| Abstract: | We describe the planuliform larval development of the high intertidal hoplonemertean Pantinonemertes californiensis using confocal microscopy. We discovered that the newly hatched planuliform larva has two pairs of epidermal invaginations that disappear later in development. The anterior pair of invaginations has an apparent counterpart in other planuliform nemertean larvae; they give rise to the cerebral organs in at least two other hoplonemertean species. Although the adult P. californiensis possesses cerebral organs, we were not able to distinguish the anterior invaginations after 3 days of development. The developmental fate and homology of the posterior pair of invaginations is uncertain. We show that the proboscis develops in newly hatched larvae as a fifth distinct invagination just ventral of the apical plate. P. californiensis possesses a transitory larval epidermis, composed of approximately 80 multiciliated cells, which is normally shed at 3–4 days of development at 12–16°C. |
