2. Behavioral Biology TALKS - Deutsche Zoologische Gesellschaft

on their developmental mechanisms, two different types of conjugation can be
distinguished (primary and secondary). In spiders both types of sperm conjugation
are present. Particularly, haplogyne spiders are of special interest because all known
sperm transfer forms common in spiders occur in this group. Nevertheless, the
evolution of sperm conjugations in Haplogynae is not understood. Whereas,
Filistatidae, the sister to all remaining haplogynes, use coenospermia (secondary
sperm conjugation) for transferring sperm, synspermia (primary sperm conjugation)
are only known from few dysderoid and sicarioid taxa, two main lineages within
haplogynes. The family Caponiidae is suggested to be the sister-group of Dysderoidea
and thus of particular interest with regard to the evolution of transfer forms. Here,
we investigated a representative of Caponiidae, Caponina alegre, using light, electron
microscopy and computer-based 3D reconstruction. Males of C. alegre transfer
sperm via synspermia, which are formed at the end of spermiogenesis and consists of
four fused sperm cells. Our results suggest that synspermia are more widespread
than assumed in former studies and evolved already in basal taxa in at least one of
the main lineages of Haplogynae.
����126 Gerd Mayer
Coexistence of native and non-indigenous gammarideans (Crustacea, Amphipoda)
in Lake Constance - functional morphology of mouthparts
Authors: Gerd Mayer 1 , Andreas Maas 1 , Dieter Waloszek 1
Affiliation: 1 University of Ulm, WG Biosystematic Documentation
In the last two decades, the amphipod communities of German inland waters have
changed dramatically. Especially the Ponto-Caspian gammarid Dikerogammarus
villosus caused severe effects on the biocoenosis of the concerned waters, e.g. in
decreasing or even eliminating populations of native or earlier established
gammarideans. Therefore, this invasive species was even named killer shrimp". In
2002 D. villosus was recorded in Lake Constance for the first time. Within only five
years it spread in the littoral of the entire lake and is now the dominant gammarid on
hard substrates. But, unlike in many other Middle European waters the native
Gammarus lacustris and the earlier established G. roeselii seem to co-exist well with
D. villosus in Lake Constance. Moreover, since 2007 a local population of another
amphipod, Crangonyx pseudogracilis, is co-existing here with D. villosus too. In our
SEM study of structures involved in food acquisition of these gammaridean species
inhabiting Lake Constance we discovered morphological differences between the
species, apparently enabling them to use different food resources. In spite of its
ecological impact, D. villosus turned out to be not a specialized predator, but is also
able to collect detritus, sieving particles out of the respiration water current and
sweeping in periphyton. G. lacustris does the same but has additional specializations
to feed on macrophytes, while the mouthparts of G. roeselii in addition possess
specializations for scraping periphyton off the substrates. In contrast, the
morphology of the mouthparts of C. pseudogracilisis implies that this species is a
specialized detritus feeder."
142