ULTRASTRUCTURE OF PRESUMED SENSORY RECEPTORS IN THE SCOLEX OF ADULT PROTEOCEPHALUS-EXIGUUS (CESTODA, PROTEOCEPHALIDEA)

The ultrastructure of six types of putative sense receptors including three nonciliate (Types I-III) and three ciliate (Types IV-VI) types f ound in the tegument of the scolex of adult Proteocephalus exiguus has been described for the first time. Type I has a simple tegumental sen sory ending, containing one electron-dense collar, circular septate de smosome, electron-lucent vesicles and microtubules. Type II is represe nted by a receptor with a large rootlet. Type III is a receptor with a very long cross-striated rootlet, with two electron-dense collars and septate junction. The ciliated receptors differ in the length of the cilium, in the number of electron-dense collars and in the shape of se nsory bulb. A comparison of structural features of receptors in differ ent systematic groups within Platyhelminthes is made. (C) 1998 Austral ian Society for Parasitology. Published by Elsevier Science Ltd. All r ights reserved.