Budding in the ascidian Aplidium petrense Michaelsen

Abstract

Asexual reproduction in the ascidian family Polyclinidae is typically by post-abdominal budding, but in Aplidium pallidum (Verrill) the abdomen is also involved (Brien, 1925). A second species A. petrense Michaelsen is shown in this paper to use both abdomen and post-abdomen in producing buds. Trophocytes migrate back to the abdomen and post-abdomen, and constrictions divide these regions of the zooid into a series of buds of which at least the anterior few contain gut tissue. Subsequently each bud regenerates to form a new zooid. the similarity of the process in A. pallidum and A. petrense may result from convergence rather than phylogenetic affinity.