- Email: [email protected]
Twins Formed on a Single Yolk of a Chicken Egg
Research Notes TWINS F O R M E D ON A SINGLE YOLK O F A C H I C K E N EGG DONALD
JACKSON
Hy-Line Poultry Farms, Des Moines, Iowa (Received for publication November 10, 1964)
FIG. 1. Two normal chicks having developed on one yolk to a late stage of incubation. The twins are attached to the yolk sac at widely separated points. slightly smaller than its twin A. The skin of the chick A was flushed in appearance. Figure 3 shows the difference between a normal chick on the left of the same hatch which died approximately the same time as the twins on the right (all eggs set were 20 ounces per dozen or greater). The shells in the background of Figure 3 were used for a
887
Downloaded from http://ps.oxfordjournals.org/ at University of Cambridge on May 24, 2015
In the course of breaking out unhatched and dead embryos after 21 days of incubation, two chicks were found to have developed on one yolk to a late stage of incubation before dying. Both Tannreuther (1919) and Newman (1940) state that complete twins on a single blastoderm are extremely rare. The phenomenon of a single yolk egg producing twins was reported in pigeons by Levi (1941). The incidence of partial duplication in the chicken as found by Byerly and Olsen (1934) under natural conditions was 0.142 percent in one breed and 0.076 percent in another, with an average of 0.111 percent. These figures were obtained from a study of over 100,000 hatched chicks and embryos. Riddle (1923) believes that both abnormalities and twins owe their origin to alterations of the developmental rate, or perhaps the metabolic rate at various and unequally susceptible developmental stages. The possible reason for duplication by division of a single blastodisc may be due to increased or decreased gas concentrations. Sturkie (1946) found duplication in a single blastodisc by hypothermia of the chicken prior to gastrulation of the embryo. Another possible cause of twinning is multiple blastodiscs on one yolk (Krizenecky et al., 19S8). In the present case of twins on a single yolk the twins were normal in external appearance and had circulation on separate areas of the yolk sac (Figure 1). As is seen in Figure 2, chick B was
RESEARCH NOTES
FIG. 2. Chick A was larger than its twin B, and A also had flushed appearance to its left side. comparison of chick size and were not the shells from which the chicks hatched. On opening the body cavities, the yolk sac was found attached to each of the twin's small intestines. Unfortunately the twins were destroyed before their sex or weight was determined. The egg producing the twins was part of a test hatch of seven hundred and twenty eggs that were used to determine effect of commercial levels of malathion application for parasites on chicken hatching eggs. The egg in which the twins were found was part of a control group which was dipped in tap water at 68°F. for four seconds after being held three days in storage prior to treatment. The flock from which these eggs were obtained was an inbred cross in their tenth month of production. All test groups were set in one Jamesway 252 A. The incubation temperature was main-
tained between 99° -100° F.; the wet bulb temperature was maintained between 8 4 ° - 8 7 ° F. In summary, when unhatched eggs were broken out after 21 days of incubation, one egg was found to contain two completely formed chicks developed separately on one yolk. Unfortunately, the twins were destroyed after preliminary observations were made. REFERENCES Byerly, T. C , and M. W. Olsen, 1934. Polyembryony in the domestic fowl. Science, 80: 247-248. Krizenecky, J., J. Sajner and R. J. Vancikova, 1958. A case of a hen yolk with seven blastodiscs. Poultry Sci. 37: 512-514. Levi, W. M., 1941. The Pigeon, R. L. Bryan Co., Columbia, South Carolina. P. 176. Newman, H. H., 1923. Twin and triplet chick embryos. J. Hered. 3 1 : 371-378. Riddle, O., 1923. On the cause of twinning and abnormal development in birds. Amer. J. Anat. 32 : 199-252. Sturkie, P. D., 1946. The production of twins in Gallus domesticus. J. Exp. Zool. 101: 51-64.
NEWS AND NOTES (Continued from page 886) 9) It is important that research be continued on the factors affecting sex determination in the offspring because of its economic importance.
10) Standardization of the methods of calculating and expressing fertility results in artificial insemination is absolutely necessary to permit com-
(Continued on page 893)
Downloaded from http://ps.oxfordjournals.org/ at University of Cambridge on May 24, 2015
FIG. 3. The single chick on the left demonstrates the difference in size of a single chick and the twins at approximately the same stage of development.
