Phylogeny and clitellar morphology of the giant Amazonian earthworm Rhinodrilus priollii (Oligochaeta: Glossoscolecidae).

Lang SA, Garcia MV, James SW, Sayers CW, Shain DH (2012) American Midland Naturalist 167:384-395.

The giant earthworm, Rhinodrilus priollii, is among the largest terrestrial invertebrates known worldwide, reaching lengths >2 m. To investigate the evolutionary history of the species and aspects of their reproductive biology, we collected R. priollii specimens from several field sites in central Amazonia. Population structures indicate episodes of gene flow between populations and their divergence within the past 1-2 million years. Histological examination of clitella identified cocoon secretory cells throughout the dorsal and dorsoventral epidermis. Unlike previously described secretory cells, those in R. priollii contained granules with a proteinaceous core covered by external glycosylation. Further, collagenous matrices formed the bulk of swollen clitella while albumin-secreting cells were noticeably absent, collectively suggesting a mechanism of cocoon production somewhat different from that described in other clitellate megadriles.