The dark-colour-inducing neurohormone of locusts in relation to an albino mutant of Schistocerca gregaria

In the albino mutant of an Okinawa strain of Locusta migratoria (L.) (Ortho ptera: Acrididae), albinism is caused by the absence of the dark-colour-ind ucing neurohormone (DCIN), which is present in the corpora cardiaca (CC) of normally coloured phenotypes. This study tests whether the absence of DCIN is responsible for albinism in an albino mutant of another locust, Schisto cerca gregaria (Forsk.) (Orthoptera: Acrididae). This seemed feasible becau se a single Mendelian unit controls albinism in both species. However, impl antation of CC, or injection of an extract of CC, from albino donors of S. gregaria, induce dark coloration in crowded nymph recipients of the Okinawa albino mutant of L. migratoria, as effectively as do implanted CC, or inje ctions of extract of CC, from normal phenotype donors of S. gregaria. There fore, DCIN is present in the albino mutant of S. gregaria, and consequently , the albinism in this mutant is not caused by its absence. Implantation of CC, or injection of extracts of CC, from albino donors of S . gregaria to conspecific albino nymphs does not induce darkening. Only ext remely high doses of synthetic DCIN injected into albino nymphs of S. grega ria are effective, inducing some darkening. The dose to induce such darkeni ng in albino nymphs of S. gregaria is 50 nmol, approximate to 5 X 10(6) tim es higher than that (10 femtomol) needed to induce equivalent darkening in nymphs of the Okinawa albinos of L. migratoria. The results are discussed a nd some possible explanations of the observed effects outlined.