Induced diploid gynogenesis and polyploidy in the ornamental (koi) carp Cyprinus carpio L.
The results of a series of experiments conducted in our laboratory on the ornamental common carp (koi), aimed at optimizing heat-shock chromosome-set manipulation procedures, are described. The timing of heat-shock initiation was expressed in the relative unit of embryological age (τ0) in order to standardize this parameter, the absolute time for heat-shock initiation being calculated from duration of one τ0 at two different pre-treatment water temperatures. Heat shocks were applied within the periods of 0.05–0.60 τ0 and 1.20–2.20 τ0 which, respectively, cover the successive phases of the 2nd meiotic division and the 1st cleavage. The highest production of diploid gynogenetic offspring was observed when heat shocks were initiated at 0.15–0.25 τ0 and at 1.5 τ0, after insemination, corresponding to anaphase of meiosis-II, and metaphase of the 1st cleavage, respectively. Similar results were obtained irrespective of the different pre-treatment water temperatures, thus confirming the possibility of standardizing heat-shock timing by τ0.
A Review of Ploidy Manipulations in Aquaculture: the Israeli Experience
Ploidy manipulation was introduced to Israel at the beginning of the 1980s. To improve existing methods, Israeli fish centers conducted intensive research in this field for more than two decades. Chromosome-set technology was adapted for ten fish species and varieties, including two marine fish. Presently, though methodology achievements are remarkable, practical implementation is applicable only for the common carp. The aim was to integrate gynogenesis and androgenic sex-reversal to generate neomales with special genetic traits in this economically important species that is extensively cultured in Israel. Carp neomales can serve as parents for production of fast-growing all-female populations. This paper describes ploidy manipulation progress and activities carried out in four Israeli fish centers. Future objectives include (a) implementation of the existing know-how to produce tilapia YY-males as broodfish for producing malemonosex populations, (b) dissemination and promotion of export to foreign markets of the advantageous female triploid grass carp and black carp, (c) continuation of genetic work with marine fish to develop breeds that could be advantageous for mariculture, and (d) reconsideration of the ploidy-manipulated koi as a genetic tool to be utilized to facilitate gene-mapping in carps.
Production of tetraploid and homozygous diploid amphibians by suppression of first cleavage
Tetraploid and genetically homozygous diploid Xenopus can be produced conveniently, in large numbers, by suppressing the first cleavage division of eggs through the application of hydrostatic pressure. The pressure-induced disruption of the mitotic spindle during the first division of a diploid zygote of the African clawed toad results in a tetraploid embryo. A homozygous diploid embryo can be derived by inhibiting the first cleavage of a parthenogenetically activated haploid egg. Both tetraploid and homozygous diploid larvae are viable and successfully undergo metamorphosis.