Tuesday, January 29, 2013

Yaks and Naks

Image from http://www.all-hd-wallpapers
.com/wallpapers/animals/511035.jpg
Today, as I was once again swimming in the internet lagoon, I decided to scout out some information about yaks. Why yaks? I cannot say, but apparently, there are plenty of interesting things to note about this creature and how it is developed for its cold, highland environment.

You may already know that yaks are those woolly, mountainous beasts that resemble a mix between a cow, a bison, and a mammoth. Despite its lumbering appearance, wild yaks (Bos mutus) make a good living in their Himalayan home. They are generally solitary and will often run for miles if they sense a human approaching. However, yaks themselves are actually quite gentle in nature. If they feel threatened, a yak may make a false charge, which is much like playing the classic game of "chicken" where the yak will drift to the side at the last moment, avoiding collision.

Image from http://www.springbrook.com/
Tibetan-yak/Tibetan-yak-picture-files/royal%
20pack%20yak%20snow%20val.jpg
Such a large animal can afford this active highland lifestyle with a few adaptations. Yaks have a digestive system that runs at a higher temperature than, say, your regular cow, which allows them to burn the food that they eat in a sufficient manner. The lungs of the yak are built to hold a large capacity of air so that they can breathe (and run) at high altitudes, and their hearts are larger. Even the blood of yaks contains fetal hemoglobin, which has a greater affinity for oxygen than does regular hemoglobin when at low atmospheric pressure. The hooves of the yak are made for digging into the snow to grip firm ground beneath, which is probably why you will not see a yak tumbling down the slopes. The fur of the yak forms a dense mat on the bottom that helps to trap heat but makes the yak more susceptible to heat exhaustion in warmer climates. Yaks stay warm and dry because they have very few sweat glands.

Although I have been writing about wild yaks, domesticated yaks are widely used in Tibet as pack animals. They do the job quite well because they survive on less that 1% of their body mass each day (a cow requires 3%), and unlike a cow, a yak will not eat grain but must forage for grass. The Tibetans will burn yak dung for fuel. Also, in Tibet, there is a distinction between a male yak (called a "yak") and a female yak (called a "nak").

And, just because yaks are so fun, there is such a sport as yak skiing. It has a simple layout whereby you have a skier at the bottom of a slope and a yak at the top. The two are tied together via a pulley system that runs up the side of the mountain. The skier will shake a bucket filled with pony nuts (a delicacy among yaks), and the yak will come barreling down the slope, sending the skier shooting to the top. I would assume this ends with the skier skiing back down the hill while the yak wanders back up.

Thursday, January 24, 2013

How Pythons Get It On

African rock python. Taken from http://largestfastestsmartest.co.uk/wp-content/uploads/2012/04/juvenile_african_rock_python__koedoesdraai.jpg
I recently learned that pythons have specialized structures called "pelvic spurs," a name that sounds crudely kinky . . . and, admittedly, kind of is. The pelvic spurs are located on the ventral side of the python's body near the tail end, and they look almost like claws that project from between scales. The male python will use his pelvic spurs to tickle the female's scales during mating. Apparently she likes it, according to a study performed by Gillingham and Chambers in 1982; soon after tapping and poking about, the female will allow him to mate with her. I would suggest you read the article yourself if you would like to learn more about the Burmese python mating ritual (http://www.jstor.org/stable/1444292). It is both to-the-point and blush-worthy of any proper snake.

A quick look on Wikipedia will tell you that "Pelvic spurs are the externally visible portion of the vestigial remnants of legs found on each side of the vent in primitive snakes . . ." This is where it would not be wise to consult the Wiki world. Although this was cited from Pough et. al's 1992 book of Herpetology, a quick search of other sources will say that pelvic spurs have absolutely nothing to do with long-gone legs. Although limb remnants can be seen in snake skeletons, the pelvic spurs have no connection to the skeletal structure. Possibly, pelvic spurs are simply modified scales.

