A cytological study of early cell populations in developing parthenogenetic blastodiscs of the Turkey.

PPROXIMATELY 17% of the eggs laid by non-mated Beltsville Small A White (BSW) turkeys showed some type (e.g., membranes, blood, embryos) of development upon incubation ( OLSEN and MARSDEN 1953,1954). The question arose as to whether the cells in such unfertilized eggs were haploid or diploid. YAO and OLSEN (1955) reported finding diploid chromosome numbers in embryonic tissue of parthenogenetic origin, and hypothesized that chromosome dottbling must occur at an early stage in development allowing regular mitotic cell division to proceed with the formation of normal embryonic tissue. POOLE (1959) extended the observations of YAO and OLSEN (1955) to hatched parthenogenetic turkeys (all males). No morphological or numerical differences were found between the chromosome complements of pinfeather cells from normal and parthenogenetic turkey. Finally, SATO and KOSIN (1960) examined the chromosome number of incubated parthenogenetic germ discs and embryos and found that most of the dividing cells contained the diploid chromosome number. Some haploid and polyploid chromosome numbers were also observed by them in the parthenogenetic material. Observations of the gonads of 67 Parthenogenetic embryos indicated they were all males (POOLE and OLSEN 1957). With the knowledge that upon incubation a certain percentage of the eggs laid by virgin turkeys will develop into diploid parthenogens, it is of interest to determine at what point in development the parthenogen attains the diploid chromosome number. The objective of this investigation was to determine if abnormal oogenesis, resulting in an unreduced oocyte, is the basis of the diploid parthenogen. To accomplish this goal blastodiscs from newly laid, unincubated eggs as well as from incubated eggs were selected for study. Embryos derived from matings of turkeys selected over a 12-year period for a higher incidence of parthenogenetic development were chosen to determine if triploids are formed.