Blastema formation and cell division during cockroach limb regeneration.

Recent models of pattern formation in insects have been derived largely from observations on regenerated cuticular patterns. Such models make assumptions about the behaviour of the underlying epidermal cells, their movement and patterns of cell division. The present study, designed to test these assumptions, looks at the patterns of wound healing and cell division after amputation at the trochanter-femur joint of the metathoracic leg in the cockroach. It shows that the wound is closed by cell migration and that regeneration occurs by dedifferentiation of the trochanter and distal coxa to form a blastema which grows and redifferentiates to form the new limb. The extent of the spread of dedifferentiation is confirmed by a scanning electron microscope study of the coxa after the moult following amputation. The results highlight the need for a greater knowledge of cell behaviour during pattern formation before we can begin to understand the processes involved in pattern formation.