JACKSON
Hy-Line Poultry Farms, Des Moines, Iowa (Received for publication November 10, 1964)
FIG. 1. Two normal chicks having developed on one yolk to a late stage of incubation. The twins are attached to the yolk sac at widely separated points. slightly smaller than its twin A. The skin of the chick A was flushed in appearance. Figure 3 shows the difference between a normal chick on the left of the same hatch which died approximately the same time as the twins on the right (all eggs set were 20 ounces per dozen or greater). The shells in the background of Figure 3 were used for a
887
Downloaded from http://ps.oxfordjournals.org/ at University of Cambridge on May 24, 2015
In the course of breaking out unhatched and dead embryos after 21 days of incubation, two chicks were found to have developed on one yolk to a late stage of incubation before dying. Both Tannreuther (1919) and Newman (1940) state that complete twins on a single blastoderm are extremely rare. The phenomenon of a single yolk egg producing twins was reported in pigeons by Levi (1941). The incidence of partial duplication in the chicken as found by Byerly and Olsen (1934) under natural conditions was 0.142 percent in one breed and 0.076 percent in another, with an average of 0.111 percent. These figures were obtained from a study of over 100,000 hatched chicks and embryos. Riddle (1923) believes that both abnormalities and twins owe their origin to alterations of the developmental rate, or perhaps the metabolic rate at various and unequally susceptible developmental stages. The possible reason for duplication by division of a single blastodisc may be due to increased or decreased gas concentrations. Sturkie (1946) found duplication in a single blastodisc by hypothermia of the chicken prior to gastrulation of the embryo. Another possible cause of twinning is multiple blastodiscs on one yolk (Krizenecky et al., 19S8). In the present case of twins on a single yolk the twins were normal in external appearance and had circulation on separate areas of the yolk sac (Figure 1). As is seen in Figure 2, chick B was
RESEARCH NOTES
FIG. 2. Chick A was larger than its twin B, and A also had flushed appearance to its left side. comparison of chick size and were not the shells from which the chicks hatched. On opening the body cavities, the yolk sac was found attached to each of the twin's small intestines. Unfortunately the twins were destroyed before their sex or weight was determined. The egg producing the twins was part of a test hatch of seven hundred and twenty eggs that were used to determine effect of commercial levels of malathion application for parasites on chicken hatching eggs. The egg in which the twins were found was part of a control group which was dipped in tap water at 68°F. for four seconds after being held three days in storage prior to treatment. The flock from which these eggs were obtained was an inbred cross in their tenth month of production. All test groups were set in one Jamesway 252 A. The incubation temperature was main-
tained between 99° -100° F.; the wet bulb temperature was maintained between 8 4 ° - 8 7 ° F. In summary, when unhatched eggs were broken out after 21 days of incubation, one egg was found to contain two completely formed chicks developed separately on one yolk. Unfortunately, the twins were destroyed after preliminary observations were made. REFERENCES Byerly, T. C , and M. W. Olsen, 1934. Polyembryony in the domestic fowl. Science, 80: 247-248. Krizenecky, J., J. Sajner and R. J. Vancikova, 1958. A case of a hen yolk with seven blastodiscs. Poultry Sci. 37: 512-514. Levi, W. M., 1941. The Pigeon, R. L. Bryan Co., Columbia, South Carolina. P. 176. Newman, H. H., 1923. Twin and triplet chick embryos. J. Hered. 3 1 : 371-378. Riddle, O., 1923. On the cause of twinning and abnormal development in birds. Amer. J. Anat. 32 : 199-252. Sturkie, P. D., 1946. The production of twins in Gallus domesticus. J. Exp. Zool. 101: 51-64.
NEWS AND NOTES (Continued from page 886) 9) It is important that research be continued on the factors affecting sex determination in the offspring because of its economic importance.
10) Standardization of the methods of calculating and expressing fertility results in artificial insemination is absolutely necessary to permit com-
(Continued on page 893)
Downloaded from http://ps.oxfordjournals.org/ at University of Cambridge on May 24, 2015
FIG. 3. The single chick on the left demonstrates the difference in size of a single chick and the twins at approximately the same stage of development.