The Australian species of Lobatocreadium Madhavi, 1972, Hypocreadium Ozaki, 1936 and Dermadena Manter, 1945 (Digenea: Lepocreadiidae), parasites of marine tetraodontiform fishes

The genera Lobatocreadium, Pseudocreadium, Hypocreadium and Dermadena are redefined and host lists given. Provisional keys to species of Lobatocreadium, Hypocreadium and Dermadena are presented. The following species are described from (1) the Great Barrier Reef: Lobatocreadium exiguum from Balistapus undulatus and Sufflamen bursa; Hypocreadium cavum n. sp. from Abalistes stellatus (type-host) and Cantheschenia grandisquamis; H. grandisquamis n. sp. from Cantheschenia grandisquamis; Dermadena spatiosa n. sp, from Cantheschenia grandisquamis; and (2) southwestern Australia: D. stirlingi n. sp. from Meeschenia hippocrepis. The following new combinations are made: Lobatocreadium vitellosum (Ozaki, 1936) n. comb. (originally Leptocreadium); Hypocrendium balistes (Nagaty, 1942) n. comb. (originally Pseudocreadium); H. biminensis (Sogandares-Bernal, 1959) n. comb. (originally Pseudocreadium); H. indicum (Madhavi, 1972) n. comb. (originally Pseudocreadium); and H. galapagoensis (Manter, 1945) n. comb. (originally Pseudocreadium). Several nominal species of Pseudocreadium and Hypocreadium are considered incertae sedis.

Preptetos and Neopreptetos (Digenea: Lepocreadiidae) from Australian marine fishes

The genera Preptetos Pritchard, 1960 and Neopreptetos Machida, 1982 are redefined. The following species are described and/or recorded from marine fishes. From the Great Barrier Reef: Preptetos caballeroi Pritchard, 1960 in Naso annulatus, N. brevirostris and N. vlamingii; P. xesuri (Yamaguti, 1940) in Zebrasoma veliferum and Z.scopas; Preptetos cannoni Barker, Bray et Cribb, 1993 in Siganus doliatus and S. fuscescens; Preptetas luguncula sp. n. in Naso unicoris (type-host); P. impar sp. n. in Lutjanus erythropterus (type-host) and L. malabaricus; Neopreptetos arursettae Machida, 1982 in Pomacanthus semicirculatus; and N. kurochkini (Toman, 1989) in Chaetodontoplus meredithi. From southwestern Australia: Preptetos rotto sp. n. in Nelusetta ayraudi (type-host), Neosebastes pandus, Oplegnathus woodwardi and Pagrus auratus. The new combination Preptetos trulla (Linton, 1907) (originally Distormum then Lepocreadium) is made and the species Lepocreadium areolatum (Linton, 1900) is considered likely to belong in Preptetos.

Postlepidapedon Zdzitowiecki, 1993 and Gibsonivermis n g (Digenea: Lepocreadiidae) from fishes of the southern Great Barrier Reef, Australia, and their relationship to Intusatrium Durio & Manter, 1968

The genus Intusatrium Durio & Manter, 1968 is redefined based on a re-examination of paratypes of the type-species, I. robustum Durio & Manter, 1968, and is considered monotypic with characteristic terminal genitalia: internal seminal vesicle elongate tubular, with rather thick wall, divided by slight change in wall thickness into longer proximal and shorter distal region; pars prostatica subcylindrical; ejaculatory duct relatively short, with wrinkled/wall. The genus Postlepidapedon Zdzitowiecki, 1993 is redefined and Intusatrium secundum Durio & Manter, 1968 is attributed to it as a new combination. Postlepidapedon secundum n. comb. is redescribed from a paratype and new material from Choerodon graphicus. P. spissum n. sp. from Choerodon venustus, C. cyanodus, C. fasciatus and C. schoenleinii is recognised on the basis of its thick-walled internal seminal vesicle. I! uberis n. sp. from Choerodon schoenleinii and C. venustus is distinguished by the shape and contents of the cirrus-sac with narrow, convoluted internal seminal vesicle, large vesicular pars prostatica and short, muscular ejaculatory duct. A new genus, Gibsonivermis, erected for Intusatrium berryi Gibson, 1987, is characterised by the elongate narrow cirrus-sac and a uroproct. G. berryi n. comb. is redescribed from Sillago ciliata, S. maculata and Sillago sp.

