How the discovery of oligochaete regeneration during the Enlightenment was pivotal to the advancement of annelid research

Abstract

Abstract Within a few months of the year 1741, Lyonet and Trembley in Holland, Bonnet in Geneva and Réaumur in Paris all experimented industriously with the regeneration of various invertebrates, including the still unknown microdrile oligochaetes. Some of these worms were prone to spontaneous fragmentation as a natural mode of asexual multiplication, preceded (paratomy) or followed (architomy) by regenerative processes. Bonnet and Réaumur raised the stakes and began to study regeneration in earthworms, a challenge that, especially in Italy, inspired scholars and educated people among the clergy and aristocracy. Spallanzani conducted the most rigorous experiments and was the first to obtain consecutive regenerations of the head in one and the same megadrile. He saw detached mid-body sections becoming complete with a new head and a new tail, and he determined the points of the body where regeneration does not take place and how much length to leave for each section so that it could reintegrate. Above all, Spallanzani obtained regeneration of the gonadic segments, both in terrestrial and in freshwater megadriles, the latter today identified as Criodrilus lacuum. This and other important anatomical and physiological findings by Spallanzani, largely unpublished during his lifetime and for a long time after, preceded the discoveries of later authors by almost 50 years.