World Congress of Malacology Antwerp ... - Unitas Malacologica

increased from March to summer (June and July), and was slightly greater in cultivated oysters,
probably related to their trophic conditioning before installation. When water temperature exceeded,
even briefly, 19°C, partial spawnings were observed between April and June in oysters from the high
turbid site vs a massive spawning in June for oysters from the low turbid site. A major decrease of the
gonosomatic ratio in August corresponded to a massive gamete atresia and resorption both within the
acini and the evacuating ducts. In December, gametogenesis was observed in 5-10% of the
individuals sampled, and in all cases these were males. Critical stages of the reproductive cycle of
oysters were mainly regulated by the water temperature, while the intensity of the reproductive effort
depended on the food supply. We suggest that environment-dependant reproduction strategy be
integrated in a deterministic growth model for this species.
Anatomy, distribution, and ecology of the slug Arion alpinus Pollonera, 1887 (Gastropoda:
Arionidae)
Dvořák, Libor 1 ; Backeljau, Thierry 2,5 ; Reischütz, Peter L. 3 ; Horsák, Michal 4 ; Breugelmans,
Karin 2 ; Jordaens, Kurt 5
1. Šumava National Park Administration, Dept. of Science and Research, Sušická 399, CZ-34192
Kašperské Hory, Czech Republic,
Email: libor.dvorak@npsumava.cz
2. Royal Belgian Institute of Natural Sciences, Dept. of Invertebrates – Malacology Section,
Vautierstraat 29, B-1000 Brussels, Belgium,
Email: Thierry.Backeljau@naturalsciences.be; Karin.Breugelmans@naturalsciences.be
3. Puechhaimgasse 52, A-3580 Horn, Austria,
Email: peter.reischuetz@gmx.at
4. Institute of Botany and Zoology, Faculty of Science, Masaryk University, Kotlářská 2, CZ-61137
Brno, Czech Republic,
Email: horsak@sci.muni.cz
5. Evolutionary Biology Group, Dept. of Biology, University of Antwerp, Groenenborgerlaan 171, B-
2020 Antwerp, Belgium,
Email: kurt.jordaens@ua.ac.be
Arion (Kobeltia) alpinus Pollonera, 1887 is a small Central European slug whose northernmost
distribution limit crosses the southern part of the Czech Republic. The species can be easily confused
with young specimens of A. (Mesarion) fuscus (Müller, 1774) or light coloured specimens of A.
(Kobeltia) distinctus Mabille, 1868. However, A. alpinus can be distinguished from both these
species by the following features: (1) the upper side of the body is yellowish, yellow-brownish or
greenish with darker lateral stripes that do not expand under the pneumostome, (2) the yellow to light
orange foot sole, (3) the pale yellowish body mucus, (4) the anatomy of the genitalia, and (5) specific
mitochondrial 16S rDNA sequences. There is also a diagnostic papilla at the inner part of the outlet
of the epiphallus that distinguishes A. alpinus from A. distinctus.
A. alpinus seems to be a typical forest species preferring hilly and mountainous regions. It is
predominantly a ground-dwelling species since it was mostly found on the ground under leaves,
stones, and pieces of wood or bark of fallen trunks and often on mushrooms.
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