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Measurement of day-length as a basis for photoperiodism and annual periodicity in the Carabid beetle Pterostichus nigrita F. by H. U. Thiele is a Environmental Science article available to read on EtoBox.

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Pterostichus nigrita undergoes a gonad dormancy which is overcome by the sequence of short-day/long-day in females and by short-day in males. Experiments with abnormal photoperiods showed that only photoperiods of 24 h and their multiples in whole numbers allowed the processes of gonad maturation, which are normally bound to short-day (i.e., previtellogenesis in the females, bundling of sperms to spermiozeugmata in the males). They were mostly suppressed by photoperiods which represent uneven multiples of 12 h (12, 36, 60). These results permit the conclusion that the short-day measurement is based on an oscillatory (circadian) process. Experiments with "dark breaks" in an extreme long-day (LD 20:4) resulted in two peaks of "short-day" effects. From these findings a model of short-day measurement was derived. It postulates that there are two dark sensitive phases every 24 h during which the beetles require darkness in order for the short-day processes to occur. One of these phases is set by dawn, reaching its peak 15 h thereafter. The other phase is set by dusk and reaches its maximum about 7 h afterwards. Thus, the steps of gonad development bound to short-day are induced if the n

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Author

H. U. Thiele

Publisher

Springer-Verlag; Springer Verlag; Springer Science and Business Media LLC (ISSN 0029-8549)

Published

1977

Language

EN

Field

Environmental Science (Physical Sciences)