Eur. J. Entomol. 91 (3): 277-283, 1994
Circadian clock and ecdysteroid titers in the wax moth, Galleria mellonella (Lepidoptera: Pyralidae) larvae
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In this mini-review, data on the circadian rhythmicity in ecdysteroid synthesis by the prothoracic glands of final instar larvae of the wax moth (Galleria mellonella), as well as ecdysteroid titers in their hemolymph are summarized. It was found that at the low temperature of 18°C and in continuous darkness (DD), the last instar of the wax moth larvae did not pupate. When these larvae were transferred to 30°C and kept in DD, they immediately initiated development and pupated in a circadian manner. They exhibited the circadian rhythmicity of ecdysteroid titers in their hemolymph, with a period of approximately 24 hours.
The mechanism underlying circadian rhythmicity of ecdysteroid titers in the hemolymph of Galleria mellonella larvae was investigated. It was found that brain removal or head-ligating of larvae in which developmental processes had been synchronized by transfer from 18°C to 30°C, did not abolish daily rhythms of ecdysteroid titers in the hemolymph. The observed rhythms persisted in continuous darkness for 5 days after treatment, which suggests that the circadian clock driving these rhythms is not located within the brain.
In further experiments, it was shown that the prothoracic glands, taken from temperature-synchronized last instar larvae of Galleria, exhibited a daily rhythm of ecdysteroid synthesis, with a maximum coinciding with the peak of ecdysteroid titers found in controls. Therefore, it is suggested that the circadian rhythm of ecdysteroid titers in the hemolymph of these larvae is regulated by a clock, located probably within the prothoracic glands.
Keywords: Physiology, wax moth, Galleria mellonella, ecdysteroids, circadian clock, prothoracic glands
Accepted: January 12, 1994; Published: August 5, 1994 Show citation
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