Luminous vibriosis in rock lobster Jasus verreauxi (Decapoda : Palinuridae) phyllosoma larvae associated with infection by Vibrio harveyi

Studies were conducted to determine the cause of outbreaks of luminous vibr iosis in phyllosoma larvae of the packhorse rock lobster Jasus verreauxi re ared in an experimental culture facility. On 2 separate occasions mortaliti es of up to 75 % over a period of 4 wk were observed in 4th to 5th and 8th to 10th instar phyllosomas at water temperatures of 20 and 23 degreesC, res pectively. Affected larvae became opaque, exhibited small red spots through out the body and pereiopods, and were faintly luminous when viewed in the d ark. Histopathology showed that the gut and hepatopancreas tubules of morib und phyllosomas contained massive bacterial plaques. The hepatopancreas tub ules of moribund larvae were atrophic and some contained necrotic cells slo ughed into the lumen. Dense, pure cultures of a bacterium identified as Vib rio harveyi were isolated from moribund larvae. The disease syndrome was re produced by in vivo challenge and V. harveyi was successfully reisolated fr om diseased larvae after apparently healthy larvae were exposed by immersio n to baths of more than 104 V. harveyi ml(-1) at 24 degreesC. injured larva e were more susceptible to infection than were healthy larvae. Survival of larvae experimentally and naturally exposed to V. harveyi was improved when antibiotics were administered via bath exposures.