The Neuronal Circuit of the Dorsal Circadian Clock Neurons in .

's dorsal clock neurons (DNs) consist of four clusters (DNs, DNs, DNs, and DNs) that largely differ in size. While the DNs and the DNs encompass only two neurons, the DNs consist of ∼15 neurons, and the DNs comprise ∼40 neurons per brain hemisphere. In comparison to the well-characterized lateral clock neurons (LNs), the neuroanatomy and function of the DNs are still not clear.

A Functional Clock Within the Main Morning and Evening Neurons of Is Not Sufficient for Wild-Type Locomotor Activity Under Changing Day Length.

A major challenge for all organisms that live in temperate and subpolar regions is to adapt physiology and activity to different photoperiods. A long-standing model assumes that there are morning (M) and evening (E) oscillators with different photoreceptive properties that couple to dawn and dusk, respectively, and by this way adjust activity to the different photoperiods. In the fruit fly , M and E oscillators have been localized to specific circadian clock neurons in the brain.

Life at High Latitudes Does Not Require Circadian Behavioral Rhythmicity under Constant Darkness.

Nearly all organisms evolved endogenous self-sustained timekeeping mechanisms to track and anticipate cyclic changes in the environment. Circadian clocks, with a periodicity of about 24 h, allow animals to adapt to day-night cycles. Biological clocks are highly adaptive, but strong behavioral rhythms might be a disadvantage for adaptation to weakly rhythmic environments such as polar areas [1, 2].

Neuroanatomical details of the lateral neurons of Drosophila melanogaster support their functional role in the circadian system.

Drosophila melanogaster is a long-standing model organism in the circadian clock research. A major advantage is the relative small number of about 150 neurons, which built the circadian clock in Drosophila. In our recent work, we focused on the neuroanatomical properties of the lateral neurons of the clock network.