Egg-associated microflora of Pacific threadfin, Polydactylus sexfilis and amberjack, Seriola rivoliana, eggs. Characterisation and properties

The microflora of rinsed eggs of Pacific threadfin, Polydactylus sexfilis, and amberjack, Seriola rivoliana, were characterised, using a combination of culture based and non-culture based methods. The adherent microflora of eggs, examined within a few hours of release, varied both qualitatively and quantitatively. Similar Pseudoalteromonas strains were recovered from the eggs of both species and Photobacterium damselae subsp. damselae was recovered from more than one batch of Pacific threadfin eggs.Many of the 16S rRNA gene sequences directly amplified and cloned from egg homogenate samples shared high homology to the partial 16S rRNA gene sequences of organisms cultured from the same samples of homogenate, suggesting that the majority of the bacteria in these samples were culturable on Marine Agar (MA).One of the organisms isolated from the eggs of Pacific threadfin, Vibrio str ME2-03, was shown to be highly virulent to hatched Pacific threadfin larvae in challenge experiments. This shows that, as with other fish species, egg-associated transfer of bacterial pathogens could be significant in Pacific threadfin culture, illustrating the likely importance of treating eggs prior to transport, either to other rearing areas or to other hatcheries.