Extraction of info chemicals inducing the production of resting eggs in cladocerans.

Abstract

Chemically mediated interactions are widespreadin aquatic ecosystems; this also applies to planktoniccrustaceans [1]. To date, ample data on the effects ofchemical substances secreted by conspecifics or competitors on the morphology, physiology, and behaviorof crustaceans have been accumulated [2]. Understanding the environmental consequences and evolutionary prerequisites of such a phenomenon is hampered, in particular, by an almost complete lack ofinformation on the chemical nature of substancessecreted by crustaceans. The main difficulties in theisolation and identification of these substances arerelated to their low concentrations in the medium,potential synergistic effects, and the absence of methods for determining the target components [3].One of the wellknown examples of chemical interactions in aquatic ecosystems is the stimulating effectof metabolic products of planktonic crustaceans onthe formation of resting eggs by females. The life cycleof many planktonic crustaceans represents an alternation of asexual and sexual reproduction. In favorableconditions, females reproduce by parthenogenesis.When conditions deteriorate, the reproduction typechanges, and females form resting eggs that can survive adverse conditions, including frozen or driedstates. Formation of resting eggs is affected by variousstimuli (reduction of photoperiod and/or temperature, decreased food supply, etc.) signaling about theonset of adverse conditions [4]. One of such stimuli isown metabolic products. For example, it was shownfor several representatives of Rotifera, Cladocera, andCopepoda that metabolic products can cause formation of resting eggs by females of respective species [5].In experiments with a model cladoceran species