Prototroch structure and innervation in the trochophore larva of Phyllodoce (Polychaeta)

Publisher Website
Google Scholar
Abstract
The prototroch and prototroch nerve in trochophores of two Phyllodoce species are described at the ultrastructural level and interpreted with reference to the observed normal behavior of larvae during swimming. The prototroch is a complex structure consisting of four tiers of cells of which the second bears the main locomotory cilia. Cells in the other tiers also have cilia but are notable chiefly for the slender processes they send to the prototroch nerve and which evidently contribute to the sheath that surrounds the nerve. Neurociliary synapses were not observed, but the prototroch arrests when the frontal organ is touched and in response to cholinergic drugs. The arrests are only partial in that the cilia continue to beat, but in a restricted register. The mechanism responsible was not identified, but several possibilities are discussed. While the capacity to arrest could be intrinsic to the main trochal cells (i.e., tier 2), the absence of obvious regions of contact between these cells and the prototroch nerve increases the likelihood that the other tiers are also involved. The arrests could in fact result simply from physical interference between the cilia of adjacent tiers. The arrest response in Phyllodoce is compared with that seen in trochal bands in other spiralian larvae.

This publication has 0 references indexed in Scilit: