World Congress of Malacology Antwerp ... - Unitas Malacologica

elation with environmental variables and the phenology of Z. marina have been also analyzed for
obtaining information on its ecology and biology.
J. striatus is the top dominant epifaunal species on the Z. marina beds from the Alboran Sea (60 -
80%) and its density is highly correlated with the leaf biomass of this seagrass. This trochid performs
vertical movements along the shoots of Z. marina within a diel cycle, with higher density of
individuals on shoots at night time. In an annual cycle, J. striatus displays maximum densities (40 -
80 individuals. m -2 ) during spring and summer due to a peak of recruitment in spring months (up to 5
juveniles . m -2 ). Nevertheless, ultrajuveniles of this gastropod (shell height < 1mm) are present in the
eelgrass bed during a longer period (from February to October) coincident with the presence of
individuals in active (gonad full of gametes) or spawning stages. The sexual maturity of the studied
population is reached at 2-3 mm (shell height) and each individual can spawn more than once a year.
The presence of spermatophores in the pallial cavity of one male may indicate some kind of internal
fecundation.
Fast trails versus hard shells: using defensive traits in aquatic gastropods as a model system for
exploring questions in evolutionary ecology
Rundle, Simon D.
Marine Biology and Ecology Research Centre, University of Plymouth, Plymouth PL4 8AA, UK,
Email: srundle@plymouth.ac.uk
Aquatic gastropods possess defensive traits that allow us to explore important questions in
evolutionary ecology. Here I present data that illustrate patterns in defensive trait expression and
plasticity at the level of species and populations. Interspecific comparisons of morphological (shell)
and behavioral (avoidance) traits demonstrated trait compensation (i.e. a negative correlation)
between these different forms of defense: in freshwater species this related to differences in shell
strength between species, whereas for marine taxa, shell shape was of more importance. A crossspecies
comparison of plasticity in defensive morphological traits (i.e. shell size and shape) in marine
gastropods suggested considerable variation between species in the type and degree of plastic
response exhibited and no clear relationship with phylogeny. Finally, a study focusing on avoidance
behavior in a freshwater gastropod (Lymnaea stagnalis) suggested that both selection and plasticity
may play a role in shaping responses in local populations. Together, these findings suggest that
gastropod defensive traits can provide valuable insights into evolutionary ecology. I conclude by
suggesting that this utility of gastropods may be extended within a framework that allows us to take a
more integrated approach to the study of evolution, including the role of developmental plasticity.
Soft part 3D visualization by computer reconstruction of serial sections
Ruthensteiner, Bernhard
Zoologische Staatssammlung München, Münchhausenstraße 21, 81247 Munich, Germany,
Email: BRuthensteiner@zsm.mwn.de
Recent increases in performance of computer hard- and software at the PC level enabled a variety of
3D graphical applications, like surface visualizations of biological specimens. This indirectly recalled
an old morphological method back to life, the investigation of soft part anatomy by light
microscopical serial section analysis.
After a brief historical review of sectioning reconstruction, approved histological and computer
graphical methods resulting in 3D surface models (“surface rendering”) of small molluscan
specimens are demonstrated. Ribboned serial sections of resin embedded specimens provide to be
most practical for 3D processing. Ribboning is achieved by applying contact cement only to the
cutting surface of the block, which is a modification of an old protocol. Details on the material, like
embedding media (epoxy resins) and knives (Ralph glass or special diamond knife) used and general
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