parthenogenesis discovered in unfertilized eggs of lecture 10-14-13.pdf · parthenogenesis...

ParthenogenesisDiscovered in Unfertilized Eggs of

Coturnix chinensis,the Chinese Painted Quail

C. D. McDaniel and H. M. Parker

Poultry Science Department, Mississippi State University Mississippi State, MS 39762

IntroductionParthenogenesis

Parthenogenesis is defined as:

embryonic development of theUNFERTILIZED egg.


Naturally occurring parthenogenesis is common in lower order animals, especially invertebrates like insects.

For example, the male drone honeybee results from the queen bee’s egg not being fertilized.

“Scientists confirm shark's ‘virgin birth’Pup carried by Atlantic blacktip shark contained

no male genetic material”

“Scientists have confirmed the second case of a "virgin birth" in a shark. In a report in The Journal of Fish Biology, scientists said DNA testing proved that a pup carried by a female Atlantic blacktip shark in the Virginia Aquarium & Marine Science Center contained no genetic material from a male.”Matthew D. Potenski / Institute for Ocean Conservation Science

MSNBC, Associated Press, October 10, 2008


Naturally occurring parthenogenesis is also present in vertebrates like fish, amphibians, reptiles and birds.

Some whiptail lizard populations in the southwestern US contain only females that reproduce by parthenogenesis.


In 2006, a 6 foot long Komodo dragon at the Chester Zoo in England made world news when she produced viable offspring by parthenogenesis.

Avian Parthenogenesis

Natural parthenogenesis in the Beltsville Small White (BSW) turkey was first reported by M. W. Olsen and S. J. Marsden in 1954.

– About 14% of the unfertilized BSW turkey eggs developed.

– The majority of development consisted only of an unorganized sheet of cells very similar in appearance to normal embryonic mortality during the first 48 hr of incubation.

Using this same BSW line of turkeys after decades of genetic selection for parthenogenesis, Cassar et al.(1998) found that about 30% of all unfertilized eggs developed with approximately .3% actually hatching.

In modern commercial turkey lines about 4% of unfertilized eggs at lay contain parthenogenic embryos (Bakst et al., 1998).

Avian ParthenogenesisAll parthenogens that hatch are male.

Parthenogens are almost perfect clones of their mother.

A parthenogen’s mother will accept his donor organs because his genetic makeup is almost the same as hers.

Fowl pox virus will increase the incidence of parthenogenesis in chickens and turkeys.

Only the Cornish breed of chickens exhibits much parthenogenesis (4%).


Unfertilized turkey egg incubated 8 days and showing no embryonic development.

Germinal Disc


Extraembryonic membrane development in unfertilized turkey eggs


Embryonic blood development in an unfertilized turkey egg


14 day old turkey parthenogenic embryo

Avian ParthenogenesisIf hens are inseminated with sperm that no longer contain active genetic material the incidence of parthenogenesis increases.

If turkeys are mated to chickens the incidence of parthenogenesis is not affected.

However……

About 1% of the eggs will yield chicken-turkey hybrids.

How could parthenogenesis affect the poultry industry?

A better understanding of avian parthenogenesis will further our knowledge of avian fertilization and early embryonic mortality.

– Do the mechanisms regulating the occurrence of parthenogenesis actually work against normal fertilization?

– Early embryonic mortality may sometimes be a result of abortive parthenogenesis (Cassar et al., 1998), because most parthenogenic development resembles very early embryonic mortality.

Because early embryonic mortality is higher in the first egg in a sequence (Fasenko et al., 1992) perhaps some of these embryos are again actually parthenogens.

Problems when StudyingAvian Parthenogenesis

Because of the very low incidence of turkey parthenogens that actually hatch and subsequently reproduce, thousands of eggs must be incubated and examined.

Therefore the major disadvantages for using the turkey as the model animal for studying avian parthenogenesis include:

– the time required to reach sexual maturity,– low egg production,– length of incubation,– large size of the bird (space required),– expense to maintain.

The Chinese Painted QuailCoturnix chinensis

The Chinese Painted quail is an excellent model animal for studying avian reproduction because:– It reaches sexual maturity at only 8 weeks of age,– has an egg production between 45 and 80%,– requires only 17 days of incubation,– weighs only 50 grams,– and is very inexpensive to maintain (Tsudzuki, 1994).

The Chinese Painted quail is in the same family, Phasianidae, as the chicken and is smallest of all species in the order Galliformes.

It is about half the size of its close relative, the Japanese Quail, Coturnix japonica.

