TA4 Integrating Sublethal Responses and Ecologically Relevant Endpoints
204 Oregon Ballroom
8:00 AM - 12:00 PM, Tuesday
() Reproductive and endocrine responses of Atlantic croaker to moderate hypoxia.
Thomas, P1, Rahman, S.1, Kummer, J.1, 1 University of Texas Marine Science Institute, Port Aransas, Texas, USA
ABSTRACT- The effects of 6-10 weeks exposure to low dissolved oxygen (DO: 2.7 ppm and 1.7 ppm) on reproductive function biomarkers in Atlantic croaker (Micropogonias undulatus) were investigated in laboratory studies during three critical reproductive periods, at the beginning of the cycle, during gonadal growth and gametogenesis, and during spawning, and compared to effects observed in fish collected from hypoxic sites in East Bay and Pensacola Bay, Florida. All three reproductive stages were sensitive to low DO exposure. Gonadal growth and gametogenesis were significantly impaired in both sexes resulting in dramatic reductions in the number of viable gametes that was accompanied by significant declines in plasma levels of estradiol, androgens and progestins. Final gamete maturation was also significantly impaired in the low DO groups. Interestingly, the decrease in sperm motility after hypoxia exposure could be restored by progestin treatment, suggesting the decreased sperm function may be due progestin deficiency. Low DO exposure resulted in decreased reproductive success as assessed by the rates of fertilization, hatching and larval survival. Equally dramatic declines in gonadal growth, gametogenesis, fecundity and endocrine disturbances were observed in croaker collected from persistent moderate hypoxic sites in East Bay during the reproductive season, September-November, 2003. As observed in the laboratory studies, practically no development of vitellogenic oocytes was observed, suggesting that individuals at these sites are unlikely to contribute to the 2003 croaker spawning population. In contrast, normal reproductive development was observed in normoxic sites in the adjoining bay, Pensacola Bay. The results indicate reproductive morphometric and endocrine functions in croaker are especially sensitive to moderate hypoxia, both in the laboratory and at field sites. These morphometric and endocrine responses are potentially useful as early warning indicators of reproductive failure, an ecologically relevant endpoint, because they correlated with declines in fecundity, gamete function and reproductive success.
Key words: reproductive function , hypoxia, endocrine effects, Atlantic croaker