Comparative physiological energetics of Mediterranean and North Atlantic loggerhead turtles

Abstract

Population of loggerhead turtles nesting in the Mediterranean Sea has probably evolved from the North Atlantic (NA) population, but is geographically and genetically distinct. We aggregated previously published and new unpublished data, and took two approaches to comparing these populations: an empirical one based on statistical analyses of morphological data, and a physiological one based on a Dynamic Energy Budget (DEB) model. We then analyzed causes of faster growth and maturation, but smaller size at puberty and ultimate size of the Mediterranean (MED) loggerhead turtles relative to their NA conspecifics. The empirical analysis showed that MED eggs, hatchlings, and nesting adults were consistently smaller in terms of length and mass. The physiological approach suggested physiological adaptations of the MED population to higher salinity and scarcer food availability. In particular, these adaptations included an increase in somatic maintenance needs, and a decrease in energy investment to reach and maintain sexual maturity. Our study therefore offers a mechanistic underpinning of previously observed but unexplained life-history traits, and showcases an application of DEB theory as a tool for comparative analysis of two distinct populations of the same species.

Can DEB models infer metabolic differences between intertidal and subtidal morphotypes of the Antarctic limpet Nacella concinna (Strebel, 1908)?

“…Such examples of comparison of energetic performance between these two species highlight the performance of DEB models to be efficiently applied for Antarctic case studies and powerful and accurate enough to enhance physiological contrasts even between closely related species; as previously discussed in other works (van der Veer et al 2006, Gatti et al 2017, Marques et al 2018, Marn et al 2019.…”

“…The subtidal morphotype has also proved to be less resistant to cold than the intertidal population (Waller et al 2006), due to extra production of mucus and stress proteins in intertidal morphotypes (Clark et al 2008) and due to diverse metabolic processes that contrast between both populations (reviewed in Suda et al 2015). The development of ecological models enables precise models to be built, that highlight subtle differences in parameters between ecologically similar or closely related species (Freitas et al 2010, Holsman et al 2016, Marn et al 2019, Lika et al 2020. The idea of building individual-specific models for understanding of physiological processes is not new (Bevelhimer et al 1985, DeAngelis et al 1994 and grew from the development of computational ecology that resulted in the possibility of generating "individual-oriented" models (IOM's) (Hogeweg andHesper 1990, DeAngelis et al 1994).…”

Quantifying impacts of plastic debris on marine wildlife identifies ecological breakpoints

“…Physiological energetics contrasts energy sources and sinks, and thus determines the proportion of ingested energy available for growth, maturation, and reproduction. We used the standard dynamic energy budget model because of an existing and detailed adaptation to loggerhead turtles (Marn et al ., 2017b,a, 2019), and straightforward application to more than 2000 other species (Marques et al ., 2018).…”

“…Recent reports put the incidence of plastics ingestion at an average of 49%, based on 42 studies that examined three or more animals (Lynch, 2018). The ontogeny of loggerhead turtles has been characterised from the perspective of physiological energetics and successfully linked to environmental forcings such as food and temperature, to capture the observed variability among individuals within and between populations (Marn et al, 2017a,b, 2019). Here, we further extend the already validated mechanistic model of the ontogeny by accounting for plastics ingestion.…”

Unusually Paced Life History Strategies of Marine Megafauna Drive Atypical Sensitivities to Environmental Variability

“…However, in, e.g., the lemon shark, smaller juveniles have higher survival rates than larger individuals of the same age, which could favor maturation at a smaller size (Dibattista et al, 2007). Additionally, several conspecific sea turtle populations differ in length at puberty (Goshe et al, 2010;Bell and Pike, 2012;Snover et al, 2013;Avens et al, 2015Avens et al, , 2017Avens et al, , 2020Marn et al, 2019). To investigate how the interaction between the benefits and costs of maturing at a smaller size affects population growth rates, we re-ran all our analyses for a scenario in which length at puberty of all cheloniid species is increased by 10% or decreased by 10% (Supplementary Appendix).…”