How life history contributes to stress response in the Manila clam Ruditapes philippinarum.
BACKGROUND
Within the last decade, numerous studies have investigated the role of environmental history on tolerance to stress of many organisms. This study aims to assess if Manila clams Ruditapes philippinarum may react differently to cadmium exposure and trematode parasite infection (Himasthla elongata) depending on their origin and environmental history in Arcachon Bay (France).


METHODS
Clams were exposed to Cd (15 microg L(-1)) and parasites (25 cercariae per clam), alone or in combination, at 15 degrees C under controlled laboratory conditions for 7 days. Metal accumulation and success of parasite infestation were examined, also physiological parameters such as metallothionein response and hemocyte counts and activities (phagocytosis, oxidative burst, viability, and adhesion).


CONCLUSIONS
Sensitivity of Manila clams to both stressors differed from one site to another, suggesting local adaptation of populations. Clams from the more parasitized site presented better resistance to trematodes than the others in terms of first line defense, i.e., avoidance of infection. On the other hand, clams that adapted to chronic Cd contamination showed better detoxification mechanisms, both in a faster transfer of metal from gills to visceral mass and in a higher metallothionein baseline, than clams which had never experienced Cd contamination. Finally, hemocyte concentration and viability differed between clam origin site, highlighting the fact that populations living in different environments may adapt their physiological and biochemical responses to environmental stressors.


CONCLUSIONS
It is therefore important to be cautious when extrapolating results from field studies of one species and one site, if the life history of the organisms is not taken into account.
Paul-Pont
Ika
I
UMR 5805 CNRS, Station Marine d'Arcachon, Université Bordeaux 1, place du Dr. Peyneau, Arcachon, 33120, France. i.paulpont@epoc.u-bordeaux1.fr
de Montaudouin
Xavier
X
Gonzalez
Patrice
P
Soudant
Philippe
P
Baudrimont
Magalie
M
D000818:Animals; D049872:Bivalvia / Q000378:metabolism* / Q000469:parasitology; D001772:Blood Cell Count; D002104:Cadmium / Q000378:metabolism / Q000633:toxicity; D002470:Cell Survival / Q000187:drug effects; D006434:Hemocytes / Q000187:drug effects; D008018:Life Cycle Stages; D008668:Metallothionein / Q000378:metabolism; D013312:Stress, Physiological; D014200:Trematoda / Q000302:isolation & purification; D014874:Water Pollutants, Chemical / Q000378:metabolism / Q000633:toxicity
D014874:Water Pollutants, Chemical; D002104:Cadmium; D008668:Metallothionein