The Health and Risk Assessment of Bottlenose Dolphin Populations (HERA) project is a major collaborative effort involving a number of individuals and institutions. The study was designed to collect and analyze various health parameters from bottlenose dolphin populations in the Indian River Lagoon (IRL), FL and Charleston Harbor, SC (CHS). Resident populations in these two regions are exposed to various contaminants and environmental stressors that may potentially lead to immunosuppression and an increased risk of illness and disease. Therefore, immune function was evaluated as part of an overall health assessment. The primary purpose of this study was to specifically assess immune function in free-ranging bottlenose dolphins live-captured in the Indian River Lagoon, FL, and Charleston Harbor, SC as part of the HERA project.
After capture, blood samples were obtained and shipped on ice to the Mystic Aquarium and Institute for Exploration. Flow cytometry was used to identify and quantify lymphocyte subsets from the peripheral blood using cetacean-specific antibodies or antibodies shown to cross-react with dolphin counterparts. Absolute numbers and percentages were quantified for T and B lymphocytes, T helper and MHC class II positive cells. Within each individual population, subsets were compared with respect to sex (male/female) and location (north vs. south region of the IRL). In addition, cell subsets were compared between the IRL and CHS dolphins.
In the IRL, no significant differences were observed in comparing male and female cell-subsets. Within the IRL, animals from the north IRL demonstrated a higher number of B lymphocytes (P=0.035), whereas animals from the south showed significantly higher T/B cell ratios (P=0.003). Females in the south IRL showed significantly higher T lymphocytes (P=0.047) and T/B cell ratios (P<0.001) than females in the north IRL. Males in the north IRL had higher T helper, B cell counts, and MHC class II positive cells (P=0.023, 0.028, and 0.023, respectively) than males in the south IRL. In Charleston Harbor, females had significantly higher B cells (P=0.002) and MHC II positive cells (P=0.011), while males from this site had significantly higher T/B cell ratios (P=0.033).
In comparing the two populations, animals in the IRL had significantly higher T lymphocytes (P=0.004), as well as T/Th and T/B cell ratios (P=0.004 and 0.002 respectively). Males in the IRL had significantly higher T lymphocytes (P=0.002) and MHC class II positive lymphocytes (P=0.026) than the males in CHS. IRL females had significantly higher T/B cell ratios (P=0.012) than CHS females.
Further comparisons in immune function between the IRL and CHS bottlenose dolphins are currently under evaluation. Data relating to toxicology, endocrinology, morphometrics, and CBCs/serum chemistries are being integrated with immune function data, in order to provide a "complete" health assessment of the bottlenose dolphin populations in the IRL and Charleston Harbor.
The authors would like to thank the Live Capture Field Team for collection of dolphin blood samples and Dr. Jeffrey Stott (UC Davis) for the cetacean specific antibodies (CD2, CD21, and CD19). This project was funded by NOS (Contract's #WC1330-02-RT0030; #WC133C04CN0012) and ONR (Grant #N00014-00-1-0041). Studies on wild dolphins were conducted under Scientific Research Permit #998-1678-00 from the National Marine Fisheries Service.