Albino corpus cardiacum extracts induce morphometric gregarization in isolated albino locusts, Locusta migratoria, that are deficient in corazonin

Abstract

Abstract The neuropeptide [His7]‐corazonin, present in the central nervous system and corpus cardiacum, is known to mimic a ‘gregarizing’ effect on phase‐related morphometric ratios (hind femur length/maximum head width and fore wing length/hind femur length) when injected into locusts reared in isolation. However, an albino strain is known to exhibit phase‐specific changes in these ratios in response to rearing density, although it is deficient in [His7]‐corazonin. To examine whether there is a second factor responsible for this phenomenon, perhaps a corazonin‐like factor that has lost its dark‐colour inducing activity, methanol extracts of corpora cardiaca taken from crowd‐reared albino nymphs of Locusta migratoria are injected into isolated‐reared second‐stadium albino nymphs and reared to adults in isolation. The hind femur length/maximum head width and fore wing length/hind femur length ratios are significantly different from those of control oil‐injected counterparts, and shift significantly towards the values typical for crowd‐reared gregarized individuals. The results indicate that the corpora cardiaca contain a factor similar to [His7]‐corazonin, although it has no dark‐colour inducing activity.