Conservation of sequence in the internal transcribed spacers and 5.8S ribosomal RNA among geographically separated isolates of parasitic scuticociliates (Ciliophora, Orchitophryidae).

Nucleotide sequence from the internal transcribed spacers (ITS1 and ITS2) and the 5.8S gene from the ribosomal RNA gene cluster of isolates of the scuticociliate Orchitophrya stellarum from 4 asteroid hosts were compared. Surprisingly, these data (495 bp) were identical for O. stellarum isolated from the testes of Asterias amurensis from Japan; Pisaster ochraceus from British Columbia, Canada; Asterias rubens from The Netherlands; and Asterias vulgaris from Prince Edward Island, Canada. These sequence data were compared to those from 3 scuticociliates which parasitise crustaceans: Mesanophrys pugettensis, M. chesapeakensis and Anophryoides haemophila. No difference was found in this region between the nucleotide sequence of M. pugettensis and M. chesapeakensis. The sequence of Mesanophrys spp. differed by 9.2% in the ITS1 and 4.7% in the ITS2 from that of O. stellarum. The sequence from the ITS1 (135 bp) and ITS2 (233 bp) of A. haemophila differed by 42.6 and 20.5% respectively from those of O. stellarum. Therefore, nucleotide sequence of the ITS regions in these scuticociliates is highly conserved.

Chytridiomycosis causes amphibian mortality associated with population declines in the rain forests of Australia and Central America.

Epidermal changes caused by a chytridiomycete fungus (Chytridiomycota; Chytridiales) were found in sick and dead adult anurans collected from montane rain forests in Queensland (Australia) and Panama during mass mortality events associated with significant population declines. We also have found this new disease associated with morbidity and mortality in wild and captive anurans from additional locations in Australia and Central America. This is the first report of parasitism of a vertebrate by a member of the phylum Chytridiomycota. Experimental data support the conclusion that cutaneous chytridiomycosis is a fatal disease of anurans, and we hypothesize that it is the proximate cause of these recent amphibian declines.

The ciliate Orchitophrya cf. stellarum and other parasites and commensals of the northern Pacific seastar Asterias amurensis from Japan.

To identify the pathogens and possible biological control agents for the introduced seastar Asterias amurensis, we examined seastars from source populations in central and northern Japan. In particular, we sought the scuticociliate Orchitophrya cf. stellarum. The ciliate was found in male A. amurensis from five sites. We also found the caprellid amphipod Caprella astericola on A. amurensis and Distolasterias nipon from Nemuro Bay. The copepod Scottomyzon gibberum was found on A. amurensis from Usujiri and polychaete scaleworms Arctonoe vittata were found on A. amurensis from Murohama and Nemuro Bay. Of these parasites and commensals, Orchitophrya cf. stellarum is the most likely agent for biological control of A. amurensis in Australian waters; however, its ability to regulate seastar populations is uncertain.

A novel clade of protistan parasites near the animal-fungal divergence.

Sequences of nuclear-encoded small-subunit rRNA genes have been determined for representatives of the enigmatic genera Dermocystidium, Ichthyophonus, and Psorospermium, protistan parasites of fish and crustaceans. The small-subunit rRNA genes from these parasites and from the "rosette agent" (also a parasite of fish) together form a novel, statistically supported clade. Phylogenetic analyses demonstrate this clade to diverge near the animal-fungal dichotomy, although more precise resolution is problematic. In the most parsimonious and maximally likely phylogenetic frameworks inferred from the most stably aligned sequence regions, the clade constitutes the most basal branch of the metazoa; but within a limited range of model parameters, and in some analyses that incorporate less well-aligned sequence regions, an alternative topology in which it diverges immediately before the animal-fungal dichotomy was recovered. Mitochondrial cristae of Dermocystidium spp. are flat, whereas those of Ichthyophonus hoferi appear tubulovesiculate. These results extend our understanding of the types of organisms from which metazoa and fungi may have evolved.

Use of molecular data to discriminate pseudocerotid turbellarians.

Nucleotide sequence data from the Internal Transcribed Spacer 1 (ITS1) in the ribosomal RNA (rRNA) gene cluster were used to determine the utility of molecular data to discriminate species and genera of pseudocerotid turbellarians. We sequenced 388, 379 and 415 bp from the ITS1 of Pseudoceros jebborum, Pseudoceros paralaticlavus and Pseudobiceros gratus respectively, to give an aligned sequence for this region of 421 positions. The nucleotide sequence of the ITS1 of Pseudoceros jebborum differed from that of Pseudoceros paralaticlavus by 6% (24/421 positions) and from that of Pseudobiceros gratus by 36% (152/421 positions). These results indicate that sequence data from the ITS1 will be a useful taxonomic tool to discriminate pseudocerotid flatworms.

Phylogenetic position of the genus Perkinsus (Protista, Apicomplexa) based on small subunit ribosomal RNA.

Parasites of the genus Perkinsus destroy marine molluscs worldwide. Their phylogenetic position within the kingdom Protista is controversial. Nucleotide sequence data (1792 bp) from the small subunit rRNA gene of Perkinsus sp. from Anadara trapezia (Mollusca: Bivalvia) from Moreton Bay, Queensland, was used to examine the phylogenetic affinities of this enigmatic genus. These data were aligned with nucleotide sequences from 6 apicomplexans, 3 ciliates, 3 flagellates, a dinoflagellate, 3 fungi, maize and human. Phylogenetic trees were constructed after analysis with maximum parsimony and distance matrix methods. Our analyses indicate that Perkinsus is phylogenetically closer to dinoflagellates and to coccidean and piroplasm apicomplexans than to fungi or flagellates.