SAM the Koala was euthanized last Thursday.
When bushfires were raging the state of Victoria earlier this year, the koala became famous after video footage was released showing her drinking water from a fire fighter’s bottle.
But the four-year-old never recovered from surgery last Thursday to remove cysts associated with Urogenital chlamydiosis, a disease which affects about 50 percent of Australia’s koala population.
Jennifer Marohasy BSc PhD is a critical thinker with expertise in the scientific method.
Jennifer,
Is chlamydia a threat to the long term survival of koalas?
Yes, John A.
It causes sterilization of the female (as in humans if not treated) Only two koala populations I know of do not have it. On French Is in Vic and on Kangaroo Is off SA. A serious threat, it threatens to wipe koalas out of regions. Was on Phillip Is recently, and apparently they are trying to quarantine the areas of affected animals (with fencing) to protect the clean ones. I did not ask if the clean ones had been imported from French Is. Could have been. Anyone have more info?
Thanks for the information re the koalas!
Hi Ann
I am no expert on koalas, but if they live as long as their distant relation, wombats (20 years and have one young per year from about age 3), then a 4year old koala female with advanced chlamydia indicates she probably would have been lucky to rear even one joey before becoming infertile. It is a serious threat to regional populations, but not to the species yet, as there are clean stocks which can be re-introduced later to areas which become wiped out.
That was what I was referring to re the Phillip Is population. Have they reintroduced clean stock (from nearby French Is) before the diseased stock dies out? If so, why?
Now that we’re on the subject of koalas, here’s my stoopid question of the day: What’s the genetic survival advantage of Koalas having a completely split brain? Or is it two mini-brains?
Do they fall out of trees frequently, and injure their heads in the process? If one of the mini-brains is severely injured in a fall, can the other one carry the full load?
To Larry,
” Interestingly, the two cerebral hemispheres are not functionally equivalent. For example, left or right-handedness reflects an asymmetry for fine motor ability, and certain visuospatial skills are more highly developed in the right hemisphere. In over 95% of right-handers, the left hemisphere is dominant for language, while in left-handers either left hemisphere dominance or bilateral language capabilities are the commonest findings.
The major connection between the two cerebral hemispheres is the corpus callosum, which integrates the functions of the right and left sides. If this structure is completely divided, the results are bizarre; a right-handed person is unable to name aloud objects felt with the left hand (anomia), cannot read aloud text presented only to the left side of the visual field (hemialexia), and cannot execute with the left hand actions described by an examiner (apraxia). Apraxia usually diminishes within in a few months, whereas the hemialexia and unilateral anomia persist for years.
However, partial or complete surgical section of the corpus callosum can benefit epileptics who experience ‘drop attacks’, when they suddenly fall to the ground with a sudden jerk (myoclonic seizure), by becoming stiff (tonic seizure) or by becoming floppy (atonic seizure). About 50% of children who undergo this procedure have a reduction in the frequency and severity of their seizures. One study of patients who had been operated on at least two years previously indicated that complete division of the corpus callosum is more effective than partial division, and that children derive greater benefit from the procedure than adults”
http://www.allaboutmedicalsales.com/medical_briefings/cerebral_cortex_090505.html
Ann,
This paragraph from the Wikipedia article on koalas was the motivation for my question. Sorry for not completing the thought at the time of my first posting.
The brain in the ancestors of the modern koala once filled the whole cranial cavity, but has become drastically reduced in the present species, a degeneration scientists suspect is an adaptation to a diet low in energy.[14] One of the smallest in marsupials with no more than 0.2% of its body weight,[15] about 40% of the cranial cavity is filled with cerebrospinal fluid, while the brain’s two cerebral hemispheres are like “a pair of shrivelled walnut halves on top of the brain stem, in contact neither with each other nor the bones of the skull. It is the only animal on Earth with such a strangely reduced brain.”
The small brain size is interesting, but not extraordinary. We can’t all be dolphins or humans. The thing that grabbed my attention was the total physical separation of the two hemispheres. I gather that koalas don’t even have a corpus callosum. Because of this, koalas probably have less epilepsy than humans. But I don’t think that that is the raison d’être for this remarkable evolutionary twist. What do you think?
Probably this is an area in neuroscience in its own. What I have read is that whales have big brains is because they eat/or move much, so if koalas don’t move or eat much they might have developed a smaller brain???? Very interesting issue btw…