The "parasite detoxification hypothesis": lead exposure potentially changes the ecological interaction from parasitism to mutualism.

In urban areas, organisms are exposed to high pollutant levels, especially element trace metals that may impact host-parasite interactions. Indeed, parasites have been reported to reduce the negative effects of pollutants on their hosts. The fitness of parasitized organisms in polluted environments may therefore be greater than that of unparasitized organisms. In our study, we used an experimental approach to test this hypothesis on feral pigeons (Columba livia), which are endemically parasitized by nematodes and exposed to high levels of lead in urban areas. We tested the combined effects of lead exposure and helminth parasitism on different pigeon fitness components: preening, immunocompetence, abundance of lice (Columbicola columbae) and haemosporidian parasites (Heamoproteus spp., Plasmodium spp.), reproduction investment, and oxidative stress. Our results show that among pigeons exposed to lead treatment, individuals harboring nematode parasites exhibit more preening activity and have fewer ectoparasites lice than nematode-free individuals. Benefits for nematode-parasitized individuals exposed to lead were not detected for other fitness parameters. Further studies are required to confirm the "parasite detoxification hypothesis" in pigeons and to identify the mechanisms by which this detoxification occurs.

Morphostructural data and phylogenetic relationships of a new cnidarian myxosporean infecting spleen of an economic and ecological important bryconid fish from Brazil.

A new cnidarian myxosporean infecting the spleen of an economic and ecological important bryconid fish (Salminus franciscanus) is described based on integrative taxonomic approach including morphological, ultrastructural, biological traits, geography, molecular data and phylogenetic analysis. In a total of thirty specimens examined, nineteen (63.3%) were infected by an undescribed parasite species belonging to the genus Myxobolus. Plasmodial development was asynchronous, with young development in the periphery and mature myxospores in the central area and without projections and microvilli in the plasmodial wall. Mature myxospores were ovoid in shape and measured 7.9 ± 0.2 µm (7.6-8.1 µm) in length and 5.4 ± 0.1 µm (5.0-5.6 µm) in width. The two polar capsules were equal in size, occupying a little more than half of the myxospore body, measuring 4.0 ± 0.2 µm (3.9-4.1 µm) in length and 1.7 ± 0.1 µm (1.5-1.8 µm) in width. The polar tubules coiled in six turns, perpendicular to the long axis of polar capsule. Phylogenetic analysis placed the new species within a clade containing nine myxobolid species from South American characiforms fish and appears as a close species of Myxobolus pantanalis. Nevertheless, the sequences of the new species and M. pantanalis have a large genetic divergence of 13.5% in their SSU rDNA. In light of the differences observed from the integrative taxonomy, we confidently considered that this isolate is a new species of cnidarian myxosporean, M. douradae n. sp., increasing the knowledge of diversity of this enigmatic group of cnidarians.

Taxonomy and 18S rDNA-based phylogeny of Henneguya multiradiatus n. sp. (Cnidaria: Myxobolidae) a parasite of Brochis multiradiatus from Peruvian Amazon.

A new myxozoan species belonging to the genus Henneguya was isolated from the serous membrane of the visceral cavity of the hognosed catfish Brochis multiradiatus from Peruvian Amazon. Whitish plasmodia, macroscopically visible, were found in four of the thirty examined fishes. Mature myxospores were ellipsoidal in shape in frontal view and had a total length of 44.5 ± 0.6 µm (43.9-45.1), spore body measured 18.7 ± 0.9 µm (16.8-19.6) in length, 7.1 ± 0.2 µm (6.6-7.4) in width and 5.5 ± 0.3 µm (4.9-5.6) in thickness. The two polar capsules were elongated and equal in size, measuring 9.1 ± 0.1 µm (8.8-9.4) in length and 1.7 ± 0.1 µm (1.6-1.8) in width, occupying half of the myxospore body. Polar tubules coiled in 10-11 turns perpendicular to the long axis of the polar capsule. The caudal appendage was not bifurcated and measured 25.8 ± 0.6 µm (24.7-26.5) in length. The sequencing of the 18S rDNA gene resulted in 1400 bp and this sequence did not match any of the myxozoans available in GenBank. Phylogenetic analysis placed the new species in a well-supported subclade of Henneguya spp. infecting callichthyid fishes, with Henneguya loretoensis being the closest species. This study is the first description of a myxozoan species, Henneguya multiradiatus n. sp. from a fish of the genus Brochis.

Discovery of a Digenean (Cryptogonimidae) Living in a Cleft-Lipped Goby, Sicyopterus cynocephalus (Teleostei: Gobiidae) from Ranongga Island, Solomon Islands: Analysis of Multiple Ribosomal DNA Regions.

