Community Research
ROTIGEN
Genetic implications in the production of rotifers in commercial finfish
hatcheries
home < objectivesObjectives of the project
In this study, we are putting the following hypotheses forward:
- Does the controlled mass culture of rotifers leads to an impoverishment in the genetic diversity of the cultured rotifers and
- does this fact in its turn make the rotifer culture more susceptible to crashes if there is a change, uncontrolled or controlled, in the biotic or abiotic conditions prevailing in the culture?
Different, commonly used, culture types (batch culture, recirculation and continuous culture) will be compared for their effect on interclonal selection. The effect of the amount of rotifers used to inoculate the culture on the diversity of the genotypic diversity will be examined starting with a mixture of known clones. Five different mixtures of clones originating from different regions will be used during the project. The results will give information on the correlation between the culture method (i.e. type and handling) and the selection rate.
The effect of some environmental parameters, such as temperature, salinity and feed, on the genotypic diversity of the rotifer will be assessed. Disinfected parthenogenetic eggs will be hatched and cultured in monoxenic conditions. After the rotifers have been cultured for several cycles at one stable condition (e.g. temperature), they will be harvested and put at another temperature. May be, the rotifer clones are able to adapt to the new situation or they may crash. The same mixtures of clones will also be inoculated in cultures with varying parameters. The selection rate will be compared to the one with stable conditions. The results will point out the effect of stable culture conditions.
Special attention will be paid to the effects of bacteria on the selection within the five mixtures of rotifer clones. Ad random mixtures of disinfected parthenogenetic eggs will be hatched and cultured with or without addition of these bacterial strains. The obtained information will help to keep the genotypic diversity higher in a rotifer culture inoculated with those bacteria. Verification of the obtained results will be done at a pilot scale. Rotifer clones originating from a commercial Mediterranean hatchery will be cultured in cold conditions and in a culture set-up for temperate conditions. Growth performance as well as genetic drift will be followed during the culture.
The methodologies for resting egg production/harvest will be fine-tuned. In the framework of this study proposal, the advantage of resting eggs resides in the fact that hatcheries could maintain the genetic pool of rotifer strains with exceptional characteristics by frequent inoculation of new cultures at regular time intervals.
During the course of the project, the genetic diversity of rotifer samples coming from commercial hatcheries situated in the north as well as in the south of Europe will be evaluated using the same techniques for clone characterization. This will provide field data on the genetic drift of rotifer cultures at different places with different culture conditions.
The experimental results will be combined with the field results in a workshop for the industry and other scientists at the end of the project period. A culture method using the common culture type that gives the best results in maintenance of genotypic diversity together with the best performing culture conditions (harvest frequency, stable or variable environmental conditions, beneficial bacteria) will be presented.