Distribution of sensory organs on surface of adult Amphilina foliacea (Plathelminthes, Amphilinida)

The distribution and morphological diversity of sensory structures on the b ody surface in adult Amphilina foliacea were investigated using scanning an d transmission electron microscopy. Amphilina foliacea is a parasite of the sterlet (Acipenser ruthenus), a valuable commercial fish from the sturgeon family. Distribution of sensory cilia differs in individuals of various si ze, Ciliate receptors of small worms (up to 1 cm) are mainly located along lateral body margins and its ends, In large individuals (1-3 cm), receptors occur rarely on crest cells and are located unevenly. The biciliate and mu lticiliate sensory structures are found the first time. Fourteen receptor t ypes are distinguished. Sensory organs are shown to be confined to the cert ain areas of the body surface, The distribution of receptors correlates wit h a way of movement of the parasite within the body cavity and organs of th e host, The number of receptors per unit area decreases with increasing age and size of worms.