<?xml version="1.0" encoding="UTF-8"?><xml><records><record><source-app name="Biblio" version="6.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">M Tsuda</style></author><author><style face="normal" font="default" size="100%">I Kawakami</style></author><author><style face="normal" font="default" size="100%">S Shiraishi</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%"> Sensitization and habituation of the swimming behavior in ascidian larvae to light</style></title><secondary-title><style face="normal" font="default" size="100%">Zoological Science</style></secondary-title></titles><dates><year><style  face="normal" font="default" size="100%">2003</style></year></dates><number><style face="normal" font="default" size="100%">1</style></number><volume><style face="normal" font="default" size="100%">20</style></volume><pages><style face="normal" font="default" size="100%">13-22</style></pages><abstract><style face="normal" font="default" size="100%">Ascidian larvae of Ciona intestinalis change their photic behavior during the course of development. Newly hatched larvae show no response to a light stimulus at any intensity. At 4 hr after hatching, larvae were induced to start to swimming upon the cessation of illumination, and to stop swimming upon the onset of illumination. At a weaker light intensity (5.0x10(-3) J/m(2).S), the larvae showed similar responses to either a single stimulus or repeated stimuli of onset and cessation of light until 10 hr after hatching. At a stronger light intensity (3.2x10(-1) J/m(2).s), when the stimulus was repeated, they showed sensitization and habituation of the swimming response.
At 3 hr after hatching the larvae failed to show any response to an initial stimulus at any intensity of light, but after several repeated stimuli (sensitization) they showed a swimming response at light intensities above 4.0x10(-2) J/m(2).s. At 5 hr and with intensity above 1.0x10(-2) J/m(2).s, the larvae showed photoresponses to the first stimulus, but after several repetitions the larvae failed to stop swimming upon the onset of light (habituation). A repeated series of stimuli at stronger intensities of light caused greater habituation; this habituation was retained for about 1 min. Since the larval central nervous system in Ciona is comprised of only about 100 neurons, learning behavior in ascidian larvae should provide insights for a minimal mechanism of memory in vertebrates.</style></abstract></record></records></xml>