World Congress of Malacology Antwerp ... - Unitas Malacologica

The allocation of energy for reproductive success in Cornu aspersum before and after
hibernation
Nicolai, Annegret 1 ; Fournier, Sandra²; Briand, Valérie³; Charrier, Maryvonne 4
1. IAF, Hochschule für Wirtschaft und Umwelt Nürtingen-Geislingen, Schelmenwasen 4-8, 72622
Nürtingen, Germany,
2. UMR EcoBio 6553, Université de Rennes 1, Bât. 14A, Campus Beaulieu, 35042 Rennes cedex,
France,
Email: annegret.nicolai@hfwu.de; valerie.briand@univ-rennes1.fr; maryvonne.charrier@univrennes1.fr
120 newly hatched snails of the species Cornu aspersum were reared on three diets of increasing
energy value: 2200kcal/kg = E- diet, 2300kcal/kg = E diet, 2400kcal/kg = E+ diet. When snails
became adult, the BH subsample was allowed to mate and lay eggs once maturity was achieved. The
AH subsample was submitted to a six-month period of hibernation before entering the breeding
activity. The purpose was to analyze the effects of the energy content on the snail reproduction before
and after hibernation. In the BH subsample, 60 snails laid 48 clutches in one month, distributed
among diets E-/E/E+ in the ratio: 20/14/14. In the AH subsample, 60 snails laid 86 clutches in one
month in the ratio: 25/32/29. By analyzing the distribution of egg and hatchling weight as well as egg
and hatchling number in each subsample with the method of resolution into gaussian components a
difference between diets appeared only for the egg weight. However, the difference in the energy
value of the three diets is too low to have an impact on reproductive success. The diet data were
pooled for further analyzes. Before hibernation snails adopt a high number/ low weight strategy for
egg laying. The hatchlings show a higher degree of cannibalism on eggs which explains the low
hatching rate and the high hatchling weight (36mg). By achieving the sexual maturity, the snails get
an endogen signal for preparing hibernation. The snails lay only one clutch, producing heavy
hatchlings with a high probability to survive hibernation. After hibernation the snails adopt a low
number/ high weight strategy for egg laying. This leads to a high hatching rate and a low hatchling
weight (30mg). By producing more than one clutch, the snails enhance their reproductive success.
Further studies should focus on the hatchling survival for each strategy.
The road to an endemic Southeast Pacific fauna: Neogene neogastropods from Chile and Peru
Nielsen, Sven N. 1 ; DeVries, Thomas J. 2
1. Institut für Geowissenschaften, Christian-Albrechts-Universität zu Kiel, Ludewig-Meyn-Str. 10,
24118 Kiel, Germany,
Email: nielsen@gpi.uni-kiel.de
2. Burke Museum of Natural History and Culture, University of Washington, Seattle, WA 98195,
USA,
Email: tomdevrie@aol.com
The Neogene record of Neogastropoda in southern Peru and Chile shows the evolution from a warmtemperate
to tropical fauna with many cosmopolitan genera to a highly endemic fauna of temperate to
cool water temperatures. Several endemic Southeast Pacific neogastropod genera apparently have
their origins in the Neogene, although their ancestors invariably are still unknown. Acanthina appears
in the latest Oligocene, several muricids and volutes are known since the early Miocene (Trophon,
Concholepas, Adelomelon, Miomelon, Pachycymbiola), the late Miocene (Chorus, Xanthochorus) or
the early Pliocene (e.g., Crassilabrum) of both countries. However, the oldest records of the volutes
(Adelomelon, Miomelon, Pachycymbiola) and Trophon are from the Eocene and Oligocene of
Argentina, respectively. Some other taxa still living in the Southwest Pacific were also established
during the early Miocene (Aeneator, Mitrella, Hima, Oliva, Mitra, Ptychosyrinx). Olivancillaria is
known from latest Oligocene to Pliocene, but is now restricted to the Atlantic coast of South
America. Endemism was always relatively high. Several endemic genera are known from the early
Miocene (Carhuaspina, Tactilispina, undescribed muricids, Testallium, Palaeomelon) and Pliocene
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