Marine Gastropod Molluscs Research Articles

The apical complex of the gregarineDigyalum oweni(Protozoa: Apicomplexa)

The aseptate gregarine Digyalum oweni is parasitic in the gut of some species of Littorina, marine gastropod molluscs. The apical complex comprises a mucron (described previously), polar ring, polar ring extension, subpellicular microtubules and rhoptries; and possibly also micronemes and dense granules. The polar ring extension is possibly a microtubule organizing centre. The method by which D. oweni attaches to its host cell may be similar to that used by intracellular apicomplexans to invade host cells. After attachment of D. oweni to the host cell the rhoptries may secrete enzymes into the host cell prior to digestion.

Structures of monodontamides A, B, C, D, E, and F, six new alkaloids isolated from the marine gastropod mollusc Monodonta labio (Linné)

Six new alkaloids monodontamides A ( 1), B ( 2), C ( 3), D ( 4), E ( 5), and F ( 6) were isolated from the marine gastropod mollusc Monodonta labio (Linné). The structures of monodontamides were established on the basis of spectral data and unambiguous synthesis. Monodontamides exhibited weak inhibitory activity against a serine protease.

Monodontamides A, B, and C, three new putrescine alkaloids from the marine gastropod mollusc Monodonta labio (Linné)

Described are the structure determination and synthesis of three new alkaloids, monodontamides A ( 1), B ( 2), and C ( 3) isolated from the marine gastropod mollusc Monodonta labio (Linné).

The mucron of the gregarineDigyalum oweni(Protozoa: Apicomplexa), parasitic inLittorinaspecies (Mollusca: Gastropoda)

The aseptate gregarine Digyalum oweni is parasitic in the gut of some species of Littorina, marine gastropod molluscs. The mucron, its anterior attachment organelle, comprises a ring of lobes and a ring of granular material embedded in the apex of the host intestinal cell. Some tissue damage is caused to the host cell but this is confined to the apical tip and otherwise the parasite does not appear to harm the snail. In addition to securing the parasite to its host, the mucron may have a role as a microtubule organizing centre and in nutrition.

Specific Inhibitors of Protein Synthesis Do Not Block RNA Synthesis or Settlement in Larvae of a Marine Gastropod Mollusk (Haliotis rufescens).

Antibiotic inhibitors of protein synthesis were tested for their effectiveness in larvae of the red abalone, Haliotis rufescens (gastropod mollusk). Emetine and anisomycin proved highly effective in this system, while cycloheximide, fusidic acid, puromycin, and tetracycline were less effective. Emetine and anisomycin specifically inhibited protein synthesis but not RNA synthesis. The contribution to protein synthesis by chloramphenicolsensitive prokaryotic contaminants was found to be undetectable, except following the onset of symptoms of toxicity resulting from prolonged exposure to emetine or anisomycin. The induction of larval settlement and plantigrade attachment by γ-aminobutyric acid (GABA), a functional analog of the natural inducer of settlement, occurred even under conditions in which most protein synthesis was inhibited, as expected for a chemosensory system response, whereas subsequent developmental metamorphosis was completely blocked. Because emetine and anisomycin block protein synthesis--including the synthesis of new transcription factors--but do not block early transcription, treatment of marine invertebrate embryos and larvae with these inhibitors can be used to obtain a selective enrichment in the mRNA population of "early gene" transcripts induced directly by GABA and other morphogenetic signals, without dilution by new mRNAs, the appearance of which is dependent on the synthesis of new protein transcription factors.

Quisqualate and ACPD are agonists for a glutamate-activated current in identified Aplysia neurons.

