Nonvisual light reception.
D000818:Animals; D001717:Birds; D001921:Brain / Q000502:physiology*; D002940:Circadian Rhythm; D003624:Darkness; D008027:Light; D008297:Male; D009043:Motor Activity; D010507:Periodicity; D010786:Photoreceptor Cells / Q000502:physiology*; D013737:Testis / Q000254:growth & development