Long-term survey of sea turtles (Caretta caretta) reveals correlations between parasite infection, feeding ecology, reproductive success and population dynamics

Abstract

Long-term monitoring of host-parasite interactions is important for understanding the consequences of infection on host fitness and population dynamics. In an eight-year survey of the loggerhead sea turtle (Caretta caretta) population nesting in Cabo Verde, we determined the spatiotemporal variation of Ozobranchus margoi, a sanguivorous leech best known as a vector for sea turtle fibropapilloma virus. We quantified O. margoi association with turtles’ δ15N and δ13C stable isotopes to identify where infection occurs. We then measured the influence of infection on reproduction and offspring fitness. We found that parasite prevalence has increased from 10% of the population in 2010, to 33% in 2017. Stable isotope analysis of host skin samples suggests transmission occurs within the host’s feeding grounds. Interestingly, we found a significant interaction between individual size and infection on the reproductive success of turtles. Specifically, small, infected females produced fewer offspring of poorer condition, while in contrast, large, infected turtles produced greater clutch sizes and larger offspring. We interpret this interaction as evidence, upon infection, for a size-dependent shift in reproductive strategy from bet hedging to terminal investment, altering population dynamics. This link between infection and reproduction underscores the importance of using long-term monitoring to quantify the impact of disease dynamics over time.

Parasite‐mediated sexual selection in a damselfly

“…Parasitism reduces males' overall condition and increases mutation load, and also probably indicates inferior genetic quality (Sharp & Vincent, 2015; Young et al, 2009). Parasite‐resistant males, on the contrary, exhibit better condition, produce more and healthier progeny, and might possess “good genes” (Lockley et al, 2020; Schad et al, 2012). In previous studies, parasite‐resistant males in damselflies were found to have better condition and immunity, which indicates the presence and expression of genes that provide resistance against parasitism (Kaunisto & Suhonen, 2013; Nagel et al, 2014).…”

“…Nonetheless, our study provides observational evidence that sexual selection is favouring mating success of parasite‐resistant males, thereby opening door for future studies to determine whether parasite‐mediated sexual selection promotes local adaptation and contribute to evolutionary rescue. Anthropogenic climate change is increasing parasites and pathogen transmission risks in insects which might cause or contribute to the global decline in insect population (Lockley et al, 2020; Schad et al, 2012). Whether parasite‐mediated sexual selection could counteract this decline deserve further theoretical and empirical attention (Lumley et al, 2015; Parrett & Knell, 2018).…”

The Status of Marine Megafauna Research in Macaronesia: A Systematic Review

“…This is particularly important, as higher environmental temperatures are expected with climate change, which may reduce hatching success, hatchling fitness (Laloë et al, 2014;Santidrián Tomillo et al, 2014;Martins et al, 2020), and increased sporadic nesting events (Carreras et al, 2018) in areas of previously low to no nesting activity (e.g., loggerhead turtles in Malaga, Spain; Gonzalez-Paredes et al, 2021), but also increase parasite abundance (Brunner and Eizaguirre, 2016). There is little information on the causes of the increase in parasite prevalence in Cabo Verde, and the functional links between environmental changes, contaminants, or population density on viral transmission (Lockley et al, 2020;Farrell et al, 2021).…”

Species‐specific biological energy storage and reuse

“…The eggs are vulnerable especially to terrestrial organisms, young ones are exploited by numerous predators, there is a possibility that may be caught or stuck in fishing gears in their entire lifespan and preyed on by large predators, F I G U R E 6 Thermodynamic system describing the work performance and nutrients uptake by the flame exhaling dragon like sharks. Infections due to parasites 35 and hypothermia are among the major hazards. 36 Only 2% of the Caretta caretta may survive in the sea.…”