World Congress of Malacology Antwerp ... - Unitas Malacologica

Mollusc identifications cards for Central Europe ("miniposters") - a tool for determination,
field work and education
Wiese, Vollrath 1 ; Richling, Ira 2
1. Haus der Natur – Cismar, Bäderstr. 26, D-23743 Cismar, Germany,
Email: vwiese@hausdernatur.de
2. Hasselkamp 29 B, D-24119 Kronshagen, Germany,
Email: ira@helicina.de
Even for the well-documented molluscan fauna of Central Europe handy and cheap identification
tools also for non-specialists are rare. Therefore laminated determination cards of about 20 x 30 cm
double-sided were created which are robust for field work. These cards illustrate almost all molluscan
species (shells of snail and slugs) of Central Europe in colour photographs. Each identification card
covers the inhabitants of a different environment. Up to date the following miniposters are available:
"Süßwassermollusken" (= freshwater molluscs, 90 species illustrated),
"Landschnecken 1" (= landsnails 1, all important lowland shell-bearing snails, 130 species),
"Landschnecken 2" (= landsnails 2, slugs, alpine and montane snails, 120 species),
"Weichtiere" (= molluscs, the most important land and freshwater species, overview for beginners),
"Nordsee-Strand, Schnecken und Muscheln" (= shells of the North Sea),
"Ostseestrand" (= litoral animals of the Baltic Sea).
The inclusion of almost all species allows the comparison of related or similar species and the
recognition of family characters. All figures are scaled and in addition, ecological information is
provided when useful for determination, e. g. in land snails. The authors hope that the miniposters
will also help to promote malacology to young and adult non-specialists by the beauty and great
variety of the molluscs shown in high quality images.
Ecophenotypic variation in the mangrove oyster, Isognomon alatus (Pterioidea: Bivalvia)
associated with a tide microhabitat gradient
Wilk, John
University of Illinois at Chicago, 845 W. Taylor St., Chicago, Illinois, USA,
Email: jwilk@uic.edu
Field Museum of Natural History, 1400 S. Lake Shore Dr, Chicago, Illinois, USA,
Email: jwilk@fieldmuseum.org
The marine bivalves of the genus Isognomon Solander, 1786 exhibit extreme phenotypic plasticity.
So much morphological variation exists within these “flat oysters” that species boundaries are
difficult to perceive and taxonomic designations cannot be made with confidence. Understanding the
environmental sources of this variation and their resulting effects would allow us to quantify and
potentially correct for this variability. However, most specimens held in museum collections do not
have records of microhabitat conditions at the collection site detailed enough to allow for any sort of
ecophenotypic correction. My current research examines the ecophenotypic responses of Isognomon
alatus (Gmelin, 1791) to a tidal gradient and asks if these morphological changes have the potential
to confound taxonomic designations.
Results indicate that abundance of this bivalve is positively correlated with average yearly air
exposure while specimen size is negatively correlated with this environmental factor. This leads to a
population of many, small individuals at high tidal positions and a few, large individuals inhabiting
permanently submerged positions. Shape analysis was carried out using geometric morphometrics on
a dataset containing both landmark and outline information. Multivariate regressions of shape show
that a small but statistically significant proportion of the variation in shell shape was correlated with
both time submerged per year and area available per oyster. Due to the strong covariation between
the two microhabitat variables, the separation of the two effects is not yet possible. The combined
morphological effect of these factors is approximately one-tenth the magnitude of allometric growth
and one-half that seen between Isognomon alatus and I. ephippium (Linnaeus, 1758), members of the
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