Polychlorinated biphenyls (PCBs) modulate both phagocytosis and NK cell activity in vitro in juvenile loggerhead sea turtles (Caretta caretta).

Threatened loggerhead sea turtles (Caretta caretta) face numerous environmental challenges, including exposure to anthropogenic chemicals such as polychlorinated biphenyls (PCBs). Despite being banned by the USA in the 1970s, PCBs persist in the environment and produce immunotoxic effects in a wide range of marine vertebrate species. This is of particular concern, as the modulation of the immune system may enhance the susceptibility to a variety of pathogens. Blood samples were collected from 19 immature, captive-reared loggerhead sea turtles. Functional immune assays phagocytosis and natural killer (NK) cell activity were used to quantify the direct effects of PCB congeners 105, 138, and 169 on innate immune functions upon in vitro exposure of sea turtle cells to increasing concentrations (control (0), 0.5, 1, 2.5, 5, 10, 15, or 20 ppm) of each PCB. PCB 105 significantly elevated eosinophil phagocytosis at 10 and 15 ppm and PCB 138 at 15 ppm compared to unexposed (0 ppm). The effects of PCB 169 on phagocytosis were not evaluated. PCB 138 and 105 significantly decreased NK cell activity at 15 and 20 ppm, compared to unexposed (0 ppm) controls. PCB 169 did not markedly modulate NK activity. This constitutes the first study to investigate the in vitro effects of these three PCBs on sea turtle innate immune functions. These results add to our understanding of PCB-induced immunotoxicity in sea turtles and may provide a framework for establishing the relationships between chemical levels and turtle immunity.

The combined effect of Macondo oil and corexit on sheepshead minnow (Cyprinodon variegatus) during early development.

During the 2010 Deepwater Horizon (DWH), oil spill an estimated 800 million L oil and 7.9 million L dispersant entered the environment. The potential adverse effects of the oil-dispersant mixture are poorly understood. The aim of this study was to investigate the impacts of this mixture on early development of sheepshead minnow (Cyprinodon variegatus), a small-bodied estuarine fish commonly found in the area affected by the DWH spill. Embryos were exposed to a chemically enhanced water accommodated fraction (CEWAF; 10:1 mixture of Macondo oil; Corexit 9500) for 48 hr, after which organisms were maintained in uncontaminated water for an additional 8 days. Impacts were assessed on embryonic (heart rate, development of eye pigmentation, embryonic movement measured) and larval (time to hatch, larval survival, standard length, and cyp1a gene expression) development. No significant alterations were found in survival, time to hatch or cyp1a at the end of the experiment. However, CEWAF induced significant decreases in heart rate of embryos, delayed development of eye pigmentation, reduced embryonic movement, and diminished standard length. These results indicate potential sublethal adverse consequences attributed to CEWAF exposure during early development, even in the absence of maintained cyp1a induction or survival rate, potentially affecting the fitness of organisms later in life.

The effects of model androgen 5α-dihydrotestosterone on mummichog (Fundulus heteroclitus) reproduction under different salinities.

Endocrine disrupting substances (EDSs) have the potential to disturb sensitive hormone pathways, particularly those involved in development and reproduction. Both fresh and estuarine water bodies receive inputs of EDSs from a variety of sources, including sewage effluent, industrial effluent and agricultural runoff. Based on current literature, freshwater species appear to respond to lower levels of EDSs than estuarine or marine species. Therefore, effects elicited by EDSs in freshwater teleosts may not be an accurate representation of how EDSs affect teleosts in estuarine and marine environments. To address this potential difference, a short-term reproductive bioassay was conducted under conditions of low and high salinity using mummichog (Fundulus heteroclitus), a euryhaline species that is native to the east coast of North America. The goals of this study were to determine the response of mummichog when exposed to an androgenic EDS and whether salinity affected the response. A model androgen, 5α-dihydrotestosterone (DHT), was selected for this experiment. Impacts on reproduction were evaluated at multiple biological levels, including physiological (sex steroid levels), organismal (gonad size and gonad morphology), and functional (egg production) endpoints. Under conditions of high salinity, egg production was significantly reduced at all exposure concentrations. Under conditions of low salinity, there were no significant differences based on DHT treatment; however, egg production in all treatment groups including the control were significantly reduced relative to the high salinity control group. Other reproductive endpoints, such as sex steroid production, showed stronger correlation to fecundity in females than males. This study demonstrates that mummichog fecundity is sensitive to androgenic endocrine disruption while also underscoring the importance of how changes in salinity, an environmental variable, can impact reproduction.

Evaluation of immune functions in captive immature loggerhead sea turtles (Caretta caretta).

Sea turtles face numerous environmental challenges, such as exposure to chemical pollution and biotoxins, which may contribute to immune system impairment, resulting in increased disease susceptibility. Therefore, a more thorough assessment of the host's immune response and its susceptibility is needed for these threatened and endangered animals. In this study, the innate and acquired immune functions of sixty-five clinically healthy, immature, captive loggerhead sea turtles (Caretta caretta) were assayed using non-lethal blood sample collection. Functional immune assays were developed and/or optimized for this species, including mitogen-induced lymphocyte proliferation, natural killer (NK) cell activity, phagocytosis, and respiratory burst. Peripheral blood mononuclear cells (PBMC) and phagocytes were isolated by density gradient centrifugation on Ficoll-Paque and discontinuous Percoll gradients, respectively. The T lymphocyte mitogens ConA significantly induced lymphocyte proliferation at 1 and 2 µg/mL while PHA significantly induced lymphocyte proliferation at 5 and 10 µg/mL. The B lymphocyte mitogen LPS significantly induced proliferation at 1 µg/mL. Monocytes demonstrated higher phagocytic activity than eosinophils. In addition, monocytes exhibited respiratory burst. Natural killer cell activity was higher against YAC-1 than K-562 target cells. These optimized assays may help to evaluate the integrity of loggerhead sea turtle's immune system upon exposure to environmental contaminants, as well as part of a comprehensive health assessment and monitoring program.