Vibrionaceae infection in phyllosomas of the tropical rock lobster Panulirus ornatus as detected by fluorescence in situ hybridisation

The total abundance of bacteria and relative abundance of Vibrionaceae cells associated with the larval stage of the tropical rock lobster Panulirus ornatus was investigated throughout a 22 day rearing trial using fluorescence in situ hybridisation. Bacterial enumeration was performed on both external tissue surfaces and internally within the hepatopancreas. A significant increase in the mean number of bacteria detected on the external tissue of P. ornatus phyllosomas was observed from day 7 of the larval rearing trial. Within the hepatopancreas, a significant increase in bacterial abundance was not observed until day 10 onwards. From hatching to day 18, the mean number of bacteria increased 5 fold on external tissue and 40 fold within the hepatopancreas. The relative proportion of Vibrionaceae cells on external tissue significantly increased from day 10 of the larval rearing trial and was 15 fold higher at day 18 compared to the relative abundance at the time of hatching. In contrast, a significant increase in the relative proportion of Vibrionaceae cells within the hepatopancreas was not detected until day 18 and was 60 fold higher than the relative abundance at hatching.