Sex-Dependent Effects of Caloric Restriction on the Ageing of an Ambush Feeding Copepod

Abstract

Planktonic copepods are a very successful group in marine pelagic environments, with a key role in biogeochemical cycles. Among them, the genus Oithona is one of the more abundant and ubiquitous. We report here on the effects of caloric (food) restriction on the ageing patterns of the copepod Oithona davisae. The response of O. davisae to caloric restriction was sex dependent: under food limitation, females have lower age-specific mortality rates and longer lifespans and reproductive periods; male mortality rates and life expectancy were not affected. Males are more active swimmers than females, and given their higher energetic demands presumably generate reactive oxygen species at higher rates. That was confirmed by starvation experiments, which showed that O. davisae males burn through body reserves much faster, resulting in shorter life expectancy. Compared with common, coastal calanoid copepods, the effects of caloric restriction on O. davisae appeared less prominent. We think this difference in the magnitude of the responses is a consequence of the distinct life-history traits associated with the genus Oithona (ambush feeder, egg-carrier), with much lower overall levels of metabolism and reproductive effort.

Population dynamics of the copepod invader Oithona davisae in the Black Sea

“…Nevertheless, the unique ability of females of O. davisae fertilized in winter to keep the sperm alive in a spermatheca for 2.5 months (Svetlichny et al, 2016) allows the birth of new generations at the spring temperature increase. The formation of such a type of reproduction may be due to, on the one hand, an adaptation to the periods when the population densities decrease to the critical minimum below which mate encounters are too rare to allow population maintenance (Kiørboe, 2006), and on the other hand the likely shorter lifespans of males, based on the high energetic cost of mating (Kiørboe, 2007;Ceballos and Kiørboe, 2011;Saiz et al, 2017). During 2013-2016, we established the trends of changes in population abundance and the duration of the overwintering period in females (Figure 2), which can be explained by the interannual variations in seasonal temperature dynamics ( Figure 5).…”

Complex interactions between local adaptation, phenotypic plasticity and sex affect vulnerability to warming in a widespread marine copepod

“…There is distinct sexual dimorphism, with females being considerably larger than males. Body size is generally temperature-dependent in copepods [34,35]. In A. tonsa , mature females are typically less than 1 mm in length, with males averaging around 0.7 mm [36].…”

Ontogenetic changes in the elemental composition and stoichiometry of marine copepods with different life history strategies

“…In this study we have compared the changes in elemental composition and molar stoichiometric ratios along the ontogeny of two copepod species with very contrasting life history traits, such as feeding rates, reproductive strategy and fecundity rates (Almeda et al, 2011;Calbet and Alcaraz, 1996;Zamora-Terol and Saiz, 2013), and their ageing patterns and total life reproductive output (Saiz et al, 2017;Saiz et al, 2015). We expected these differences would reflect in their elemental content and C:N:P ratios.…”

“…davisae seem to be severely constrained in comparison to the naupliar ones, likely because its egg-carrying reproductive strategy (Kiørboe and Sabatini, 1994;Saiz et al, 2017).…”

“…The differences in life history between marine calanoid and cyclopoid copepods are accompanied by other traits (e.g. feeding rates, metabolic activity, total reproductive output, lifespan, egg mortality) that determine their capability to cope with environmental variability and recruit populations (Almeda et al, 2011;Paffenhöfer, 1993;Saiz et al, 2017). Both groups of copepods also differ in the growth pattern exhibited along ontogeny.…”