. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 342 M. R BOWLBY ET AL. Table I kinetics and intensities ofpyrosome llasht" ). increments) at constant quantal irradiance, or irradiance was varied with neutral density niters, between X 106 and X 10'° photons-s"1 -cm 2, at constant wave- length. The stimulus duration was controlled by a Uniblitz electronic shutter at s for all trials. Individual colonies were allowed to dark adapt for a minimum of one hour before testing. In preliminary trials to determine the op- timum interstimulus period, colonie
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 342 M. R BOWLBY ET AL. Table I kinetics and intensities ofpyrosome llasht" ). increments) at constant quantal irradiance, or irradiance was varied with neutral density niters, between X 106 and X 10'° photons-s"1 -cm 2, at constant wave- length. The stimulus duration was controlled by a Uniblitz electronic shutter at s for all trials. Individual colonies were allowed to dark adapt for a minimum of one hour before testing. In preliminary trials to determine the op- timum interstimulus period, colonies produced less con- sistent responses (flash strength and number) to inter- stimulus periods of less than 3 min. Increasing the inter- stimulus interval beyond 5 min made no further improvement in response uniformity. Consequently, stimuli were delivered every 4 to 5 min, with the colony remaining undisturbed in the light-tight sphere during the interstimulus periods. The temperature of the seawater gradually increased from 12 to approximately 18°C during an experimental session, but no change in excitability was observed. Colonies produced few flashes in the absence of applied stimuli. Stimulus irradiance was calibrated with a radiometer (United Detector Technology, Model S370) equipped with o *O A x "*" a * 02- 1 1 »- — 0- D l'6 20 30 4C Time (s). 10 20 30 Time (s) Figure 1. Varying luminescent responses ofpyrosome colonies to photic stimuli at 475 nm, measured in an integrating sphere. The first flash is the stimulus artifact: it is followed by the bioluminescent response after a brief latency. The height of the stimulus flash does not represent the true intensity ot the stimulus, due to detector saturation. (A) A simple response from Pyrosomella vcmcillata. due to simultaneous zooid light production. (B) A complex response from Pyrosoma atlanticum with two distinct peaks of luminescence. a silicon photodiode detector and a 180° cosine diffuser in the t
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