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Nicolai A.,University of Rennes 1 | Nicolai A.,University of economics and Environment Nurtingen Geislingen | Filser J.,University of Bremen | Briand V.,University of economics and Environment Nurtingen Geislingen | Charrier M.,University of economics and Environment Nurtingen Geislingen
Canadian Journal of Zoology | Year: 2010

When a life history is characterized by both seasonality in reproduction and seasonality in offspring fitness, trade-offs in reproductive traits might be adjustments to seasonal time constraints to optimize reproductive success. Therefore, we compared in the laboratory the trade-offs in reproductive traits between early (after maturity) and delayed (after dormancy) reproduction in young land snails Cornu aspersum (Müller, 1774) (syn. Helix aspersa), depending on food energy content. We also investigated the maternal investment in reproductive output in both breeding periods. After attaining maturity, snails produced single clutches with many small eggs, which resulted, in contrast to previous studies, in large offspring with a low hatching rate owing to high within-clutch cannibalism. The young cannibals may have a higher survival probability in the following hibernation. Snails starting to reproduce after hibernation had smaller clutches of larger eggs, resulting in high quantity of lighter offspring. The clutch mass was positively correlated with maternal mass in snails reproducing after having attained maturity and negatively correlated in snails reproducing after hibernation. Multiple oviposition occurred only after hibernation, thereby enhancing reproductive success. An energy-rich diet did not affect reproductive strategies. Further studies should focus on seasonal plasticity of reproductive strategies in natural populations of C. aspersum and investigate survival probabilities of breeders and juveniles in an evolutionary context.

Nicolai A.,French National Center for Scientific Research | Nicolai A.,University of economics and Environment Nurtingen Geislingen | Rouland-Lefevre C.,IRD Montpellier | Ansart A.,French National Center for Scientific Research | And 4 more authors.
Malacologia | Year: 2015

Among the multifaceted environmental factors, the bacterial community ingested with soil and food might play an important role in physiological processes of terrestrial gastropods, with consequences on population dynamics and species distribution patterns. Therefore, we investigated the bacterial gut community structure and seasonal dynamic in three populations of the protected endangered land snail Helix pomatia. The PCR-DGGE fingerprinting analysis followed by Nonmetric Multidimensional Scaling (NMDS) showed that Gamma-and Alphaproteobacteria were common to all populations, while Mollicutes and Betaproteobacteria were population specific. Allochthonous strains might be transiently abundant in the gut of foraging snails with respect to habitat conditions. Autochthonous strains were permanently present in the gut, even after expulsion of the gut content at hibernation beginning. Some of these permanent strains are known to have ice-nucleating activity, which is consistent with the limited cold hardiness in this species. Snails that did not enter hibernation despite being exposed to winter conditions had a poor bacterial community. In conclusion, the bacterial community structure differed between habitats and physiological states, and might be important for physiological processes and survival. Further studies should focus on the individual variation in bacterial community and investigate how it is affected by environmental changes.

Nicolai A.,French National Center for Scientific Research | Nicolai A.,University of economics and Environment Nurtingen Geislingen | Filser J.,University of Bremen | Lenz R.,University of economics and Environment Nurtingen Geislingen | And 2 more authors.
Physiological and Biochemical Zoology | Year: 2012

Hemolymph metabolite composition in ectothermic species is mainly constrained by trophic and climatic habitat conditions. In temperate regions, ectothermic species have to face subzero temperatures in winter, to which they typically respond with a state of inactivity. With use of ultra-performance liquid chromatography and gas chromatography-mass spectrometry techniques, we investigated the hemolymph metabolite composition of the land snail Helix pomatia with respect to physiological states (activity and hibernation) in a mountain population (800 m above sea level) and a valley population (150 m above sea level) in Germany. The dry masses of active snails as well as the saccharide and amino acid concentrations in active snails were higher in the mountain population than in the valley population. These differences between populations might reflect differences in microhabitat conditions, such as climate and vegetal food, and consequent differences in metabolic activity. Galactose was the most abundant component in hemolymph besides glucose. Both saccharides might indicate glycolytic activity, which could provide energy for locomotion and foraging. In hibernation, glutamate, a-alanine, glycine, aspartate, serine, homoserine, hydroxyproline, glycerol, and triglycerides were accumulated in both populations. The concentrations were correlated with a decrease in body supercooling point. Therefore, these metabolites might have a role in the cold hardiness of H. pomatia that should be further investigated in a functional study. © 2012 by The University of Chicago.

Nicolai A.,French National Center for Scientific Research | Nicolai A.,University of Bremen | Filser J.,University of Bremen | Lenz R.,University of economics and Environment Nurtingen Geislingen | And 2 more authors.
Journal of Comparative Physiology B: Biochemical, Systemic, and Environmental Physiology | Year: 2011

In temperate regions, land snails are subjected to subzero temperatures in winter and hot temperatures often associated to drought in summer. The response to these environmental factors is usually a state of inactivity, hibernation and aestivation, respectively, in a temperature and humidity buffered refuge, accompanied by physiological adjustments to resist cold or heat stress. We investigated how environmental factors in the microhabitat and body condition influence the metabolite composition of haemolymph of the endangered species Helix pomatia. We used UPLC and GC-MS techniques and analyzed annual biochemical variations in a multivariate model. Hibernation and activity months differed in metabolite composition. Snails used photoperiod as cue for seasonal climatic variations to initiate a physiological state and were also highly sensitive to temperature variations, therefore constantly adjusting their physiological processes. Galactose levels gave evidence for the persistence of metabolic activity with energy expenditure during hibernation and for high reproductive activity in June. Triglycerides accumulated prior to hibernation might act as cryoprotectants or energy reserves. During the last month of hibernation snails activated physiological processes related to arousal. During activity, protein metabolism was reflected by high amino acid level. An exceptional aestivation period was observed in April giving evidence for heat stress responses, like the protection of cells from dehydration by polyols and saccharides, the membrane stabilization by cholesterol and enhanced metabolism using the anaerobic succinic acid pathway to sustain costly stress responses. In conclusion, physiological adjustments to environmental variations in Helix pomatia involve water loss regulation, cryoprotectant or heatprotectant accumulation. © 2010 Springer-Verlag.

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