ULTRASTRUCTURE OF SENSORY RECEPTORS OF AN UNDESCRIBED SPECIES OF LURIDAE (PLATYHELMINTHES, RHABDOCOELA)

Nine types of uniciliate sensory receptors are described from an undes cribed species of Luridae: a collar receptor with a collar formed by 7 -8 rods; a receptor with a long vertical and short horizontal rootlet and a thick ring-like electron-dense collar; a receptor with an approx imately 2-mum-long cilium that has a narrow bent tip; a bulbous recept or with a short bulbous cilium; an intraepidermal receptor with a shor t cilium enclosed in an epidermal cavity; a receptor with a long ciliu m, short ciliary rootlet and electron-dense rod; pharyngeal receptors with long (at least 4 mum long) and short (0.5 mum long) cilia; and a pharyngeal receptor with a cilium of intermediate length. Centrioles i n nerve cells and (in cross-section) butterfly-shaped cilia may also b e of a sensory nature. Ecological implications of the large variety of sensory receptors are discussed: in the variety of stimuli to which a nimals have to respond for survival, interstitial beach habitats are c omparable to habitats on or in hosts used by platyhelminth parasites ( which have a comparable number of receptor types).