World Congress of Malacology Antwerp ... - Unitas Malacologica

pinnatifida, associated respectively to the hydrozoa Aglaophenia pluma dichotoma and Nemertesia
antennina.
In this communication, the results of the carried-out temporary study as well as the information
collected over the years are presented by setting out the main identifying features of the adult
specimens of Doto koenneckeri, the chromatic and anatomical variation and evolution of its young
stages, its trophic and reproductive biology, spatial arrangement in the colony and population cycle.
Effects of isolation and body size on the mating behaviour of the hermaphroditic land snail
Succinea putris (Gastropoda, Pulmonata, Succineidae)
Dillen, Lobke 1 ; Jordaens, Kurt 1 ; Backeljau, Thierry 1,2
1. University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp, Belgium,
Email: lubina.dillen@ua.ac.be; kurt.jordaens@ua.ac.be
2. Royal Belgian Institute of Natural Sciences, Vautierstraat 29, B-1000 Brussels, Belgium,
Email: Thierry.Backeljau@naturalsciences.be
We examined the combined effect of isolation and body size on (1) the likelihood of mating, (2) the
activity role, (3) the pre-copulatory behaviour, (4) copulation duration, (5) the reciprocity of sperm
transfer and the number of (reciprocally) transmitted sperm in the hermaphroditic land snail Succinea
putris. In addition, we assessed the effects of isolation on the size of the prostate and albumen gland.
We show for the first time that both body size and sexual motivation influence mating behaviour in a
hermaphroditic species with reciprocal internal sperm transfer: isolated individuals showed an
increased eagerness to mate, were more likely to adopt the active role and mounted shells of partners
more than nonisolated individuals. Moreover, isolated individuals transferred more sperm than
nonisolated individuals. Smaller individuals also showed a preference for the active role. Copulation
duration and the reciprocity of sperm transfer were unaffected by isolation or body size. Isolation
resulted in an increase of the size of the prostate gland; the effect of isolation on the size of the
albumen gland was less pronounced. We suggest that the motivation to mate after a period of
isolation reflects a motivation to donate sperm, rather than to receive sperm and that this motivation
is regulated by the size of the prostate gland.
Sperm transfer and sperm digestion in the land snail Succinea putris (Gastropoda, Pulmonata,
Succineidae)
Dillen, Lobke 1 ; Jordaens, Kurt 1 ; Backeljau, Thierry 1,2
1. University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp, Belgium,
Email: lubina.dillen@ua.ac.be; kurt.jordaens@ua.ac.be
2. Royal Belgian Institute of Natural Sciences, Vautierstraat 29, B-1000 Brussels, Belgium,
Email: Thierry.Backeljau@naturalsciences.be
Sperm competition may be as important in hermaphrodites as in species with separated sexes.
Consequently, sperm donor strategies that manipulate the sperm receiver’s reproductive physiology
may also have evolved in hermaphrodites. Manipulation of the partner during copulation may result
in an increase of copulation duration. We studied the relation between sperm transfer and copulation
duration in the hermaphroditic land snail Succinea putris. Sperm transfer is completed within the first
five hours of the copulation, although the mean copulation time is eight hours. Therefore, the
prolonged copulation duration could be interpreted as ‘contact mate guarding’. No sperm is digested
during copulation but took place within the first 72 hours after the end of copulation. We found that
remaining in copula after sperm transfer also prevents sperm digestion and therefore may promote
allosperm storage. Finally, sperm transfer was mostly sequential with one individual donating all its
sperm before its partner started to reciprocate and is not related to the activity role.
50