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

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.