Dendromonocotyle species (Monogenea: Monocotylidae) are the only monocotylids to parasitize the skin of chondrichthyan hosts. Currently 11 species are recorded from the skin of ray species in the Dasyatidae, Myliobatidae and Urolophidae. There have been increasing reports of Dendromonocotyle outbreaks on rays kept in public aquaria. This paper provides a broad review of Dendromonocotyle that should assist taxonomists and aquarists with species identification and help decisions on potential control methods for Dendromonocotyle infections. The taxonomy and host-specificity of Dendromonocotyle are discussed and a key to current species is provided. We summarise what little is known about the biology of Dendromonocotyle including egg embryonation and hatching, feeding, camouflage and reproduction. The efficacy of freshwater baths, chemical treatments and biological control measures such as the use of cleaner fish for Dendromonocotyle is also discussed. We demonstrate that effective control of Dendromonocotyle on captive rays is hampered by the lack of basic biological data on the life cycle of the parasites. A case history is provided outlining the success of a public aquarium (Underwater World, Mooloolaba, Queensland, Australia) in managing D. pipinna infections on captive Taeniura meyeni without chemical intervention simply by taking measures to reduce host stress.
Dendromonocotyle colorni sp. n. (Monogenea: Monocotylidae) is described from the dorsal skin surface of two specimens of Himantura uarnak (Forsskål) kept at the Eilat Underwater Observatory in Israel. Dendromonocotyle colorni is distinguished from the other eight species in the genus by the morphology of the terminal papillar sclerite on the haptor, the distal portion of the male copulatory organ and the morphology of the vagina. The development of the male copulatory organ is detailed for D. colorni and the adaptations of species of Dendromonocotyle to life on the dorsal skin surface of rays are discussed. Dendromonocotyle octodiscus Hargis, 1955 was identified from the dorsal skin surface of the southern stingray Dasyatis americana Hildebrand et Schroeder off Bimini, Bahamas and represents a new host record.
Empruthotrema quindecima sp. n. (Monogcnea: Monocotylidae) is described from the nasal fossae of the blue-spotted fantail ray Taeniura lymma (Forsskâl, 1775) collected from the reef flats of Heron Island and Lizard Island located at the southern and northern sections, respectively, of the Great Barrier Reef in Queensland, Australia. Empruthotrema quindecima has 15 marginal loculi on the haptor which distinguishes it from the other five members of the genus which have either 13 or 14 marginal loculi. The generic diagnosis of Empruthotrema Johnston ct Ticgs, 1922 is amended to accommodate the new species, a key to species is provided and the evolution of the different configurations of the haptoral loculi within the genus is discussed.
Heliocotyle ewingi sp. n. (Monogenea: Monocotylidae) is described from the gills of Myliobatis australis Macleay, 1881 (Myliobatididae) collected from Norfolk Bay near Hobart, Tasmania, Australia. Heliocotyle ewingi can be distinguished readily from the only other species in the genus, Heliocotyle kartasi Neifar, Euzet et Ben Hassine, 1999, by the presence of a single pseudoseptum on each of the peripheral loculi except the posteriormost, eyespots and by the morphology of the male copulatory organ which is a short, straight sclerotised tube which lacks a sclerotised accessory piece. The generic diagnosis is revised to accommodate the new species and the anterior glands are discussed.
Nine Pteromylaeus bovinus (F., Geoffroy St. Hilaire) (Euselachii: Myliobatinae) from the Tunisian coast were examined l'or ectoparasites during 1995, 1996 and 1997. A monogenean found on the gills of seven host specimens is described as a new species and a new genus, Heliocotyle, is proposed to accomodate it. The presence of a single sclerotized haptoral structure on the dorsal surface of the haptor leads us to place this species in the Heterocotylinae Chisholm, Wheeler ct Beverley-Burton, 1995. The genus Heliocotyle is characterized by a haptor with only one dorsal structure and seven loculi, six being subdivided by pseudosepta. Heliocotyle kartasi sp. n. is the type and the only species in this genus.
Five new species of Potamotrygonocotyle (Monocotylidae) are described and Paraheteronchocotyle amazonense Mayes, Brooks et Thorson, 1981 (Hexabothriidae) is redescribed from monogenoideans collected on the gills of species of Potamotrygonidae from the Negro River, Amazon, Brazil. Potamotrygonocotyle quadracotyle sp. n. and P. umbella sp. n. were found parasitizing an undescribed species of Potamotrygon; Potamotrygonocotyle rarum sp. n. is described from Potamotrygon schroederi; Potamotrygonocotyle rionegrense inhabits Potamotrygon cf. motoro; Potamotrygonocotyle aramasae sp. n. is a parasite of Paratrygon aiereba; and Paraheteronchocotyle amazonense is reported from Potamotrygon orbignyi. The diagnosis of Paraheteronchocotyle is emended, and P. amazonense is redescribed.
Dendromonocotyle lotteri sp. n. is described from the dorsal skin surface of the stingray Himantura gerrardi (Gray) on exhibit in the public aquarium at the Atlantis resort in Dubai. It is differentiated from all other Dendromonocotyle species by the unique morphology of the distal portion of the sclerotised male copulatory organ. Dendromonocotyle lotteri is the second representative in the genus with 56 marginal haptoral papillae having a papillae to loculus association represented numerically as 6-6-8-8. We found Dendromonocotyle colorni Chisholm, Whittington et Kearn, 2001 on the same host specimens at the Atlantis resort public aquarium and Dendromonocotyle kuhlii Young, 1967 on Neotrygon kuhlii (Müller et Henle) kept at Burgers' Zoo Aquarium in Arnhem, The Netherlands. Supplemental information is provided for both D. colorni and D. kuhlii. The presence of Dendromonocotyle infections in public aquaria and host specificity are discussed. A key to the 17 species of Dendromonocotyle is also provided.
Myliocotyle borneoensis sp. n. and M. multicrista sp. n. (Monocotylidae: Heterocotylinae) are described from the gills of the mottled eagle ray, Aetomylaeus maculatus (Gray), and the banded eagle ray A. nichofii (Bloch et Schneider) (Myliobatidae), respectively, collected from the northern coast of Malaysian Borneo. These are the first monogeneans to be described on elasmobranchs from Borneo. The formerly monotypic Myliocotyle (for M. pteromylaei) was distinguished from other monocotylids by the distribution and morphology of the eight sclerotised dorsal haptoral accessory structures and the morphology of the male copulatory organ. However, we have determined that M. pteromylaei has ten structures on the dorsal surface of the haptor. Myliocotyle borneoensis is distinguished from M. pteromylaei by the morphology of the male copulatory organ and its accessory piece. Myliocotyle multicrista has 12 sclerotised dorsal haptoral accessory structures and a male copulatory organ with two accessory pieces. Additional sclerotised ridges across the ventral surfaces of each loculus (except the posterior-most pair) are also present in M. multicrista. The diagnosis for Myliocotyle is revised given our discovery of additional dorsal haptoral accessory structures in the type species and to accommodate other new characters of the two new species. Anterior secretions of Myliocotyle are discussed.