DEVELOPMENT AND USE OF GENETICALLY UNIFORM STRAINS OF COMMON CARP IN EXPERIMENTAL ANIMAL RESEARCH

Fish are widely used in numerous fields of basic and applied research. Currently, they are the third laboratory animal group in numbers, and will become increasingly important. Common carp is a major species in both aquaculture and research. Inbred strains of carp by gynogenetic (only female inheritance) and androgenetic (only male inheritance) rep roduction techniques were developed at our university. With these meth ods, homozygous animals are produced in one generation and we present the production of homozygous inbred and F1 hybrid strains of common ca rp. As in mammalian research, using genetically well defined fish is a methodological necessity since in outbred stocks: (1) repeatability b etween experiments is low, (2) high levels of inbreeding may have accu mulated and (3) high intrastrain variability might obscure treatment e ffects. Within inbred strains, the variation is reduced and as a resul t, less animals (compared to outbreds) are necessary to obtain statist ically significant results. We illustrate this with experimental data from an F1 hybrid and partly outbred strain of common carp, both subje cted to an antibiotic treatment resulting in reduced gonadal growth.Re sults obtained from a single inbred strain should be generalized with the use of a panel of inbred strains. We show that optimal allocation of animals between and within inbred strains depends on the ratio (var iation between strains) : (variation within strains). When selecting a panel of inbred strains, attention has to be paid to genetic relation s between strains to avoid testing within a limited genetic range. It should be considered that in inbred strains, (genic) dominance and int eraction effects are absent, due to the absence of heterozygous genoty pes. In general, variation within inbred strains will be reduced for t raits with a high degree of genetic determination. However, in inbred strains of carp produced by gynogenesis or androgenesis, the chromosom e manipulation treatment induces considerable (environmental) variatio n. By using F1 hybrids of carp, derived from crossing homozygous clona l siblings this source of variation can be avoided. Still, variation i n F1 hybrids of carp is relatively large and varies greatly between st rains when compared to inbred strains of laboratory rodents. It is ass umed that their poikilothermic nature makes them more susceptible to e nvironmental variation. Using inbred fish lines will increase experime ntal duality and leads to a more efficient use of experimental animals .