Growing diversity supports radiation of an Ellipsomyxa lineage into the Amazon freshwater: Description of two novel species parasitizing fish from Tapajos and Amazon rivers

Author(s)

Zatti, Suellen A. ; Maia, Antonio A. M. ; Adriano, Edson A.

• Document type: Journal article
• Source: Acta Tropica; v. 211, p. 10-pg., 2020-11-01.

Abstract

Species of the genus Ellipsomyxa Koie, 2003, parasitize mostly marine and brackish fish around the world. In the present study, we describe two novel species of Ellipsomyxa: Ellipsomyxa plagioscioni n. sp. parasitizing the gall bladder of Plagioscion squamosissimus (Sciaenidae), a freshwater fish but commonly found in brackish water in the Amazonian estuarine environment; and Ellipsomyxa paraensis n. sp. infecting Cichla monoculus (Cichlidae), a strictly freshwater fish. The host specimens were caught from the Amazon and Tapajos rivers, in the municipal region of Santarem, in the State of Para, Brazil. The study was performed using a combination of morphological, biological, and SSU rDNA-based phylogeny, which suggested that marine transgressions of the Miocene epoch, in the central region of South America, were a pathway for the adaptation and radiation of these cnidarian parasites in the freshwater environment. Both disporic plasmodia and mature myxospores were found floating freely in the bile. Mature myxospores from both species were ellipsoidal in the valvular and sutural views, with thin smooth valves elongated in the direction perpendicular to the plane of the transverse sutural line. Ellipsomyxa plagioscioni n. sp. myxospores measured 11.1 (10.2-12.8) mu m in length and 6.6 (5.6-7.6) mu m in width. Two pyriform polar capsules discharging on opposite sides, some distance from both the sutural line and the spore ends, measured 3.8 (3.2-4.4) mu m in length and 2.8 (2.3-3.3) mu m in width, with 5-6 coil polar tubules. Ellipsomyxa paraensis n. sp. myxospores measured 11.5 (10.5-12.4) mu m in length and 7.5 (6.6-8.6) mu m in width. Two pyriform polar capsules which discharged on opposite sides some distance from both the sutural line and spore ends, measured 3.2 (2.1-3.9) mu m in length and 2.6 (2.0-3.3) mu m in width, with 2-3 coil polar tubules. Valvular protrusions were observed, associated with the tips of the polar capsules. Molecular analysis based on the SSU rDNA sequences indicated that the two novel Ellipsomyxa species were distinct from all other sequences deposited in the GenBank database. The phylogenetic trees clustered E. plagioscioni n. sp. as a basal species of a lineage of the marine/estuarine Ellipsomyxa, while E. paraensis n. sp. clustered together with other Amazonian species. (AU)

• FAPESP's process: 16/22047-7 - Myxosporean parasites of commercially important Perciformes fish (Cichlaspp. and Plagioscion spp.) in the Amazon Basin
• Grantee: Edson Aparecido Adriano
• Support Opportunities: Regular Research Grants
• FAPESP's process: 18/19285-9 - Systematics, host-parasite interaction and population genetic studies of myxozoans (Cnidaria: Myxozoa) parasites of fish of the genus Plagioscion (Perciformes, Sciaenidae)
• Grantee: Suellen Aparecida Zatti
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 13/21374-6 - Systematics and host-parasite interaction of parasites of the phylum Myxozoa in fishes economically important in Amazon Basin
• Grantee: Edson Aparecido Adriano
• Support Opportunities: BIOTA-FAPESP Program - Regular Research Grants