. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. Figure 4. Capture of a plastic sphere by an actinotrocha (Phoronopsis viridis) in anterior view. The black bar is below the plastic sphere. Numbers at the upper right of each frame are time in seconds from the first frame in the sequence. The sphere approached and contacted the tentacle between 0 and s. The hood began to lift at about s, with the change in shape of hood evident at s. Between and s the particle was drawn rapidly under the hood. It then moved more slowly toward the mouth whi
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. Figure 4. Capture of a plastic sphere by an actinotrocha (Phoronopsis viridis) in anterior view. The black bar is below the plastic sphere. Numbers at the upper right of each frame are time in seconds from the first frame in the sequence. The sphere approached and contacted the tentacle between 0 and s. The hood began to lift at about s, with the change in shape of hood evident at s. Between and s the particle was drawn rapidly under the hood. It then moved more slowly toward the mouth while the hood remained lifted (at and s). The width of the oral hood in the first frame is 465 /jm. lengths observed for the adults of Phoronis vancouver- ensis (Strathmann, 1973). Estimates of cilium lengths from an arrested telotroch ranged from 51 to 57 ^m (me- dian 53 /j,m, n = 7). Estimates of cilium lengths from a beating telotroch ranged from 50 to 61 /jm long (median 56 /Jtn. n = 1). Tentacles (not including the cilium length) were 30 to 33 ^m wide. The largest particle found in the stomach of an actino- trocha of P. viridis was a Sephadex sphere 55 fjm in diameter, but we did not test for the maximum size that could be captured and ingested. Discussion Roles of cilia and hood lift in capturing particles The demonstrated role of the oral hood in transport of particles does not preclude the presence of ciliary mecha- nisms for particle capture similar to those in other larval forms. Our study focused on the role of the oral hood, but movements of particles suggest that cilia play an es- sential role in capture and transport of particles. Cilia bring particles to the tentacles, initially detain them there, and aid in transporting them. The hood lift supplements a ciliary feeding mechanism but has not replaced it. The actinotrochas appear to have two active responses to particles, with the ciliary one acting before the hood lifts. Cinefilms of particle capture by a
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
