Developmental Continuity Between Larval and Adult Leg Patternings inCoccinella septempunctata(Coleoptera: Coccinellidae)

Abstract

Complete metamorphosis, a key innovation in insect development, promotes diversification of species, but whether larval and adult morphologies evolve independently remains unknown. To analyze morphological continuity between the legs of the larva and the adult, the regeneration frequencies and lengths of regenerated legs of the seven-spotted lady beetle, Coccinella septempunctata (Coccinella: Coccinellidae), were studied in the laboratory. The results showed the regenerated legs appeared only in the adult stage rather than in the larval instars. Regeneration frequency was greater following half ablation than after complete ablation and decreased with increasing instar of the ablated larvae, but it was unaffected by the thoracic location of the ablated leg or the side of the body to which the leg was attached. The length of the regenerated leg was longer in half ablation than in complete ablation, but it had no significant relationship with the above locations and the number of the instar. Partially regenerated legs in complete ablation were shorter than in half ablation, while completely regenerated legs appeared to be slightly shorter than the contralateral legs, which had not been ablated. A critical point in time of development when the frequency of leg regeneration began to decline was found to be at day 3.5 of the fourth instar's stadium. Subsequently on day 4, the regeneration frequency became quite small. The present study indicated that adult leg patterning is inherited from the larval leg and does not develop independently of the larval leg. Thus larval morphology constrains adult morphology in C. septempunctata.