Unicellular adhesive secretion glands and other cells in the parenchyma ofTemnocephala novaezealandiae(Platyhelminthes, Temnocephaloidea): Intercell relationships and nuclear pockets

Abstract

The nucleus of a unicellular adhesive gland of Temnocephala novaezealandiae possesses a “honeycomb” layer and is closely surrounded by many asymmetrical desmosomes. The gland is deeply invaginated by trophic prolongations of parenchymal cells ending at the juxtanuclear desmosomes, a characteristic cytomorphology shared by other cell types in the parenchyma, including rhabditogenic glands. Perinuclear mitochondria, typically of indented form, are associated with the penetrative processes. Individual muscle fibres are inserted between apposed plasma membranes of the gland and parenchymal cells within the gland cell's outermost boundaries, and are completely surrounded by the compartmentalised cytoplasm. Nuclear pockets were observed in an undifferentiated cell with the extensively invaginated morphology. The pockets contained cytoplasmic regions, probably undergoing catabolism, enveloped by extensions of both inner and outer nuclear membranes and segregated from the general matrix. Reutilisable cytoplasmic constituents may be returned to the general cytoplasm from nuclear pockets of this type. Corresponding intercell relationships and examples of nuclear pockets in other phyla are cited.