You are here:
REPRODUCTIVE AND DEVELOPMENTAL SCREENING PROTOCOLS FOR ENDOCRINE DISRUPTORS USING ESTUARINE CRUSTACEANS
Citation:
McKenney Jr., C L. REPRODUCTIVE AND DEVELOPMENTAL SCREENING PROTOCOLS FOR ENDOCRINE DISRUPTORS USING ESTUARINE CRUSTACEANS. Presented at Endocrine Disruptors Workshop, RTP, NC, Oct. 29-31, 2002.
Description:
The objective of this research is to develop in vivo screening protocols for endocrine disruption in marine crustaceans, invertebrates of ecological and economic importance. A series of comparative developmental and reproductive studies were performed on several species of estuarine crustaceans in response to three juvenile hormone agonists (JHAs)(methoprene, fenoxycarb, and pyriproxyfen). Larval development of the grass shrimp, Palaemonetes pugio,was greater than two orders of magnitude more sensitive to disruption by JHAs than was embryonic development. Fenoxycarb-exposed larvae had significantly altered levels of ecdysone, the hormone which along with juvenoids is known to regulate the metamorphic process in decapod crustaceans. For two of the three JHAs under similar static exposure conditions, developing larvae of the xanthid mud crab, Rhithropanopeus harrisii, exhibited reduced metamorphic success at lower concentrations than grass shrimp larvae. These comparative responses suggest that the more rigidly controlled metamorphic process in crabs is more sensitive to compounds acting as endocrine disruptors than is the more plastic
metamorphic pattern seen in shrimp. The final crab larval stage, the megalopa, was more sensitive to JHA exposure than earlier zoeal stages. Mud crab larvae exposed to fenoxycarb had reduced biomass and lipid content, particularly triglycerides and free sterols, at concentrations below which inhibited metamorphic success. Concentrations of fenoxycarb which reduced the reproductive capacity in single life-cycle exposures of the estuarine mysid, Americamysis bahia, were similar to those concentrations which inhibited metamorphosis in grass shrimp under similar flow-through exposure conditions. Juvenile mysids released by
exposed adults and reared through maturation without further exposure, however, produced fewer young and had altered sex ratios (reduced percentage of males) at lower parental-exposure concentrations than directly impacted parental reproduction. Since the endocrine glands responsible for regulating mysid sexual differentiation and reproduction develop during larval stages, these transgenerational responses may well be a product of irreversible effects during developmental exposures which become apparent following maturation and initiation of reproduction. These findings suggest the necessity of at least a two-generational mysid exposure protocol for adequately predicting the ecological risk of chemicals acting as endocrine disruptors on crustaceans which function as the dominant secondary producers in estuarine ecosytems.