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Python reproductive physiology

by Winslow Murdoch

My recollections having attended Dave Barkers lecture

At the Mid Atlantic show, I had the chance to hear a great lecture (by Dave Barker) on reproductive biology of pythons. He had great slides of actual developing (but dead) eggs, ovarian function, and anatomy. Unfortunately, all the pictures came as a direct cause of death by natural causes to various desirable pythons, but when you have over a thousand snakes, s#%* happens! I also learned a few pearls that some of you might find interesting.

What follows is my recollection of the presentation, though my terminology is a bit rusty...bear with me

  1. the reproductive effort for a given cycle is predetermined two years before a given cycle. as a result, if a female was ill, or stressed two years ago, and now has a small clutch, this would be totally explainable, even if the animal had since gained lots of weight and looked huge, it still might have only a few eggs/babies. Conversely, a thin/ dehydrated/ stressed animal may have been fat two years ago, and now drops a huge clutch of eggs/babies. this might stress her out and lead to her death, but more commonly, she will deposit a large number of infertile small unfertilized ovum (slugs), and two years later, regardless of how well she ate, etc., she will have a small clutch. Perhaps if you extrapolate this, you should give the third year off to maximize the fecundity, and maternal health of your animals


  2. Sexually mature male pythons produce live active motile sperm in large quantities year round. This occurs as early as 9 months of age, and continues throughout their lives. they do go into a cycle when cooled that induces the testes to increase in mass, but if they are paired with a receptive cycling female at any time of the year, they should still be able to sire good offspring. therefore, the females state, and cycling is the most important factor determining breeding success.

  3. The paired male copulatory organ only acts as a surface conduit for the inseminating sperm to swim over to the female. there is no hollow tube etc. the hemipenes usually bifurcate at the tip. there is a shallow groove that runs along the length of the hemipene, and also bifurcates at the tip (the spermatic sulcus). the sperm swim and divide up, and follow one of the two end grooves, which sit up in the female's cloaca, and end at each opening of the females paired oviducts. they then swim up to the oviduct cephalad (head directed) end, and stay there for insemination. this can occur weeks or even months later, but is more successful if the mating occurred a few weeks before ovulation.

  4. the ovaries are like a thin ribbon of tissue that runs along either side, about one fifth of the snakes length. the follicles for the next years mating are predetermined, and start very slow growth two years before that season. on any given season, predetermined follicles will start vitellogenesis. stored fat is mobilized from the coelomic fat bodies in the peritoneal cavity, into the blood stream, and is taken up by the liver. the liver converts this fat into vitellagin? and albumin proteins. These are then carried by the blood stream to the follicles. Follicles start off the size of tiny amber raisins (tapioca), and grow within the ribbon of tissue.

  5. If the female was under nourished, dehydrated, ill, or in any way stressed during vitellogenesis, she will either arrest the process (if stressed early in the cycling attempt), or will produce most or all slugs at the time of egg laying. The follicles will never attain the viable size of a full term viable egg, and will be ovulated too small and sometimes too early for them to develop further. If healthy, the ovary has these huge full term egg sized follicles that are like water melons in panty hose. the ovarian tissue is stretched as thin as paper.

  6. Ovulation occurs when the ovum tear out of the "panty hose", and settle free in the peritoneal cavity. the snake then goes through a "regurgitation like sequence" that starts at the tail, and works the ovum forward (cephelad) into the paired lateral (side) positioned oviductal funnel structures that open up facing the tail and funnel the ovum up toward the snakes "chest". The oviducts then each immediately take a 180 degree bend, letting the ova drop caudally (towards the tail) into first the right , then the left oviduct in an alternating fashion, until all the ovum have been put into their new panty hose like structures. as the ovum pass into the oviducts, they are met by the stored sperm that then inseminate/fertilize them. this whole ovulation process takes between 8-24 hours, and has been described as lumping (as there are two sets of ovum passing each other in opposite directions at the same time). The female should be left alone while lumping!

  7. in the oviducts, eosinophil white blood cells surround the ovum, and scamper all along and around them, depositing a trail of protein and calcium substances that makes up the shell (like spiders webbing an egg case). once the shells are fully formed, the proper term for these developing babies is an egg.

