Induction of darkening by corazonins in several species of Orthoptera and their possible presence in ten insect orders

[His(7)]-corazonin is known to play an important role in the control of body-color polymorphism in the migratory locust, Locusta migratoria (Orthoptera: Acrididae). Another neuropeptide, [Arg(7)]-corazonin, which has been isolated from other insects, is also known to induce darkening in this locust. These two neuropeptides were injected into nymphs of other orthopteran species to determine if they could induce darkening in those species. The test species belonged to 4 families: Acrididae (Acrida cinerea, Gastrimargus marmoratus and Nomadacris succincta), Catantopidae (Oxya yezoensis), Pyrgomorphidae (Atractomorpha lata) and Tettigoniidae (Euconocephalus pallidus). Except for the katydid, E. pallidus, all species injected with I nmol of [His(7)]-corazonin turned dark as compared with oil-injected controls. [Arg(7)]-corazonin showed a similar effect in the two acridid species tested, but no effect in the katydid. These results suggest that [His(7)]-corazonin or a similar neuropeptide may be involved in the control of body color in the locusts and grasshoppers, but not in the katydid. When a brain and/or corpora cardiaca (CC) taken from nymphs of each test species were implanted in albino nymphs of L. migratoria, dark color was induced in the latter, indicating that all test orthopterans contained some factor identical or similar to [His(7)]- or [Arg(7)]-corazonin. Likewise, brain-CC complexes from 47 other species of 10 insect orders including Orthoptera, Dermaptera, Dictyoptera, Isoptera, Homoptera, Hemiptera, Odonata, Hymenoptera, Lepidoptera and Diptera induced darkening in albino locusts, whereas those from 8 species of Coleoptera all failed to do so.