BioQuakes

AP Biology class blog for discussing current research in Biology

Tag: mammals

Is the Difference in Size of a German Shepherd and a TeaCup Poodle Due to a Gene Mutation?

Out of all the mammals on the planet, dogs differ in size the most. The biggest dog breeds are around 40 times bigger than the smallest breeds. A recent study has shown that this occurs because of a gene mutation that lies near a gene called IGF1. This gene was originally flagged 15 years ago as playing a major role in the variations of dog sizes. Ancient dogs that were domesticated from wolves in the past 30,000 years differ very little in size, however, in the past 200 years the largest difference in breed size has been recorded as people began to breed the more modern dog breeds during this time. 

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The IGF1 gene was studied comparing to body size of dogs and wild canids. There was one variant that stood out to researchers; this gene mutation was found in a stretch of DNA that works to encode a molecule called a long non-coding RNA. Long non-coding RNAs are a type of mammalian genome that lack protein coding capabilities. Specifically, the long non-coding RNA that was found to affect the size of dog breeds is involved with the levels of the IGF1 protein in the dogs bloodstream. As we learned in AP Biology, mutations in genes occur during the DNA replication phase of mitosis. Mitosis is the division of one mother cell into two daughter cells. DNA replication happens during the S phase of interphase. During this phase, the single stranded chromosome will duplicate and turn into two identical sister chromatids. The mutation will occur when copying the DNA, which would cause the sister chromatids to not be identical. 

This study identified that there are two alleles of this variant. Dogs carrying two copies of the small-bodied allele were most likely to weigh 15 kilograms or less, meanwhile, dogs carrying two copies of the large-bodied allele were most likely to weigh more than 25 kilograms. Dogs that carry one copy of each allele tend to be of an intermediate size. Additionally, dogs containing the larger-bodied allele contain  higher levels of the IGF1 proteins in their bloodstream compared to dogs who carry the smaller-bodied allele. Researchers also recorded a similar relationship in wild canids.

Prior to this study, researchers believed that certain dog breeds were smaller-bodied because of relatively new genetic changes. However, scientists now believe that the smaller-bodied allele is evolutionary and is actually much older than the bigger-bodied allele. They believe this to be true because the smaller-bodied allele was found in coyotes, foxes, jackals, and other smaller canids; this leads us to believe that this allele was present in one common predecessor. More studies must be done to truly determine how these variants impact the levels of  IGF1 proteins in a mammals bloodstream. The IGF1 gene only accounts for about 15% of size variation in dogs, so there is still much more research do be done. This study is just the beginning to really figuring out how we came to have dogs as large as German Shepherds and as small as TeaCup Poodles. Which allele do you think your dog has?

 

Regeneration of Lost Limbs in Axolotls

Many salamanders have the special ability to regenerate a lost limb, but adult mammals cannot. The axolotl is a Mexican salamander that is an endangered species in the wild. However, it is unlike most salamanders.

Metamorphosis frog Meyers

Normally, amphibians, like salamanders and frogs, go through the process of metamorphosis which begins with an egg that hatches into a larvae with gills to live underwater. As they gradually reach the adult stage, salamanders and frogs begin to lose and gain certain traits that allow them to adapt from an aquatic environment to a terrestrial habitat.

Axolotl

Axolotls are adorable creatures that are a special species of salamanders. Instead of going to the process of metamorphosis, they go through the process of paedomorphosis in which they retain their aquatic juvenile state for the rest of their life cycle.

Most salamanders have regenerative abilities but none to the extent of the axolotl. Axolotls can regenerate almost any body part, including the brain, heart, lungs, spinal cord, skin, tail and more. This possibly has to do with their juvenile state. Mammalian embryos and juveniles have the ability to regenerate to some extent, such as the heart tissue and fingertips. However, once mammals reach the adult stage, regeneration just simply isn’t the solution anymore. Mammals being to form a scar at the location of injury.

A team of scientists led by James Godwin, Ph.D., of the Mount Desert Island Biological Laboratory in Bar Harbor, Maine, approached the mystery of molecular regeneration by studying the axolotl, a highly regenerative salamander, versus an adult mouse, a mammal that has limited regenerative ability. In this research, Godwin compared immune cells called macrophages in the axolotl to the macrophages in the mouse to identify the factor that contributed to regeneration. It turns out that the macrophages are crucial to the process of regeneration. When the macrophages were depleted in the axolotl, it formed a scar like mammals do instead of regenerating. Macrophage signalling was similar in both axolotls and mammals when exposed to pathogens such as bacteria, funguses, and viruses. However, when the axolotl was exposed to these pathogens, the signalling promoted new tissue growth while in the mouse, it promoted scarring. Continual research of macrophage signalling in axolotls might one day be able to pull us closer to human regeneration.