1. Glutamate is an important neurotransmitter in both vertebrates and invertebrates, yet the characterization of molluscan glutamate receptors and their relationships to vertebrate receptors is incomplete. This study uses two-electrode voltage clamp to characterize glutamate-evoked currents in cultured neurons from the marine gastropod mollusk Aplysia californica. 2. The identified buccal ganglion neurons, B1 and B2, display two pharmacologically distinct current responses to pressure-applied glutamate. One response is a desensitizing chloride current similar to that found in other large buccal ganglion neurons. The other is a nondesensitizing potassium current that is strongly outwardly rectifying. 3. The potassium current response has a higher sensitivity to glutamate than the chloride response. 4. Individual neurons, isolated in primary cell culture, exhibit different relative proportions of the two currents. 5. The glutamate agonists quisqualate and (1S,3R)-aminocyclopentane-1,3-dicarboxylic acid specifically evoke the potassium response but not the chloride response. The glutamate agonist (RS)-alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid does not evoke any appreciable response. Kainate and N-methyl-D-aspartate also have no effect on these cells. Another glutamate analogue, ibotenate, evokes the transient chloride current but not the potassium current. 6. These results indicate that the glutamate receptor mediating the outward potassium response does not conform in its pharmacological profile to any of the known vertebrate glutamate receptor types.

Inactivation of 6-phosphofructo-2-kinase during anaerobiosis in the marine whelk Busycon canaliculatum.

6-Phosphofructo-2-kinase (PFK-2) was analyzed in four organs of the anoxia-tolerant marine gastropod mollusk Busycon canaliculatum. Whelk PFK-2 resembled the nonhepatic enzyme from mammals with highest activity occurring in gill (22 pmol.min-1.g-1). Hepatopancreas PFK-2 was purified over 8,000-fold to a final specific activity of 11 mU/mg protein (at 20 degrees C) and gave a single band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The enzyme was a dimer with a native molecular mass of 142 kDa and a subunit molecular mass of 67 kDa. The purified enzyme showed negligible fructose-2,6-bisphosphatase (FBPase-2) activity, although the activity ratio of PFK-2 to FBPase-2 was 0.625 in crude extracts. In response to environmental anoxia, the activity of PFK-2 dropped in all organs to 34-56% of the corresponding aerobic value (half-time was 2 h in gill), and the Michaelis constant for fructose 6-phosphate increased by 50% (to 92 microM in gill). These changes paralleled decreases in organ fructose 2,6-bisphosphate concentration and pyruvate kinase activity and contribute to the overall glycolytic rate depression induced by anoxia in this facultative anaerobe. In vitro treatment of the anoxic form of hepatopancreas PFK-2 with alkaline phosphatase increased enzyme activity, suggesting that the aerobic and anoxic enzyme forms are interconverted by reversible protein phosphorylation. However, the protein kinase involved in this process is not yet known; incubation of aerobic PFK-2 with Mg-ATP plus adenosine 3',5'-cyclic monophosphate-dependent protein kinase or protein kinase C did not alter enzyme activity.

Histamine in the nervous system ofMacoma balthica (Bivalvia)

The distribution of histamine(HA)-immunoreactivity of the molluscan species Macoma balthica was mapped with an antiserum against a histamine-protein conjugate. The main ganglia of the central nervous system of M. balthica, the cerebropleural ganglia, the pedal ganglion and the visceral ganglion all contained strongly HA-positive fluorescent cell bodies. The positive cell bodies were situated in clusters in the outer region of the ganglia. Immunoreactive fibres were located in the inner neuropil region of the ganglia. Also the commissure and the connectives of the ganglia as well as many nerve roots contained HA-positive fibres. These results agree well with the recent finding of the wide distribution of histamine in the nervous system of two marine gastropod molluscs, Aplysia and Pleurobranchaea supporting the thought that histamine has an important role in many physiological function of molluscs.

In vitro attachment of Vibrio parahaemolyticus to hemocytes of two gastropod molluscs.

Vibrio parahaemolyticus D-3 was observed to attach to hemocytes of a marine gastropod mollusc, Nerita albicilla, regardless of the presence of N. albicilla serum. The organism attached to hemocytes of an estuarine gastropod, Clithon retropictus, in the presence of C. retropictus serum while the attachment to the hemocytes was decreased significantly in the absence of the serum. These evidences suggest that N. albicilla hemocytes would facilitate the clearance of V. parahaemolyticus from the alimentary tract of the mollusc and that C. retropictus hemocytes would protect C. retropictus against the invasion of V. parahaemolyticus to hemocoel of the mollusc.

