Ecophysiological traits of highly mobile large marine predators inferred from nucleic acid derived indices

F Alves,R Valente,M A Teodósio,A M Correia,E Froufe,A Dinis,M Rosso,E Dias,V Baptista,M Weyn,M Dromby,R Ferreira,I Sousa-Pinto

doi:10.1038/s41598-020-61769-7

Abstract

Nucleic acid-derived indices such as RNA/DNA ratios have been successfully applied as ecophysiological indicators to assess growth, nutritional condition and health status in marine organisms given that they provide a measure of tissue protein reserves, which is known to vary depending on changes in the environment. Yet, the use of these biochemical indices on highly mobile large predators is scarce. In this study, we tested the applicability of using nucleic acids to provide insights on the ecophysiological traits of two marine mammal species (common bottlenose dolphins and short-finned pilot whales) and explored potential related factors (species, sex, season, and residency pattern), using skin tissue (obtained from biopsy darts) of apparently healthy and adult free-ranging animals. Significantly higher RNA/DNA ratios were obtained for bottlenose dolphins (p < 0.001), and for visitor pilot whales when compared with resident pilot whales (p = 0.001). No significant changes were found between the sexes. Based on the percentile approach, the samples contain individuals in a general good condition (as the 10th percentile is not closer to the mean than the 75th percentile), suggesting that the studied region of Macaronesia may be considered an adequate habitat. The combination of this effective tool with genetic sexing and photographic-identification provided an overall picture of ecosystem health, and although with some limitations and still being a first approach, it has the applicability to be used in other top predators and ecosystems.

Highlights

Nucleic acid-derived indices such as RNA/DNA ratios have been successfully applied as ecophysiological indicators to assess growth, nutritional condition and health status in marine organisms given that they provide a measure of tissue protein reserves, which is known to vary depending on changes in the environment
Taking advantage of the privileged location of Madeira to study the ecology of highly mobile large predators in a truly pelagic environment, our main goal was to test the applicability of using RNA/DNA ratios for assessing the ecophysiological condition in two cetacean species of different size and with distinct social structure and feeding habits, based on a multi-disciplinary approach
Such relative nutritional condition of these highly mobile top predators indicate that the marine biogeographic region of Macaronesia may be considered an adequate habitat for those species, but that future population and ecosystem www.nature.com/scientificreports monitoring should be carried out

Summary

Introduction

Nucleic acid-derived indices such as RNA/DNA ratios have been successfully applied as ecophysiological indicators to assess growth, nutritional condition and health status in marine organisms given that they provide a measure of tissue protein reserves, which is known to vary depending on changes in the environment. Taking advantage of the privileged location of Madeira to study the ecology of highly mobile large predators in a truly pelagic environment, our main goal was to test the applicability of using RNA/DNA ratios for assessing the ecophysiological condition in two cetacean species of different size and with distinct social structure and feeding habits, based on a multi-disciplinary approach. We explored (i) whether there are interspecific differences, and (ii) factors that may affect nutritional condition and health status at the intraspecific level, such as (a) sex, due to possible behavioural or hormonal differences, (b) season, due to possible environmental and/ or gestation/lactating intra- and inter-annual differences, and (c) residency pattern, due to possible differences in the spatial structure and/or prey types

Methods

Results

Conclusion