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Evolution in metal-contaminated environments
Abstracts / Comparative Biochemisto' and Physiology, Part A 126 (2000) S1-S163
AQUACULTURE
$93
AND EXSITU CONSERVATION
L e v e r o n i C a l v i S., L a b b 6 C. a n d M a i s s e G. INRA S C R I B E , I c h t y o d i v e r s i t y a n d C r y o p r e s e r v a t i o n G r o u p , C a m p u s de B e a u l i e u , F - 3 5 0 4 2 RENNES cedex The creation of fish sperm and embryos cryo-banks is justified by the development of genetic selection programmes in fish farming together with the need for protection of biodiversity in wild fish populations. The studies undergone to elaborate freezing extenders point out how important are the considered species or cells and the interactions between components inside the extender. Sperm cryopreservation ability depends on the species, salmonids sperm being especially difficult to control by comparison with marine fish sperm. The ATP content and the composition of the plasma membrane play a major role in the freezing resistance of fish spermatozoa. Cryopreservation of the whole fish embryos has not yet been successful with regards to the knowledge available today. However, recent results on cryopreservation of isolated blastomeres of sal monids and cyprinids are very promising with high survival rates after freeze-thawing. -
The problem of the regeneration of live fish from cryopreserved cells (spermatozoa and embryonic cells) is linked with the activity of the cryobanks. Different methods have been successfully tested to regenerate fish from fresh cells: Androgenesis and blastomeres grafting. In androgenesis, the ova genome is first inactivated by gamma-rays, X-rays or UV-irradiation. The irradiated ova are fertilised and then the genome transmitted by the spermatozoa is duplicated using pressure shock or heat shock. In blastomeres grafting, dissociated embryonic cells from the donor embryo are injected in the deeper part of the recipient embryo. The goal of this grafting is the production of germ-line chimeras. In the frame work of the cryopreservation these methods have to be adapted to the use of frozen cells.
EVOLUTION
IN METAL-CONTAMINATED
ENVIRONMENTS
L e v i n t o n J. D e p a r t m e n t o f E c o l o g y and E v o l u t i o n , State U n i v e r s i t y o f N e w Y o r k , S t o n y B r o o k N Y U S A 11794 [email protected] Metals often accumulate in natural settings and natural populations are often exposed to metals at levels that reduce physiological performance or even that cause death. Because there may be genetic variation in mechanisms of metal detoxification the physiolocial stress imposed by metals might result in natural selection for improved detoxification. Metals are often detoxified by binding with proteins or by deposition in granules. Thus evolutionary mechanisms are readily hypothesized. A site formerly rich in cadmium was a source of stress for aquatic benthic invertebrates and we were able to document intense natural selection for resistance to cadmium. Resistant animals apparently were rich in a metalbinding protein and also stored cadmium in metal-rich granules. Variation in resistance could be ascribed completely to genetic variation, probably at a single locus. The resistance results in increased uptake of cadmium, which in turn increased the potential for trophic transfer of metals. The genetic mechanism may have involved gene duplication, which suggests that metal-binding proteins could be produced more rapidly with duplicated structural genes. This mechanism would not necessarily encumber an evolutionary cost.
AQUACULTURE
$93
AND EXSITU CONSERVATION
L e v e r o n i C a l v i S., L a b b 6 C. a n d M a i s s e G. INRA S C R I B E , I c h t y o d i v e r s i t y a n d C r y o p r e s e r v a t i o n G r o u p , C a m p u s de B e a u l i e u , F - 3 5 0 4 2 RENNES cedex The creation of fish sperm and embryos cryo-banks is justified by the development of genetic selection programmes in fish farming together with the need for protection of biodiversity in wild fish populations. The studies undergone to elaborate freezing extenders point out how important are the considered species or cells and the interactions between components inside the extender. Sperm cryopreservation ability depends on the species, salmonids sperm being especially difficult to control by comparison with marine fish sperm. The ATP content and the composition of the plasma membrane play a major role in the freezing resistance of fish spermatozoa. Cryopreservation of the whole fish embryos has not yet been successful with regards to the knowledge available today. However, recent results on cryopreservation of isolated blastomeres of sal monids and cyprinids are very promising with high survival rates after freeze-thawing. -
The problem of the regeneration of live fish from cryopreserved cells (spermatozoa and embryonic cells) is linked with the activity of the cryobanks. Different methods have been successfully tested to regenerate fish from fresh cells: Androgenesis and blastomeres grafting. In androgenesis, the ova genome is first inactivated by gamma-rays, X-rays or UV-irradiation. The irradiated ova are fertilised and then the genome transmitted by the spermatozoa is duplicated using pressure shock or heat shock. In blastomeres grafting, dissociated embryonic cells from the donor embryo are injected in the deeper part of the recipient embryo. The goal of this grafting is the production of germ-line chimeras. In the frame work of the cryopreservation these methods have to be adapted to the use of frozen cells.
EVOLUTION
IN METAL-CONTAMINATED
ENVIRONMENTS
L e v i n t o n J. D e p a r t m e n t o f E c o l o g y and E v o l u t i o n , State U n i v e r s i t y o f N e w Y o r k , S t o n y B r o o k N Y U S A 11794 [email protected] Metals often accumulate in natural settings and natural populations are often exposed to metals at levels that reduce physiological performance or even that cause death. Because there may be genetic variation in mechanisms of metal detoxification the physiolocial stress imposed by metals might result in natural selection for improved detoxification. Metals are often detoxified by binding with proteins or by deposition in granules. Thus evolutionary mechanisms are readily hypothesized. A site formerly rich in cadmium was a source of stress for aquatic benthic invertebrates and we were able to document intense natural selection for resistance to cadmium. Resistant animals apparently were rich in a metalbinding protein and also stored cadmium in metal-rich granules. Variation in resistance could be ascribed completely to genetic variation, probably at a single locus. The resistance results in increased uptake of cadmium, which in turn increased the potential for trophic transfer of metals. The genetic mechanism may have involved gene duplication, which suggests that metal-binding proteins could be produced more rapidly with duplicated structural genes. This mechanism would not necessarily encumber an evolutionary cost.