Ultrastructural and molecular characterization of Glugea serranus n. sp., a microsporidian infecting the blacktail comber, Serranus atricauda (Teleostei: Serranidae), in the Madeira Archipelago (Portugal)

Abstract

A new microsporidian infecting the connective tissue of the coelomic cavity of the blacktail comber Serranus atricauda, in the Madeira Archipelago (Portugal), is described on the basis of morphological, ultrastructural, and molecular features. The microsporidian formed large whitish xenomas adhering to the peritoneal visceral organs of the host. Each xenoma consisted of a single hypertrophic cell, in the cytoplasm of which mature spores proliferated within parasitophorous vacuoles surrounded by numerous collagen fibers. Mature spores were ellipsoidal and uninucleated, measuring an average of 6.5 ± 0.5 μm in length and 3.4 ± 0.6 μm in width. The anchoring disk of the polar filament was subterminal, laterally shifted from the anterior pole of the spore. The isofilar polar filament coiled in 18-19 turns, forming two rows that surrounded the posterior vacuole. The latter occupied about one third of the spore length. The polaroplast surrounding the apical and uncoiled portion of the polar filament displayed two distinct regions: a lamellar region and an electron-dense globule. Molecular analysis of the rRNA genes, including the internal transcribed spacer region, and phylogenetic analysis using maximum likelihood and neighbor joining demonstrated that this microsporidian parasite clustered with some Glugea species. Based on the differences found both at the morphological and molecular levels, to other members of the genus Glugea, the microsporidian infecting the blacktail comber is considered a new species, thus named Glugea serranus n. sp.

First record of Glugea plecoglossi (Takahashi & Egusa, 1977), a microsporidian parasite of ayu (Plecoglossus altivelis altivelis Temminck & Schlegel, 1846) in Mainland China

“…The mature spores showed monomorphism with isofilar polar tube coiled into 16 turns in single layer, similar to the major Glugea species such as G. hertwigi (Lovy et al., ). However, several new Glugea species revealed different characteristics in spore type, organization and number of coils compared to the common criteria (Abdel‐Baki et al., ; Azevedo, Abdel‐Baki, Rocha, Al‐Quraishy, & Casal, ; Casal, Rocha, Costa, Al‐Quraishy, & Azevedo, ), leading to the difficulty and unreliability of species identification. Phylogenetic analysis based on SSU rDNA sequence demonstrated that G. plecoglossi fell into the Glugea subclade and was most closely related to G. anomala , G. hertwigi , Glugea sp.…”