Fig 4.

Infection cycle of V. owensii DY05 in the larviculture ecosystem of early-stage P. ornatus phyllosomas. The pathogen enters the larviculture environment through an unascertained source as a free-living planktonic form. Live prey Artemia nauplii actively ingest the bacteria, resulting in bioaccumulation in the gut. Early-stage phyllosomas (stages 1 to 3) capture and masticate the Artemia nauplii, triturating food particulates along with the pathogen through the foregut into the hepatopancreas. The pathogen proliferates in the distal ends of the hepatopancreas, eventually colonizing the entire organ, with planktonic cells dispelled from the midgut and evacuated back into the ambient environment. These planktonic cells are ingested by Artemia nauplii, which perpetuates invasion of the phyllosomas through the oral route. Eventually, the condition progresses to systemic infection in association with acute mortality. By utilizing and inhabiting the tissues of moribund and dead hosts, the pathogen can also be transmitted to new hosts through occasional cannibalism. Continuous shedding of bacteria from dead hosts likely contributes to the ambient bacterioplankton, again reactivating the oral infection pathway.