with a band of fine cilia encircling the head, with the exception of the dorsal part (Fig.
elegans are free-swimming planktotrophic animals with a ciliated prototroch
and metatroch and a collar (Fig.
The trochophoredeveloped into diamond-shaped covered by crown of cilia called prototroch
at anterior part.
has abundant, elongated cilia and forms a crown towards the anterior end; granules of dark green vitellus can be observed at the posterior end of the larvae (Fig.
The onset of development is intracapsular, a rapid formation of the locomotory prototroch
is no longer necessary, and the free-swimming phase is postponed to later developmental stages.
A non-feeding pilidium with apparent prototroch
tenuis appeared to have only simple cilia in the prototrochal ciliary band; among planktotrophic larvae of annelids, simple cilia in the prototroch
were previously known only from members of Oweniidae.
Also during gastrulation, the blastopore and pretrochal region were ventrally displaced, situating the blastopore ventrally just below the developing prototroch
like those of all known feeding larvae of gastropods, capture food particles between two "opposed bands" of compound cilia (the prototroch
and metatroch) borne on the edge of large velar lobes; particles are then carried to the mouth by short cilia in the gap between the opposed bands, the food groove (Fig.
Two bands of ciliated cells, the prototroch
and metatroch, and an intervening food groove with shorter cilia ran along the periphery of each velar lobe, which also had patches of yellow pigment.
Strathmann and Grunbaum (2006) later published a single still image clearly showing prototroch
and metatrochal cilia in larvae of S.
For instance, the accessory trochoblast cells that contribute to the formation of the prototroch
in many spiralians (2q derivatives) have been co-opted to form the secondary opposed feeding band ("metatroch") in C.