Digynic triploidy in rabbit blastocysts after delayed insemination

Abstract

The origin of triploid (3N) 5j-day blastocysts in rabbits is inferred from the segregation of sex chromosomes and of an autosomal M-marker whose properties are described. 39 triploids and no tetraploids were scored among 1454 chromosomally scored blastocysts. A delay of 8 h between an ovulatory injection and subsequent insemination raised the estimated normal incidence of 0-59 % triploid blastocysts to 3-13 %. The increase is ascribed primarily to digyny (17 blastocysts), and to diandry probably mediated by dispermy (1 blastocyst). The triploid components of the two 2N/3N mosaics and the one 3N/6N were digynic. Neither superovulation nor insemination of excessive numbers of spermatozoa could be shown to give rise to triploid embryos. The diandric triploid was XYY, the first of this constitution apparently reported in the rabbit. There was some evidence that XX Y triploid blastocysts up to 5^-day gestation are more viable than XXX. In the 2N/3N mosaics each component had been entered by one spermatozoon, and the diploid component could not have been merely a contamination by diploid maternal somatic cells. In 2N/4N, 2N/4N/8N and 3N/6N mosaics, each polyploid component showed an exact doubling of the marker chromosome constitution of a component of lower ploidy; their origin is ascribed to doubling or redoubling of chromosome number in isolated embryonic cells. With earlier data included, 49-08 (+ S.B. 1-96) % of 652 diploid blastocysts were 1 7 . 460 non-experimental weaned rabbits were all diploid.

Mechanisms involved in the spontaneous occurrence of diploid-triploid chimerism in the mink <i>(Mustela viso</i><i>n</i>) and chicken (<i>Gallus domesticu</i><i>s</i>)

“…and XY,/? (Fechhcimer and Beatty, 1974;Beatty and Coulter, 1978). Six male calico cats had complements of XX/XXY (four) and XY/XXY (two) (Centcrwall and Benirschke, 1973).…”

“…Of the total of 43. none was XX/XYY. Two of the rabbit embryos (Beatty and Coulter, 1978) were from parents bearing different Cband autosomal markers. It was established that the triploid cell line of both was digynic; both cell lines of both embryos contained a single paternal genome.…”

“…mouse (Beatty, 1957), rabbit (Beatty and Coulter, 1978). cat (Benirschke, 1972), pig (McFeely, 1967), cattle (Dunn et al.…”

Diploid ‐ triploid chimaerism (64, XX/96, XXY) in an intersex foal

“…No opportunity was afforded to examine genetic markers in the present case. There may be species differences involved as studies such as that of Beatty and Coulter (1978) in rabbits showed that the majority of triploids were due to digyny. These, however, were induced triploids due to delayed insemination.…”