|Effects of short term feeding of microalgae on the bacterial flora associated with juvenile Artemia franciscana|
Olsen, A.I.; Olsen, Y.; Attramadal, Y.; Christie, K.; Birkbeck, T.H.; Skjermo, J.; Vadstein, O. (2000). Effects of short term feeding of microalgae on the bacterial flora associated with juvenile Artemia franciscana. Aquaculture 190: 11-25
In: Aquaculture. Elsevier: Amsterdam; London; New York; Oxford; Tokyo. ISSN 0044-8486, more
|Authors|| || Top |
- Olsen, A.I.
- Olsen, Y.
- Attramadal, Y.
- Christie, K.
- Birkbeck, T.H.
- Skjermo, J.
- Vadstein, O.
Artemia franciscana cultivated for 2 days for use as feed for Atlantic halibut larvae (Hippoglossus hippoglossus L.) had high numbers of associated bacteria with high counts of presumptive vibrios (TCBS-agar) and haemolytic bacteria (blood agar). The food used for the cultivation of A. franciscana, fish meal and fish oil, is a rich substrate for proliferation of opportunistic bacteria. A procedure for incubation of 2-day-old A. franciscana with the microalga Tetraselmis sp. was used to test the hypothesis that a change in the gut bacterial flora of A. franciscana could be induced by incorporating algal cells into the diet. It was expected that this would reduce bacterial proliferation in the Artemia, and introduce new bacterial species from the algal culture resulting in a more stable and diverse flora associated with the animals. The standard 2-day-old A. franciscana had 24,000±10,700 colony forming units (CFU, mean±STD) per animal with presumptive vibrios and haemolytic bacteria constituting 58% and 10% of the total, respectively. The flora was dominated by Vibrio alginolyticus-like bacteria that constituted 34 out of 40 isolates tested. During 4-h incubation the numbers of associated bacteria were reduced, on average by 75%, with the flora less dominated by V. alginolyticus. The relative diversity (J') of the associated bacterial flora increased from 0.17 to 0.40. A 24-h incubation to simulate first feeding conditions for halibut larvae gave further decreases in bacterial numbers associated with both treated and untreated A. franciscana. The prevalence of Vibrio was lower in these two samples, and the flora was now dominated by isolates of other genera. The relative diversity of the flora of A. franciscana increased to 0.82 and 0.63 for samples previously incubated with Tetraselmis sp. and those which were not, respectively. Data from a first feeding experiment showed that the bacterial flora of the live feed was directly transferred to the larvae. The algal component was shown to influence the numbers and composition of the associated flora of the live feed, giving A. franciscana with lower numbers of bacteria as well as a more diverse bacterial community.