Hydrocarbon accumulation effects in gonadal tissue of Crassostrea virginica and expression patterns of sexual maturity related genes.

Crassostrea virginica oyster is an oviparous lamellibranch that presents protandric asynchronous hermaphroditism. Due to its capacity of bioaccumulate certain xenobiotics, as hydrocarbons, it is widely known as a bioindicator of its distribution ecosystems health. In the present work, gonadal samples from C. virginica organisms exposed to different hydrocarbons concentrations (100 and 200 μg/l) were taken at 7, 14 and 21 exposition days, and were used for histological analysis (sex and gonadal maturity stage determination, damage indicators identification and gonadal coverage), bioaccumulation analysis (hydrocarbons concentration in soft tissue) and quantitative real-time PCR (expression patterns of genes related to cell cycle and reproduction). It was found a greater female proportion in almost all times and treatments, except for the 200 μg/l treatment at 14 days and, Control and 200 μg/l at 21 days. In females, the prevalent stage was IV (46.34%), while in males the most common stages were III (33.92%) and II (26.78%). Regarding the damage, in females, the uppermost level was moderated (45.78%), and in males was the light damage (39.28%). The gonad coverage area in females was higher in Control treatment at the start of the experiment and in Control and 100 μg/l at 7 days; in males, the higher coverage was in the 100 μg/l treatment at 7 days. In the bioaccumulation data, the polycyclic aromatic hydrocarbons (PAHs) showed a higher concentration (average 162.4 ng/d.w) against aliphatic hydrocarbons (average 3.26 ng/d.w), being the 200 μg/l treatments the ones that exhibited the highest values. From the 6 genes evaluated, AURKA, MIS, NCOA4 and PIWIL1 revealed a higher expression in males, while in CATB and GTSF1 the expression was similar in both sexes.