Nereis

These larvae are most likely to be confused with Ophryotrocha sp., which is superficially similar, but lacks the tentacular cirri and the dark spots on the parapodia. Nereis has larger parapodia with longer chaetae, but lacks the obvious jaw apparatus that Ophryotrocha has.

Nereidid larvae are usually found at the 3-4 chaetiger stage in our samples. They have visible antennae and tentacular cirri projecting from the sides of the head, as well as a pair of anal cirri. The parapodia are well-developed and there are usually dark or reddish spots visible at the bases of two adjacent pairs, as shown above. This is presumably Nereis sandersi Blake, the only nereidid at 9°N.

Size under dissecting microscope: ~300-450µm, depending on number of chaetigers
Size under compound microscope: same