Individual preparations were dark-adapted
until the response to a dim test flash remained constant for 1 h.
Experiments were conducted on seven dark-adapted
specimens at 3 [degrees]C, five of which were again tested under light-adaptation (478 nm) at 3 [degrees]C.
To measure the spectral efficiency of luminescent countershading, dark-adapted
animals were first exposed to a 490-nm stimulus (at 2.24 X [10.sup.13] photons [m.sup.-2] [s.sup.-1]) for 25 min to induce counterillumination.
Figure 1A shows the intensity response functions for a single dark-adapted
ommatidium during the day and at night.
In this study, all factors, with the exception of the stimulus intensity, were equal for all the species: they were all completely dark-adapted
before being presented with a flickering light stimulus, the background intensity was 0, and the eye was always bathed with a circle of light that was larger than the eye itself.
MSP recordings were further performed on photoreceptors of a dark-adapted
, 4-month-old cuttlefish.
GOOD OBSERVING PROJECTS usually take planning and preparation, not to mention optical aid and dark-adapted
Following techniques described elsewhere (5), we mounted a crab on a rigid platform in an aquarium contained in a lightproof, shielded cage and, using corneal electrodes, recorded electroretinograms (ERGs) from their dark-adapted
lateral eyes in response to 20-ms light flashes generated by a green LED.
All white lights are banned after sundown, giving observers the chance to become fully dark-adapted
during the event.
The flash duration at which the maximum ERG amplitude was reached and maintained for three consecutive measurements was taken as the length of the flash response for a dark-adapted
Finally, ensure that you're fully dark-adapted
before you peer into the eyepiece.
Pieces of retina extracted from dark-adapted
animals were teased apart in Ringer solution, placed between two coverslips, sealed, and individual photoreceptors examined with the dichroic microspectrophotometer (2).