The Asian fish tapeworm, Bothriocephalus acheilognathi, in Australian freshwater fishes

Bothriocephalus acheilognathi was collected from 13 of 38 carp (Cyprinus carpio), 2 of 4 mosquito fish (Gambusia holbrooki), and 2 of 12 western carp gudgeon (Hypseleotris klunzingeri) in waterways of the Australian Capital Territory and New South Wales. This is the first record of this parasite in Australia, and its presence in H. klunzingeri is a new host record. B. acheilognathi presumably arrived in Australia with its introduced fish hosts and has since crossed into native fishes, This cestode may infect other native fish species, a potential that is significant given the high pathogenicity associated with infection in other known hosts.

Tubular eyes of deep-sea fishes: A comparative study of retinal topography

The world's deep oceans are home to a number of teleosts with asymmetrical or tubular eyes. These immobile eyes possess large spherical lenses and subtend a large binocular visual field directed either dorsally or rostrally. Derived from a lateral non-tubular eye, the tubular eye is comprised of a thick main retina, subserving the rostrally or dorsally directed binocular visual field, and a thin accessory retina subserving, the lateral, monocular visual field. The main retina is thought to receive a focussed image, while the accessory retina is too close to the lens for a focussed image to be received. Several species also possess retinal diverticula, which are small evaginations of differentiated retina located in the rostrolateral wall of the eye and thought to increase the visual field. In order to investigate the spatial resolving power of these retinae (main, accessory and diverticulum), the distribution of cells within the ganglion cell layer was analysed from retinal wholemounts and sectioned material in ten species representing four genera. In all species, the main retina possesses a marked increase in cell density towards a specialised retinal region (area centralis), with a centro-peripheral gradient range between 7.1 and 60:1 and a peak density range of between 30 and 55 x 10(3) cells per mm(2). The accessory retinae and the transitional zone between the main and accessory retinae possess relatively low cell densities (between 1 and 10 x 10(3) cells per mm(2)) and lack an area centralis. Retinal diverticula examined in four species possess mean ganglion cell densities of between 7.2 and 109.4 x 10(3) cells per mm(2). Analyses of soma areas show that the ganglion cell layer of most species possesses cells with areas in a range of 8.0 to 15.4 mu m(2) in the main retina and between 15.1 and 17.4 mu m(2) in the accessory retina. The peak spatial resolving power of the main retina of the ten species varies from 4.1 to 9.1 cycles per degree. The positions of the retinal areae centrales relative to each species' binocular visual field are discussed in relation to what is known of feeding behaviour of these fishes in the deep-sea.

The strain-driven pyrochlore to "defect fluorite" phase transition in rare earth sesquioxide stabilized cubic zirconias

The relationship between the ordering characteristic of the pyrochlore structure type and that characteristic of the defect fluorite structure type (immediately on either side of two phase regions separating the two structure types) in a range of rare eath sesquioxide stabilized cubic zirconias is investigated via electron diffraction and imaging. Systematic structural change as a function of composition and relative size of the constituent metal ions is highlighted and a multi-q to single-q = 1/2 [111]* model proposed for the observed pyrochlore to defect fluorite phase transition. Strain introduced into the close-packed {111} metal ion planes of the defect fluorite average structure by the local cation and oxygen vacancy distribution is pointed to as the likely origin of the observed behavior. (C) 2001 Academic Press

Weketrema gen.n., a new genus for Weketrema hawaiiense (Yamaguti, 1970) comb. n. (Digenea : Lecithasteridae) recently found in Australian marine fishes

A new genus, Weketrema, is erected in the family Lecithasteridae for the species hitherto known as Lecithophyllum hawniiense. Weket, ema hawaiiense (Yamaguti, 1970) comb, n. is redescribed from Scolopsis bilineatus (Bloch) (Perciformes: Nemipteridae) from Lizard Island and Heron Island, Queensland, Plectorhinchus gibbosus (Lacepede) (Perciformes: Haemulidae) from Heron Island and Cheilodactylus nigripes Richardson (Perciformes: Cheilodactylidae) and Latridopsis forsteri (Castelnau) (Perciformes: Latridae) from Stanley, northern Tasmania. The new genus is distinguished from related members of the family Lecithasteridae by its complete lack of a sinus-sac. Although placed in the subfamily Lecithasterinae pro tem, its true subfamily position is not entirely clear. Comment is made on its unusual distribution, both in terms of zoogeography and hosts.

