Immunohistochemical analysis of nervous system regeneration in chimeric individuals of <i>Dorvillea bermudensis</i> (Polychaeta, Dorvilleidae)

Abstract

In regeneration experiments, 0.5% of the two- or five-segmented fragments of the polychaete Dorvillea bermudensis were found unexpectedly transplanted: two fragments of each that were lying close together during the initial period, fused and regenerated a chimeric individual. Of the three theoretical possibilities (i.e. fusion of (i) two posterior ends; (ii) one anterior and one posterior end; (iii) or two anterior ends) only the last two were realized. The similarly oriented fragments regenerated a normal animal while anterior-anterior fused ones produced two heads or a double head. Whether the ventral cords of the fragments are located vis-a-vis or adjacent, influences the course of regeneration as well. Immunohistochemical methods (anti-acetylated alpha-tubulin) in conjunction with confocal laser scanning microscopy were used to investigate the wiring pattern of the nervous systems of the grafts. In all cases, at least two supraesophageal ganglia were formed and palps, antennae and nuchal organs were innervated by the correct nerves but, in special cases, were innervated vice versa from the other brain. From these results it can be concluded that fusion of a regenerating connective with another connective results in formation of a new brain, irrespective of whether it belongs to the same nerve cord or not.