Photoresponse and Learning Behavior of Ascidian Larvae, a Primitive Chordate, to Repeated Stimuli of Step-Up and Step-Down of Light

Authors: Kawakami I.; Shiraishi S.; Tsuda M.

Source: Journal of Biological Physics, Volume 28, Number 3, 2002 , pp. 549-559(11)

Publisher: Springer

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Abstract:

Ascidians are lower chordates and their simple tadpole-like larvae share a basic body plan with vertebrates. Newly hatched larvae show no response to a stimulus of light. 4 h after hatching, the larvae were induced to swim upon a step-down of light and stop swimming upon a step-up of light. At weaker intensity of light, the larvae show the same response to a stimulus after presentation of repeated stimuli. When intensity of actinic light was increased, the larvae show sensitization and habituation of the swimming response to a stimulus after repeated stimuli of step-down and step-up of the light. Between 2 h 20 min and 3 h 40 min after hatching the larvae did not show any response to the first stimulus, but after several repeated stimuli they show swimming response to a step-down of light. A repeated series of stimulus cause sensitization. Between 4 h and 7 h after hatching, the larvae show photoresponse to the first stimulus, but after several repetition of the stimuli, the larvae could not stop swimming to a stimulus of a step-up of the actinic light. A repeated series of stimulus cause greater habituation. Both sensitization and habituation depend upon intensity of actinic light.

Keywords: ascidian; habituation; larva; memory; photic behavior; sensitization; vision

Language: English

Document Type: Research article

Affiliations: 1: Department of Life Science, Himeji Institute of Technology, Harima Science Garden City, Akoh-gun, Hyogo 678-1297, Japan

Publication date: 2002-01-01