eMail:Thomas.Savage@oregonstate.edu
Abstract. Embryonic parthenogenetic failures in turkey eggs can be assigned to one of four categories. Most commonly, parthenogenetic expression consists of unorganized embryonic tissues that may be closely aggregated (1cm. dia.), or extend over the entire surface of the yolk. The embryonic tissues may have a delicate and irregularly shaped appearance. The second category is that of embryonic tissues associated with a ruptured vitelline membrane resulting in the dispersion of the yolk's contents. Typically, the inner shell membrane of an egg with this parthenogenetic form is opaque rather than translucent. A third, less commonly observed form of parthenogenesis is embryonic tissue accompanied by dispersed aggregates of blood islets or an organized pattern resembling a 'blood ring'. The least frequently encounterd form of parthenogenetic expression is the embryo whose embryonic development is visibly delayed by two days when compared to a normal embryo of the same incubation period. Macroscopic differentiation between parthenogenetic and normal embryos can be achieved after 4 days of artificial incubation, but due to the variability in parthenogenetic expression, accuracy of detection is improved after 6 days of incubation.
The phenomena of avian parthenogenesis is described as a process
of cell division in an unfertilized egg that may result in the
formation of embryonic tissues and in extreme situations a fully
developed individual (Olsen,1975).
The parthenogenetic process has been described in various avian
species and appears to have potentially greater economic significance
in turkeys than chickens. In most observations of avian
parthenogenesis, the abortive expression of early embryonic
development can be incorrectly identified as an early embryonic
failure associated with the incubation process associated with
fertilized eggs. The parthenogenetic tissues that develop in
infertile eggs is diploid (Yao
and Olsen, 1955; Sato and
Kosin, 1960) which makes differentiation between normal and
parthenogenetic embryos a difficult task.
The ability to macroscopically recognize embryonic failures
attributable to parthenogenesis in fertilized eggs can result in
improved reproductive efficiency. Since the first major period of
early embryonic mortality in incubating turkey eggs occurs between
the third and fifth days, a portion of this mortality may
characterized by delayed blastoderm development. Olsen
and Marsden (1950) described a line of turkeys having a high
incidence of early embryo mortality and a concomittant low
hatchability. The early embryonic mortality and poor hatchability
(28%) may have been attributed to a high incidence of infertility and
parthenogenesis. Without the proper diagnosis to determine the cause
of an embryo's failure to develop, the poultry producer/hatchery
person may direct their attention to the incubation process rather
than the breeder's reproductive management and not improve
hatchability as quickly as would be desired.
The scientific literature provides descriptions of studies
influencing parthenogenesis in the turkey but lack illustrations
and/or photographic images of the phenomenon that would allow the
reader to more efficiently recognize the process. Therefore, the
following guide was created to:
The following guide has been constructed such that the reader can navigate through this program at their convenience. Comments and suggestions pertaining to this program and its contents are invited. The quality of the images viewed will vary with the monitor and its video support software. This web site was updated February 11, 2008.