Clock Control of Circadian Changes of Ommatidial Structure in the Cockroach, Leucophaea Maderae (L.)

• Main Author: Zhang, Zhuming
• Format: Others
• Published: TopSCHOLAR® 1993
• Subjects: Biology; Life Sciences
• Online Access: https://digitalcommons.wku.edu/theses/3025; https://digitalcommons.wku.edu/cgi/viewcontent.cgi?article=4032&context=theses

All eukaryotic organisms display rhythms which persist under constant environmental conditions with periods of approximately, but very seldom exactly, 24 hours. Such rhythms are "circadian" and are driven by an internal "biological clock." Circadian rhythms of locomotor activity, retinal sensitivity to light and ommatidial morphology have been characterized in the cockroach, Leucophaea maderae (L.). It is not known whether the same clock(s) controls both circadian rhythms of electroretinogram (ERG) amplitude and morphological changes of the compound eye. In order to determine whether the location of the clock that controls morphological changes is in the same location as the one that controls ERG, brain lesions were made proximal or distal to the region of the putative clock regulating the expression of a circadian rhythm in eye sensitivity to light in anesthetized cockroaches. These and sham operated control animals were held for approximately two weeks under LD 12:12 at 25±2°C conditions in environmental chambers. After this time period, conditions of continuous darkness were established in order to allow rhythms to free run. Eye tissue was removed on subjective midday two and subjective midnight two, fixed, embedded, sectioned and the sections were examined and photographed using a Zeiss transmission electron microscope. Observations were made to establish the presence or absence of a circadian rhythm of submicrovillar cysternae area (SMC), as well as rhabdom area and screening pigment granules organization (SPG). The results indicate that the clock, located in the lobular neuropil region of the optic lobe that controls the rhythm of morphological changes in the eye, is in the same proximity as that which controls the changes in ERG amplitude.