Cyclic layer deposition in the cockroach (Blaberus craniifer) endocuticle: A decentral circadian "clock"?
1989
Lukat, R. | Weber, F. | Wiedenmann, G.
As shown by lesions and transplantation experiments, the circadian rhythm of endocuticle deposition in the legs of the cockroach Blaberus craniifer is independent of any neuronal or hormonal centre tested. Instead it is controlled by a decentral "clock", which is presumably localized in the epidermal tissue itself. (1) Removal of both optic lobes--with all probability the sites of the circadian pacemakers of the cockroach locomotor rhythm--did not abolish the circadian endocuticle rhythm. It continued with a temperature-compensated period close to 24 h. (2) Following decapitation or after removal of the thoracic or the abdominal ganglia the circadian deposition rhythm continued in the endocuticle for several days. (3) Circadian double layers were also formed in leg pieces from newly moulted adult donors, transplanted into the haemocoel of male or female hosts, which had already terminated their own endocuticle growth. The number of double layers was mostly smaller, but never larger, than the number of the respective days inside the hosts. Since the average number was the same in 25.5 and 30.5 degrees C, a temperature-compensated rhythm has to be assumed. (4) In addition to the circadian double layers, a multilamellate type of endocuticle was deposited in the transplanted leg pieces as well. The number of "double lamellae" generally exceeded the number of days spent inside the host. It is concluded that the multilamellate type was deposited in areas of the leg pie ces, where the endocuticle deposition was no longer under the control of the decentral circadian "clock".
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