Orientation to shorelines by the supratidal amphipod Talorchestia longicornis: Wavelength specific behavior during sun compass orientation
If released in water or on sand the supratidal amphipod Talorchestia longicornis Say amphipods moves in the onshore direction. The present study was designed to determine whether this species uses the sun as a cue for orientation and if so, which visual pigment in the compound eyes is involved. When tested in an apparatus with a view of only the sun and sky amphipods were disoriented when the sun was obscured by clouds. However, when the sun was visible, they oriented in the onshore direction of their home beach in both water and air during both the morning and afternoon. Resetting the time of their circadian rhythm in activity with either an altered light:dark or diel temperature cycle also reset the chronometric mechanism associated with sun compass. orientation. T. longicornis has two visual pigments with absorption maxima near 420 nm and 520 nm. Only the 420 nm pigment is used for sun compass orientation, which may be an adaptation for increasing the contrast between the sun and background scattered skylight or for detecting the radiance distribution of skylight. Irradiating the 520 nm absorbing pigment alone induced positive phototaxis to the sun but not onshore orientation. Thus, T. longicornis shows wavelength specific behavior by using only one of its visual pigments for sun compass orientation. © 2009 Elsevier B.V. All rights reserved.
Forward, RB; Bourla, MH; Lessios, NN; Cohen, JH
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