Photoresponses of second-instar Chaoborus larvae


Journal Article

The diel vertical migration of Chaoborus larvae varies with larval instar. Although light is involved in the control of vertical migration the contribution of larval photoresponses is unknown. In order to describe ontogenetic changes in larval photoresponses we measured photoresponses of second-instar Chaoborus punctipennis larvae in the laboratory. The response spectrum of these larvae had peaks in sensitivity at 420 and 620 nm with a wide plateau of lower sensitivity from 460 to 600 and 640 to 680 nm. Dark adapted larvae were positively phototactic at intensities from 10-7 to 101 Wm-2 at 420 nm. The level of response decreased somewhat above 10-4 Wm-2, and above 10-2 Wm-2 a small proportion of larvae shifted to a negative phototaxis. At 420 nm the threshold intensity was about 10-7 Wm-2 for positive phototaxis and 10-2 Wm-2 for negative phototaxis. Light adaptation increased the threshold intensity for positive phototaxis. The differences in larval photoresponses between second- and fourth-instar larvae suggests that the young instars are adapted to the photoenvironment of the water column and older larvae are adapted to avoid the water column except at very low light intensities. These predictions match the diel distribution of these larvae. © 1982.

Full Text

Duke Authors

Cited Authors

  • Swift, MC; Forward, RB

Published Date

  • January 1, 1982

Published In

Volume / Issue

  • 28 / 2

Start / End Page

  • 183 - 187

International Standard Serial Number (ISSN)

  • 0022-1910

Digital Object Identifier (DOI)

  • 10.1016/0022-1910(82)90127-5

Citation Source

  • Scopus