AN ACTION SPECTRUM FOR THE LIGHT-DEPENDENT INHIBITION OF SWIMMING BEHAVIOR IN NEWLY-HATCHED WHITE STURGEON, ACIPENSER-TRANSMONTANUS

Newly hatched white sturgeon (Acipenser transmontanus) yolk-sac larvae are negatively phototactic, photokinetic and geotactic-seeking cover in the substrate during daylight hours. If cover is unavailable and th e light intensity is low, they move into the water column and alternat e periods of rapid, upward swimming with periods of quiescence during which they sink. In the dark they swim almost continuously. A flash of light inhibits swimming activity totally for a period dependent on th e light intensity. Using this observation, we obtained an action spect rum for swimming inhibition for 30 newly hatched larvae. This action s pectrum is best fit by a single visual pigment with absorbance maximum at 537 nm. The lack of red sensitivity fits well with previous work s howing that red-sensitive photoreceptor cells are absent in young stur geon. The possible significance of red insensitivity is discussed from both ecological and practical standpoints. (C) 1997 Elsevier Science Ltd.