The Sweet Sugar Glider – Petaurus breviceps

Sugar Glider, climbing down from a plant

Image via Wikipedia

– Scientific Classification –

The sugar glider is a small, arboreal marsupial that can be kept as a pet. They are native to New Guinea, Australia, Tasmania, and neighboring Indonesian Islands. Sugar gliders are only about 5 or 6 inches long in body with their tail being around the same length. This species of marsupial actually does have a pouch for the young. The skin membrane on each side of their body that aids in gliding, is called the patagium (also found in bats).

Gliders are a social animal (so having at least 2 is a necessity) that can live up to 15 years. Being marsupials, they are capable of embryonic diapause (see related articles) and, in 3 or 4 separate litters a year, can have 1-3 joeys, despite the mother only having 2 teats. For breeders, unsuspecting owners and wild populations, this sort of increase in numbers can be a bit of a shock. July – November is the “normal” breeding period so that young are reared during peak food availability in spring and summer. The joeys spend around 2 months in the pouch then another month in the nest.

Gliders can be finicky little things. The first time I heard of a sugar glider, I was watching Emergency Vets (Dr. Fitzgerald was the man) on Animal Planet and one was brought in in pretty bad shape. Sugar gliders are expensive. Upwards of $150 just from a pet store ($300-ish from a breeder). Then, necessities like the cage and toys are also costly. Gliders are insectivorous and also feed on gum and sap from acacia and eucalyptus trees, adding to the difficulties of captive care. Their scent glands are pretty constantly in use, making sugar gliders smelly little things. If you like sleep, this is probably not the right pet for you:

Dang nocturnal animals. So this post won’t be just bashing them in a captive aspect, here are some wild gliders leaving the nest:

Aaaaaand doing a little bit of gliding:

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Sources:

  1. Wikipedia – Sugar Glider
  2. Sugarglider.com
  3. Unique Australian Animals
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Maintaining 3 Joeys – Marsupial Lactation and Embryonic Diapause

Tammar Wallaby (Macropus eugenii)

Image via Wikipedia - Tammar Wallaby (Macropus eugenii)

An interesting fact that gets glossed over, is the number of young a mother marsupial can maintain at once. In the case of a kangaroo or the Tammar Wallaby, mothers can have up to 3 young in 3 completely different stages. This is due in part to their lactation (producing milk) being so variable. Embryonic diapause (the name for this reproductive strategy wherein development is delayed at the blastocycst stage) is one of my favorites, and I even wrote a paired paper on it  which included the hormonal aspects of delaying embryonic development for my college Mammalogy course. There are two types of embryonic diapause, obligate and facultative. “Obligate or seasonal diapause is more frequent in mammals with a single litter per year while facultative diapause is more frequent in mammals with multiple litters per year” (#2).

via Illinois.edu - Newborn Wallaby attached to nipple (provided by K Nicholas, University of Melbourne)

There are three phases of lactation in marsupials. “Phase 1 is actually comparable to mammary development during gestation in eutherian mammals. Phase 2 is the early period of milk secretion when the joey is still in the pouch. Phase 3 coincides with the joey beginning to leave the pouch” (#1). Milk secretion usually occurs about 24 hours after birth of the joey. While a newborn may suckle one of the four teats, an older joey out of the pouch may be using another of the four teats. The unused nipples regress due to lack of stimulation and the two being suckled develop independently. Early lactation (phase 1- 2) milk composition is about 50% carbohydrate and low in lipids, followed by low carbs and up 60% or more lipid in phase 2-3. Protein levels are relatively constant throughout lactation.

“Shortly after the first joey is born, the mother mates again. This new embryo stays at an early dormant stage of development until the first joey begins to leave the pouch. The decline in suckling stimulus associated with the first joey leaving the pouch allows the second joey embryo to develop, be born and enter the pouch” (#1). This then frees the uterus and allows the mother to mate again and develop a third joey. In the event of disaster, Kangaroos can quickly repopulate during a poor season thanks to being so consistently pregnant. While the Tammar Wallaby is the most studied individual, other species that practice embryonic diapause include rodents, badgers, bats and minks. About 100 species use this reproductive strategy.

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Sources

 

  1. Illinois.edu : Lactation – Marsupials
  2. My group project on embryonic diapause

 

  • Group, Gale. 2000. Whatever that is, it’s scary – tammar wallaby behavior. Find Articles – Science News. Accessed Nov. 9, 2010. { http://findarticles.com }
  • Lopes, F.L., J.A. Desmarais, and B.D. Murphy. 2004. Embryonic diapause and its regulation. Reproduction 128(6):669-678.
  • Renfree, M.B., G. Shaw. 2000. Diapause. Annual Review of Physiology 62:353-375.
  • Sadlier, R.M.F.S, Tyndale-biscoe, C.H. 1977. Photoperiod and the Termination of Embryonic Diapause in the Marsupial Macropus eugenii. Biology of Reproduction 16: 605-608.
  • Shaw, G. 1996. The Uterine Envrionment in Early Pregnancy in the Tammar Wallaby. Reproductive Fertiliazation and Development (8): 811-818.
  • Shine, R., Brown, G. 2008. Adapting to the unpredictable: reproductive biology of vertebrates in the Australian wet-dry tropics. Philosophical Transactions of the Royal Society: Biological Sciences: 363-373.
  • WAZA. Tammar Wallaby. World Association of Zoos and Aquariums. Accessed Nov. 9, 2010 { http://www.waza.org }
  • Yamaguchi, N., H.L. Dugdale, and D.W. Macdonald. 2006 Female receptivity embryonic diapause, and superfetation in the European badger (Meles meles): Implications for the reproductive tactics of males and females. The Quarterly Review of Biology 81(1):33-48.

Corpus Callosum : The Brain Bridge

List of images in Gray's Anatomy: IX. Neurology

Image via Wikipedia

In the two preceding posts, I’ve mentioned how marsupials, monotremes, and reptiles lack a corpus callosum, so I’d like to take the time to explain what this structure is. The corpus callosum, or colossal commissure, is a part of the brain that connects the right and left cerebral hemispheres and allows for communication between the two. It is the largest white matter structure in the brain. It also happens to be absent in fish, birds, and amphibians. Some groups have a different form of cerebral connection, like marsupials with their anterior commissure. The corpus callosum aids in functions such as brachiation (swinging through tree limbs using their arms) in arboreal primates by allowing coordination of the limbs.

Agenesis of the corpus callosum is a rare congenital disorder in which the corpus callosum is partially or completely absent. Common symptoms include:

  • vision impairments
  • low muscle tone (hypotonia)
  • poor motor coordination
  • delays in motor milestones such as sitting and walking
  • low perception of pain
  • delayed toilet training
  • chewing and swallowing difficulties
  • cognitive disabilities
  • social difficulties (possibly due to impaired facial processing)
There is currently no treatment, but therapy may be beneficial. The corpus callosum is not capable of regeneration.

If you’d like to see a pretty neat episode of House MD that involves “split brain“, check out Season 5 Episode 24, Both Sides Now.

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Sources