observed both in fed and starved molluscs and reduced ammonia efflux during emersion.

Lasaea, a genus of brooding bivalves which is made up of minute crevice-dwelling intertidal molluscs, and the Amphi-Atlantic phylogeography of its direct-developing lineages are discussed. The importance of each of three dispersal hypotheses for bringing about colonization of North Atlantic oceanic islands has been tested. It appears that closeness to continental source populations is better as a predictor of phylogenetic relationships in North Atlantic Lasaea spp. than existing oceanic surface circulation patterns.

Ca(super 2+) channel inactivation in the neurons of the freshwater snail, Lymnaea stagnalis, was studied using patch-clamp techniques. In the presence of a high concentration of intracellular Ca(super 2+) buffer (5 mM EGTA), the inactivation of these Ca(super 2+) channels is entirely voltage dependent; it is not influenced by the identity of the permeant divalent ions or the amount of extracellular Ca(super 2+) influx, or reduced by higher levels of intracellular Ca(super 2+) buffering. Inactivation measured under these conditions, despite being independent of Ca(super 2+) influx, has a bell-shaped voltage dependence, which has often been considered a hallmark of Ca(super 2+)-dependent inactivation. Ca(super 2+)dependent inactivation does occur in Lymnaea neurons, when the concentration of the intracellular Ca(super 2+) buffer is lowered to 0.1 mM EGTA. However, the magnitude of Ca(super 2+)-dependent inactivation does not increase linearly with Ca(super 2+) influx, but saturates for relatively small amounts of Ca(super 2+) influx. Recovery from inactivation at negative potentials is biexponential and has the same time constants in the presence of different intracellular concentrations of EGTA. However, the amplitude of the slow component is selectively enhanced by a decrease in intracellular EGTA, thus slowing the overall rate of recovery. The ability of 5 mM EGTA to completely suppress Ca(super 2+)-dependent inactivation suggests that the Ca(super 2+) binding site is at some distance from the channel protein itself. No evidence was found of a role for serine/threonine phosphorylation in Ca(super 2+) channel inactivation. Cytochalasin B, a microfilament disrupter, was found to greatly enhance the amount of Ca(super 2+) channel inactivation, but the involvement of actin filaments in this effect of cytochalasin B on Ca(super 2+) channel inactivation could not be verified using other pharmacological compounds. Thus, the mechanism of Ca(super 2+)-dependent inactivation in these neurons remains unknown, but appears to differ from those proposed for mammalian L-type Ca(super 2+) channels. Keywords: molluscs; cytochalasin B; intracellular Ca(super 2+); Ca(super 2+) buffering

Osmoregulation and free amino acids in the intertidal pulmonate Onchidium tumidium, a marine, slug-like, snail which is naturally exposed to salinity changes twice a day, are discussed based on a study in Singapore. It was found that the species tolerates hyperosmotic stress more effectively that hypoosmotic stress.

Ultrastructural and histological investigation of the mollusk Dendrodoris nigra has revealed the presence of symbiotic bacteria in the vestibular gland and in egg masses. Further examination of the bacteria indicate that they are not contaminants but are stored within the reproductive system of nudibranch mollusk for a specific functional purpose, possibly one related to the mucous layer breakdown of the mollusk's egg capsule during intracapsular development. The bacteria are also believed to have a protective function for Dendrodoris nigra embryos.

Research was conducted to study peptides in two functionally related neurons, VD1 and RPD2, which established a network associated with heartbeat modulation in Lymnaea. Tiny hooks were utilized to dissect individual neurons from L. stagnalis while sequence fragments elucidated the primary structure of a peptide as Lymnaea small cardioactive peptide. Results showed that the effects of the alpha2 peptide on the contract rate were consistent and fast.

K+ channels are targeted by inhibitory synaptic transmitters ad neuropeptides. The Phe-Met-Arg-Phe-NHsub2 (FMRFa) family of neuropeptides are putative neurotransmiters in vertebrates and invertebrates. The properties of the FMRFa-activated K+ current of the Lymnaea stagnalis mollusc was analyzed. FMRFa was found to activate novel K+ current, with the response involving the formation of arachidonic acid.