World Congress of Malacology Antwerp ... - Unitas Malacologica

could potentially represent a sentinel species to evaluate environmental pollution during summer
when pesticide application rates increase in orchards.
Preliminary works permitted to characterize in vitro cholinesterase (ChE) activity of this snail and its
sensibility to pesticides. In order to validate this biomarker, we performed a simulated field study
(microcosm) to test the effects of organophosphate (OP/chlorpyrifos/Pyrinex) and carbamate
(CB/carbaryl/Sevin) pesticides as well as a field bioassay performed in a peach orchard before
Pyrinex application.
Microcosm consisted of Potter tower used to spray Petri dishes (8 snails/box) and nominal
concentrations (0, 0.01, 0.1, 1 and 10 ppm) of pesticides were delivered. ChE activity was measured
at 1, 2, 4 and 7 days after pesticide exposure. In the field experiment, snails were released in the
orchard before the Pyrinex treatment and were sampled at 2, 4 and 7 after OP application.
Cholinesterase activity was significantly decreased in the snails exposed in the microcosms to
concentrations close to Predicted Environmental Concentration of both pesticides. The carbamate
caused a higher snail ChE decrease compared to chlorpyrifos, and esterase decrease took place more
quickly (1 day after CB treatment). The highest doses of carbaryl decreased ChE activity
permanently while chlorpyrifos caused a maximum decrease during the second day after exposure
but ChE activity recovered after 4 days. In the field bioassay, chlorpyrifos caused a slight ChE
decrease after 2 days of spraying.
These results demonstrate that ChE decrease of X. derbentina is a suitable early and sensitive
biomarker of neurotoxic pesticides and, in addition, X. derbentina represents an excellent sentinel
organism to assess pesticide impact on non-target invertebrates in agroecosystems of Mediterranean
climate regions.
The freshwater thiarid Tarebia granifera as tramp: Molecular systematics and reproductive
biology of a tropical invader
Lamers, Rebecca; Stein, André; von Rintelen, Thomas; Glaubrecht, Matthias
Museum of Natural History, Humboldt University Berlin, Invalidenstrasse 43, 10115 Berlin,
Germany,
Email: rebecca.lamers@museum.hu-berlin.de
Recently studies on bioinvasions have revealed that various characteristics and strategies of the neozoon
taxa are essential to understand invasiveness. Within an evolutionary ecology framework the
phylogenetic relatedness of an invader (e.g., to existing native communities) and reproductive strategies
provides clues to understand bioinvasions, and can even be used as predictive tool. Among
limnic gastropods some Thiaridae were found to act as tropical invaders in recent years, as e.g.
species of the viviparous Tarebia Adams & Adams, 1854. The Tarebia granifera complex comprises
several taxa from Southeast Asia which were described as morphospecies based on slightly distinct
conchological features in combination with different geographical occurrences. A comparative
approach of representative populations from the entire range using phenotypical variability (including
anatomy) and molecular genetics (mtDNA fragment of the 16S gene) allows to distinguish four taxa
within this species complex for which, however, monophyly could not be established. One of these
species, T. granifera (Lamarck, 1822) is originally distributed in Southeast Asia from Thailand to the
Pacific islands Fiji and Vanuatu. It started decades ago to invade the Caribbean from southern USA
to northern South America, and are recently reported also from South Africa. We found various
differences in the reproductive strategies not only among autochthonous populations from the
Oriental region, but also among the invasive ones. Typically, compared to autochthonous populations
the allochthonous populations exhibit a higher percentage of eggs than shelled juveniles carried in the
brood pouch; however, at the same time the absolute number of eggs and juveniles is remarkably
lower in the invaders. We contrast these reproductive biology features of the invasive populations
with strategies found in populations in particular on the Indonesian island of Sulawesi, serving here
as a natural laboratory, in order to evaluate their contribution and effect in bioinvasions.
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