The ephippial eggs of Daphnia pulex require light for the initiation of development. The ephippial capsule prevents the completion of development but is not a barrier to an adequate light stimulus. Working with decapsulated eggs, the response to light increased to 100 % within 9 days of storage in the dark and remained at 100% for up to 60 days of storage in the dark. The response was not dependent on drying the ephippia. Ephippia stored in the light did not reach 100% response to illumination when decapsulated, indicating that activation was dependent on prior dark reactions. About 4500 ft-c-min of fluorescent light energy was required for 100% activation. The effective wavelengths were between 350 and 475 mµ with 2 x 106 ergs/cm2 sufficient to initiate nearly 100% development at 410 mµ, the most effective wavelength. Low temperature interfered with photoactivation but not with subsequent development. Chilling the ephippia resulted in an increased light requirement. Kinetic studies with chilled ephippia stored for various times in the dark indicated a diphasic process of photoactivation which has tentatively been interpreted as a light-dependent release of inhibition.
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May 01 1969
Activation of the Ephippial Egg of Daphnia pulex
John Davison
John Davison
From the Zoology Department, University of Vermont, Burlington, Vermont 05401
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John Davison
From the Zoology Department, University of Vermont, Burlington, Vermont 05401
Received:
October 25 1968
Online ISSN: 1540-7748
Print ISSN: 0022-1295
Copyright © 1969 by The Rockefeller University Press
1969
J Gen Physiol (1969) 53 (5): 562–575.
Article history
Received:
October 25 1968
Citation
John Davison; Activation of the Ephippial Egg of Daphnia pulex . J Gen Physiol 1 May 1969; 53 (5): 562–575. doi: https://doi.org/10.1085/jgp.53.5.562
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