@article {3511, title = {Effects of acute exposures to mecoprop, mecoprop-p and their biodegradation product (2-MCP) on the larval stages of the Pacific oyster, Crassostrea gigas.}, journal = {Aquat Toxicol}, volume = {146}, year = {2014}, month = {2014 Jan}, pages = {165-75}, abstract = {

Studies have shown that pesticides are sometimes detected at rather high levels in seawater and it has been suggested that these chemical compounds could act as additional stress factor for oysters cultured in coastal environments. The effects of pesticides on marine molluscs could be particularly harmful in the early stages which correspond to critical life stages. This study aimed to assess the effects of mecoprop, mecoprop-p and their degradation compound 2-methyl-4-chlorophenol on two larval stages of Crassostrea gigas. Embryotoxic effects were assessed on veliger larvae after 36 h exposures, and both percentages of normal larvae and types of abnormalities were taken into account. The effects of the three substances were evaluated on 21-day-old pediveliger larvae by calculating metamorphosis rates after 24h exposures. The results of the embryotoxicity assay indicated that 2-methyl-4-chlorophenol was more toxic (EC50: 10.81 mg L(-1)) than its parent compounds (EC50 mecoprop: 42.55 mg L(-1); EC50 mecoprop-p: 78.85 mg L(-1)). Mecoprop in particular injured shell formation with an increase of shell abnormalities following herbicide concentrations. The active substances were not toxic to metamorphosis processes, but 2-MCP was revealed to be more toxic to the success of metamorphosis (EC50: 7.20 mg L(-1)) than to embryo-larval development. However, the toxic concentrations were several orders of magnitude higher than environmental concentrations.

}, keywords = {2-Methyl-4-chlorophenoxyacetic Acid, Animals, Chlorophenols, Crassostrea, Embryo, Nonmammalian, Larva, Metamorphosis, Biological, Water Pollutants, Chemical}, issn = {1879-1514}, doi = {10.1016/j.aquatox.2013.11.008}, author = {Mottier, A and Kientz-Bouchart, Val{\'e}rie and Dubreule, Christelle and Antoine Serpentini and Jean-Marc Lebel and Katherine Costil} } @article {3639, title = {Neuroendocrine gene expression reveals a decrease in dopamine D2B receptor with no changes in GnRH system during prepubertal metamorphosis of silvering in wild Japanese eel.}, journal = {Gen Comp Endocrinol}, volume = {206}, year = {2014}, month = {2014 Sep 15}, pages = {8-15}, abstract = {

Silvering is a prepubertal metamorphosis preparing the eel to the oceanic reproductive migration. A moderate gonad development occurs during this metamorphosis from the sedentary yellow stage to the migratory silver stage. The aim of this study was to elucidate the molecular aspects of various endocrine parameters of BPG axis at different ovarian developmental stages in wild yellow and silver female Japanese eels. The GSI of the sampled female eels ranged between 0.18 and 2.3\%, corresponding to yellow, pre-silver and silver stages. Gonad histology showed changes from previtellogenic oocytes in yellow eels to early vitellogenic oocytes in silver eels. Both serum E2 and T concentrations significantly increased with ovarian development indicating a significant activation of steroidogenesis during silvering. In agreement with previous studies, significant increases in pituitary gonadotropin beta subunits FSH-β and LH-β transcripts were also measured by qPCR, supporting that the activation of pituitary gonadotropin expression is likely responsible for the significant ovarian development observed during silvering. We investigated for the first time the possible brain neuroendocrine mechanisms involved in the activation of the pituitary gonadotropic function during silvering. By analyzing the expression of genes representative of the stimulatory GnRH control and the inhibitory dopaminergic control. The transcript levels of mGnRH and the three GnRH receptors did not change in the brain and pituitary between yellow and silver stages, suggesting that gene expression of the GnRH system is not significantly activated during silvering. The brain transcript levels of tyrosine hydroxylase, limiting enzyme of DA synthesis did not change during silvering, indicating that the DA synthesis activity was maintained. In contrast, a significant decrease in DA-D2B receptor expression in the forebrain and pituitary was observed, with no changes in DA-D2A receptor. The decrease in the pituitary expression of DA-D2BR during silvering would allow a reduced inhibitory effect of DA. We may raise the hypothesis that this regulation of D2BR gene expression is one of the neuroendocrine mechanisms involved in the slight activation of the pituitary gonadotropin and gonadal activity that occur at silvering.

}, keywords = {Animals, Cells, Cultured, Dopamine, Eels, Female, Follicle Stimulating Hormone, beta Subunit, Gene Expression Regulation, Gonadotropin-Releasing Hormone, Immunoblotting, Immunoenzyme Techniques, Luteinizing Hormone, beta Subunit, Metamorphosis, Biological, Neurosecretory Systems, Oocytes, Ovary, Real-Time Polymerase Chain Reaction, Receptors, Dopamine D2, Reproduction, Reverse Transcriptase Polymerase Chain Reaction, RNA, Messenger, Sexual Maturation, Skin Pigmentation}, issn = {1095-6840}, doi = {10.1016/j.ygcen.2014.08.001}, author = {Jeng, Shan-Ru and Wen-Shiun Yueh and Pen, Yi-Ting and Lee, Yan-Horn and Chen, Guan-Ru and Sylvie Dufour and Chang, Ching-Fong} }