World Congress of Malacology Antwerp ... - Unitas Malacologica

of egg-shell from an average of 8.1 µm in eggs laid by control snails to about 7.1 µm in those laid by
exposed snails. About 50% to 60% of eggs laid by snails exposed to sublethal concentrations of
Delvap were also cracked before the attainment of full development. The implication of the use of the
insecticide on snail populations in the wild especially as it relates to reproductive failures due to eggshell
thinning and cracking were discussed. Additionally, the inclusion of the biological responses
such as avoidance (for example artificial aestivation), egg-shell thinning and cracked eggs of snails as
biomarkers of organophosphate insecticide contamination in the wild populations was recommended.
Extreme length development of the penis in the terrestrial slug genus Limax: a case of sexual
selection? (Gastropoda: Limacidae)
Falkner, Gerhard 1 ; Klee, Barbara 2
1. Staatliches Museum für Naturkunde Stuttgart, Rosenstein 1, D-70191 Stuttgart, Germany,
Email: falkner@malaco.de
2. Zoologische Staatssammlung München, Münchhausenstraße 21, D-81247 München, Germany,
Email: Barbara.Klee@zsm.mwn.de
The luxuriant development of the male copulatory organs in some representatives of the European
slug-genus Limax (penis up to eight times the body length) and the pertaining exceptional behaviour
are among the most rousing natural wonders. The phenomenon has already been aptly described in
late Humanism (F. Redi), but these observations have long been taken as unreliable
misinterpretations. It was only in the 20 th century that a spectacular copulation behaviour in Limax
was described that corroborated the observations from the 17 th century (B. Peyer, E. Kuhn, U.
Gerhardt). All modern investigators (U. Gerhardt, L. Forcart, A. Wiktor, A. J. de Winter) took the
presence of an extreme long penis as a crucial character indicating close phylogenetic relationship of
these forms, or even supporting the idea of specific identity. Our combined morphological,
behavioural and molecular genetical research revealed that the extreme penis length is not a character
that indicates common ancestry. It must have evolved independently at least seven times in different
branches of the phylogenetic tree. Of special interest is the group of Limax corsicus, distributed over
the adjoining Italian continent and the islands of the Tyrrhenian Sea. In this group we have side by
side closely related forms with very different penis lengths. The comparison of the bionomics of
these forms shows that there exists in all probability an environmental selective pressure in the
direction to develop a shorter penis, but the inverse evolution seems to take place only if the
environmental factors allow it. Forms with an extra long penis are more demanding and especially
vulnerable against environmental disturbations. The strong selective forces that lead to extreme
length development must therefore be of endogenous nature. If we declare the adaptive value of the
long penis as induced by sexual selection, this is not yet an explanation, but must be taken as a
programme for further research.
Genetic differentiation in Maakia herderiana (Mollusca, Gastropoda)
Fazalova, Varvara; Sherbakov, Dmitry
Limnological Institute Siberian Branch of the Russian Academy of Sciences, Irkutsk 664033, Russia,
Email: varvara@fazalova.com; sherb@lin.irk.ru
Explaining the origin and development of species’ diversity is one of the greatest challenges for
biologists. Fast rate of the speciation, morphological variability, and also a low dispersal rate allow
considering the molluscs of the lake Baikal (Russia) as suitable for investigation of
microevolutionary processes involved in speciation. Maakia (Eubaicalia) herderiana is one of the
species dominating the stone littoral of the lake. This species exhibit variation in their shell sculpture:
from a ribbed to a smooth type (both: across the depth of the lake and along the shore). Ribbed and
smooth shell morphs do not differ neither if the anatomy of the reproductive system is considered nor
when the food composition is examined.
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