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Physiological markers suggest energetic and nutritional adjustments in male sharks linked to reproduction

  • Physiological ecology – original research
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Abstract

Energetic condition is one of the most important factors that influence fitness and reproductive performance in vertebrates. Yet, we lack evidence on how energetic states change in response to reproduction in large marine vertebrates. In the present study, we used a non-lethal approach to assess relationships among reproductive stage, circulating steroid hormones (testosterone and relative corticosteroid levels), plasma fatty acids, and the ketone body β-hydroxybutyrate in male sharks of two species with divergent ecologies, the benthic nurse shark (Ginglymostoma cirratum) and the epipelagic blacktip shark (Carcharhinus limbatus). We found higher relative corticosteroid levels in adult nurse sharks during the pre-mating period and in blacktip sharks during the mating period. Higher levels of β-hydroxybutyrate were found in adult nurse sharks during the mating period, but concentrations of this ketone body did not significantly vary across reproductive stages in blacktip sharks. We also detected reduced percentages of essential fatty acids during the mating period of both nurse and blacktip sharks. Taken together, our findings suggest that nurse and blacktip sharks differ in their energetic strategy to support reproduction, however, they likely rely on physiologically important fatty acids during mating, to support spermatogenesis.

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Acknowledgements

We deeply acknowledge the members of the University of Miami Shark Research and Conservation Program, especially Abigail Tinari, for research support. We also thank Kelly Quinn and Alexandre Huber for the courtesy of allowing us to use the illustrations.

Funding

Disney Conservation Fund, The Batchelor Foundation, Save Our Seas Foundation, Fundação de Amparo à Pesquisa do Estado de São Paulo- FAPESP (Grants #2014/16320-7 and #2017/25273-0, PhD’s scholarship to BSR).

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Correspondence to Bianca S. Rangel or Neil Hammerschlag.

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The authors declare that they have no conflict of interest.

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All applicable institutional and/or national guidelines for the care and use of animals were followed.

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Communicated by Donovan P German.

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S. Rangel, B., Hammerschlag, N., Sulikowski, J.A. et al. Physiological markers suggest energetic and nutritional adjustments in male sharks linked to reproduction. Oecologia 196, 989–1004 (2021). https://doi.org/10.1007/s00442-021-04999-4

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  • DOI: https://doi.org/10.1007/s00442-021-04999-4

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