The Chinese Painted Quail

Adult MaleAdult Female

Amount of Research about the Chinese Painted Quail

Since 2000, over 25 peer reviewed research articles have been published using the Chinese Painted quail, because of its small size as well as ease and expense to maintain .

However, because the Chinese Painted quail has not been studied extensively much remains to be discovered.

Objectives

1) To determine if unfertilized Chinese painted quail eggs will develop embryos upon incubation and the resulting size of the embryo.

2) To determine if position of an egg in a clutch affects the occurrence of parthenogenesis.

Materials and Methods

With the initial appearance of some adult plumage at 4 wk of age, Chinese Painted Quail hens were separated from males.

At 8 weeks of age, 300 hens were placed in individual 16 x 25 cm laying cages.

Eggs were individually labeled, collected daily and stored from 0 to 3 days at 20 C before being incubated for 10 days at 37.8 C and 50% relative humidity.

The first 20 eggs laid by each hen in 90 days were examined for parthenogenesis.

After 10 days of incubation, each egg was candled and opened under an illuminated magnifying lamp.

The germinal disc was examined for gross embryonic development.

Those germinal discs exhibiting development were measured across the greatest width to the nearest mm.

To determine the amount of embryonic development, the size of the 145 parthenogens obtained were compared to the size of the blastoderms or germinal discs of:

– fresh fertilized eggs (111) from hens with males – fresh infertile eggs (183) and– 10 d incubated infertile eggs without parthenogens (273)

Resultsfor

Objective 1: Incidence of Parthenogenesis and Size of Parthenogens

Germinal Disc of Fresh Fertilized Chinese Painted Quail Egg

Fresh Fert 4mm-1-3 from 1/12/07 Greatest width is 4mm

Area opacaArea pellucida

PeriblasticRing

Germinal Disc of Fresh Infertile Egg

Fresh Infert 3mm 230-3 from 1/12/07 Greatest width is 3mm

Vacuole

Infertile Egg Incubated 10 Days Without Parthenogenic Development

Infert 011607 2mm 222-2 Greatest width is 2mm

Vacuole

Parthenogen from an Infertile Egg Incubated 10 Days Showing

Unorganized Irregular Development

Greatest width is 5 mm


More Organized Development



Parth 011607 4mm 85 2nd egg

PeriblasticRing


Very Organized Development



Parth 040207 3mm 149

PeriblasticRing

00.5

11.5

22.5

33.5

44.5

Fresh Fertile Fresh Infertile 10 dayIncubated

Infertile

10 dayIncubated

Parthenogen

Ger

min

al D

isc

(mm

)Germinal Disc Size of Fresh Fertile and

Infertile Eggs as well as Incubated Infertile Eggs With and Without Parthenogens

C

BA

D

P<.0001

Hen Population Distribution forPercentage of Eggs Containing a

Parthenogen

0

2

4

6

8

10

12

14

0 10 20 30 40 50 60 70 80 90 100

Perc

enta

ge o

f Hen

Pop

ulat

ion

Unfertilized Eggs Containing Development (%)

mean=4.8%sd=12.8n=298 hens

73% of hens never produced a parthenogen27% of hens produced a parthenogen

Hen Population Distribution forParthenogen Width

05

101520253035404550

1 2 3 4 5 6

Perc

enta

ge o

f Hen

Pop

ulat

ion

Parthenogen Width (mm)

mean=3.70 mmsd=.90n=81 hens

Resultsfor

Objective 2: Position of egg in clutch and Parthenogenesis

Percentage Parthenogenesis and Clutch Position

0

1

2

3

4

5

6

7

8

0 1 2 3 4 5 6

% P

arth

enog

enes

is

Position of Egg in Clutch

B

BC

A

BC

BC

C

Summary

27% of the hens exhibited parthenogenesis with about 4% of the eggs containing parthenogens.

After 10 days of incubation, parthenogen width ranged from 1 to 8mm with the average parthenogen being 4 mm wide which is:– about the same size of the fresh fertile eggs embryo– twice the size of the infertile eggs germinal disc

The incidence of parthenogenesis in first of sequence eggs was double that of second of sequence eggs with a slower cubic decline in parthenogenesis in subsequent eggs of a sequence.

Conclusions

The Chinese Painted Quail does exhibit an abortive form of parthenogenesis.

Because clutch position of an egg affects the occurrence of parthenogenesis, it is very possible that early embryonic mortality of normal fertilized eggs may be influenced by parthenogenesis.

Further research is being conducted to determine if hens exhibiting parthenogenesis have altered fertilization and elevated early embryonic mortality.

parthenogenesis discovered in unfertilized eggs of lecture 10-14-13.pdf · parthenogenesis...

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