. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. CONTROL OF CIOKA CILIA 385 In response to mechanical, electrical, or chemical stim- ulation, all the cilia lining a stigma perform a single rapid reverse stroke and lie flat against the stigmatal walls for 1-2 s in an arrest position inclined beyond the end of the normal recover, stroke (Fig. IB). Ciliary arrest halts water flow into the pharynx and leaves the stigmata completely open, allowing muscular contractions to "squirt" water out of the branchial siphon. Following an arrest, the cilia gradually rise to an u
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. CONTROL OF CIOKA CILIA 385 In response to mechanical, electrical, or chemical stim- ulation, all the cilia lining a stigma perform a single rapid reverse stroke and lie flat against the stigmatal walls for 1-2 s in an arrest position inclined beyond the end of the normal recover, stroke (Fig. IB). Ciliary arrest halts water flow into the pharynx and leaves the stigmata completely open, allowing muscular contractions to "squirt" water out of the branchial siphon. Following an arrest, the cilia gradually rise to an upright position, closing the stigmatal opening (Fig. 1C). The cilia remain in this straight "inactive" state for a few seconds before beating resumes and normal metachrony is re-es- tablished. In both excised pieces of branchial basket and exposed intact baskets, some stigmata are always observed with cilia that stand upright in an "inactive" posture for long periods. It is not known whether this long-lasting inactive state was, in any case, preceded by an arrest; but a direct transition from beating to the inactive position has never been reported (Takahashieffl/., 1973; Mackie et a!.. 1974: Arkett, 1987). Upon stimulation, inactive cilia as well as beating cilia perform an arrest response together (Taka- hashi et ui. 1973: Mackie et a/.. 1974). Effects of calcium ionophore Perfusion of pieces of branchial basket with 100 nM A23187 in normal seawater for 15-30 min had no no- ticeable effect on stigmatal ciliary activity. Addition of 50 m\l CaCl: to both the bath and the ionophore suspension caused most of the cilia to assume an upright inactive position (stigmata closed) within 5 s after perfusion of ionophore. Cilia remained in this posture for as long as observed (up to 5 min). The addition of 100 CaCl: to the bath and ionophore suspension resulted in stigma- wide ciliary arrests throughout the field of view within 5 s after perfusion of A23187 (Fig.
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
