World Congress of Malacology Antwerp ... - Unitas Malacologica

Immunohistochemistry reveals neural processes that respond to anti-serotonin antibody. A
serotoninergic antagonist, methysergide, reduces the amplitude of EJPs in the AV valve. IJPs are
blocked by cholinergic antagonists, such as Mytolon and d-tubocurarine. IJPs in the AV valve of
Mercenaria mercenaria invert to depolarizing potentials in low chloride medium. Serotoninergic
control of the heart of the chiton, Acanthopleura japonica, indicates that serotoninergic excitatory
control appeared early in molluscan evolution. Serotoninergic fluorescence histochenistry identifies
fibers in the chiton heart and pericardium. Serotonin excitation of pericardial beating may be
compared to serotoninergic excitation of the whole chiton heart. The ventricle of Busycon
canaliculatum has been used as a test organ for identification of the characteristics of neuropeptides
which determine relative levels of excitation of ventricular inotropism. This work is complemented
by work with T. Fort and a number of collaborators, using the whelk radular protractor muscle as
itself a model of molluscan cardiac muscle. Excitatory interaction of serotonin and acetylcholine
provides a model for interaction between biopeptides. The radular protractor muscle, mounted in a
double sucrose gap, has served for modeling, implementation and application of a new digital voltage
clamp. This work, with the collaboration of Leon Collis and Jiang Wu has made a new Universal
Clamp practicable. This digital voltage clamp has in turn been applied to ventricular trabeculae of
Spisula solidissima.
Metal speciation and metallothionein induction after cadmium exposure in the terrestrial snail
Helix aspersa (Gastropoda, Pulmonata)
Hispard, Florian 1 ; Schuler, Dietmar 2 ; de Vaufleury, Annette 1 ; Dallinger, Reinhard 2
1. University of Franche-Comté, Department of Environmental Biology, EA 3184 aff. INRA, Place
Leclerc, 25030 Besançon Cedex, France,
Email: Annette.devaufleury@univ-fcomte.fr; Florian.HISPARD@igh.cnrs.fr
2. Institut für Zoologie, Universität Innsbruck, Technikerstrasse 25, A-6020 Innsbruck, Austria,
Email: reinhard.dallinger@uibk.ac.at; Dietmar.Schuler@student.uibk.ac.at
The effect of Cd 2+ exposure on metallothionein induction and on the speciation of metals (Cd, Cu,
Zn) were studied in the terrestrial pulmonates Helix aspersa (syn. Cantareus aspersus), to better
understand their possible contribution to the trophic transfer of trace elements, and the potential
bioavailability of the Cd they stored for consumers and predators. The soluble and non-soluble pools
of the accumulated metals and their tissue distribution in uncontaminated and contaminated edible
snails were investigated after a two-week exposure to Cd2+. In the soluble cytosolic pool of the
hepatopancreas of H. aspersa, three metal-specific putative metallothionein (MT) isoforms were
separated following a fractionation protocol with DEAE cellulose, size exclusion chromatography,
ultrafiltration, and reversed phase (RP) HPLC. Interestingly, one of the above isoforms seems to bind
both Cd and Cu which may in addition mobilize, after induction by Cd2+, some of the intracellular
Cu, and thus perhaps increase the bioavailability of the Cu pool in the cytosolic fraction. The cDNA
and its translated amino acid sequence of a Cd2+ binding MT isoform from the snail hepatopancreas
was also characterized and attributed to one of the putative MT isoforms obtained upon RP-HPLC.
The amino acid sequence of this Cd-MT isoform of H. aspersa was found to differ from similar
sequences described in other terrestrial pulmonates, such as Helix pomatia or Arianta arbustorum, by
only a few amino acids (6 and 10, respectively). That the identified Cd-MT from H. aspersa is
inducible by Cd2+ was also shown, chromatographical evidence laid aside, by a specific PCR
protocol on a cDNA basis, which included a non-inducible, house-keeping gene as a control.
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