Stoichiometric consequences of size-selective mortality: An experimental test using the Japanese medaka (Oryzias latipes)

Abstract

The determinants of intraspecific stoichiometric variation remain difficult to elucidate due to their multiple ori- gins (e.g. genetic vs. environmental) and potential interactive effects. We evaluated whether two size-selected lines of medaka (Oryzias latipes) with contrasted life-history strategies (small- and large-breeder lines with slow growth and early maturity vs. fast growth and late maturity) differed in their organismal stoichiometry (percentage and ratios of carbon [C], nitrogen [N] and phosphorus [P]) in a mesocosm experiment. We also tested how size-selection interacted with environmental conditions (i.e. two levels of fish density and light intensity), body condition and sex. Results showed that large-breeder fish were significantly N-enriched compared to small-breeders, while the two size-selected lines did not differ in body P composition. Size-selection interacted with density – high density only affected small-breeders leading to decreasing %C and C: N – and with sex – large-breeder females had higher %C and C:N values than large-breeder males. Finally, C:P and N:P ratios in- creased with body condition due to decreasing %P. Overall, our results show that the ecological consequences of size-selective mortality extend to organismal stoichiometry and may, from there, change nutrient cycling and ecosystem functioning.