Skin infection of greater amberjack (Seriola dumerili) by monogenean ectoparasite neobenedenia girellae: A morphological and histopathological descriptive study

Abstract

Neobenedenia girellae is considered an epizootic infection for intensively cultured fish species. Particularly, for greater amberjack (Seriola dumerili) N. girellae causes high mortality rates and supposes a bottleneck during its on-growing period. Thus, the objective of this work was to describe the skin morphological alterations caused by a N. girellae infection on greater amberjack. Greater amberjack juveniles were sampled pre and post experimental infection with N. girellae obtaining cranial and dorsal skin samples. Samples were processed for morphological and ultrastructural studies and revealed clear differences in the structure of both regions, confirming the cranial region as the most susceptible region to be parasitized due to an absence of scales and lower goblet cells density. N. girellae adhesion disrupted the structure of epidermal epithelial cells by overpressure. Stratum spongiosum surface-epithelial cells located near the parasite presented a clear cell degradation process, associated in some cases with cellular detachment. N. girellae infection induced epidermal hydropic degeneration and, in some cases, focal spongiosis. Tissue ulcerative lesions caused by the parasite's attachment structures were characterized by a specific mobilization of leucocytes to the fixation areas. Thus, N.girellae induces important alterations in greater amberjack epidermis independently of the skin region that explain the appearance of secondary infections and associated mortalities.