Diel rhythmicity of prey-search activity and its predominance over starvation in the lady beetle, Coccinella septempunctata bruckii

ABSTRACT. The locomotor activity of the lady beetle, Coccinella septempunctata bruckii Mulsant (Coleoptera: Coccinellidae), was recorded during food deprivation in LD 16:8 h and continuous light. Activity was relatively low immediately after the lady beetle was fed to satiation but increased from 4 to 24 h later. It thereafter gradually decreased to a low level when the food was withheld for several days. Over a period of 10 days of starvation the beetles showed a high level of activity throughout the photophase and a low level during the scotophase in LD 16:8 h. In continuous light this rhythmic pattern persisted, with a free-running period of c. 22 h, significantly shorter than 24 h. The results suggest that the endogenous circadian timing predominates over 'hunger' as a determinant of search activity. The lady beetle accepted and consumed aphid prey presented at night, but the number of prey consumed was significantly lower than in the light. This suggests that, during the dark, activity related to prey-searching is suppressed, though lady beetles are able to accept and consume prey even at night.     

NEURAL COMPETENCE AND CELL LINEAGE OF GASTRULA ECTODERM OF NEWT EMBRYO

The change in the capacity to form neural structures was quantitatively analyzed in both intact and isolated ectoderms of Cynops pyrrhogaster gastrula. The frequency of explants with induced neural structures abruptly decreases between stage 12c and stage 13b in intact ectoderm, and between 12 hr and 18 hr preculture in isolated ectoderm. The quantitative analysis also made clear that the size of the cell population of induced neural structures was gradually reduced with the aging of the ectoderm. The authors simultaneously examined the cell proliferation of early gastrula ectoderm and confirmed that all ectodermal cells divided at least once within 18 hr at 23°C, after which the neural competence of the ectoderm completely disappeared.
The relationships between neural competence and cell lineage (cell generation) of the ectoderm are discussed in the light of these findings.