MELATONIN AND THE PEA APHID, ACYRTHOSIPHON-PISUM

Pea aphids, Acyrthosiphon pisum, were fed on artificial diet containin g various concentrations of melatonin. Under long-day conditions (16 h light: 8 h dark) their progeny included males and virginoparous/ovipa rous (asexual/sexual) intermediate females, which normally occur only in short days or around critical night-length. Endogenous melatonin in pea aphids was measured by radioimmunoassay and verified by paralleli sm with a melatonin standard curve and by thin layer chromatography. H owever, melatonin titres showed large variations and although they ten ded to be higher during the scotophase than during the photophase they were not significantly different. The possibility of melatonin being involved in photoperiodism is discussed. (C) 1997 Elsevier Science Ltd .