The present study consists of a detailed phylogenetic analysis of myxosporeans of the Myxobolus and Henneguya genera, including sequences from 12 Myxobolus/Henneguya species, parasites of South American pimelodids, bryconids and characids. Maximum likelihood and maximum parsimony analyses, based on 18 S rDNA gene sequences, showed that the strongest evolutionary signal is the phylogenetic affinity of the fish hosts, with clustering mainly occurring according to the order and/or family of the host. Of the 12 South American species studied here, six are newly described infecting fish from the Brazilian Pantanal wetland. Henneguya maculosus n. sp. and Myxobolus flavus n. sp. were found infecting both Pseudoplatystoma corruscans and Pseudoplatystoma reticulatum; Myxobolus aureus n. sp. and Myxobolus pantanalis n. sp. were observed parasitizing Salminus brasiliensis and Myxobolus umidus n. sp. and Myxobolus piraputangae n. sp. were detected infecting Brycon hilarii.

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Bovines present contrasting, heritable phenotypes of infestations with the cattle tick, Rhipicephalus (Boophilus) microplus. Tick salivary glands produce IgG-binding proteins (IGBPs) as a mechanism for escaping from host antibodies that these ectoparasites ingest during blood meals. Allotypes that occur in the constant region of IgG may differ in their capacity to bind with tick IGBPs; this may be reflected by the distribution of distinct allotypes according to phenotypes of tick infestations. In order to test this hypothesis, we investigated the frequency of haplotypes of bovine IgG2 among tick-resistant and tick-susceptible breeds of bovines. Sequencing of the gene coding for the heavy chain of IgG2 from 114 tick-resistant (Bos taurus indicus, Nelore breed) and tick-susceptible (B. t. taurus, Holstein breed) bovines revealed SNPs that generated 13 different haplotypes, of which 11 were novel and 5 were exclusive of Holstein and 3 of Nelore breeds. Alignment and modeling of coded haplotypes for hinge regions of the bovine IgG2 showed that they differ in the distribution of polar and hydrophobic amino acids and in shape according to the distribution of these amino acids. We also found that there was an association between genotypes of the constant region of the IgG2 heavy chain with phenotypes of tick infestations. These findings open the possibility of investigating if certain IgG allotypes hinder the function of tick IGBPs. If so, they may be markers for breeding for resistance against tick infestations.Electronic supplementary materialThe online version of this article (doi:10.1007/s00251-011-0515-y) contains supplementary material, which is available to authorized users.

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We investigated the toxic effect of indole-3-acetic acid (IAA) combined with horseradish peroxidase (HRP) on Prototheca zopfii from bovine mastitis. P. zopfii isolates were identified and characterized by morpho-physiological parameters; presences of P. zopfii genotype 2 were also investigated. Subsequently, P. zopfii was incubated in the absence (control) or presence of IAA/HRP and examined for: (i) cell viability; (ii) colonies number formation; (iii) antioxidant enzyme activity; and (iv) DNA integrity. Significance of differences was calculated using ANOVA and Tukey's test (P < or = 0.05). As evidenced by Trypan blue exclusion and colony formation in Sabouraud dextrose agar, IAA/HRP addition to the culture reduced respective P. zopfii viability and P. zopfii colony formation in a concentration- and time-dependent manner. IAA/HRP specifically reduced cell viability in 10, 15, 20, 25, and 32% after 4, 6, 8, 10, and 12 h of incubation, respectively, compared with the control at the same time. The number of colony formation was inhibited (45, 82, and 88%) by IAA/HRP after 4, 6, and 9 h of incubation, respectively, compared with the control at the same time. In addition, P. zopfii antioxidant activity increased measurably in the presence of IAA/HRP (6 h); superoxide dismutase, catalase, glutathione reductase, and glutathione peroxidase increased by 90, 120, 150% and 3.4 times, compared with the controls. IAA/HRP did not appear to effect P. zopfii DNA integrity when examined by electrophoresis. In conclusion, IAA/HRP appears to function as a microbicidal mechanism on P. zopfii genotype 2 from bovine mastitis.

In a survey of myxozoan parasites of ornamental freshwater fish from the Rio Negro river, it was found that seven of 30 (23.3 %) Corydoras melini specimens examined had plasmodia of a new Myxidium species (Myxidium amazonense n. sp.) in the gallbladder. The fish were caught in the Rio Negro river, in the municipality of Santa Isabel do Rio Negro, in the state of Amazonas, Brazil. The plasmodia had a tubular shape, which was organized as a spiral spring with several turns in the gallbladder. The development of the myxospores was asynchronic, with disporic pansporoblasts. Mature myxospores were elongated, with 17.0 ± 0.9 (16.1-17.9) μm in length and 3.7 ± 0.7 (3.0-4.4) μm in width, and lightly arcuate from the valval view, with their bodies tapering slowly until ending in rounded extremities. The valval surface had nine to ten grooves in each valve. The polar capsules, one at either end of the spore, had a length of 5.4 ± 0.5 (4.9-5.9) μm and a width of 3.4 ± 0.6 (2.8-4.0) μm. Ultrastructural analysis showed that the wall of the plasmodia had numerous microvilli-like structures, pinocytotic canals, and cytoplasmic bridges connecting the pansporoblasts to each other and to the ectoplasm zone. Phylogenetic analysis, based on a small subunit ribosomal RNA (ssrRNA), identified the new species as a sister species of Myxidiumceccarelli, the unique South American Myxidium species whose ssrRNA sequence is available in the NCBI database. This study is the first description of Myxidium species in ornamental freshwater fish from Amazon.

Henneguya leporinicola is a parasite of the gill filament of Leporinus macrocephalus, a characiform fish belonging to the Anostomidae family, which is of major economic importance. Despite the damage it causes in fish, little is known about this parasite. Therefore, a study was undertaken with fourteen specimens of L. macrocephalus taken from fish farms in the state of Sao Paulo. The fish were collected and examined searching for lesions and/or myxosporean plasmodia. One of the specimens (7.14%) contained white elongated plasmodia in the gill filament. The mature spores had elongated bodies with polar capsules of equal size and a caudal length greater than body length. Morphological characteristics identified the parasite as H. leporinicola. Molecular analysis of the 18S rDNA sequence resulted in a 1954 bp, demonstrating significant genetic differences with previously described species of Henneguya/Myxobolus. Phylogenetic analysis comparing the 18S rDNA sequence of H. leporinicola with other species, previously described in South America, and the 20 closest species as indicated by BLASTn Max Score showed H. leporinicola as a basal branch of a subclade composed by Henneguya spp. parasite of characiform hosts.