A presentation on reproduction in kangaroos including embryonic diapause, tyranny of the estrous cycle, and forelimb vs hindlimb development

1. Saundra Swain
Image: images.nationalgeographic.com

2.  Bifurcated (paired) reproductive
tract
 Lateral vaginae
 Medial vaginal canal
 (Feldhamer et al 2007)
Image: palaeo.gly.bris.ac.uk

3.  Kangaroo Choriovitelline placenta
 Eutherian chorioallantoic placenta
 Less villi – less surface area- less gas exchange-
less gestation time
 (Feldhamer et al 2007)
Kangaroo
Eutherian
Image: (Feldhamer et al 2007).

4.  Eutherian: progesterone creates
negative feedback loop inhibiting
new estrous cycle
 (Sharman 1970)
Image: www.ansci.wisc.edu

5.  Kangaroo: no negative feedback loop does not
inhibit estrous cycle. Short gestation
 (Sharman 1970)
Image: www.ansci.wisc.edu

6.  Except grey kangaroo
 Delayed implantation
 Egg arrests in blastocyst stage (100
cells)
 Can be pregnant, have young in
pouch and young at foot at same
time
 (Renfree and Shaw 2000, Dawson 1995)

7. Image: greatunansweredquestions.blogspot.com

8.  Temporary reduced egg shell
 Lasts 2/3 of gestation
 Prevents mother’s immune system
from rejecting egg
 (Dawson 1995)

9.  Kangaroos have short gestation and longer
lactation when compared to Eutherians
 Kangaroos develop more in pouch
 (Dawson 1995)
Image: www.kangaroocenter.com Image: upload.wikimedia.org

10.  Can produce 2 different types of
milk synchronously
 Separately controlled mammary
gland and teat for young in pouch
than for young at foot
 (Krockenberger 1996; Joss et al 2009; Nicholas 1988)

11.  Different composition of milk in each teat
 Four phases of milk production
 (Krockenberger 1996; Joss et al 2009; Nicholas 1988)
Image: 1.bp.blogspot.com

12.  Forelimbs must develop quickly to be usable
for climb to pouch
 Hindlimbs have more time to develop
 Forelimbs show much less diversity
 Hindlimbs show much more diversity
 (Cooper and Steppan 2010).

13. Image: brattahlid.tripod.com Image: australianstamp.com

14.  Cooper, James W., and Scott J. Steppan. 2010. Developmental constraint on the
evolution of marsupial forelimb morphology. Australian Journal of Zoology 58: 1-
15.
 Dawson, Terence J.. 1995. Kangaroos: Biology of the Largest Marsupials. Cornell U.
P., Ithaca, New York.
 Feldhamer, George A., Lee C. Drickamer, Stephan H. Vessey, Joseph F.
Merritt, and Carey Krajewski. 2007. Mammalogy: Adaptation, Diversity, Ecology.
Third ed. The Johns Hopkins U. P. Baltimore, Maryland.
 Joss, Janice L., Mark P. Molloy, Lyn Hinds, and Elizabeth Deane. 2009. A
longitudinal study of the protein components of marsupial milk from birth to
weaning in the tammar wallaby (Macropus eugenii). Developmental and
Comparative Immunology 33: 152-161.
 Krockenberger, Andrew K. 1996. Composition of the milk of the
koala, Phascolarctos cinereus, an arboreal Folivore. Physiological Zoology 69(3): 701-
718.
 Nicholas, Kevin R.. 1988. Asynchronous dual lactation in a marsupial, the tammar
wallaby (Macropus eugenii). Biochemical and Biophysical research Communications
154(2): 529-536.
 Renfree, M.B., and G. Shaw. 2000. Diapause. Annual Review of Physiology 62: 353-
375.
 Sharman, G.B.. 1970. Reproductive physiology of marsupials. Science 167(3922)
1221-1228.