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

Abstract

The fine structure analysis of the proboscis teeth in the genus Carcharodorhynchus Meixner and of the proboscis hooks in the genus Diascorhynchus Meixner 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. In Diascorhynchus the hooks are specializations within the basement lamina enclosing the proboscis. The proboscis teeth in Carcharodorhynchus seem to be either an intracellular differentiation within the modified proboscis sheath epithelium or, as in Diascorhynchus, 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 genus Carcharodorhynchus. 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).

Morphology of the Turbellaria at the ultrastructural level

“…the kalyptorhynch proboscis) Rieger & Doe (1975) suggest that supportive and hard structures in the phylum Plathelminthes have not evolved through 'true' cuticularizations, 2 but through elaborations of the intracellular fibrous system (cell web, terminal web) or the intercellular fibrous system at the base of the epidermis (basement membrane). The macrostomid type of epidermis represents a trend towards a domination of the cell web for mechanical support, whereas the neoophoran type of epidermis represents a trend towards a domination of the basement membrane system for the same function.…”

Hard Parts in the Female System of Syndesmis longicanalis (Platyhelminthes, Rhabdocoela, Umagillidae) Are Basement Membrane Derivatives

“…Sperm appear to have the same structure as described in Syndisyrinx punicea (HICK-MAN 1956) by Rohde & Watson (1988). That so-called "sclerotic" elements can in fact be derivatives of the basement membrane has been shown: spines and hooks on the proboscis of some Kalyptorhynchia (Rieger & Doe 1975), stylets and cirrus spines in the copulatory organ of the Monocelididae (Martens & Schockaert 1981;Martens 1984Martens , 1986. It is therefore not surprising that hard parts in the female system of Platyhelminthes can also be derived from basement membrane.…”

“…It is therefore not surprising that hard parts in the female system of Platyhelminthes can also be derived from basement membrane. Rieger & Doe (1975) and Rieger (1981) pointed out that in the absence of "true" cuticular formations in Platyhelminthes, sclerotic parts can differentiate only from intracellular components (such as the terminal web: Rieger 1981) or from extracellular matrix (such as the basement membrane). Intracellular hard parts probably will be found in the female system of some Platyhelminthes and other species are now under investigation.…”

“…So far two exceptions have been found: the proboscis teeth and hooks in the Schizorhynchia (Kalyptorhynchia)-Carcharodorhynchus sp., Diascorhynchus sp. (Rieger & Doe 1975), and Cheliplana sp. (Doe 1976)-on the one hand, and the stylet and spines of the cirrus of representatives of the proseriate family Monocelididae (Martens & Schockaert 1981;Martens 1984Martens , 1986 on the other hand.…”

Observations on the ultrastructure of the copulatory organ of Archilopsis unipunctata (Fabricius, 1826) (Proseriata, Monocelididae)

“…with the same appearence as the vasa deferentia and efferentiaunpublished data). Considering now the cirrus and its spines it has been revealed that hard structures in Turbellaria are either derivatives of the basement lamina, as the proboscis armature of Carchorodorhynchus and Diascorhynchus (Rieger & Doe 1975), or are intracellular condensations, as the proboscis hooks in Cheliplana and Gnathorhynchus (Doe 1976), the copulatory needles in Carenscoilia bidentata (Ehlers & Ehlers 1980) and the rods of the copulatory organ in Paratomella rubra (Mainitz 1977). A true cuticula, i.e.…”