Then, soon after sunrise, after the clock-driven efferent neurons stop firing (Chamberlain et ai, 1987), the concentration of Rh-LpOps1-4 drops precipitously during a burst of what is called transient rhabdom
These inclusions seem to be concentrated in the background of the eye and may represent a tapetum (corroborating Shear's observation 1993a, b) and thus correspond to the peculiar positioned proximal, open rhabdom
of the retina (see above).
An additional synapomorphy for Leptopodomorpha is the shape of the rhabdom
resembling a "5" pattern on a dice (Fischer et al.
appears to be homologous to, yet highly elaborated from, these small microvillar arrays.
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).
These types vary primarily in the construction of the rhabdom
, so only this part of each ommatidium is diagrammed in Figure 3.
In most arthropod species that have superposition compound eyes, light reflected by the tapetum and not absorbed by the rhabdoms
is visible as eyeshine (Kunze, 1979).
Such data can be used to calculate the spectral sensitivity of a photoreceptor containing this visual pigment by first calculating the spectral absorptance of an axially illuminated rhabdom
. To do this, two additional pieces of information are required: rhabdom
length and the specific absorbance (i.e., absorbance [micro][m.sup.-1]) of the visual pigment in the photoreceptor.
Quantitative measurements were made from both electron micrographs (diameters of microvilli) and light micrographs (rhabdom
volume density and microvillar surface area).
A core-filament, usually identifiable in the lumen of a single rhabdom
microvillus of the crustacean eye, was mostly lost or fragmented into smaller pieces [ILLUSTRATION FOR FIGURE 7 OMITTED].
Quantitative measurements from light and electron micrographs were used to determine the entrance aperture of the eye, the number of ommatidia, the volume density of the rhabdom
, and the area of microvillar membrane per unit volume of rhabdom
Besides, the rhabdoms
of the ALEs have been shown (Kovoor et al.