Natural occurrence of an experimental developmental phenotype in the leech Erpobdella punctata (Leidy 1870) (Annelida: Clitellata: Hirudinea)

ABSTRACT In the embryonic blast cells of leeches, segmental identity is conferred in a cell-intrinsic manner (i.e., with temporal rather than spatial signals), at or shortly after the birth of the cell. If these blast cells are destroyed in only one of the two germinal bandlets that form the ventral midline, this can result in segment-specific features that fall out of register on either side of the leech body. Here we present a specimen of the leech Erpobdella punctata, in which the gonopores have been duplicated and the male and female reproductive tracts are out of register between the left and right sides of the body. To confirm the identity of the specimen, we use a phylogenetic approach and high-resolution stereo microscopy. The probable cause of the phenotypic anomaly is discussed.