Identification and pathological analysis of parasite Haliotrema bilobatus associated with haliotremasis in gill of twin-spot puffer Takifugu bimaculatus
Abstract: The incidence of haliotremasis was investigated in twin-spot puffer Takifugubimaculatus cultured in ponds along the coastal area of Fujian Province from June 2016 to June 2019,and the morphology and chitin structure feature of parasite Haliotrema sp.were observed and analyzed by molecular biology.The haliotremasis was found to occur in late spring,early summer,and autumn,in both juvenile and adult fish.The clinical symptoms included slow swimming in upper layer,anorexia,pale body color,weight loss,caudal and anal fin defect,and hemorrhagic liver and spleen.There were a large number of worms on the mucus covering the gill lamellae and gill filaments,which was identified as Haliotremabilobatus based on the morphological observation and structural characteristics of chitin.This is the first report that H.bilobatus caused haliotremasis in twin-spot puffer.The 18S rDNA(1 282 bp)and 28S rDNA gene sequence (C1-D2)region (886 bp)and sequence alignment analysis showed that H.bilobatus had the similar 18S rDNA gene to that of H.ctenochaeti,H.angelopterum,H.aurigae,H.leporinus,H.scyphovagina,and H.macracantha (with the identity of 97.68%-98.30%),with the most close to H.sicklocirrus (only identity of 90.28%)in 28S rDNA gene.Phylogenetic trees constructed based on 18S rDNA and 28S rDNA genes revealed that H.bilobatus is in an independent branch.The histopathological observation of gill tissue showed that H.bilobatus caused the damage of gill filaments,resulting in the proliferation or shedding of gill epithelial tissues.In the case of severe infection,the gill fragments were necrotic,disintegrated,and infiltrated with a large amount of mucus,interfering oxygen exchange across the gill surface and causing fish to die due to hypoxia.The findings indicate that H.bilobatus is a pathogen causing haliotremasis usually in late spring,early summer,or fall in twin-spot puffer cultured in ponds in Fujian Province.
2022, Vol. 37 
