no 



Figure 7 1 : Bipinnaria of Luidia foliolata 



(from Strathmann, 1971). 

 adp — anterodorsal projection (arm) 

 mdp — mediodorsal projection (arm) 

 mvp — medioventral projection (arm) 

 pdp — posterodorsal projection (arm) 

 pip — posterolateral projection (arm) 

 pop — postoral projection (arm) 

 prop — preoral projection (arm). 



Ciliated bands range from 20-30 |im 

 in length. The band is about ten cells wide 

 and each cell bears one cilium. Cells bor- 

 dering the ciliated band secrete a mucus 

 (Tattersall and Sheppard, 1934; Strathmann, 

 1971). Such cells occur on the aboral side 

 of the band and are absent in the oral field. 

 Cilia beating at right angles to the ciliated 

 band create a water current directed away 

 from the perioral field, which moves the 

 larva forward. A flow is thereby created in 

 front and from the sides, which is directed 

 toward the perioral field. Food particles 

 trapped on the ciliated band are transported 

 by it and the cilia of the perioral field to 

 the mouth. The mechanism of filtration of 

 particles by the ciliated band is presumably 

 as follows: Particles of sufficient size which 

 touch the cilia of the band during active 

 beating (directed from the perioral field), 

 mechanically or chemically induce a local 

 temporary reversal of beating of the cilia 

 touched. The particles captured in this 

 movement are transported to the perioral 

 field and then to the mouth. Once these 

 particles have been transferred to the 

 perioral field, the initial direction of effec- 



tive ciliary beating is resumed. Some par- 

 ticles may be trapped directly by cilia in the perioral field, bypassing the 

 ciliated band. These particles reach the oral cavity through the upper and 

 lateral areas of the adoral band. The cilia of these areas, like those of the 

 esophageal loop of the band, beat in the direction of the intestine. Transpor- 

 tation of food particles toward the mouth is facilitated by the secretion of the 

 mucous cells located alongside the ciliated band. Food particles entering the 

 mouth cavity may remain there for over 20 niin, congealing into a compact 

 mass; individual particles pass through the mouth cavity without stopping and 

 enter the esophagus (Strathmann, 1975). Coal particles added to the culture 

 of bipinnariae of Aphelasterias japonica were detected in the esophagus after 

 50-60 sec, and in the stomach after 2 min (Dautov, 1979). 



All sections of the digestive tract are lined with ciUated cells that assist 

 in the passage of food particles. The passage of food particles through the 

 esophagus is also aided by large circular esophageal muscles; their wavelike 



