World Congress of Malacology Antwerp ... - Unitas Malacologica

Associations between shell strength, shell morphology and heavy metals in the land snail
Cepaea nemoralis (Gastropoda, Helicidae)
Jordaens, Kurt 1 , Vandecasteele, Bart 2 ; Backeljau, Thierry 1,3
1. University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp, Belgium,
Email: kurt.jordaens@ua.ac.be
2. ILVO-Plant-Teelt en Omgeving, Burg. Van Gansberghelaan 109 bus 1, 9820 Merelbeke, Belgium,
Email: bart.vandecasteele@ilvo.vlaanderen.be
3. Royal Belgian Institute of Natural Sciences, Vautierstraat 29, B-1000 Brussels, Belgium,
Email: Thierry.Backeljau@naturalsciences.be
In snails there is an intimate relation between shell size, thickness, strength and calcium content
which may be influenced by environmental factors such as predation and heavy metal pollution. The
snail Cepaea nemoralis shows variability for shell colour and banding pattern, and frequencies of
colour morphs are highly variable in natural populations. We used C. nemoralis to investigate (i) the
relations between shell morphology, shell Ca and heavy metal content (Cd, Cr, Zn), and shell
strength, (ii) differences in shell morphology and shell strength among localities and yellow and pink
shells and (iii) whether snails from polluted sites show increased levels of heavy metals in their shell.
Larger shells were heavier, thicker, needed a higher force to be crushed but did not have a higher Ca
concentration. Cd and Zn concentrations were higher in shells from polluted plots compared to shells
from unpolluted plots but Ca levels in the shell were comparable among plots. Zn concentration was
negatively correlated with shell traits. Although there was substantial variation in shell strength,
thickness and dry weight among localities, none of the shell traits differed between individuals from
polluted and reference plots nor between colour morphs. Our results suggest that the effect of heavy
metal pollution on shell strength and morphology is limited in the investigated populations.
Shell shape and mating behaviour in hermaphroditic gastropods (Mollusca, Pulmonata)
Jordaens, Kurt 1 ; Dillen, Lobke 1 ; Backeljau, Thierry 1,2
1. University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp, Belgium,
Email: kurt.jordaens@ua.ac.be; lubina.dillen@ua.ac.be
2. Royal Belgian Institute of Natural Sciences, Vautierstraat 29, B-1000 Brussels, Belgium,
Email: Thierry.Backeljau@naturalsciences.be
Previous work suggests that low-spired hermaphroditic snails mate face-to-face and have reciprocal
sperm exchange, whereas high-spired snails mate by shell mounting and have unilateral sperm
exchange. This observation has stimulated others to speculate on the evolution of enigmatic mating
behaviours and whole-body enantiomorphy. We reviewed the literature on mating behaviour in
pulmonate snails and show that i) several pulmonate species show considerable intraspecific variation
in mating behaviour, ii) mating position does not predict reciprocity of penis intromission and sperm
exchange, iii) dart-shooting may be correlated with reciprocity of sperm exchange but other factors
must explain the gain or loss of darts, iv) it seems unlikely that the degree of reciprocity is the most
important factor in explaining the relation of whole-body enantiomorphy and shell shape, and v) the
reciprocal intromission of penises does not necessarily involve the reciprocal transfer of sperm.
Therefore, current ideas on the evolutionary relationship between shell shape and reciprocity with
whole-body enantiomorphy and sexual selection (including dart-use) in hermaphroditic snails should
be refined.
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