So as it's not too complicated I've kept it brief
A good place to start is the question what makes a marsupial a marsupial? The obvious answer is the pouch, but not all marsupials have a permanent pouch, and some don’t have a pouch at all! The main thing that makes a marsupial different to eutherian (placental) animals is the reproductive system and method.
(Before I go further, I’ll be using the term eutherian rather than placental as Marsupials do also use a placenta during reproduction.)
I’m not going to go into anatomy and the reproductive process in too much detail, I don’t see how knowing the shape and size of spermatozoa will be of any assistance to you, it won’t make any difference to your suggies whether you know that or not.
The male reproductive organs consist of the penis and testicles as well as the epididymides, the vasa deferentia, a prostate gland, and the Cowpers gland.
In English then, the epididymides (plural of epididymis) are tubes that are connected to the testes; the vasa deferentia which is the plural of vas deferens, are connected to the epididymides; the vasa deferentia transport sperm from the testes to the penis. The prostate gland produces a clear fluid that along with sperm makes up the semen. The Cowpers gland (or bulbourethral gland) produces ‘pre-ejaculate’ which lubricates the urethra to allow sperm to pass easily. The urethra is the tube that stretches the length of the penis to an opening at the end.
Marsupial testicles are positioned above (anterior to) the penis, unlike the eutherian mammals. The Sugar Glider testicles are positioned ‘on the belly’; they have a fine covering of fur to regulate the temperature of the testes, during warm weather they will move away from the body so that the sperm doesn’t overheat. In cold weather they are pulled close to the body by the cremaster muscle.
The Sugar Glider penis is kept in an ‘S’ shaped sheath inside the body when not erect, it is forked at the end which is known as bifurcated. Although only the end is bifurcated, the ‘split’ runs all the way up the length of the penis. Each ‘half’ has its own urethra; it was thought that this was to ensure that sperm was deposited in each of the lateral vaginae (I’ll explain shortly). “However, since macropodids have a single, uncleft penis and yet the sperm still travel up the two lateral vaginae (Tyndale-Biscoe and Rodger, 1978), this explanation does not seem to be sufficient.”
As with the male reproductive system, I’ll try and keep it brief, knowing the muscular arrangement of the uteri will not help you breed your suggies ethically nor will it make your breeding more successful.
Female Sugar Gliders have two uteri (wombs), each uterus has a cervix (opening), so that’s two cervices, and there are also two permanent lateral vaginae. Just before birth, a median vagina opens in between the two lateral vaginae through which the young is born. Although two wombs are present, there are still only two ovaries; each womb is connected to only one ovary. The oestrus cycle lasts about 30 days in Sugar Gliders.
Most female Marsupials have a pouch. Some don’t have one at all, some only develop a pouch when they are pregnant and some just have a pouch made of matted fur. Sugar Gliders have a permanent pouch on their belly and inside are 4 teats.
The stage at which a joey is born is equivalent to a eutherian foetus, completely un- developed, the joey’s eyes aren’t even developed at this stage, nor are the ears, the heart, lungs or jaw. They are born with the skills to navigate from cloaca to pouch, and to latch on to a nipple. If the joey doesn’t make it to the pouch then it will die.
Once in the pouch the joey will find a nipple and attach itself to it, where it will suckle and develop in the pouch for around 60 days. After about 40 days in the pouch the joey will release the nipple for the first time. There is a common belief that joeys remain attached for the entire 60 days, and a little after, but this is NOT the case. After about 40 days, the joey will begin to move around more in the pouch, single joeys have even been known to swap sides.
The really interesting thing about marsupials is their capability to suckle different aged joeys at the same time. The marsupial milk changes in composition as the joey grows, each nipple can produce a different stage of milk. This is known as Asynchronous Concurrent Lactation.
Alongside the short oestrus cycle, asynchronous concurrent lactation allows gliders to breed rapidly to replace any losses.
Captive Sugar Gliders will breed all year round provided the diet is adequate; in the wild Sugar Gliders breed seasonally, the breeding coincides with an increase of protein (insects) during the nursing to weaning stages.
© Shropshire Exotics 04/11/07
