Ultrastructure of glands in a scutariellid (Platyhelminthes) and possible phylogenetic implications

Subepidermal glands of the body of Troglocardicola sp. (from the cavernicol ous shrimp Troglocaris sp. in eastern Italy) were observed by transmission electron microscopy. The reservoir and duct of the glands are lined with lo ngitudinal microtubules. Membrane-bound granules inside the gland show a di stinctive pattern: they contain fibres, 18 nm in diameter, regularly arrang ed in bundles with a 5 nm space between fibres. From a survey of the availa ble literature on glands of Platyhelminthes, it is concluded that this stru cture is known only in this species. Glands with regularly arranged 18 nm f ibres, if characteristic for the Scutariellidae, could be considered an aut apomorphy of this family, distinguishing it from other members of the Temno cephalida.