title: Embryonic diapause in the Australian plague locust relative to parental experience of cumulative photophase decline.
abstract: The Australian plague locust Chortoicetes terminifera (Walker) exhibits facultative embryonic diapause during autumn. To approximate natural photoperiod changes during late summer and autumn, locust nymphs were reared under different total declines in laboratory photophase (-0.5, -0.75, -1.0, -1.25, -1.5, -1.75, -2 h each lowered in 15 min steps) in a 24 h photoperiod to quantify any effect on the subsequent production of diapause eggs. Induction of diapause eggs was significantly affected by accumulated photoperiod decline experienced by the parental generation throughout all development stages from mid-instar nymph to fledgling adult. The incidence of embryonic diapause ranged from nil at -0.5 h to 86.6% diapause at -2 h. Continued declines in photoperiod for post-teneral locusts (transitioned from -1h until fledging to -1.75 h) produced a further increase in the proportion of diapause eggs. The results were unaffected by time spent at any given photoperiod, despite a previously indicated maximal inductive photoperiod of 13.5h being used as the mid-point of all treatments. Implications for the seasonal timing processes of photoperiodism in C. terminifera, which has a high migratory capacity and a latitudinal cline in the timing of diapause egg production across a broad geographic range, are discussed.
authors.affiliation: Australian Plague Locust Commission, Australian Government Department of Agriculture, GPO Box 858, Canberra 2601, Australia; Fenner School of Environment and Society, College of Medicine, Biology and Environment, Australian National University, Canberra 0200, Australia. Electronic address: ted.deveson@agriculture.gov.au.
authors.forename: Edward D
authors.initials: ED
authors.lastname: Deveson
authors.affiliation: Australian Plague Locust Commission, Australian Government Department of Agriculture, GPO Box 858, Canberra 2601, Australia.
authors.forename: James D
authors.initials: JD
authors.lastname: Woodman
mesh_terms: D000818:Animals; D064666:Diapause, Insect / Q000528:radiation effects*; D006110:Grasshoppers / Q000196:embryology / Q000254:growth & development / Q000528:radiation effects*; D009758:Nymph / Q000528:radiation effects; D017440:Photoperiod; D012621:Seasons
keywords: Chortoicetes terminifera; Diapause induction; Locust; Photoperiod