Functional role of
micro-organisms in larviculture: Artemia as test organism
Aquaflow Technical Leaflet 2002-98
European Network for the Dissemination of Aquaculture
RTD Information (Q5CA-2000-30105) and previously FAIR-3837, URL: http://www.aquaflow.org/
Despite the growth of the aquaculture industry over
the last decades, high mortalities in the larviculture phase still remain.
Until recently, antibiotics were a temporary solution, but at present there
is a general trend towards a more natural suppression of opportunistic and
obligate pathogens. In recent
years, several research groups have proved that new zootechnical approaches,
primarily the use of selected microbiota (e.g. “mature water”, “green
water”, specific micro-algae, probiotic yeasts and bacteria), result in
better/more reproducible data. Now there is a consensus about the critical
role of microbial interactions in the larviculture of aquatic organisms.
However, studies have failed to provide answers to the numerous
hypotheses about the actual biological processes involved in these microbial
interventions, mainly due to the fact that the test organisms are not
cultured axenically, which results inevitably in interactions with the
already present micro-organisms. Consequently, the causal effect cannot be
determined unequivocally.
The purpose of this recently started project,
financed by FWO-Vlaanderen (Fund for Scientific Research of the Flemish
Community, 2002-2005) is therefore to study the mode of action of a limited
number of microbial organisms and to verify existing hypotheses by the use
of a well-known organism that can be cultured axenically. The feedback of this functional knowledge will enable the
targeted selection of micro-organisms or the optimisation of their mode of
action and a better planning and understanding of experiments with other
organisms, crustaceans and fish. The brine shrimp Artemia is
preferred as test organism for the following reasons: 1) its nutritional
requirements and culture conditions are well known and can easily be
standardised; 2) an axenic culture test was recently designed and
successfully applied for the selection of probiotic and pathogenic bacteria;
3) the histology of its digestive tract is relatively simple; 4) a large
range of micro-organisms (bacteria, yeasts, micro-algae) is ingested by Artemia;
5) with an annual consumption of more than 1500 tons of cysts Artemia
is the most important food resource in larval aquaculture.
The experimental work will focus on four hypotheses
with Artemia as test organism: 1) certain micro-organisms find
suitable adhesion sites in the digestive tract, where they can proliferate
and are able to maintain themselves there; 2) some micro-organisms are able
to inhibit pathogenic bacteria; 3) micro-organisms or components of their
cells are able to induce a faster maturation of the wall of the digestive
tract; 4) certain micro-organisms have a positive influence on the water
quality.
The research programme will cover the following
steps:
Demonstration of colonisation of the intestine by
selected micro-organisms by application and/or adaptation of several methods
(FISH, GFP, DFA)
Screening of micro-organisms (bacteria and algae)
with an inhibiting effect on pathogens
Demonstration of the effect of selected
micro-organisms on the growth of cultured aquatic organisms by the enhanced
maturation of the intestine
Demonstration of the effect of microbiota on the
water quality.
This project is a collaboration between the
Laboratory of Aquaculture & Artemia Reference Center (Ghent University,
Belgium), the Laboratory for Microbial Ecology and Technology (idem), and
the Laboratory for Aquatic Ecology (Catholic University of Leuven, Belgium).
For more information:
SORGELOOS Patrick (patrick.sorgeloos@rug.ac.be)
Laboratory of Aquaculture & Artemia Reference Center - Ghent University
Rozier 44
B9000 Gent
Belgium
Phone : +32-9-264 37 54
Fax : +32-9-264 41 93
E-mail:
Patrick.sorgeloos@rug.ac.be