|Diel vertical migration: zooplankton photobiology and behaviour|
Forward Jr., R.B. (1988). Diel vertical migration: zooplankton photobiology and behaviour. Oceanogr. Mar. Biol. Ann. Rev. 26: 361-393
In: Oceanography and Marine Biology: An Annual Review. Aberdeen University Press/Allen & Unwin: London. ISSN 0078-3218, more
Behaviour; Circadian rhythms; Photoperiodicity; Vertical migrations; Zooplankton; Marine
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Diel vertical migration occurs among most zooplankton with either the nocturnal or twilight pattern most commonly observed. This review considers zooplankton photoresponses and the involvement of endogenous rhythms in migration. It is predicted that zooplankton spectral sensitivity should agree with the Sensitivity Hypothesis and be matched to the available light spectrum. Spectral sensitivity is not adapted to daytime quantal irradiance spectra underwater but is matched to the available spectrum at the time of migration at twilight. Normal photic orientation is only possible when experimental illumination conditions approximate the angular light distribution underwater. In this situation positive phototaxis is uncommon, and for many species this response is a laboratory artifact resulting from stimulation with an abnormally narrow stimulus beam. The Preferendum and Rate of Change Hypotheses are the two dominant hypotheses for the way in which light acts during migration. There are studies which support each hypothesis and suggest that explanations of the mechanisms underlying migration may result from a synthesis of these hypotheses. Light may act as a controlling, an initiating and an orientating cue during migration. Endogenous rhythms are important for some species but for others migration appears to result from responses to changes in exogenous environmental factors.