Only 2 of 25 anterior halves regenerated a complete gut and telotroch
or a ciliated band at the posterior end of the animal (Fig.
with a circle of cilia was observed near the posterior end (Fig.
This photographically well-documented research report describes the development of an unusual telotroch
(the free-swimming, re-colonizing stage) from a zooid that was broken-off from a spasmoneme-bearing, colonial, contractile, stalked Peritrich protozooan.
A non-feeding pilidium with apparent prototroch and telotroch
At about 16 d post-fertilization, a new circumferential ciliary band, the telotroch
, appeared just anterior to the anus (Fig.
Most annelid larval forms, feeding or not, can be readily related to the trochophore ground plan, which Nielsen (2001, 2004) defined as a larva bearing an apical tuft, a preoral ciliated band derived from trochoblasts (prototroch), an adoral ciliary zone, and postoral metatroch, gastrotroch, and telotroch
, all of which bands consist of multiciliate cells with compound cilia.
The perianal part of the cirCumblas-toporal band became the telotroch
. Planktotrophic trochophores are found in a number of spiralians, and the trochophore is believed to be the ancestral larval type of the spiralians (lophotrochozoans) (Nielsen, 2004, 2005; Raff, 2008).
The muscular framework that will be used by the juvenile worm after metamorphosis is already in place (3), but swimming is powered by two bands of cilia, an anterior prototroch, and a posterior telotroch
. A large cluster of cilia, the neurotroch, is apparent on the ventral surface in scanning electron micrographs (4).
dilatata, clearly defined patches of cilia around the mouth, at the ventral anterior (presumptive head vesicle) and ventral posterior (telotroch
) areas of the embryo, and lateral to the mouth (presumptive velum) begin to develop.
Two days after oviposition the presumptive apical tuft and prototroch on the apical region, and the telotroch
at the caudal end of the ectodermal trunk, became evident (Figs.
Larvae emerge from the brood tube after approximately 8 days as many-segmented metatrochophores, each bearing a prototroch and telotroch
, the classic trochophore stage being bypassed.
Larvae also bear a midventral neurotroch, posterior to the mouth, and a telotroch