Ethanol-induced flagellar autotomy in Dunaliella tertiolecta Butcher (Chlorophyta: Volvocales)

Abstract

A variety of green algal flagellates shed their fla­ gella when exposed to adverse chemical or phys­ ical conditions (Lewin et al 198 2). The phenom­ enon of flagellar autotomy has been used experimentally to detach flagella from a number of plant and animal cells (Alexandrov 1981; Des­ roche 19 1 2; Goldstein 19 74; Huber et al 1986; Witman et al 19 78). We undertook studies of ethanol-induced flagellar autotomy, or shedding, in Dunaliella tertiolecta Butcher (Chlorophy­ ceae: Volvocales) as part of an investigation of the phenomenon of flagellar autotomy in phy­ toflagellates. D. tertiolecta was chosen for com­ parison with two other organisms also under study, Chlamydomonas reinhardtii Dangeard (Chlorophyceae), a fresh-water alga, and Tetra­ selmis subcordiformis (Wille) Hazen (Prasino­ phyceae), which is marine. Like T. subcordifor­ mis, Dunaliella tertiolecta is a marine organism, though it is more euryhaline and has an unusu­ ally high sodium requirement for growth (Allen 1956; Butcher 1959; Ginzberg & Ginzberg 1985; McLachlan 1960). This report describes investigations of flagellar shedding in Dunaliella tertiolecta in response to ethanol, and of the effects of pH, Ca2+, and Na+ on the response. By studying the effects of various ions on autotomy in Dunaliella tertiolecta, we sought further insights into ecological and phys­ iological correlates of flagellar autotomy in phy­ toflagellates. Axenic cultures of Dunaliella tertiolecta were grown at 20°C in an artificial seawater medium (ASWM) consisting of 0. 2 g 1-1 KN03, 0.0 2 g 1-1 KH2PO., and trace metals (Lewin & Lewin 196 7) in 80% strength 'Instant Ocean.' Cultures were grown under constant illumination (c. 60 ILmol m-2 s -I) from 'cool-white' fluorescent tubes. We concentrated cells by centrifugation in an IEC clinical centrifuge at 2000 r min-I for 6 min,