Exposure to environmentally relevant concentrations of di-(2-ethylhexyl) phthalate (DEHP) induced reproductive toxicity in female koi carp (Cyprinus carpio)

A frequently utilized plasticizer is di-(2-ethylhexyl) phthalate (DEHP), considered a ubiquitous contaminant in the environment and reported to have severe impacts on animals. Although it disrupts the female reproductive system in mammals, little is known about how it effects on fish reproduction. The reproductive parameters of female adult koi carp (Cyprinus carpio) were investigated in this study subjected to environmentally relevant exposure of DEHP (1, 10 and 100 μg/L). After 60 days experiment, significantly lower GSI was recorded in females of 10 and 100 μg/L DEHP-exposed groups. The examination of ovarian histology showed defective histoarchitecture, which included the existence of atretic oocytes, the emergence of intra-oocyte vacuoles as well as necrosis. The groups exposed to DEHP (10 and 100 μg/L) showed significant decreases in fecundity and ova-diameter values. Significant changes in the biochemical (total protein, glucose and cholesterol) and ionic (sodium, potassium, calcium and magnesium) composition were noticed in the ovarian fluid of exposed groups. The groups treated with DEHP showed higher levels of 11-ketotestosterone along with reduced levels of 17β-estradiol. Using real-time PCR, the mRNA expression of several genes linked to reproduction, such as Fshr, Lhr, Ar, Erα and Erβ were assessed and observed that there was a concentration-dependent alternation. The pairing of exposed females with untreated males significantly lowered the rates of fertilization, hatching and larval survival. In summary, the results of this investigation validated that exposure to DEHP in a nominal concentration could potentially reduce the reproductive health of female fish.