Biochemical and functional characterization of Rapana thomasiana hemocyanin

1. 1. The hemocyanin (Hc) of the marine gastropod mollusc Rapana thomasiana was collected from animals living on the west coast of the Black Sea and characterized for its biochemical and functional properties. 2. 2. This Hc is very similar to other gastropod Hcs as far as amino acid composition, general structure and reactivity of the binuclear copper active site are concerned. 3. 3. Some peculiarities in the dissociation-reassociation pattern are observed in comparison to other gastropod Hcs, in particular with respect to the ability to form sopramolecular aggregates. 4. 4. Changes in pH disclose a strong reverse Bohr effect. Different R and T states are required to describe the oxygen binding curves at the different pHs.

New metabolites from the marine mollusc siphonaria grisea

Four new metabolites 6, 7, 8and 9 possessing a polypropionate carbon skeleton, have been isolated from the marine gastropod mollusc S. grisea. Their structures and absolute configurations have been determined by spectroscopical and chemical methods. The absolute configuration of pectinatone 5, is reassigned on the basis of its chemical degradation and X-ray analysis.

Heavy metal effects on cellular shape changes, cleavage, and larval development of the marine gastropod mollusk, (Ilyanassa obsoleta Say).

The spawning areas for many marine invertebrates are in intertidal zones which can be exposed to surface water run-off containing heavy metals. The cellular shape changes and cleavage patterns of Ilyanassa embryos greatly resemble those of bivalve mollusks, such as Mytilus edulis, that occur in the same intertidal areas. Determining the concentrations of heavy metals tolerated by the molluscan embryos inhabiting such clam and mussel beds therefore is of some economic significance. Moreover, such research may providedata on the heavy metal effects on the cytoskeleton. There is increasing evidence that components of the cytoskeleton, directly or indirectly, are targets for toxic agents. Polar lobe formation is a cellular shape change that resembles cytokinesis. It is seen in the fertilized eggs of many marine mollusks. Recent data with inorganic and organic Ca/sup 2 +/ antagonists suggest that both polar lobe formation and cytokinesis utilize Ca/sup 2 +/ released from sequestered, intracellular sites. Both of these cellular constrictions are associated with microfilaments and are preceded by activation steps requiring microtubules. The data presented below suggest that several heavy metals affect the microfilament-dependent steps.

IONIC CONTROL OF SETTLEMENT AND METAMORPHOSIS IN LARVALHALIOTIS RUFESCENS(GASTROPODA)

An increase in the concentration of K+ in defined sea water medium is demonstrated to induce settlement and metamorphosis in larvae of the marine gastropod mollusc, Haliotis rufescens. A decrease in external K+ ion concentration can inhibit the larval response to γ-aminobutyric acid (GABA), a stereochemically specific inducer of metamorphosis of H. rufescens. Stimulation of the metamorphic response by GABA or by increased K+ may depend on transmembrane movement of ions, since induction is sensitive to neuropharmacological blockers of ion conductance. Sulfonyl isothiocyanostilbene (SITS, an anion exchange blocker) inhibits the larval response to GABA, but does not affect induction by increased external potassium. In contrast, the larval response to potassium is inhibited by tetraethylammonium (TEA, a potassium channel blocker), while induction of metamorphosis by GABA is independent of the presence of TEA. Most manipulations of the concentrations of the other predominant cation components of sea water are ...

A monoamine-detecting histofluorescence technique for use on wholemounts of molluscan tissues

A histochemical procedure is described which has been used to visualize monoamine-containing neurons, fibers and varicosities within wholemounts of a number of tissues of the marine gastropod mollusc, Philine aperta. The method is rapid and simple and the morphology of the specimen is preserved without distortion. This technique may facilitate studies of the distribution of monoamines in the tissues of other marine molluscs.

