Myxosporean parasites in Australian frogs: Importance, implications and future directions

Detection and characterization of Hyaloklossia kasumiensis (Apicomplexa: Sarcocystidae) from Nagoya Daruma pond frog, Pelophylax porosus brevipodus

The Nagoya Daruma pond frog (Pelophylax porosus brevipodus) is an endangered anuran species endemic to the semi-aquatic environment of Japan. On June 11, 2021, four of the six Nagoya Daruma pond frogs captured from the wild and kept in an aquarium died in rapid succession. Pathological and/or parasitological examinations of two of the four carcasses revealed protozoan infection in their kidneys. The pathogen identified as Hyaloklossia kasumiensis (Apicomplexa: Sarcocystidae: Hyaloklossiinae) based on their morphological and molecular characterization. This is a new host record of H. kasumiensis. Mitochondrial cox1 sequence analysis suggest that the present species detected from Nagoya Daruma pond frog belongs to the same lineage as those found in the Tokyo Daruma pond frog (P. p. porosus) from Ibaraki Prefecture, Japan. This particular lineage may be prevalent among Pelophylax porosus ssp. distributed in Japan.

GENETIC DIVERSITY OF CYSTODISCUS SPECIES IN AMPHIBIANS IN THE SOUTHERN UNITED STATES

Myxosporean species in the genus Cystodiscus are parasites of amphibians and have been reported from several continents. Typically used for the identification of myxozoans, the spores produced by these species are similar to one another, possessing 2 polar capsules and being ovoid. The number of transverse depressions on the spore can be useful for delineating species, but these can sometimes be difficult to distinguish. In North America, Cystodiscus serotinus and Cystodiscus melleni have been described, and for C. serotinus in particular, numerous reports and a wide range of hosts have been associated with this species. Given the challenges of identifying some of these species, we questioned whether all encounters of Cystodiscus species can be attributed to these 2 described species, or if there may be additional undescribed species or cryptic species. Over 7 yr, 383 amphibians representing 13 species of toads, frogs, and salamanders were collected from sites in Oklahoma and Arkansas. Cystodiscus infections were found in 56 individuals (14.6%). Tissues from these infected individuals were preserved in alcohol for genetic analysis. The small subunit (SSU) and large subunit (LSU) ribosomal RNA genes were partially sequenced and analyzed phylogenetically. Nine distinct SSU sequence types and 7 distinct LSU sequence types were identified. Phylogenetically, sequence types were attributable to C. serotinus, C. melleni, Cystodiscus axonis, and an undescribed species. For the previously described species, there were multiple SSU sequence types: 4 for C. serotinus and 2 for both C. melleni and C. axonis. Phylogenetic patterns were similar for the LSU sequence analysis using a shorter sequence than the SSU, and we propose that the LSU is useful for initial barcoding of Cystodiscus species in any future surveys. In our qualitative assessment of sequence types compared to geography and host species, SSU types C1 and C2 (C. axonis) were only found in Union County, Arkansas, and McCurtain County, Oklahoma, respectively. Also, salamanders were only infected with SSU types B or D (C. melleni), and type B was only found in salamanders. Our finding of C. axonis in North America is notable because this species was described in Australia and is associated with host pathology. Our work reveals that there are cryptic species of Cystodiscus in the United States, one of which may be a pathogen, highlighting the importance of genetic analysis for future surveys of these species.

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.