Mullets inhabit a wide range of habitats from tropical to temperate regions and play a critical role in their ecosystems. This commercially important fish group constitutes a significant source of food in several geographic regions, and the production of some species for consumption is an increasing trend. About 64 myxosporean species have been reported in mullets, some of which are cryptic, as is the case of Myxobolus exiguus, and M. muelleri. This paper provides, for the first time, a detailed and critical revision of the data available for myxobolids reported in mullets, determining the species that have bona fide mugiliform fish hosts, in accordance with the original species descriptions, the available molecular data and the currently accepted taxonomic and phylogenetic criteria. Phylogenetic analyses using Bayesian inference and maximum-likelihood methodologies suggest that the evolutionary history of myxobolids with bona fide mugiliform fish hosts reflects that of its vertebrate hosts, while reinforcing known evolutionary factors and old systematic issues of the clade of myxobolids. A comprehensive morphological, ultrastructural and molecular redescription is also provided for the cryptic species M. exiguus, from infections in the visceral peritoneum of the thinlip-grey mullet Chelon ramada in the River Minho, Portugal.

The aim of this study was to determine whether foxes might act as definitive hosts of Sarcocystis alces in moose. In 2 experiments, 6 silver foxes (Vulpes vulpes) and 6 blue foxes (Vulpes lagopus) were fed muscle tissue from moose containing numerous sarcocysts of S. alces, and euthanased 7–28 days post-infection (p.i.). Intestinal mucosal scrapings and faecal samples were screened microscopically for Sarcocystis oocysts/sporocysts, which were identified to species by means of species-specific primers and sequence analysis targeting the ssu rRNA gene. All foxes in both experiments became infected with Sarcocystis; the oocysts were fully sporulated by 14 days p.i., containing sporocysts measuring 14–15×10 μm. Molecular identification revealed that the oocysts/sporocysts belonged to 2 species, S. alces and Sarcocystis hjorti, although sarcocysts of S. hjorti were only identified in moose subsequent to the infection of foxes. In the first experiment, all 8 foxes also became infected with a Hammondia sp. derived from moose, shedding unsporulated, subspherical oocysts, measuring 10–12 μm in diameter, from 6–7 days p.i. onwards. The study proved that canids (the red fox and arctic fox) are definitive hosts for S. alces and S. hjorti, as had been inferred from the phylogenetic position of these species.

Muscle tissue from 37 red deer from Norway was examined for sarcocysts. Sarcocysts from 2 reindeer were obtained for comparative studies. Cysts were excised and morphologically classified by light microscopy, scanning electron microscopy, and DNA sequence analysis. Five Sarcocystis species, Sarcocystis hjorti n. sp., Sarcocystis hardangeri, Sarcocystis ovalis, Sarcocystis rangiferi, and Sarcocystis tarandi, were found. All 5 species have previously been identified from either reindeer or moose by their sarcocyst morphology and/or ssu rRNA gene sequence. S. hjorti was the most prevalent species. Multiple variants of the ssu rRNA gene and the first internal transcribed spacer were found in S. rangiferi and S. tarandi from both red deer and reindeer. Phylogenetic analyses indicated that S. tarandi occurs in both red deer and reindeer, but it could not be clearly demonstrated whether the sequence variation within S. rangiferi between hosts was due to different paralogues or/and different species. DNA sequencing was necessary for definitive species identification, since the hair-like protrusions on the cysts of S. hjorti were not always recognizable by light microscopy and since different cervids harbour Sarcocystis species with highly similar cyst morphology of which at least some are not intermediate host specific.

A Minchinia sp. (Haplosporidia: Haplosporidiidae) parasite was identified infecting rock oysters and morphologically described by Hine and Thorne (2002) using light microscopy and transmission electron microscopy (TEM). The parasite was associated with up to 80% mortality in the host species and it is suspected that the parasite would be a major impediment to the development of a tropical rock oyster aquaculture industry in northern Western Australia. However, attempts to identify the parasite following the development of a specific probe for Haplosporidium nelsoni were unsuccessful. The SSU region of the parasite's rRNA gene was later characterized in our laboratory and an in situ hybridization assay for the parasite was developed. This study names the parasite as Minchinia occulta n sp. and morphologically describes the parasite using histology, scanning electron microscopy and transmission electron microscopy. The non-spore stages were unusual in that they consisted primarily of uninucleate stages reminiscent of Bonamia spp. The parasite's spores were ovoid to circular shaped and measured 4·5 μm–5·0 μm×3·5–4·1 μm in size. The nucleus of the sporoplasm measured 1·5–2·3 μm and was centrally located. The spores were covered in a branching network of microtubule-like structures that may degrade as the spore matures.