Physiological adaptations to entosymbiosis in three species of graffillid rhabdocoels

Three entosymbiotic graffillid rhabdocoels (Paravortex scrobiculariae, P. cardii and Graffilla buccinicola) from marine bivalve and gastropod molluscs show several physiological adaptations to their life-style which are intimately related to the nutritional physiology and ecology of their respective hosts.

Stoichiometry and apparent dissociation constant of the calcium-arsenazo III reaction under physiological conditions

In vitro and in situ tests have been run to characterize the reaction of the mettalochromic indicator, arsenazo III, with calcium. Job plots as well as plots of indicator absorbance vs. [Ca2+] at different indicator concentrations show a 1:1 reaction stoichiometry. Equilibrium analysis and analysis using Adair's equation are also consistent with 1:1 complexes being formed and give estimates of 34 and 45 muM for the apparent dissociation constant. In situ tests were carried out using giant neurons from Archidoris monteryensis, a marine gastropod mollusc. Dye absorbance changes were measured during voltage clamp pulses which produced a fixed calcium influx. The dependence of absorbance change on total dye concentration is consistent with the formation of a 1:1 complex of Ca with ArIII if measurements are made during the initial period of the loading pulse, less than 300 ms, although the apparent dependency changes with longer delay in measurements from the onset of the pulse.

GABA induces metamorphosis in Haliotis, V: Stereochemical specificity

Larvae of the marine gastropod mollusc, Haliotis rufescens, display an absolute requirement for GABA (or specific GABA homologs and analogs) for induction of genetically programmed behavioral and developmental metamorphosis to the juvenile form. Systematic investigation of the Stereochemical specificity of this requirement, its sensitivity to inhibition by non-inducing GABA analogs, and the effects of neuropharmacological probes of GABA function reveal the involvement of GABA receptor and/or early processing sites similar to those in mammalian brain. Convenient, quantitative analyses of the GABA-dependent behavioral and developmental transition in these experimentally tractable larvae can provide fundamental information on the mechanisms of induction and control of developmental processes by this major neurotransmitter, and the sensitivities of these processes to GABA agonists and antagonists.

FISH PREDATION AND THE EVOLUTION OF GASTROPOD SHELL SCULPTURE: EXPERIMENTAL AND GEOGRAPHIC EVIDENCE.

EvolutionVolume 33, Issue 2 p. 697-713 ArticleFree Access FISH PREDATION AND THE EVOLUTION OF GASTROPOD SHELL SCULPTURE: EXPERIMENTAL AND GEOGRAPHIC EVIDENCE A. Richard Palmer, A. Richard Palmer Department of Zoology, University of Washington, Seattle, Washington, 98195Search for more papers by this author A. Richard Palmer, A. Richard Palmer Department of Zoology, University of Washington, Seattle, Washington, 98195Search for more papers by this author First published: June 1979 https://doi.org/10.1111/j.1558-5646.1979.tb04722.xCitations: 121AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume33, Issue2June 1979Pages 697-713 ReferencesRelatedInformation

Biphasic constant-current stimulator for whole-animal shocking of marine animals

A constant-current stimulator delivering biphasic pulses was designed and constructed for whole-animal shocking during aversive conditioning of Pleurobrartchaea, a marine gastropod mollusk used for behavioral and neurophysiological research. The advantages of whole-animal stimulation are discussed and results are briefly described with regard to the factors involved in evaluating the procedure. The circuit design and electrode considerations are presented in detail. The basic stimulator design has potential for use as a general instrument for behavioral and physiological research.

Heavy metal complexation in polluted molluscs I. Limpets ( Patella vulgata and Patella intermedia)

The accumulation of cadmium, zinc and copper by the marine gastropod molluscs Patella vulgata and Patella intermedia has been studied by gel permeation chromatography of water-soluble extracts of environmentally contaminated shellfish. A major proportion of the water-soluble cadmium and copper in these molluscs is associated with a protein of molecular weight 10 800 daltons. Evidence is presented supporting the similarity of this protein with mammalian metallothionein. This protein contained only a small proportion of the zinc found in the samples.