Wolf Bite

So! Between my online statistics class and petsitting, I will be a busy busy bee for the rest of April. But I shall do my best to post science! Even if it is the science of statistics.
For now, check out this melanistic wolf. Melanism is the result of an abundance of dark pigment (melanin) in the skin, hair, feathers, scales or fur. Dark colors can be very adaptive and help animals hide from predators or prey, but in certain environments they’re highly detrimental to survival. Plunk this pup in the arctic and see how much food he catches. Conversely, an albino animal does great in the arctic snow. Albinism is the absence of any pigment in the skin. This is often highly detrimental because you’ll stand out even in shadow. Certain animals have evolved to be semi-albino (their skin can produce melanin, it just won’t) in the winter and melanistic in the summer. A lot of the animals that do this are actually arctic animals. Since winter camouflage is so important to survival but retaining that through the summer is such a problem, they evolved to switch coats seasonally. People do this too, but it’s usually a wool to cotton kind of change.
Anyway, if you’re not an albino, even if you’re fish-belly pale like me, you have a little melanin in your skin. More is released from melanocytes (melanin producing cells in the skin) when you’re out in the sun. This prevents UV damage and results in a nice golden tan. Unless you’re me, then nothing happens except a growing conviction you’re descended from highly sun-resistant vampires.

Fluffcake Behavior

Now for something near and dear to my heart. No, not the cluster of nerves forming the natural pacemaker, I mean my dogs. These two fluffcakes are Wheaten Terriers, a non-shedding breed originally bred to hunt rats and mice (like other terriers). Mine are similarly fond of all things small and furry; Emer (the one is the grey sweater) could sit in the rodent aisle of Petco for HOURS. It’s Terrier TV and her favorite channel is always on. Anyway, getting to my main point, terriers also bred to be very good with people since effective ratting required them to live together. But the result was a breed that forms a strong pack with humans.
These packs are based on those found in wolves, the ancestors of dogs. At the top of the pack is the alpha male and female, the only members who breed (although care of pups is shared amongst the pack members). Alphas will stand over submissive pack members and grasp the sub’s throat with their teeth to display dominance. Establishing dominance can be more aggressive and violent if the alpha is either new or there are new, less submissive members entering the pack. Wolves hunt as a pack (with a couple staying behind to watch the kids) but feed according to rank, with the most dominant feeding first. Rest time also is stratified; everyone rests in a clump, but the alphas reside in the center with the more dominant wolves closest to them.
How does this translate in dogs? Let’s look at the fluffcakes. Good training, besides smoothing interactions with a pet, establishes hierarchy. Trouble dogs are often much less submissive than obedient ones. Makes sense, huh? Obedient dogs see their humans as the alpha members of the pack. When Emer was little, she’d often roll on her back when we would return home from something; she was acknowledging our dominance. She also used to pee, which is a hypersubmissive display that we discouraged for obvious reasons. Namely, the carpet. Many years later, we brought home Zeppo. Zeppo was the belligerent jerk of the litter, but Emer was knocking over the other puppies like bowling pins, so we got the one that liked knocking back. Even though Zeppo is now bigger and not so easy for twelve year-old Emer to pin to the couch, he’s not assertive enough to challenge the order.
In other breeds, trouble can arise if the dog is bred to have a very specific concept of pack. Dogs bred to fight and guard are like that; they consider their human family (traditionally a single aloof handler) the alpha(s) and everyone outside that is a stranger. When they dogs become pets, they need extra help to keep from reacting aggressively to outsiders. Some still have trouble with a human alpha; sled dogs take direction very well, but are NOT house pets. Their pack is focused within the sled team, they just learn to adjust to the hairless thing in thick clothes shouting at them before giving them treats.
Hope that helps you hairless things with furry family understand the pack dynamic. Cheers!

Source

Grandjean, Dominique. 2000. The Royal Canin Dog Encyclopedia. Royal Canin, Paris.

