MORPHOLOGICAL CHARACTERS AND DNA IDENTIFICATION OF SEVERAL ACTINOSPOREAN COLLECTED FROM OLIGOCHAETE BRANCHIURA SOWERBYI

Myxozoans are common microparasites in wild and farmed fish, and some species cause severe disease in cultured gibel carp. During the investigation of actinospores in oligochaetes from the gibel carp ponds form April 2018 to July 2019, nine actinospore types were found in the oligochaete Branchiura sowerbyi Beddard. Based on morphological characteristics, they were identified into six collection groups, including one Raabeia-type, two Aurantiactinomyxon-types, two Neoactinomyxum-types, two Triactinomyxon-types, two Echinactinomyxon-types and one Hungactinomyxon-type. The present study described six of them, Triactinomyxon type HZ, Triactinomyxon type DF, Echinactinomyxon type LY1, Echinactinomyxon type LY2, Neoactinomyxum type LY1 and Hungactinomyxon type DF. Blastn search using SSU rDNA gene sequences indicated that Triactinomyxon type HZ and Triactinomyxon type DF have the highest 93.39% and 94.48% homology similarity with Triactinomyxon type CZ, respectively. Echinactinomyxon type LY1 and Myxobolus lentisuturalis have the highest similarity (96.88%, AY119688); Echinactinomyxon type LY2 has the highest similarity with Hungactinomyxon type 1 (97.86%, AY779062); Neoactinomyxum type LY has the highest similarity with Thelohanellus sp. (92.48%, MK412938); Hungactinomyxon type DF has the highest similarity with Hungactinomyxon (99.41%—99.64%). Phylogenetic analyses showed that Triactinomyxon type HZ and Triactinomyxon type DF clustered in the Chloromyxum subclade; Echinactinomyxon type LY1 and Echinactinomyxon type LY2 clustered in the Myxobolus clade; the Neoactinomyxum type LY1 clustered in the Thelohanellus clade.