Similar metatrochal arrests during prototrochal beat were visible at times in a brief video clip of a larva of the Echiuridae
. In the polygordiid, sabellariid, serpulid, and opheliid, rows of metatrochal cilia arrested in alignment at or near the beginning of the effective stroke, pointing away from the food groove and positioned near the surface of the larval body (Fig.
3 All crabs 2 3 Majidae Oregoniidae, Chionoecetes bairdi Chionoecetes opilio 3 Hyas lyratus 2 All Sipuncula 3 All Echiuridae
19 27 All Bryozoa Clypeasteroida, sand dollar 2 All Ascidiacea, tunicates 7 Chelysoma spp.
Like some planktotrophic larvae in the closely related Echiuridae
and Opheliidae, larvae of N.
Feeding: Hatschek (1880); Miner et al (1999) Opheliidae Feeding: Miner et al (1999) Oweniidae Feeding: Emlet & Stralhmann (1994) Polygordiidae * Feeding: Hatschek (1878); Woltereck (1904); Pernet, pers.
Our study describes ciliation and mechanisms of particle capture in larvae of two families of annelids, the Opheliidae and the Echiuridae. We use these observations to compare the feeding capabilities of different annelid larvae and to suggest possible evolutionary transitions among annelid larval forms.
McHugh's (1997) molecular evidence shows that they are derived annelids, and she suggests that they should be placed in the annelid family Echiuridae. Larvae of the echiurid Urechis caupo bear prototrochal, metatrochal, and food-groove cilia (Newby, 1940; Suer, 1982), but how they capture particles has been unknown.
Our observations demonstrate that larvae in the annelid families Opheliidae and Echiuridae are able to capture particles both with opposed bands and directly at the mouth.
Our observations add the Opheliidae and Echiuridae to those annelid families known to possess larvae with opposed-band feeding.