How cadmium could compromise the completion of the European eel's reproductive migration.
The European eel (Anguilla anguilla L.) is severely threatened with extinction. Surprisingly, even though their unusual life cycle makes them particularly vulnerable to pollution, the possible contribution of contamination remains especially poorly known. Here we have investigated the possible effect of cadmium (Cd), a widespread nonessential metal, on eel reproductive capacities. Both control and Cd precontaminated female silver eels were experimentally matured and forced to swim in metal-free conditions to mimic their reproductive migration. Cd pre-exposure was found to strongly stimulate the pituitary-gonad-liver axis of maturing female silver eels leading to early and enhanced vitellogenesis. This was followed by a strong phenomenon of oocyte atresia and eel mortality. These phenomena occurred before oocytes could reach full maturation and were associated with a large entry of both vitellogenin and Cd into the ovaries. Indeed, a redistribution of previously stored cadmium, even from the low Cd levels of control eels, was observed during sexual maturation. Atresia and mortality phenomena were also associated with an overexpression of the pituitary gene encoding the growth hormone, a marker of physiological stress and energy reserves exhaustion. Significantly, these devastating effects of Cd were observed in organisms that presented liver and kidney Cd concentrations still below those observed in eels from Cd contaminated hydrosystems. Our research shows how common levels of cadmium contamination could disrupt endocrine pathways implicated in gonad maturation and subsequently impair reproductive capacity of eel future genitors.
Pierron
Fabien
F
UMR CNRS 5805 EPOC, team GEMA, Université Bordeaux 1 et CNRS, Place du Dr Peyneau, 33120, Arcachon, France.
Baudrimont
Magalie
M
Dufour
Sylvie
S
Elie
Pierre
P
Bossy
Angélique
A
Baloche
Sylvie
S
Mesmer-Dudons
Nathalie
N
Gonzalez
Patrice
P
Bourdineaud
Jean-Paul
JP
Massabuau
Jean-Charles
JC
D025041:Animal Migration / Q000187:drug effects*; D000818:Animals; D002104:Cadmium / Q000633:toxicity*; D004524:Eels / Q000502:physiology*; D012098:Reproduction / Q000187:drug effects*; D020133:Reverse Transcriptase Polymerase Chain Reaction
D002104:Cadmium