Ellipsomyxa ariusi sp. nov. (Myxosporea: Ceratomyxidae), a new myxosporean infecting the gallbladder of threadfin sea catfish Arius arius in India

Phylogenetic analysis of Ellipsomyxa species (Myxosporea) and description of Ellipsomyxa gordeyi n. sp. from the gall bladder of mullets (Mugiliformes: Mugilidae) in Nha Trang Bay of the East Sea, Vietnam

The coastal waters of Vietnam are home to a wide diversity of fishes, but the parasite diversity of these potential hosts is much less well characterized. To begin addressing this knowledge gap, we carried out surveys of myxozoan parasites in fishes collected from Nha Trang Bay in Vietnam's East Sea in 2018-2019. Mugilid fishes were collected in March-April 2018, January-February 2019, and November-December 2019, and examined for myxozoans. Myxospores consistent with those of the genus Ellipsomyxa were found in the gall bladder of four mullet species, and we thoroughly characterized those from Planiliza melinoptera. Myxospores were elliptoid and devoid of striation, with a distinct sinuous suture line. Polar capsules were pyriform and oriented toward the poles of the spore. Morphological features were compared to nominal species and this species from Vietnam was distinct. Phylogenetic analysis based on partial small subunit rDNA sequence revealed that broadly, Ellipsomyxa species split into three phylogenetic lineages, and although in some branches there are groupings by host family, habitat or locality, there are no clear phylogenetic patterns. The new species we encountered in P. melinoptera had a close sister relationship with Ellipsomyxa adlardi, with both species part of a larger subclade within the Ellipsomyxa lineage. Despite this phylogenetic similarity, these species were morphologically distinct, and partial large subunit DNA sequences were only 93% similar to each other. A combination of the morphological characteristics and molecular data suggest that this is an undescribed species and we propose the name Ellipsomyxa gordeyi n. sp.

A new species of Ellipsomyxa Køie, 2003 (Bivalvulida) infecting the gall bladder of Pangasius macronema Bleeker (Siluriformes: Pangasiidae) from the Mekong River Delta, Vietnam

During a parasitological survey of freshwater fishes in the Mekong River Delta, Vietnam, disporic plasmodia containing myxospores morphologically consistent with Ellipsomyxa Køie, 2003 (Bivalvulida) were observed infecting the gall bladder of Pangasius macronema Bleeker (Siluriformes: Pangasiidae). Herein, we use morphology and small subunit ribosomal DNA (SSU rDNA, 18S) sequence data to describe Ellipsomyxa intravesica Ksepka & Bullard n. sp. and relate it to other myxozoans. The new species resembles Ellipsomyxa adlardi Whipps & Font, 2013, which infects the naked goby, Gobiosoma bosc (Lacepede) (Gobiiformes: Gobiidae) in Lake Pontchartrain, Louisiana, but differs from it by having a longer myxospore (mean = 13.3; range = 12.0-15.0 vs. 12.4; 11.3-14.4) and shorter polar capsules (3.7; 3.0-4.0 vs. 4.3; 3.9-4.9). The 18S phylogenetic analysis recovered the sequence of the new species sister to those ascribed to Ellipsomyxa ariusi Chandran, Zacharia, Sathianandan & Sanil, 2020 and Ellipsomyxa sp. (MK561979); both of which infect the gall bladder of the threadfin sea catfish, Arius arius (Hamilton) (Siluriformes: Ariidiae) from the southwest coast of India. Consistent with previous phylogenetic analyses of Ellipsomyxa spp., Ellipsomyxa was recovered as monophyletic. The new species is the first species of Ellipsomyxa reported from a freshwater fish in Asia and the first myxozoan reported from P. macronema.

An update of the species of Myxosporea (Cnidaria, Myxozoa) described from Indian fish

A synopsis of Myxosporea (Cnidaria, Myxozoa) species described in about the last 14 years in Indian fish is provided. The synopsis include a total of 97 new species, and 18 species redescribed including significant new data, namely molecular characterization, distributed by 19 genera. For each species are indicated, in tabulated format, the morphological characteristics and the Gen Bank Accession Number whenever possible. Data about the type host and type locality are included also, and a complete list of references is provided. The information presented, combined with former synopsis, allow an update general view about these parasites infecting Indian fish hosts.

Ellipsomyxa tucujuensis n. sp. (Myxozoa: Ceratomyxidae), a parasite of Satanoperca jurupari (Osteichthyes: Cichlidae) from the Brazilian Amazon

The present study describes a new coelozoic, eukaryotic microparasite of the genus Ellipsomyxa Køie, 2003 (Ceratomyxidae: Myxozoa) found parasitizing the gallbladder of Satanoperca jurupari Heckel, 1840 collected in the Curiaú River Environmental Protection Area in Macapá, Amapá state, Brazil. The fish were collected using mesh cast net. The gallbladders were examined, preserved in 80% alcohol for molecular analysis (SSU rDNA gene), and fixed in Davidson for histological slide preparation. The new parasite had a prevalence of 81% in the gallbladder, asymmetric plasmodia, irregular free spores in the bladder fluid, with no cyst formation. The spores are elliptical, with characteristics of the genus Ellipsomyxa, and they had a mean length of 10.11 (8.56-10.5) μm, mean width of 7.81 (5.96-9.56) μm, and thick walls. The polar capsules are sub-spherical in shape, slightly asymmetrical, with a mean length of 3.12 (2.31-3.99) μm and mean width of 2.5 (2.22-2.95) μm, containing polar filament with five or six coils perpendicular to the longitudinal axis of the capsule. The Bayesian Inference assigned the new species to a subclade formed by a lineage of Ellipsomyxa species from the Amazon region. Ellipsomyxa tucujuensis n. sp. is the sixth species of this genus described in fish from the Amazon region, and the first for the state of Amapá.

A novel myxozoan parasite, Ellipsomyxa boleophthalmi sp. nov. (Myxozoa: Ceratomyxidae) in the brackishwater fish, Boleophthalmus dussumieri Valenciennes, 1837 (Perciformes: Gobiidae) from India

A novel myxozoan parasite is identified and described from mudskipper, Boleophthalmus dussumieri, collected from a brackishwater ecosystem in Maharashtra, India. Ellipsomyxa boleophthalmi sp. nov. was found in the gallbladder of 58 of 60 fish examined (96.7%). The parasite formed disporous plasmodia that varied in size and shape, and the thin-walled, ellipsoidal and elongated myxospores measured 9.0-10.7 × 6.0-7.8 μm. The two, spherical polar capsules measured 2.7 μm in diameter and enclosed 3-4 coils of polar tubules. Histological observations of infected gallbladder revealed the attachment of disporous plasmodial stages of the parasite to the gallbladder wall with fine pseudopodia. Under the scanning electron microscope (SEM), the myxospores showed a distinct central sutural line and two distinct depressions on the opposite sides at the openings of polar capsules. SEM also revealed the engulfment of microvilli of gallbladder wall by pseudopodia of the plasmodial stages. Analysis of the partial fragment of the SSU rDNA region (1386 bp) showed less than 98% sequence similarity with the other reported Ellipsomyxa spp. In the phylogenetic tree, the present species formed as a distinct subclade within the major clade of Ellipsomyxa spp. The unique morphological and morphometric features of the myxospore, together with the molecular analysis, allowed us to conclude that the present myxozoan is a new species and is named Ellipsomyxa boleophthalmi sp. nov., after the generic name of the host. This is the first report on the occurrence of the genus Ellipsomyxa in B. dussumieri.