This study results from a continued investigation of the occurrence and diversity of parasites of freshwater fish in the Solomon Islands. Thus, we revealed a new host as well as a new site of infection and a new geographical area for the cryptogonimid parasite, Stemmatostoma cribbi (Digenea: Cryptogonimidae). The cryptogonimid species was identified based on general morphology and on molecular data of metacercariae found in the gills of the cleft-lipped goby, Sicyopterus cynocephalus, from Ranongga Island, Western Province of the Solomon Islands. This is the first report of a Stemmatostoma sp. digenean parasitizing fish of the genus Sicyopterus in the Indo-Pacific region and the first report of S. cribbi infection in a fish from the Solomon Islands. Phylogenetic analysis performed by Bayesian inference and maximum likelihood confirmed the presence of the cryptogonimid in a well-supported subclade of Stemmatostoma spp.

Development of Graphidium strigosum (Nematoda, Haemonchidae) in its natural host, the rabbit (Oryctolagus cuniculus) and comparison with several Haemonchidae parasites of ruminants.

The morphogenesis (studied for the first time) and the chronology of the life cycle of Graphidium strigosum (Dujardin, 1845) were studied in detail in its natural host, Oryctolagus cuniculus. Naive rabbits were each infected per os with G. strigosum infective larvae (L3). Animals were euthanized each day for the first 10 days after infection (DAI), then every 2 days from 12 to 40 DAI. The free living period lasted 5-8 days at 24°C. By 1 DAI, all the larvae were exsheathed in the stomach. The third molt occurred between 9 and 17 DAI. The last molt occurred between 24 and 32 DAI. The prepatent period lasted 42-44 DAI, while the patent period lasted at least 13 months. For each experiment, the morphology of the different stages of the life cycle was described. The chronology of the G. strigosum life cycle and its morphogenesis were compared to those of different Haemonchidae parasites of ruminants (Ostertagia ostertagi, Teladorsagia circumcincta, Haemonchus contortus, and Haemonchus placei) in their natural hosts.

Phylogenetic analysis and characterization of a new parasitic cnidarian (Myxosporea: Myxobolidae) parasitizing skin of the giant mottled eel from the Solomon Islands.

Myxosporeans are microscopic cnidarians associated with severe diseases in aquaculture and wild fish populations. This group of parasitic cnidarians thus warrants close attention concerning its potential impact on susceptible fish stocks. At present, little is known about this group of parasites infecting anguillid eels. From myxospore specimens collected from a freshwater eel (Anguilla marmorata) in the Solomon Islands, we describe a new species belonging to the genus Myxobolus based on an integrative taxonomic analysis of morphological, biological traits and molecular data. Furthermore, we determined the phylogenetic position and relationships of this species among other platysporine myxosporeans. Molecular phylogenetic assessment of small subunit ribosomal DNA showed that the species clusters together with Myxobolus portucalensis and Echinactinomyxon type 5 Özer, Wootten and Shinn, 2002, in a well-supported subclade. This is the first report of a myxosporean parasite infecting fish from the Solomon Islands.

Molecular Phylogeny and taxonomy of a new Myxobolus species from the endangered ornamental fish, Otocinclus cocama endemic to Peru: A host-parasite coextinction approach.

A new Myxobolus species is described infecting gill filaments of the endangered ornamental fish Otocinclus cocama from Peruvian Amazon. In a total of 35 fish examined, five (14.3%) had myxozoan plasmodia. Taxonomic analysis was performed integrating multiple characters, including morphometrical, biological traits, ssrDNA sequence data and host ecological characters. Myxospores of M. iquitoensis n. sp. were ovoid in shape from the frontal view and measured 17.6±1.2 µm (16.2-19.8 µm) in length and 10.5±0.7 µm (9.8-12 µm) in width. The two polar capsules were elongate in shape, equal in size and occupying almost half of the myxospore body. They measured 8.7±0.4 µm (6.9-9.3 µm) in length and 3.3±0.2 µm (3-3.6 µm) in width. The polar tubules presented six to seven turns. Molecular phylogenetic analysis revealed that the obtained ssrDNA sequence did not match any existing sequences in GenBank but showed M. iquitoensis n. sp. to be a close species of M. figueirae. Nonetheless, the ssrDNA sequences of those species show large genetic divergence. This is the first description and phylogenetic study of a myxozoan parasitizing fish of the genus Otocinclus from South America, as well the first report of these parasites infecting a fish belonging to the Loricariidae family from Amazon basin. Considering the endangered status of the host, the high degree of host-specificity of freshwater histozoic myxobolids, the low occurrence shown by the new myxozoan, and the fact that this is the only host known for this myxozoan, the conservation status of the new species of myxozoan is likely to be connected to the future survival of its host.