Physiological consequences of environmental contamination in an elasmobranch with matrotrophic histotrophy, the Round Stingray (Urobatis halleri)
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2018-01-15
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Abstract
A range of physiological biomarkers were compared in two populations of Round Stingray (Urobatis halleri) that differed primarily in PCB exposure. Females, and their embryos, were sampled each month of pregnancy at both sites, while adult males were matched with a 40-day subset of females to investigate the effect of sex and its interaction with PCB exposure. I hypothesized that exposure would have negative energetic outcomes for PCB-exposed, compared to reference population, stingrays. Adverse impacts were widespread. Number of offspring was not affected by PCB exposure; however, exposure exacerbated maternal tissue mass, and quality, loss during pregnancy. PCB-exposed females also compromised osmoregulation with urea, an important osmolyte, reduced in maternal plasma. Higher liver quality in contaminant-exposed females was not associated with higher embryo quality, suggesting contaminants increase metabolic demands in adult females and lead to inefficiencies in embryos’ use of maternal resources. Embryos also influenced their uterine environment, as they were steroidogenic and capable of osmoregulating very early in development. I found sex- related differences in embryo mass only at the reference site, suggesting that contaminant effects on males begin in utero. These contaminant sex-related effects extended into adulthood, as relative liver mass and energy content were lower in comparably-sized adult males than females, whereas fewer differences were found between adults at the reference site. Higher energy generation potential, combined with lower tissue quality in contaminant-exposed adult males suggests they are more energetically compromised than females, despite the latter’s costly pregnancy demands. Regardless of sex, contaminant exposure had negative impacts on the ability of adult stingrays to mount a robust secondary stress response as reflected by lower plasma glucose levels after stress, thus potentially impairing their ability to respond to acute stressors. Effects found both in utero and in adulthood suggest that contaminants have a significant, and potentially life-long, impact on Round Stingray homeostasis. This has implications for other species with greater contaminant burdens. Contaminant exposure, and its interactive effects with sex and age, should be included as part of effective elasmobranch management.
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Lyons, K. (2018). Physiological consequences of environmental contamination in an elasmobranch with matrotrophic histotrophy, the Round Stingray (Urobatis halleri) (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.