Extent and properties of the regeneration field in the larval legs of cockroaches (Leucophaea maderae):II. Confirmation by transplantation experiments

Abstract

ABSTRACT The investigation of the regeneration field of the larval legs of cockroaches (Leucophaea maderae), which commenced in a previous paper with extirpation experiments, has been continued by transplantation experiments. The extirpation experiments showed that there are two regions near the leg which are indispensable for leg regeneration: the basal sclerites, and the membranous region extending behind the leg up to the spiracle of the next segment, called Teg-inducing membrane’ (LIM). The LIM is followed by ‘sclerite-inducing membrane’ (SIM) which, upon contact with sclerites, only allows formation of sclerite structures. The results of the extirpation experiments have been confirmed by transplantation experiments. When the whole leg including the basal sclerites is removed, no leg regeneration occurs. The regenerative ability can be restored by implantation of part of the basal sclerites (for instance, the trochantin), but leg regeneration takes place only when the implantation area is covered by LIM. When the sclerites are transplanted to a region which is covered by SIM only additional basal sclerites are formed. Whole sets of basal sclerites have been implanted at different distances behind the uninjured hindleg. Additional legs are regenerated only in the anterior half of the membranous field extending between the hindleg and the first abdominal segment. Thus, there is a distribution of LIM and SIM in the region of the hindleg, similar to that near the midleg. Whole sets of basal sclerites have been implanted at various sites on the dorsal or ventral surfaces of the abdomen. Legs are formed on both surfaces, but only when the transplanted sclerites contact the intersegmental membranes. This means that the intersegmental membranes of the abdomen also have leg-inducing capacities. The implantation of a trochantin into a field of LIM is followed by the development of two regenerates -a normal one at the posterior border of the field, and one with reverse anterior-posterior polarity at the anterior border. When the trochantin is transplanted together with the praecoxa in a similar way, only one normal regenerate is formed at the posterior margin of the trochantin. The praecoxa prevents contact of the anterior margin of the trochantin with LIM, and contact of the anterior margin of the praecoxa with LIM does not promote leg regeneration.