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

We describe the ontogenetic variation in elemental and stoichiometric composition of two copepod species with very contrasted life history patterns, the calanoid Paracartia grani and the cyclopoid Oithona davisae. The first species is a broadcasting, highly productive copepod, whereas the latter is an egg-carrying copepod, much less productive. We reared cultures of both species under conditions of excess food and analyzed their C, N and P composition, and their molar ratios, along development. Both species differed on their specific P content, whereas the specific C and N content were similar. As expected, the specific P content of P. grani was higher, resulting in lower C:P and N:P ratios. Furthermore, we compared our elemental composition data with previously reported stage-specific (nauplii and adult female) maximum growth rates of these two species. We found that for O. davisae, the ontogenetic variation in specific P content agreed with the reported differences in growth rate along development; however, in the case of P. grani, in which juvenile and adult maximum growth rates are similar, the variations in specific P content along development did not reflect the growth rate pattern.