Music of the Neuron: Schwann Lake or I, Robo-Ophid

OK folks, here’s where things get technical and y’all start liking me less. I mean, I don’t blame you; if you’re not at least an aspiring neurobiologist, learning how the movements of ions in and out of neurons control muscle flexion is less Music of the Spheres and more Music of the Drying Paint. But gaining at least a rudimentary understanding of how changes in electrical potential, running down wire-like axons through your body to conduct every movement you make and orchestrate each separate muscle to work in harmony with the others is pretty musical. At the very least you’ll feel like a badass robot. Who doesn’t want that?

Let’s talk about Robo-Ophid’s wires (in third person, apparently?). By wires, I mean the axons, the single, looooong branch of a neuron/nerve cell that is insulated by myelin, a lipid layer produced by Schwann cells on the axon and that increases the conduction speed of signals. The axons only conduct signals away from the main body of the neuron, dendrites (shorter branches) connect to other axons and receive signals. Signals for muscle movement are called action potentials, drastic changes in membrane potential that are propagated from one neuron to another in an un-diminishing fashion until the target muscle is reached. Neuron membrane potential, the difference in electrical charge between the inside and outside of the cell, is about -70mV. For Robo-Ophid to move, the membrane potential is depolarized (given a more positive charge), repolarized (given a more negative charge) and hyperpolarized (given a much more negative charge than it needs). Here’s the quick and dirty explanation of how: sodium channels open, allowing positive ions in; neuron becomes positive, hits peak of action potential/positive charge; sodium channels close; potassium channels open, allowing positive ions to exit; cell goes overboard and gets extra negative (perhaps even buys an emo CD) before returning to normal. Neurons like you, so the action potential itself is easy; the action potential just spreads down the axon to its target. In this case, lets say the spine, and that to another neuron that connects to a muscle. Not so bad, right?

Now, Robo-Ophid needs more than just one action potential to do things. Unlike the autoclave doors at her work, where you have to hold the damn button until the door is all the way shut or it comes open, Robo-Ophid needs multiple action potentials to do anything. Robo-Ophid doesn’t know if this makes her a worse machine than the autoclaves at work, but she doesn’t make inexplicable alarm noise for hours on end so I think we know who wins this round. Me. I win.

Anyway, along with other action potential-dependent signals (like skin temperature), graded contractions depend on the frequency of the action potentials. A higher frequency will lead to a stronger contraction and a lower frequency to a weaker contraction. Take physiology and you’ll get to test this out by poking your lab partners with electrical probes to force their muscles to contract. This is how biologists make friends; by poking people and laughing. Laughing so hard.

 

Source

Sherwood, Lauralee, Hillar Klandorf and Paul Yancey. 2005. Animal Physiology: From Genes to Organisms. Thomson Brookes/Cole, Belmont, CA.

Heat Regulation in the Forgotten Marx Brother

Okay, let’s take a look at this little bastard.

My little demon puppy, looking all sweet and innocent in his sweater. As inclined as many of us are to scoff at dressing up our pets, it is often necessary (as long as it’s tasteful); Zeppo is a Wheaten Terrier, who, through selective breeding, does not shed and has no undercoat of fur. That dense undercoat would help with bodily heat retention in the winter and shield against environmental heat in the summer. As it is, he’s vulnerable to hypothermia and heat stroke. My family can assist him in regulating his temperature, but his body is not without regulating mechanisms. Since dogs don’t sweat, without an undercoat Zeppo relies largely on vasodilation and vasoconstriction. That is the opening and closing of sphincters (ring-like gate) in the blood vessels to allow or prevent blood flow into capillary beds in the extremities. So if it’s cold, Zeppo will experience less blood flow into his ears, feet, tail, etc. to prevent heat loss and to keep his core warm. When it’s hot, blood flow will increase along with heat loss and by panting Zeppo increases the surface area from which he can lose heat. If all else fails, he finds the grossest mud puddle possible. Thanks, Zeppo. Thanks.

 

Source:

-. 2010. GRE Subject Test: Biology 5th Ed. Kaplan, New York.