Mercury and selenium concentrations in lanugo of free-ranging California sea lions in the southern Gulf of California, Mexico.

Total mercury ([THg]) and selenium ([TSe]) concentrations were determined in California sea lion (Zalophus californianus) lanugo from the Gulf of California in 2021 and 2022. Relationships with sex, morphometrics, and year were evaluated. Following toxicological thresholds of concern for piscivorous mammals, most pups had a [THg] < 10 ppm, one pup (2021) had a [THg] > 20 ppm, no pups had a [THg] > 30 ppm. Females had significantly higher [TSe] than males; sex did not influence [THg]. [THg] and [TSe] in 2022 were significantly higher in the general population and male cohorts compared to 2021. Significant negative correlations were observed between [THg], [TSe], and morphometrics (2021). These results indicate that, compared to other pinniped species, regional California sea lions may have a decreased likelihood of experiencing Hg-related adverse health effects. Year-related changes in element concentrations suggest continued monitoring of this population to assess pinniped, environmental, and potentially, human health.

Indicators of oxidative stress in leukocytes isolated from bottlenose dolphins (Tursiops truncatus) in response to a proinflammatory challenge.

Few studies have analyzed the indicators of oxidative stress in marine mammals following exposure to lipopolysaccharides (LPS); sex and maturity-related differences have not been explored. The objective of this study was to compare the indicators of oxidative stress following exposure to LPS for 24 and 48 h in isolated Pacific bottlenose dolphin (Tursiops truncatus; N = 12) leukocytes in relation to sex and maturity stage, using spectrophotometry. Following 48 h under experimental conditions (10 µg LPS mL-1), the leukocytes from males (n = 5) produced significantly more superoxide radical (O2•-; F (1, 8) = 13.965, p = 0.006) and displayed significantly greater activities of catalase (CAT; F (1, 8) = 9.465, p = 0.015) and glutathione S-transferase (GST; p = 0.028) compared to the leukocytes from females (n = 7). Following 48 h under experimental conditions, maturity-stage did not significantly influence the indicators of oxidative stress. Mature bottlenose dolphins (n = 7) had a significantly higher average daily dietary intake compared to immature bottlenose dolphins (n = 5; F (1, 10) = 5.825, p = 0.036). These results suggest that sex-related strategies for coping with a proinflammatory challenge may be present within the leukocytes from bottlenose dolphins, while potential maturity stage-related strategies require further investigation.