Dermocystidium sp. in the gills of farmed Oreochromis niloticus in Brazil.

The genus Dermocystidium is very comprehensive in the host and site of infection, however this is the first report of the occurrence of Dermocystidium sp. in the gills of Nile tilapia. This study was carried out in a fish farming located in the state of Santa Catarina, Brazil. No mortalities were reported in the facility studied and the animals were clinically healthy. During the histopathological analysis of the gills, 8.33% of the fish presented spores of Dermocystidium sp. in the gill tissue. The spores reported herein had a mean length and width of 6.206 x 5.233 µm and a refractile body diameter of 1.965 µm and were studied by histopathology and Transmission Electron Microscopy. This study highlights the importance of a new branchial pathogen in farmed tilapia, as well as to its pathogenic potential, considering the outbreaks of mortalities associated with other fish species.

Two New Species of Marine Saprotrophic Sphaeroformids in the Mesomycetozoea Isolated From the Sub-Arctic Bering Sea.

The genus Sphaeroforma previously encompassed organisms isolated exclusively from animal symbionts in marine systems. The first saprotrophic sphaeroformids (Mesomycetozoea) isolated from non-animal hosts are described here. Sphaeroforma sirkka and S. napiecek are also the first species in the genus possessing endogenous DNA-containing motile propagules and central vacuoles, traits that have previously guided morphological differentiation of sphaeroformids from the genus Creolimax. Phylogenetic analysis of DNA sequences from the 18S rRNA and the ITS1-5.8S--ITS2 loci firmly place S. sirkka and S. napiecek within Sphaeroforma, extending the number of known species to six within this genus. The discovery of these species increases the geographical range, cellular variation and life history complexity of the sphaeroformids.

A nuptially transmitted ichthyosporean symbiont of Tenebrio molitor (Coleoptera: Tenebrionidae).

The yellow mealworm, Tenebrio molitor, harbors a symbiont that has spores with a thick, laminated wall and infects the fat body and ventral nerve chord of adult and larval beetles. In adult males, there is heavy infection of the epithelial cells of the testes and between testes lobes with occasional penetration of the lobes. Spores are enveloped in the spermatophores when they are formed at the time of mating and transferred to the female's bursa copulatrix. Infection has not been found in the ovaries. The sequence of the nuclear small subunit rDNA indicates that the symbiont is a member of the Ichthyosporea, a class of protists near the animal-fungi divergence.

Facing unknowns: living cultures (Pirum gemmata gen. nov., sp. nov., and Abeoforma whisleri, gen. nov., sp. nov.) from invertebrate digestive tracts represent an undescribed clade within the unicellular Opisthokont lineage ichthyosporea (Mesomycetozoea).

During a culture-based survey of opisthokonts living in marine invertebrate digestive tracts, we isolated two new eukaryotes that differed from described taxa by more than 10% in their small subunit ribosomal DNA sequences. Phylogenetic analysis showed that the two isolates represented a divergent clade of ichthyosporeans known previously only from environmental clone sequences. We used light and electron microscopy to describe the isolates as new genera and species Pirum gemmata and Abeoforma whisleri. A. whislerihad a complex life cycle that remains incompletely known but involved walled spherical cells, plasmodia and amoebae. Asexual reproduction occurred via dispersal amoebae, endospores, binary fission and budding. In contrast P. gemmatahad a less complex life cycle with no amoeboid or plasmodial stages. Both species had membrane-bound tubular extensions of the cytoplasm embedded in the inner layers of their cell walls. By comparing P. gemmata and A. whislerito other ichthyosporea we speculate on the characters that may have been present in the ancestral ichthyosporean. P. gemmata and A. whisleri illustrate the unique and diverse forms that can be found by capturing taxa belonging to divergent and uncultured lineages.

A Daphnia parasite (Caullerya mesnili) constitutes a new member of the Ichthyosporea, a group of protists near the animal-fungi divergence.

Caullerya mesnili is a protozoan endoparasite in the gut epithelium of Daphnia, which causes regular epidemics in lakes throughout Europe. Its classification has remained unchanged for over a century, leaving it placed with the Haplosporidia, despite speculation that this position is incorrect. The difficulty in classifying C. mesnili stems from its few known morphological and ecological characteristics, as well as a lack of genetic markers. Here we sequenced the nuclear small subunit (SSU) and internal transcribed spacer rDNA regions of C. mesnili samples from 10 locations. Based on sequence similarities, we suggest the re-classification of C. mesnili to the Ichthyosporea, a class of protists near the animal-fungi divergence. We report average intragenomic variation of 0.75% and 2.27% in the SSU and internal transcribed spacer regions, respectively. From electron micrographs and light microscopy of histological sections we determined that C. mesnili spores grow within the intestinal epithelium where they establish themselves intercellularly. In addition, we confirmed previous accounts regarding the high virulence of this parasite. Caullerya mesnili reduces host lifespan, the number of clutches, and the total number of offspring. This high selection pressure placed on hosts supports the importance of C. mesnili as a model parasite for the study of host-parasite biology in permanent lakes.