Meeting Abstract

P3.46  Tuesday, Jan. 6  Fine structure of pigment cup ocelli in Micrura verrilli (Nemertea) HANSEN, H.*; SCHWARTZ, M.L.; Seattle University; Seattle University schwartzm@seattleu.edu

Most benthic nemerteans possess the ability to sense and respond to light and have evident ocellar structures. However, the fine structure of nemertean eyes has been studied only in two closely related species, which revealed microvillar photoreceptive cells within a pigment cup. The nemertean Micrura verrilli bears, anteriorly within the head, two prominent orange bulbs thought to be ocelli, although histological sections have been inconclusive. We examined these bulbs with transmission electron microscopy and show that each is a pigment cup ocellus directed anteriorly and that each photoreceptor cell has an apical crown of microvilli within the cup. These results accord with observations that newly hatched juveniles posses a pair of small orange-pigmented ocelli.