Bactrocera dorsalis had a smaller eye width and a smaller individual square ommatidium
area than the other 2 species, and the largest number of ommatrichia.
saltator, like some other amphipods, possesses an undifferentiated cornea, a fused-type rhabdom attached to the crystalline cone, and five retinula cells in each ommatidium
(Ball, 1977; Meyer-Rochow, 1978; Hallberg et al., 1980; Mayrat, 1981), including one small cell producing a rhabdomere and four other larger retinula cells (Ercolini, 1964).
exotica grew, the visual angles, representing optical catchment per ommatidium
, also remained basically the same (i.e., 30[degrees]) for different body lengths (Fig.
With the high magnification of a stereomicroscope, we identified the ommatidium
whose optic axis was aligned with that of the microscope.
Normally, all photoreceptors in a single ommatidium
view an identical receptive field, which may be imaged onto several photoreceptor types for spectral or polarizational analysis.
After isolating the response of a single optic nerve fiber, we align the animal so that the optic axis of the recorded ommatidium
views the center of the pattern.
The video frames were taken 6 s after the beginning of the response records (arrows), when the grey-black edge of the cylinder began to enter the field of view of the recorded ommatidium
from the right.
Figure 1A shows the intensity response functions for a single dark-adapted ommatidium
during the day and at night.
The final step was to optically isolate the ommatidium
of the single active nerve fiber by aligning a fiber optic light pipe (70 [[micro]meter] diameter) along the axis of the ommatidium
and in contact with the cornea (4).
Because photon catch is proportional to the cross-sectional area of ommatidial corneal facets, a single Limulus ommatidium
(0.029 m[[Mu].sup.2]) should catch [approximately]1.8 times more photons than a Tachypleus ommatidium
A glass microelectrode filled with 3 M KCl (25 M[Omega]) was connected to a DC bridge amplifier (Electronics Shop, Rockefeller University) and advanced into an ommatidium
using a Burleigh Inchworm (Burleigh Instruments, Fishers, NY) attached to a manipulator.
Biometrical data of the constituent parts of one representative central ommatidium
of the compound eye of the two crustaceans are given in Table I.