A comparison of anterior adhesive areas and secretions in Troglocephalus rhinobatidis and Neoheterocotyle rhinobatidis (Monogenea : Monocotylidae) from the gills of the shovelnose ray, Rhinobatos typus (Rhinobatidae)

This study continues the collection of data on the anterior adhesive areas and secretions of monopisthocotylean monogenean (flatworm) parasites and be gins an investigation of their phylogenetic usefulness. Here, two species o f parasitic worms from an elasmobranch, Troglocephalus rhinobatidis (Monoco tylidae: Dasybatotreminae) and Neoheterocotyle rhinobatidis (Monocotylidae: Heterocotylinae), are compared and contrasted. It has been suggested in re cent literature that these two taxa are more closely related than is curren tly recognised. Our data support this view. Both species have multiple aper tures on the ventral anterior margin through which adhesive is secreted. Tw o types of secretion exit from multiple adjacent duct endings terminating i n each aperture: rod-shaped (S1) and spherical-shaped (S2) bodies. S1 bodie s of both species show nano-banding of similar size and are membrane bound. Ultrastructure of the glands, ducts, duct endings and secreted adhesive is similar for both species, but aperture shape differs. Away from the adhesi ve areas, tegumental inclusions are found to differ between the two species and another, apparently non-adhesive, secretion is found in N. rhinobatidi s.