The Proboscis Armature of Turbellaria‐Kalyptorhynchia, a Derivative of the Basement Lamina?

Publisher Website
Google Scholar
Abstract
The fine structure analysis of the proboscis teeth in the genusCarcharodorhynchusMeixner and of the proboscis hooks in the genusDiascorhynchusMeixner revealed that these structures are not derived from local cuticularizations of the epidermis, but rather are closely associated with the basement lamina of the proboscis sheath epithelium. InDiascorhynchusthe hooks are specializations within the basement lamina enclosing the proboscis. The proboscis teeth inCarcharodorhynchusseem to be either an intracellular differentiation within the modified proboscis sheath epithelium or, as inDiascorhynchus, a derivative of the basement lamina. The latter is supported by the finding of similar, dermal teeth clearly derived from the basement lamina in the body wall of several species of the genusCarcharodorhynchus.It appears from this study that most “cutic‐ular” differentiations of the body wall in Turbellaria are either derivatives of the basement lamina or of the cytoplasm of the epidermis cells. These considerations are discussed in the light of possible evolutionary pathways leading from a ciliated epidermis (e.g. free‐living acoelomates) to a cuticularized hypodermis (e.g. Aschelmimhes and Articulata).