Long-term pyrene exposure of grass shrimp, Palaemonetes pugio, affects molting and reproduction of exposed males and offspring of exposed females

The objective of this study was to investigate the impact of long-term pyre ne exposure on molting and reproduction in the model estuarine invertebrate , the grass shrimp (Palaemonetes pugio). Grass shrimp were exposed to measu red concentrations of 5.1, 15.0, and 63.4 ppb (mu g/L) pyrene for 6 weeks, during which time we determined molting and survivorship. At the end of the exposure, we immediately sacrificed some of the shrimp for biomarker (CYP1 A and vitellin) analyses. The remaining shrimp were used to analyze fecundi ty and embryo survivorship during an additional 6 weeks after termination o f pyrene exposure. Male shrimp at the highest pyrene dose (63 ppb) experien ced a significant delay in molting and in time until reproduction, and show ed elevated ethoxycoumarin o-deethylase (ECOD) activity immediately after t he 6-week exposure period. In contrast, 63 ppb pyrene did not affect these parameters in female shrimp. Females produced the same number of eggs per b ody weight, with high egg viability (98-100%) at all exposure levels, but w ith decreased survival for the offspring of the 63-ppb pyrene-exposed femal es. In addition, vitellin levels were elevated only in females at 63 ppb py rene after the 6-week exposure. We hypothesize that the elevated vitellin b inds pyrene and keeps it biologically unavailable to adult females, resulti ng in maternal transfer of pyrene to the embryos. This would account for th e lack of effect of pyrene exposure on ECOD activity, molting, and reproduc tion in the adult females, and for reduced survival of their offspring.