Abstract. The tetraphyllidean metacestode diversity of 310 teleost fishes, including 87 species from 31 families, was examined from Heron Island, The Great Barrier Reef, Australia. Eleven metacestode 'types' were identified with the use of light microscopy. Host-specificity varied greatly among metacestode types. Incorporation of in vitro cultivation allowed generic identification for some types. Types 1 and 2 belong to Uncibilocularis Southwell, 1925, and have triloculate bothridia and one pair of forked hooks with unequal prongs; Type 3 has quadriloculate bothridia. Hook development was insufficient to determine in which genus, Acanthobothrium van Beneden, 1849 or Calliobothrium van Beneden, 1850, this type may belong. Type 4 has unilocular bothridia with simple edges and belongs to Anthobothrium van Beneden, 1850. Type 5 has multiloculated bothridia which are invaginated within pouches. This type belongs to the Rhinebothriinae although its generic identity cannot be determined. The bothridia of Type 5 everted within 24 hours of in vitro cultivation and revealed the presence of two forms, one having 48 loculi per bothridium, the other 72 per bothridium. In vitro studies provide additional support for existing theories of onchobothriid scolex development.Tetraphyllidean metacestodes have traditionally been difficult to identify due to their relatively featureless scolex morphology, which lacks the diagnostic features of the adult cestodes. These metacestodes have long been known from the intestines of teleost fish and the genus Scolex Mueller, 1788 was proposed to accommodate them with Scolex pleuronectis Mueller, 1788 the type species (Stunkard 1977). Subsequently, other species were described and placed in this genus until Rudolphi (1819), doubting the validity of these species, synonymised them as Scolex polymorphus Rudolphi, 1819. Observations since then have suggested that the above species represent a number of tetraphyllidean species so that the names S. pleuronectis and S. polymorphus have become collective names encompassing metacestodes that share features common to this order of cestodes (Wardle and McLeod 1952, Caira and Ruhnke 1991, Dick and Choudhury 1995.Many species of fish on The Great Barrier Reef are known to harbour tetraphyllidean metacestodes (Lester and Sewell 1989) but no real attempt has been made to distinguish them. A number of workers have endeavoured, using in vitro techniques, to induce maturation of the metacestode scolex to more closely represent that of the adult, thus allowing at least partial identification of the species (Hamilton and Byram 1974, Carvajal et al. 1982). With that purpose in mind, in vitro cultivation was used in addition to morphological techniques to identify and quantify the number of species of tetraphyllidean metacestodes found parasitising teleost fishes of Heron Island, The Great Barrier Reef, Australia.
MATERIALS AND METHODSMetacestodes were dissected from their hosts with the aid of a dissecting microscope. Specimens for morphological examination were...