Embryonic diapause

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Embryonic diapause is a reproductive strategy used by close to 100 different mammals in seven different orders. In embryonic diapause, the embryo (blastocyst) does not immediately implant in the uterus, but is maintained in a state of dormancy. No development takes place as long as the embryo remains unattached to the uterine lining. As a result, the normal gestation period is extended, sometimes up to a year. ^[1] ^[2] While much of the molecular regulation involved in activating dormant blastocysts has been characterized, little is still known about entry into diapause, and the conditions which enable a blastocyst to remain dormant.

Some mammals that undergo embryonic diapause include rodents, mustelids (e.g. badger), and marsupials, (e.g. kangaroo). Some groups only have one species that undergo embryonic diapause, such as the roe deer in the order Artiodactyla. ^[3]

1 Purpose
2 Types
- 2.1 Facultative diapause
- 2.2 Obligate diapause
3 Remarks
4 References

[edit] Purpose

Mammals use embryonic diapause to time the birth of their offspring for favorable metabolic and/or environmental conditions. Reproduction has a large energy cost and it is to a female's benefit to have ideal conditions (e.g. available food, mild weather, not before previous offspring have been weaned) to ensure the survival of her offspring before giving birth. [4] [5]

[edit] Types

Two types of embryonic diapause have been identified.

[edit] Facultative diapause

Facultative diapause is a mechanism that is associated with metabolic stress, normally lactation. If a female copulates while still lactating for her original offspring, the sucking stimulus will cause the embryos to enter into diapause. This is known to occur in some rodents, insectivores and marsupials. ^[6] Facultative diapause can also be referred to as facultative arrest.

[edit] Obligate diapause

Obligate diapause is a mechanism that allows mammals to time the birth of their offspring for favorable environmental conditions. This mechanism occurs as a regular part of the reproductive cycle in many of the pinnipeds, mustelids, ursids, armadillos, one fruit bat and the roe deer. ^[7] ^[8] Obligate diapause can also be referred to as obligate arrest.

[edit] Remarks

Embryonic diapause can also be referred to as delayed implantation.

Diapause is a term used to refer to the temporary halt in development at an early life history stage in insects and plants.

[edit] References

↑ J.C. Daniel, Jr. (1970). "Dormant embryos of mammals". BioScience 20: 411-415.

↑ Flavia L Lopes, Joëlle A Desmarais and Bruce D Murphy (2004). "Embryonic diapause and its regulation". Reproduction 128: 669-678.

↑ J.A. Desmarais, V. Bordignon, F.L. Lopes, L.C. Smith and B.D. Murph (2004). "The escape of the mink embryo from obligate diapause". Biology of Reproduction 70: 662-670.