ONTOGENY OF PHOTOTAXIS DURING LARVAL DEVELOPMENT OF THE SEDENTARY POLYCHAETE, SERPULA VERMICULARIS (L.)

¹ Department of Zoology, University of Alberta, Edmonton, Alberta T6G 2E9, Canada

Responses of Serpula vermicularis larvae to light were studied in the laboratory during all stages from hatching to settlement. Early trochophores swam upward but were indifferent to light until development of an eyespot at three days. After this, and for most of larval life (about 25 days), dark-adapted larvae initially displayed a positive phototaxis when exposed to horizontally directed light. After a period of adaptation, they changed the sign of their response to negative, the time required for the onset of this change being an inverse function of intensity. Trochophores responded to all wavelengths of light from 350 nm to 625 nm, but were most sensitive to those below 525 nm. Metatrochophores, which had two eyespots, were continuously and strongly photonegative. Benthic nectochaete larvae were indifferent to light while crawling on the bottom, but at metamorphosis they generally oriented the primary tube aperture away from the light. Based on laboratory behavior, a twilight migration pattern is predicted for S. vermicularis trochophores, and a hypothesis is suggested which could account for the evolution of diel migration in larvae of coastal species.

This article has been cited by other articles:

				S. P. Leys and B. M. Degnan Cytological Basis of Photoresponsive Behavior in a Sponge Larva Biol. Bull., December 1, 2001; 201(3): 323 - 338. [Abstract] [Full Text] [PDF]