Unfortunately,  I cannot find a single reference to pelvic spurs in my own herpetology textbook (Herpetology, 3rd by Vitt and Caldwell). I have not even found a reference to whether female snakes have pelvic spurs, whether or not they use them. A firsthand look at the UMM ball python would be unhelpful to answer this question because he is male.

In sum, pelvic spurs are NOT vestigial legs but ARE a plus with the lady snakes.
Pelvic spurs. (http://upload.wikimedia.org/wikipedia/en/thumb/4/42/Anal_spurs.jpg/250px-Anal_spurs.jpg)

Saturday, January 19, 2013

Pictures from the Microbiology Lab #1

1. Ascidia metamorphosis, 5x
 Earlier this week, I messed around with the microbiology lab microscope. Mostly, I just tried playing around with lighting and colored filters. It was particularly difficult to focus the lens on anything that wasn't planar, such as the starfish in early development. My favorite images actually came from larger organisms. I liked focusing on a single part of the organism to see the intricate parts, even if I didn't know what those parts were.

I am considering posting these on Facebook so that my friends can see what I'm up to when I shut myself in the science building for hours on end. Enjoy!
2. Blenny teleostfish fin, 5x, red filter

3. Blenny teleostfish body, 5x, yellow filter

4. Chick embryo at 33hr, 10x

5. Early starfish development, 10x
6. Early starfish development, 10x, yellow filter

7. Early starfish development, 10x

8. Tunicate, 5x, yellow filter

Wednesday, January 16, 2013

Narwhal Tusk

Over winter break, I was exploring the curiosities on Wikipedia, which is where I came across this picture of a narwhal skull with two tusks (http://upload.wikimedia.org/wikipedia/commons/thumb/a/a7/Narwalschaedel.jpg/140px-Narwalschaedel.jpg). Since then, I have done some investigating on narwhals (Monodon monoceros). Most narwhals, both male and female, have only one tusk, which is actually a tooth that extends from the left side of the narwhal's skull. The right side is usually bare of teeth. However, some narwhals develop differently and grow only a tusk that protrudes from the right side. Even stranger, some narwhals develop both tusks, one on the right and one on the left. This leads to a specimen like that in the image below. Male narwhals will rub tusks with other male narwhals during mating season, possibly as a display of dominance. Some researchers claim that the tusk acts as a sort of sensory organ, which I presume is much like a cat's whiskers only much less delicate.

I have tried to find research that may explain why some narwhals develop one tusk while others develop two. As of yet, I have found nothing. However, I came across research performed by Nweeia et al. (2012) that examines the tusks in-depth. There has been some debate as to whether the narwhal's teeth are best described as incisors or canines. I admit that they appear to be both. Nweeia et al. conclude that the narwhal's tusks are "surrounded by maxillary bone over the entire length of their bone socket insertion, and are thus more accurately termed caniniform or canine teeth." Furthermore, Nweeia et al claim that the wide range of phenotypes among narwhal tusks suggest that the development of the narwhal's tusks are "no longer guided by function but rather by random germ cell differentiation."

This still leaves me wondering exactly what determines whether a narwhal will have a left or a right tusk (or both). Could it be genetic? Must something happen to the narwhal during its development either as a young cetacean or as an embryo? Is this at all similar to people who are left-handed or right-handed? I guess I still don't have a clue, and I will probably just keep wondering.

Also, just for fun, I have included an image of "The Avenging Narwhal Play Set (with 4 Magical Tusks and 3 Adorable Animals to Impale)" (http://tommcmahon.typepad.com/photos/uncategorized/2008/05/05/narwhal2.jpg).

External links: http://onlinelibrary.wiley.com.ezproxy.morris.umn.edu/journal/10.1002/(ISSN)1932-8494 http://wwf.panda.org/what_we_do/where_we_work/arctic/wildlife/whales/narwhal/
The Avenging Narwhal Play Set

Two-tusked narwhal skull.