Integrative Taxonomy Reveals a Panmictic Population of Henneguya longisporoplasma n. sp. (Cnidaria: Myxozoa) in the Amazon Basin

Purpose Henneguya Thelohan, 1892 is one of the most species-rich genera of myxosporean parasites and infects fish around the world. The present study describes a new species infecting the gill filaments, fins, and kidneys of Plagioscion squamosissimus (Heckel, 1840), an economically important freshwater fish distributed in watersheds in the north of South America. Methods A total of 108 P. squamosissimus specimens were examined from three geographic localities in the Amazon basin: the Lago Grande do Curuai, a marginal lake of the Amazon River; the Tapajos River, in the state of Para; and the Solimoes River, in the state of Amazonas, Brazil. The analyses were based on the myxospore morphology, ribosomal DNA sequencing, phylogeny, prevalence, and geographic distribution of the host and its parasite. Results Parasite prevalences were 50% in both the Tapajos and Solimoes rivers, and 35.4% in the Lago Grande do Curuai. In terms of the site of infection, the prevalence total was 23.1% in the gill filament, 29.6% in the fins, and 1.8% in the kidney. Regarding gender, the prevalence was 59.5% for males, 32.5% for females, and 21.7% for undetermined sex. The specimens found here were both morphologically and molecularly identical regardless of the infected organ and geographic locality, but distinct from all other Henneguya species, revealing that the parasite reported represents a novel species named Henneguya longisporoplasma n. sp. Despite the sampling being carried out in three different geographic localities of the Amazon basin, no population-level genetic variation was observed, even in the typically more variable ITS-1 region, revealing a panmictic population of H. longisporoplasma n. sp. in this large watershed. Maximum likelihood and Bayesian analyses showed the novel Henneguya clustered as a sister branch of the subclade formed of Henneguya that infect fish belonging to the family Cichlidae. Conclusions A novel Henneguya species was identified parasitizing P. squamosissimus. The parasite presented wide geographic distribution in the Amazon basin and genetic analyses showed it as revealing a panmictic population.