Identification, characterization and infection dynamics of Vibrio strains in phyllosoma of Thenus unimaculatus

The present study investigates Vibrio outbreak in the hatchery system designed for larval rearing of shovelnosed lobster Thenus unimaculatus in India. High larval mortalities during the episode led to an almost complete loss of the larval stock during the first 10 days. Microscopic examination revealed heavy fouling of the phyllosoma appendages. Histopathological analysis showed the presence of bacteria in larval tissues. Investigation by scanning electron microscopy revealed the formation of bacterial plaques on appendages and adhesion of bacteria on fine setae in heavily infected larvae. Bacteria isolated from larvae and identified by 16S rRNA sequencing and phylogenetic analysis indicated that the strains were closely related to luminescent Vibrio campbellii and Vibrio harveyi. The virulence potential of Vibrio strains isolated from larvae was evaluated through an experimental infection. The study helps to understand microbial infection and its impact on phyllosoma survival and may allow a more effective health management regime to improve larval survival in the hatchery phase