Five invaginations and shedding of the larval epidermis during development of the hoplonemertean Pantinonemertes californiensis (Nemertea: Hoplonemertea)

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.

Keywords:

• Nemertea
• Pantinonemertes californiensis
• planuliform larva
• transitory epidermis
• organogenesis

Acknowledgements

We would like to thank Professor Jim Carlton for telling us about the Glasgow collecting site of Pantinonemertes californiensis.