Lecithophyllum kitrii n. sp (Digenea : Lecithasteridae) from Australian coral reef fishes of the genus Siganus

Lecithophyllum kitrii n. sp. is described from Siganus punctatus and S. lineatus off Heron Island on the southern Great Barrier Reef, Australia. It differs from most other species in the genus in its elongate pars prostatica and globular sinus-sac, and from all other species in having the seminal vesicle almost always entirely in the hindbody.

Amphicreadium n. g. (Digenea : Lepocreadiidae) from monacanthid fishes (Tetraodontiformes) from the coast of northern Tasmania

A new lepocreadiid genus, Amphicreadium, is erected for the species A. denspeniculus n. sp. from Acanthaluteres vittiger and for an unnamed species from Meuschenia freycineti, both from off northern Tasmania. The new genus is distinguished from all other members of its family by its amphistomatous body plan.

Identical digeneans in coral reef fishes from French Polynesia and the Great Barrier Reef (Australia) demonstrated by morphology and molecules

Three coral reef fish species, Zanclus cornutus, Chaetodon vagabundus and Naso lituratus, were collected in French Polynesia and on the Great Barrier Reef, Queensland. These fish species were each infected by one morphologically similar digenean species in both localities; Schistorchis Zancli Hanson, 1953 was found in Zanclus cornutus. Preptetos laguncula Bray and Cribb, 1996 in Naso lituratus and Neohypocreadium dorsoporum Machida and Uchida, 1987 in Chaetodon vagabundus. In addition, on the Great Barrier Reef P. laguncula was also found in Naso unicornis and N. dorsoporum in Chaetodon ephippium and Chaetodon flavirostris. Morphometric differences between the species from the two sites were only slight. Sequences from the second internal transcribed spacer of the ribosomal DNA of each worm revealed total homology or negligible divergence between samples from hosts caught in French Polynesia and on the Great Barrier Reef. These results show that across more than 6000 km these digeneans are similar in morphology and genotype. Some species of fishes and molluscs a-re considered to have distributions that encompass the entire tropical Indo-West Pacific. These findings suggest that at least some of their parasites have similarly broad distributions. (C) 2001 Australian Society for Parasitology Inc. Published by Elsevier Science Ltd. All rights reserved.

The nature and evolution of the association among digeneans, molluscs and fishes

Patterns of association of digenean families and their mollusc and vertebrate hosts are assessed by way of a new database containing information on over 1000 species of digeneans for lift-cycles and over 5000 species from fishes. Analysis of the distribution of digenean families in molluscs suggests that the group was associated primitively with gastropods and that infection of polychaetes, bivalves and scaphopods are all the results of host-switching. For the vertebrates. infections of agnathans and chondrichthyans are apparently the result of host-switching from teleosts. For digenean families the ratio of orders of fishes infected to superfamilies of molluscs infected ranges from 0.5 (Mesometridae) to 16 (Bivesiculidae) and has a mean of 5.6. Individual patterns of host association of 13 dipenean families and superfamilies are reviewed. Two, Bucephalidae and Sanguinicolidae. are exceptional in infecting a range of first intermediate hosts qualitatively as broad as their range of definitive hosts. No well-studied taxon shows narrower association with vertebrate than with mollusc clades. The range of definitive hosts of digeneans is characteristically defined by eco-physiological similarity rather than phylogenetic relationship. The range of associations of digenean families with mollusc taxa is generally much narrower. These data are considered in the light of ideas about the significance of different forms of host association. If Manter's Second Rule (the longer the association with a host group, the mure pronounced the specificity exhibited by the parasite group) is invoked, then the data may suggest that the Digenea first parasitised molluscs before adopting vertebrate hosts. This interpretation is consistent with most previous ideas about the evolution of the Digenea but contrary to current interpretations based on the monophyly of the Neodermata. The basis of Manter's Second Rule is. however, considered too flimsy for this interpretation to be robust. Problems of the inference of the evolution of patterns of parasitism in the Neodermata al-e discussed and considered so intractable that the truth may be presently unknowable. (C) 2001 Australian Society for Parasitology Inc. Published by Elsevier Science Ltd. All rights reserved.