Nectochaete larva of Harmothoe sp.

This polycheate nectochaete larva was found in a plankton tow collected in the Charleston, OR boat basin. Using a plankton identification guide (Crumrine 2001) with a dichotomous key I identified this larva as belonging to the genus Harmothoe (Family Polynoidae, commonly known as scale worms). This larva has nine setigers (segments bearing setae) and five pairs of elytra (scales that characterize the worms of this family).

The first picture was taken on the day when the larva was collected – April 12, 2012. It is a dorsal view, so one can clearly see the five pairs of large scales (elytra) running along the anterior-posterior axis. The third pair of elytrae is unpigmented, whereas the rest of them have a pigmented margin (appears golden in dark field). The larva has three pairs of large ocelli (two of which are in focus). There are also three pointed antennae on the anterior-most segment (called prostomium), all tinted with the same golden pigment as the elytrae.

The second picture was taken six days later. This is a ventral view, so one can clearly see the nine pairs of parapodia (appendages) with chaete (setae), the two ventral palps with bulbous base – one on each side of the mouth, and the two anal cirri (appendages on the posterior-most segment, called the pygidium). Worms in the genus Harmothoe either brood early embryos or spawn (release eggs and sperm) directly into the plankton. I hope to continue to follow this larva through its development during the course and try to determine which species it belongs to.

Crumrine, L. 2001. Polychaeta. In: An Identification Guide to the Larval Marine Invertebrates of the Pacific Northwest. Edited by Alan Shanks. OSU Press, Corvallis.