Fig. 4

SEM micrographs of the surface topography of Phyllodistomum angulatum. a, c Body of a mature worm, ventral view. b Oral sucker rim; note a constant pattern of 20 sensory papillae: four papillae localised on each side of the frontal pit; six papillae arranged in an outer ring; six papillae arranged in an inner ring and four papillae are situated within the sucker cavity (inset, papilla of oral sucker, scale-bar: 10 μm). d Four papillae within oral sucker cavity. e Evaginated cirrus; note smooth tegumental surface around and on evaginated cirrus. f Posterior notch, dorsal view. g Ventral sucker rim showing six large constant papillae and four small papillae; note negligible ‘acetabular fold’ (inset, papilla of the ventral sucker, scale-bar: 10 μm). Abbreviations: af, acetabular fold; ec, evaginated cirrus; fb, forebody; fp, frontal pit; gp, genital pore; hb, hindbody; ip, papilla of the inner ring; lp, lateral papilla surrounding frontal pit; op, papilla of the outer ring; os, oral sucker; p, papilla; pn, posterior notch; rc, radial corrugations of the sucker rim; sa, sucker aperture; sp, small papilla within sucker cavity; tr, transverse tegumental ridges; vlp, large papilla of the ventral sucker rim; vs, ventral sucker; vsp, small papilla of the ventral sucker rim