FLAGELLAR PHOTORESPONSES OF CHLAMYDOMONAS CELLS HELD ON MICROPIPETTES.3. SHOCK RESPONSE

Using high-speed microcinematography flagellar shock responses of a gr eat number of Chlamydomonas cells, free-swimming as well as immobilize d on micropipettes, were investigated in this study. Responses were el icited by flashes, by blue, red or white light steps or occurred ''spo ntaneously''. A large variety of shock responses has been found, in pa rt due to various kinds of flagellar deactivations. Typical courses of flagellar responses are described in detail. The major part of the an alyzed responses consists of a transition back from undulatory beats, characteristic for shock responses, to the normal breaststroke beats, probably as a result of a decreasing Ca++ concentration at the axoneme . It is known that undulatory beats are triggered by a transient stron g influx of Ca++ ions into the flagella. Responses are initiated simul taneously in the two flagella but are finished independently. Differen ces in cis (= next to the stigma) and trans (= far from it) flagella w ere observed but were not consistent. The origin of the deactivations during the shock responses is discussed, as well as an involvement of basal body-associated structures in flagellar beating and in the chang e between the two beating modes. The comparison of the two fundamental ly different types of beating and a close study of transitional beats may convey insight into the complexity of flagellar beating in Chlamyd omonas.