Slow Flicks Show Star Tricks: Elapsed-Time Analysis of Basketstar (Astrophyton Muricatum) Feeding Behavior
Abstract:Aspects of the nocturnal activity of the basketstar, Astrophyton muricatum, were studied with elapsed-time cinematography. A basketstar, situated on a coral pinnacle in a tidal channel, fed during the periods of moderate water speed associated with ebb and flood currents. It changed feeding position in response to tidal flow by directing its arms into the current. At slack tide (2110-2154 h) prey capture ceased and the basketstar's arms covered its disc. Also, in a strong flood tide (0225 h), Astrophyton did not ingest prey. Instead, it held its arms stiffly outstretched for an hour and retreated to its diurnal niche by 0400 h. Although feeding activity commenced at dusk, the cessation of feeding before dawn and absence of response to changes in moonlight intensity indicated that feeding behavior is not a rectilinear function of ambient light. The timing of feeding movements may reflect a response to randomly distributed patches of prey plankters. Feeding movements did not occur at regular intervals or in fixed series, but generally only one arm curled at a time. The central arms in the feeding fan were more active, and therefore may have captured more plankters than the lateral arms. In each feeding sequence, a feeding branch curled against the disc in about 1 min, remained near the disc for about 5 min, and uncurled in 1–2 min. The movements of feeding branches seemed to be coordinated with shifts in the position of adjacent locomotor branches. An examination of the pattern of curling and uncurling movements suggested that food was transferred to the mouth by side arm-branches while the main axis of the feeding branch remained coiled against the disc. When relocating and for repositioning the disc, locomotor branches released the substratum, formed an umbrella over the disc, and acted as ambulatory appendages. The basketstar appeared to follow an identical course during the ascent and descent from its feeding perch.
Document Type: Research Article
Publication date: October 1, 1982
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