cucurbitae females had smaller individual square ommatidium
area than males (376.7 [+ or -] 5.03 [micro]m and 391.7 [+ or -] 5.26 [micro]m, respectively), and B.
In essence, each ommatidium
is an individual, low-resolution eye.
The confining effects of microbial mats and algae might also promote phosphatization of soft parts, such as gut tracts of fish and aquatic insects and of insect ommatidium
contains four large retinula cells (R1-4) and one small (R5).
Using this reconstruction of the molt as a base, we added to it every ommatidium
in the Stage X post-molt animal (prosomal width, 37 mm) that was not present or distinguishable in the molt (Fig.
The diameter of an individual ommatidium
, measured either from the surface of the eye as facet diameter or from cross sections of the eye at corneal levels, increased nearly linearly with eye size and, when plotted against the body length of an animal, with growth of the whole animal as well (Fig.
We observed a gradient of ommatidial diameters within the array, with the largest ommatidium
at the posterior apex, and the smallest at the base.
Our strategy for examining the retinal code underlying behavior is to first videotape the lateral eye's view of its underwater world with an animal-mounted camera ("CrabCam") while simultaneously recording from a single optic nerve fiber of an ommatidium
viewing the central region of the videotaped scene (Passaglia et al., 1997a).
In compound eyes, the unitary structure composed of optics, photoreceptors, and associated pigment cells is called an ommatidium
The field of view of a single ommatidium
defines the narrow excitatory center, whereas the neural network connecting neighboring ommatidia ([sim]200) generates the wide inhibitory surround.
We tease away a single active optic nerve fiber corresponding to a single ommatidium
and pull it into a micro-suction electrode.
The strobic illumination by the beams strongly modulates the firing rate of an ommatidium
, with peak firing rates reaching three times the mean .
To evaluate the possible clock influence on the strength of lateral inhibitory interactions, we compared the steady state optic nerve discharge of a single dark-adapted ommatidium
over a wide range of light intensities during the day and at night.
The three circadian changes that have the most pronounced effect on retinal responses are an increase in "photon catch" (the number of photons absorbed by each ommatidium
), an increase in "gain" (the steady-state optic nerve response to each absorbed photon), and a decrease in "noise" (spontaneous optic nerve activity in the absence of light).