Die Bewegungsaktivität der weiblichen Schabe Leucophaea maderae (F.) im Laufe des Fortpflanzungszyklus und ihre experimentelle Beeinflussung

Abstract

The ovoviviparous cockroach Leucophaea maderae exhibits cyclic motor activity that is correlated with the reproductive cycle. This latter cycle takes about 85 days. The cycle of motor activity is characterized by low activity during pregnancy; a rapid and large increase about 8 days before parturition; medium activity at the beginning of oögenesis. With progressive egg development, the degree of activity gradually decreases until the pregnancy phase is reached again. In its natural environment, the onset of activity of this nocturnal insect is at sunset. Under conditions of constant darkness, the total activity could be clearly subdivided into two components: one regularly distributed over the whole day which was termed ‘basic activity’; the second, strictly periodical, termed ‘circadian activity’. The basic activity component was taken as an indicator of the internal state of excitement. This component is extremely low during the whole period of pregnancy and reaches its peak during the first half of oögenesis (after parturition). The curve of activity resembles the normal curves of oxygen consumption and food consumption. These findings support the hypothesis concerning the activity of the corpora allata. It is possible that the basic activity is enhanced by the c. allata. This has been shown by allatectomy and implantation experiments. However, the results are only statistically weakly significant. Presumably the c. allata effect involves still another system. The circadian activity is superimposed on the basic activity, especially in the 8 day period preceding parturition, but also after optical, mechanical, and acoustical disturbances. It is based on a constant, inborn rhythm of about 24 hr. The rhythmic control of the circadian activity occurs exclusively via nervous pathways originating in the brain. The rapid increase in circadian activity preceding parturation does not occur after cutting the nervous connexions between abdomen and thorax, although circadian behaviour as such may continue. It is therefore concluded that the brain receives information about the state of development of the embryos through the ventral nerve cord. The biological significance of increased motor activity is still unclear. As far as investigated, the circadian rhythmic activity of Leucophaea supports Aschoff's (1964) ideas regarding nocturnal animals.