World Congress of Malacology Antwerp ... - Unitas Malacologica

7. Institute of Biology, Leiden University, P. O. Box 9516, 2300RA Leiden, the Netherlands,
8. Sustainability Group, Victoria University, P. O. Box 14428, Melbourne City MC, Victoria 8001,
Australia
While the vast majority of higher animals are fixed for one chiral morph or another, the cause for this
directionality is known in only a few cases. In snails, rare individuals of the opposite coil are unable
to mate with individuals of normal coil, so directionality is maintained by frequency-dependent
selection. The treesnail subgenus Amphidromus presents an unexplained exception, because dextral
(D) and sinistral (S) individuals occur sympatrically in roughly equal proportions (so-called
“antisymmetry”) in most species. Here we show that in Amphidromus there is sexual selection for
dimorphism, rather than selection for monomorphism. We found that matings between D and S
individuals occur more frequently than expected by chance. Anatomical investigations showed that
the chirality of the spermatophore and the female reproductive tract probably allow a greater
fecundity in such inter-chiral matings. Computer simulation confirms that under these circumstances,
sustained dimorphism is the expected outcome.
Potamopyrgus antipodarum as a test organism for the assessment of endocrine active chemicals
Schmitt, Claudia 1 ; Bervoets, Lieven 2 ; De Deckere, Eric 1 ; Meire, Patrick 1
1. University of Antwerp, Universiteitsplein 1, 2610 Antwerp, Belgium,
Email: claudia.schmitt@ua.ac.be; eric.dedeckere@ua.ac.be; patrick.meire@ua.ac.be
2. University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium,
Email: lieven.bervoets@ua.ac.be
Within the last years, the research on endocrine disruption in invertebrates increased and nowadays
there are several examples reported in the literature. Especially, prosobranch snails have been
recommended as promising candidates for test organisms regarding the assessment of endocrine
active chemicals. The reproduction of Potamopyrgus antipodarum seems to be a very sensitive
endpoint for xeno-estrogens (bisphenol A, octylphenol and ethinylestradiol) and xeno-androgens
(triphenyltin, tributyltin and methyltestosterone). Due to many practical advantages for
ecotoxicological testing, by means of easy culturing and test performance, P. antipodarum appears to
be an appropriate species to be introduced into the OECD guideline program for standardisation.
The presentation will introduce biotests with P. antipodarum for water- and sediment exposure in the
laboratory and point out the advantages of P. antipodarum compared to other prosobranch snails
which are used in ecotoxicological tests. Furthermore, results of laboratory experiments and
biological effect monitoring surveys in the field will be discussed.
Melanoides from Lake Turkana: a documentation of speciation and case study
for “punctuated equilibrium”?
Scholz, Henning; Glaubrecht, Matthias
Museum für Naturkunde, Invalidenstrasse 43, 10115 Berlin,
Email: henning.scholz@museum.hu-berlin.de; matthias.glaubrecht @museum.hu-berlin.de
The Plio-Pleistocene molluscs of the Turkana Basin were considered as ideal documentation of
speciation and the theory of "punctuated equilibrium" in the past. The hypothesis of "punctuated
equilibrium" is debatable in general and was in particular disputed for Williamson's Turkana
molluscs. For example, the question of simultaneous emergence of new genotypes, the problems of
phenotypic variability of freshwater molluscs in general and the implications of time averaging of
Williamson's findings were repeatedly addressed. After being hottly debated in the 1980 th , no further
studies were carried out, neither based on Williamson's collections nor on new material collected in
situ. Here, we report on an re-evaluation of the Melanoides collection of Williamson in order to test
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