World Congress of Malacology Antwerp ... - Unitas Malacologica

The Azores archipelago provides the geological history and the biological settings needed to capture
punctuated equilibrium alive. Morphological and anatomical analyses show that older islands have
species of the endemic Drouetia with various degrees of relatedness whereas younger islands include
cases of allotopic diversification and of interspecific closeness. Volcanic activity can be interpreted
as the “serious environmental perturbation” associated with the diversification episodes.
Spanish lower cretaceous freshwater molluscs
Delvene, Graciela 1 ; Araujo, Rafael 2 ; Bermúdez-Rochas, David D. 1
1. Museo Geominero (IGME), C/. Ríos Rosas, 23, 28003 Madrid (Spain),
Email: g.delvene@igme.es, d.bermudez@igme.es
2. Museo Nacional de Ciencias Naturales (CSIC). José Gutiérrez Abascal 2. 28006 Madrid. Spain,
Email: rafael@mncn.csic.es
Two associations of molluscs from the Lower Cretaceous have been recognized at Cameros Basin
(North of Spain), famous location due to the presence of dinosaur tracks. Samples were collected
from Valdehierro and Valdemadera sites, which belong to the lithological Urbión Group, upper
Hauterivian-lower Barremian in age. The palaeoecosystem is interpreted as a meandering fluvial
floodplain with temporary small shallow carbonate lakes. Valdehierro site has a rich freshwater
bivalve association dominated by the naiad Margaritifera idubedae, with representatives of both
juvenile and adult specimens registered in marls. Valdemadera outcrop has a very similar association
dominated by Margaritifera idubedae registered in marls with levels where gastropods and bivalves
are accumulated in a high number. Among gastropods, Planorbidae and Bythinidae families have
been identified. Among bivalves, there are juveniles of Margaritifera idubedae which shows a heartshaped
characteristic umbonal ornamentation, some specimens of Unio, and some juvenile
representatives of the Sphaeriidae family. Although until now we have not found a direct relation
between naiads and fish (that is, the presence of glochidia), we have found in both sites of Urbión
Group ichthyological remains corresponding mainly to ganoid scales of fishes belonging to the order
Semionotiformes (Actinopterygii, Neopterygii). All taphonomic features of both fossil groups
(molluscs and fishes) suggest this association as a palaeocommunity. Assuming both, that
Margaritifera used the same dispersion method in the past than today, and that most of the extant
fishes used like host were inexistent or not abundant in the Early Cretaceous, it is plausible that
Semionotiformes were a valid host for the naiads at this time. This fishes were very abundant in
Mesozoic and very extended paleogeographically in both, marine and freshwaters ecosystems.
Control of a mollusc heart by 5-hydroxytryptamine and acetylcholine receptor subtypes
Devlin, C. Leah; Folger, Peter; Heinz, Justin; Nieves, Joyce; Sverzhin, Maksim
Department of Biology, Penn State University, Abington College, Abington, Pennsylvania, USA,
Email: cld5@psu.edu
We conducted a neuropharmacological study on the respective receptor subtypes involved in
cardioexcitation by 5-hydroxyptrytamine (5HT) or cardioinhibition by acetylcholine (ACh), using as
our model the heart of bivalve, Mercenaria mercenaria. Treatment of the heart with 5HT increased
cardiac contractions, heart rate and basal tone. 5HT1 receptor agonist, buspirone mimicked the action
of 5HT. Pindolol, a 5HT1 antagonist, decreased buspirone-induced contractions yet increased heart
rate. 5HT2 receptor agonist, α-methylserotonin maleate (α-MSM) also had an excitatory effect on
both heart rate and contractile force. 5HT2 antagonist, metergoline increased force yet decreased heart
rate of α-MSM-induced rhythmicity. These combined data suggest the presence of both 5HT1 and
5HT2-like receptors in the bivalve heart. 5HT-induced rhythmicity was blocked completely by
treatment with neurotransmitter, ACh. Like ACh, the muscarinic agonists, arecoline, carbachol and
methacholine inhibited the action of 5HT. Curiously, other muscarinic agonists such as oxotremorine
or pilocarpine had no efficacy in blocking 5HT-induced rhythmicity.
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