Behavioural modifications imposed to the ciliate protist Euplotes crassus by caulerpenyne: the major toxic terpenoid of the green seaweed, Caulerpa taxifolia
1999; Elsevier BV; Volume: 35; Issue: 3 Linguagem: Inglês
10.1016/s0932-4739(99)80007-8
ISSN1618-0429
AutoresNicola Ricci, Chiara Capovani, Fernando Dini,
Tópico(s)Marine and coastal ecosystems
ResumoCaulerpenyne is the most abundant, toxic terpenoid produced by Caulerpa taxifolia, one of the few toxigenic, green seaweed endemic in the tropics. Owing to the bewildering high concentration of this harmful secondary metabolite, associated with largely magnified homeostatic and reproductive potentialities, the strain(s) of C. taxifolia invading the Mediterranean Sea are a potential risk for biodiversity and ecotoxicity. The effects of caulerpenyne on the biology of the marine ciliate protist Euplotes crassus were studied by means of the ethogram, that is, by the qualitative and quantitative analysis of its creeping behaviour. Concentrations as low as 1.5 μg/ml (= 4 μM) sufficed to induce several clear-cut changes in the creeping of E. crassus and 6 μg/ml (=16 μM) affected significantly the entire ethogram: (a) the cell “activity” was reduced decreasing velocities as well as lengths of the “Long Lasting Elements” (LLE) and largely increasing the percentage of motionless Euplotes; (b) the adhesion to the substrate was relaxed causing disappearance of the “Smooth Trajectory Change” (STC); (c) the electrophysiological states were altered modifying the Side Step Reaction (SSR) which lasted longer (prolonged Side Step Reaction, p-SSR). It follows that the Euplotes’ adaptive behaviour becomes aberrant dooming individuals to a short-term death even under conditions of largely sublethal concentrations of caulerpenyne. The complex of the foregoing induced, behavioural variations is discussed in view of clues to the underlying mechanisms.
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