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Abstract:
Predatory larvae of the genus Chaoborus release a chemical compound (kairomone) into the water which induces morphological changes, as antipredatory defenses, in daphnids. We present a method for enriching the active compounds released by the larvae directly from their aquatic environment by sorbent extraction. We developed a fast microscale bio-test based on Daphnia pulex morphological response to the kairomone to obtain new information about the kairomone's chemical nature. Carboxyl and hydroxyl groups are essential for kairomone activity. The kairomone can be characterized as a low-molecular weight, non-olefinic hydroxy-carboxylic acid. Separation by reversed-phase HPLC yields only one active fraction. The kairomone can be purified by anion exchange and HPLC. This is the first time a kairomone, which is sensed by Daphnia, has been enriched from water by sorbent extraction technology. This technique of enrichment offers the possibility of following seasonal kairomone concentrations in natural environments.
