Regeneration of antennae and its control of molting in the terrestrial isopod, Armadillidium vulgare

AbstractThe interactions of regeneration and pregnancy controls on the duration of different stages of molting in the pillbug Armadillidium vulgare were determined by removing the antennae during different stages of the molt cycle of the nonovigerous and ovigerous animals. Removal of one or two antennae from the males during the beginning of stage C (intermolt period) of their molting cycle resulted in regeneration and shortening of stage C and thereby in acceleration of ecdysis. Further, removal of both antennae induced the animals to ecdyse within 1–4 days of each other, thus providing a convenient method of synchronizing the molt cycle. Amputation of both antennae from males in late stage C also resulted in regeneration; however, the duration of stage C was lengthened, resulting in a delay in ecdysis. Amputation of both antennae from males and nonovigerous females in the middle of preecdysis (stage D) resulted in molting without regeneration and on schedule like the control animals. However, the antennaless animals regenerated their antennae, shortened their intermolt period (stage C), and ecdysed precociously. From these results, we conclude that amputation, before the critical period in the molt cycle of the pillbugs (during stage C), prevents the release of ecdysteroids and, consequently, generalized apolysis until regeneration is completed, whereupon this block is removed and generalized apolysis and further events of molting occur. Once ecdysteroid release has been initiated to cause generalized apolysis, as in stage D, amputation does not prevent the further events of molting. Amputation of both antennae during the beginning of the intermolt period in the ovigerous females, although permitting regeneration, did not immediately stimulate ecdysis as in the nonovigerous animals; instead, it occurred only after release of the larvae from the brood pouch. When compared to the control ovigerous animals, the overall length of stage C was shortened. The results obtained from the antennal amputations during different physiological stages of the pillbug show that of all the stages of the molt cycle, stage C is labile, and its duration is affected by regeneration and pregnancy.