Birth Control Effects of Diatoms on Copepod Reproduction: Implications for Aquaculture Studies

Abstract

Copepods are probably the most numerous multicellular organisms on Earth. With over 11,500 species, they are more numerous than insects on land, even though insects are far more diverse (Humes 1994). The success of these small crustaceans seems to largely depend on their high reproductive rates and fast development times. This chapter reviews some of the literature on the factors controlling egg production and development of a few dominant species of marine planktonic copepods, with particular emphasis on foodquality effects, since these have recently been shown to be extremely important in determining high survivorship of copepods. In particular, the chapter focuses on diatom–copepod interactions and on the production by diatoms of plant metabolites that strongly modify reproductive and developmental processes in these crustaceans, beyond the classical primary metabolites such as proteins, fatty acids, and vitamins. These metabolites include a family of unsaturated aldehydes that are produced as an activated chemical defense against predatory animals, potentially sabotaging future generations of copepods by inducing abortions, birth defects, and poor development rates. This biological model is new for the marine environment, since most of the known negative plant–animal interactions are generally related to poisoning processes, or feeding deterrence, but never to reproductive failure. The production by diatoms of teratogens that induce structural malformations in the offspring exposed to them during gestation should be assessed prior to using certain diatom species in aquaculture as live feed for the mass cultivation of copepods.