Hormonal control of lutein incorporation into pupal cuticle of the butterfly Inachis io and the pupal melanization reducing factor
1997
Starnecker, G.
Morphological colour adaptation of pupae of the butterfly Inachis io L. (Lepidoptera: Nymphalidae) is controlled by a factor which reduces cuticular melanization (Buckman & Maisch, 1987). This so-called pupal melanization reducing factor (PMRF) is located throughout the entire central nervous system of prepupae (Starnecker et al., 1994). Extracts of abdominal ganglia also stimulated dose-dependently lutein incorporation into pupal cuticle. In the bioassay higher doses were required to increase cuticular lutein content than to reduce melanization. Ligatures during the prepupal stage demonstrated two different critical periods for these pigmentation effects: an early one for melanization reduction and a late one for lutein incorporation. An initial chromatographic purification yielded only two adjacent fractions which contained both the PMRF and the stimulation of lutein incorporation activity. Therefore it is assumed that only one hormone with a dual function may be responsible for pupal pigmentation. Lutein content was found in gut, fat body, epidermis and haemolymph of I. io. Lutein incorporation into cuticle occurred within 1.5 days of the pupal moult when the cuticle was not yet fully sclerotized. Lutein content is significantly higher in cuticle of yellow pupae than of black ones.
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