Changes
in the gut-associated microflora during the development of Atlantic halibut
(Hippoglossus hippoglossus L.) larvae in three British hatcheries
D.W.
Verner-Jeffreys, R.J. Shields, I.R. Bricknell, T.H. Birkbeck-2003
Aquaculture, 219(4): 21-42
Abstract:
The
bacterial flora of reared Atlantic halibut eggs, larvae, juveniles and
adults from three different UK halibut hatcheries was monitored using a
combination of traditional biochemical tests, the BIOLOG GN bacterial
identification system, PCR-RFLP of 16S rRNA genes and partial 16S rDNA gene
analysis.
A
gut microflora was detected towards the beginning of the non-feeding
yolk-sac stage, with a substantial increase as the larvae started to feed.
Bacteria isolated from non-feeding yolk-sac larvae were predominantly
non-fermentative Gram-negative rods, in particular Pseudoalteromonas
species; by contrast, the presumptive gut microflora of first-feeding larvae
was generally dominated by members of the Vibrio genus.
There
was evidence of a bacterial succession after the larvae started to feed.
Initially, first-feeding halibut reared on enriched Artemia were
generally colonised by live food-associated bacteria, particularly Vibrio
splendidus and V. alginolyticus-type organisms. Genetically
similar V. splendidus isolates were recovered from enriched Artemia
and the guts of first-feeding halibut larvae in all three hatcheries.
However, only a selected proportion of the Artemia-associated
bacteria appeared able to establish themselves within the guts of larval
halibut.
First-feeding
halibut larvae were sometimes colonised by opportunistic bacteria. The gut
floras of two individual batches of halibut larvae were briefly dominated by
a Pseudoalteromonas and a Photobacterium phosphoreum isolate,
respectively.
Genetically-similar
V. salmonicida-type organisms were present in larvae sampled from all
three hatcheries, both from copepod and Artemia-fed fish. The guts of
the adult halibut analysed had a culturable flora dominated by Photo.
phosphoreum.
(Division of Infection and Immunity, Institute of Biomedical and Life Sciences, University of Glasgow, Joseph Black Building, Glasgow, Scotland G12 8QQ, UK, e-mail of T.H. Birkbeck: h.birkbeck@bio.gla.ac.uk)