  8. python embryos are well developed by the time they are laid. as a result, they have high oxygen demands that outstrip their mothers blood supply's ability to meet. any delay in egg deposition (into the life giving oxygen in the nest pile) causes the egg to die (i.e., egg bound females never have the eggs salvaged that aren't laid, as they suffocate almost as soon as the last normally delivered egg has passed). any inadvertent laying of the eggs in the water bowl will also cause the egg to drown in a matter of a minute or two. I hope this is informative to some of you, and not too pseudo scientific or esoteric.

Probing issues were also discussed at the lecture, and I will also include some of my own observations.. Interestingly, the anatomy of males and females is not that different. Both have paired, rather large musk (or scent) glands in the base of the tails. These have a duct that goes to a papilla opening just to the mid-line of the opening of the "sac" in females, and inverted hemipene sac in males. The papilla points in toward the mid-line at an angle, and has an opening the size of a pin. This would be essentially impossible to perforate while probing, even if you tried. Males inverted paired hemipene sheaths run varying lengths (eight to fifteen subcaudal scale equivalents) down inside the base of the tail, and end in a blind sac. These sacs then have a fragile connective tissue strand that attaches their ends to the vertebral column near the tip of the tail. Females have a similar sac-like structure, but it ends in a much shallower blind cavity that is rarely more than three to five subcaudal scale equivalents deep. There are also similar connective tissue strands that end up in the tail tip. During ecdesis, the inner lining of these hemipene, and analogous female shallow sacs are shed. The resultant cast is much more obvious in males, and is actually one way to sex your snake without probing. They can sometimes be found floating in the water bowl, and have been mistaken for tapeworm segments by surprised novice herpetoculturalists (like me every time I see one). At times, this cast fails to shed, and it forms a plug that fills the hemipenal orifice to the cloaca. This gets mixed with secretions from the scent glands, and takes on a brownish color. It can often be seen coming out of the cloaca, from the direction of the tail. It can be manually pulled out of the hemipenal sac, and has therefore been given the improper but descriptive term "sperm plug". Probing requires that any sperm plugs be removed, although their presence almost guarantees a male, unless it is mistaken for something else. A clean or sterile probe is lubricated with sterile water, saline, or surgi-lube water soluble medical lubricant (which has been noted to be spermicidal, but likely not a clinically significant cause of infertility). The probe is then inserted under the cloacal vent scale, and then directed into the cloaca, and down either side of the vent toward the tail. In males, you expect to have the probe slip into the sac, and progress unobstructed for at least five, but commonly nine to fifteen subcaudal scale equivalents. In females, the average distance is three to five. Probing distances are largely species dependent. One common mistake is to use too small a probe, with just a little too much force. The sac is easily punctured in this scenario, and a female can easily be mis-probed as male. Occasional blood may be found on withdrawing the probe. This can be from a puncture of the sac, or can happen without other serious discernible trauma. Punctured sacs generally heal without a problem, but rarely can lead to cloacitis, and infections which can be fatal.

Babies can also be popped accurately, especially in the first two weeks of life. At this young age, they do not have the muscular tone to resist popping. Older snakes can still sometimes be accurately sexed with this method but you are only sure if you have a male when the hemipene pops out. If itís not an obvious male, you still need to probe it as it could be a tense, non popping male or a female. The technique requires two hands. One hand holds the base of the body just above the cloaca, and the other hand is held such that the thumb pad sits on the ventral aspect of the tail, just caudal to the vent, with the thumb tip pointed up toward the vent. Gentle firm pressure is exerted in a rocking motion up towards the vent (squeezing toothpaste), and the scent gland papillae will protrude. Just next to these, and often looking like the same structure, you will either find a protruded hemipene, or the hemipenal sac orifice, which has a little vascular red rim to the tip. The females also protrude their scent papillae, but you donít see the hemipene, or the red tip to the bulge. Sounds easy, but itís not, and in delicate snake neonates like green tree pythons, it has been associate with severing the vertebrae, and later causing "kinky tail" syndrome. Thatís all for now. Sorry for all the med speak and descriptions, but this is snake lingo at the non professional level, and if you are into it, it goes with the territory.


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