The Fine Morphology of the Osphradial Sense Organs of the Mollusca. IV. Caudofoveata and Solenogastres

The fine morphology of the osphradial (= dorsoterminal) sense organs of seven Caudofoveata and two Solenogastres is described. In the Caudofoveata the organ forms a longitudinal groove bordered by swellings. It is well developed in the Chaetodermatidae, less developed in the Limifossoridae and vestigial in the Prochaetodermatidae. Within the Solenogastres there occurs great variation in number (total lack up to six) and structure, and no correlation with systematics or ecological factors could be found. Owing to special structures (paddle cilia) the osphradial sense organs of the aplacophoran classes are regarded as chemoreceptors. A role in sexual biology (coordination of spawning) is suggested for the Caudofoveata. The role of the organs in the Solenogastres remains still unclear.