Anatomy of the sensory nervous system in Craspedella pedum (Plathelminthes, Temnocephalida): DiO staining after fixation and in vivo

Abstract

 The microanatomy of the nervous system of Craspedella pedum is described based on staining of the sensory nerves with DiO (3,3′-dioctadecyloxacarbocyanine perchlorate) in whole worms after fixation. The high resolution and reproducibility of this method revealed that the microanatomy of the nervous system is uniform within this species to rather minute details. Although the lateral and ventral cords have a similar diameter, the ventral nerve cords are very poor in sensory fibres. Such a high level of functional differentiation of nerve cords has not been known in representatives of the Plathelminthes. In vivo staining reveals numerous DiO-accumulating sensory neurons in the anterior portion of the body and a few pairs in its posterior half. The morphology of some neurons is described. Several neurons were identified and our data suggest that most, if not all, sensory neurons are identificable cells.