1999 Progress Report: The Mechanisms and Effects of Endocrine Disruption on Infertility in the Bonnethead Shark on Florida's Gulf CoastEPA Grant Number: R826128
Title: The Mechanisms and Effects of Endocrine Disruption on Infertility in the Bonnethead Shark on Florida's Gulf Coast
Investigators: Manire, Charles A. , Cortes, Enric , Rasmussen, L. E.L.
Current Investigators: Manire, Charles A. , Cortes, Enric , Gelsleichter, James , Rasmussen, L. E.L.
Institution: Mote Marine Laboratory , National Marine Fisheries Service , Oregon Graduate Institute of Science & Technology
EPA Project Officer: Hahn, Intaek
Project Period: January 1, 1998 through December 31, 2001
Project Period Covered by this Report: January 1, 1998 through December 31, 1999
Project Amount: $399,653
RFA: Endocrine Disruptors (1997) RFA Text | Recipients Lists
Research Category: Economics and Decision Sciences , Endocrine Disruptors , Health , Safer Chemicals
Objective:The objectives of this study are to: (1) determine the degree to which the infertility observed in the bonnethead shark, Sphyrna tiburo, in the Tampa Bay/Anclote River area of Florida is caused by disruption of the shark's endocrine system; (2) determine the mechanism(s) of such disruption; (3) determine if this infertility is correlated with organochlorine levels in the shark's serum and/or liver; and (4) estimate the effects that the infertility rates, as well as other possible effects of the contaminants, observed in three different geographical areas, may have on the rate of population growth of the species in the different areas.
Progress Summary:As of the end of the second year of this 3-year study, a vast majority of all samples have been collected from all three study sites, and analysis of all samples is well under way. Most of the RIAs to be performed by Oregon Graduate Institute and Oregon Regional Primate Center have been completed and most of the histology and immunocytochemistry have been completed. The organochlorine analysis is under way and all samples have been extracted and should be analyzed within the next 2 months. The samples for RIAs to be run at University of Florida have been delivered to them, but the samples await the completion of the development of the RIA for 1 -hydroxycorticosterone (which is behind schedule but should be completed within the next 2 months) before they will be run. The vertebra analysis (of age and growth) is completed on most samples. We fully expect to complete the entire project within the time frame proposed.
Efforts to extract and purify vitellogenin (VTG) from bonnethead shark serum have been conducted and suggest low circulating levels of VTG in this species. This also has been demonstrated in another elasmobranch, the little skate, Raja erinacea (Perez and Callard, 1993). As a result, we have directed most of our effort toward the isolation and purification of the yolk protein lipovitellin, which Perez and Callard (1993) had used to produce antibodies for the detection of VTG in R. erinacea. Yolk proteins have been extracted following the methods described in Perez and Callard (1993), and we are in the process of validating the purification of putative bonnethead shark LPV via western blot. Once this is completed, antibodies will be produced against bonnethead LPV and used to detect the presence of VTG in serum. Treatment of male bonnethead sharks with 17 -estradiol has demonstrated the induction of a high molecular weight protein (putative VTG), which is not normally present in untreated animals. Although these results require validation, they strongly support the use of VTG as a marker for estrogenic compounds in this species.
At the current time, we have samples from 178 sharks from the Tampa Bay/Anclote River area, 155 from the Florida Bay area, and 92 sharks from the Apalachicola Bay area. Of the ones collected from Tampa Bay, they are divided as follows: 40 immature females, 46 mature females, 44 immature males, and 48 mature males. All sharks from this area have been collected. Of the sharks collected from Florida Bay, they are divided as follows: 41 immature females, 41 mature females, 32 immature males, and 41 mature males. All sharks from this area have been collected with the exception of 8 immature males. The immature males are the smallest individuals that we are seeking and they are often not captured by the net when all other groups are routinely captured. Of the sharks collected from Apalachicola Bay, they were divided as follows: 34 immature females, 12 mature females, 29 immature males, and 17 mature males. There are a number of mature animals that could not be collected from this area due to different migratory patterns. This means that mature animals are absent from the area during at least three of the eight stages to be collected.
The sample analysis phase of this study is well under way. We observed during our field collections, that infertility rates were much higher in the Tampa Bay/Anclote River area than in the Florida Bay area. We found 17 infertile ova that were distributed in 28 percent of the potential females captured in the Tampa Bay/Anclote River area and found only two infertile ova (one each in two females) in sharks from Florida Bay. We also observed that sperm viability from mated females was decreased in the Tampa Bay/Anclote River population as compared to the Florida Bay population. We further observed that sperm counts from males prior to mating and from females after mating and prior to ovulation from the Tampa Bay/Anclote River population were lower than those of the Florida Bay population. Regarding serum hormone comparisons, females, both mature and immature, from the Florida Bay population have a mean estradiol concentration that is double that of the females from the Tampa Bay/Anclote River population, although it is significant only in the immature females. Immature females from Florida Bay have a significantly higher testosterone concentration and immature males from Tampa Bay/Anclote River have a significantly higher dihydrotestosterone concentration. Serum samples from Apalachicola Bay have not been fully analyzed to include them in this comparison.
Analysis of age and growth have yielded some significant differences between the three populations. Sharks from the Florida Bay population are born smaller, grow more slowly, mature at a smaller size, reach a smaller maximum size, but the same maximum age as the Tampa Bay sharks. The sharks from the Apalachicola Bay population are born larger, grow more rapidly, mature at a larger size, reach a larger maximum size, but do not reach as high a maximum age as the Tampa Bay sharks. It is not known at this point whether these are latitudinal differences or are caused by something else.