In the future, when we need to surgically remove parts of our organs, axolotl regeneration might come in quite handy to regrow our important organs!

This research article relates back to AP Biology because macrophages work together with the its lysosomes to break down foreign pathogens. These macrophages will engulf these invading pathogens into intracellular membrane vesicles through the process of phagocytosis. Once entrapped in the vesicles, the pathogens will be killed with acid.

Do Birds Think Like Us?

Contrary to popular belief, a bird’s brain is indeed intelligent. Pigeons are able to identify the painting of Picasso and Monet, with training and ravens are able to identify themselves in a mirror. For a long time, it was believed that bird brains are not complex, however, according to an article from Scientific American, recently it has been discovered that bird brains have many similarities to the brains of mammals. 

The neocortex is the outer layer of the brain that allows cognition and creativity, in mammals. Although the brains of birds hold a different shape, new research can compare their structure to the neocortex in mammals. It is found that the layout of the brain is similar to humans, explaining their advanced behavior and abilities. Originally, it was believed that avian brains were a  group of neurons located in a region known as DVR, and an individual nucleus called the wulst, whereas mammal brains consist of six layers with columns of neurons that transfer information horizontally and vertically. These clusters of neurons, each contained a nucleus which ultimately allows for the production of proteins in the cell. However, In a study done by, senior author Onur Güntürkün, a neuroscientist at Ruhr University Bochum in Germany, along with his colleagues they discovered that, ”in both pigeons and barn owls, these brain regions are constructed much like our neocortex, with both layerlike and columnar organization—and with both horizontal and vertical circuitry” (Stetka). This research rejects the once accepted understanding of avian brains. Additionally, “We can now claim that this layered, corticallike organization is indeed a feature of the whole sensory forebrain in most, if not all, birds,” says Martin Stacho, co-lead author of the study and Güntürkün’s colleague at Ruhr University Bochum. Ultimately, it is confirmed that the DVR of avion brains is related to the cortex of mammal brain, thus explaining many of birds unique abilities. Although this theory was suggested by Harvey Karten in the 60s, it was not supported, but new this research credits Kartens hypothesis

This new discovery raises more questions of the possibility of sensory consciousness in avian brains and ancient animal brain evolution. The latest common ancestor of birds and mammals are reptiles, from 320 million years ago, and its brain is believed, “it wasn’t like the neocortex or the DVR. It was probably something in between that, in mammals, developed a six-layered neocortex and, in birds, to the wulst and DVR”, said Martin Stacho.

 

With the current discoveries on bird brains, new possibilities are being researched and many scientist are realizing that our brains may hold more similarities to different animals than previously believed.

 

 

Tiny Devils Take Down Gentle Giants all due to Climate Change!

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A innocent female moose, about to be attacked by an onset of terrible parasite in Northeast Canada.

Winter Ticks, not containing Lyme Disease or other Human-harming diseases, are rising exponentially in population throughout New England and Canada, all due to increasingly warmer and snow-free springs and later winters everywhere. As a result, an unlikely species in this region is being targeted by these tick epizootics, Moose, because ticks search for hosts in the fall and other warmer temperatures and stop once freezing weather and snow befalls the land. Yet, when these conditions occur much later, it gives these ticks more time to feast on peaceful animals, and also giving more time for female ticks to fall off its host and create tons more larvae, not making this issue any better. As these raisin sized parasites latch onto to these large creatures, draining so much blood at a time that they simply are unable to function anymore and weakly fall, succumbing to the environment, other predators, or even more ticks. But it’s not simply a few ticks, no, these moose can carry up to around 90,000 ticks! Because of this, there has been “an unprecedented 70 percent death rate of calves over a three-year period” according to a similar source from the University of New Hampshire. Plus, this problem has gotten so bad that now a threatened species in this region of British Columbia, the boreal Caribou, are being eaten alive as well!” If blood loss from heavy tick loads does not directly kill animals, it can make them susceptible to other health risks, Schwantje adds in the original source. “They have spent so much time scratching and chewing on themselves that they haven’t been feeding, so they are in poor body condition,” she says, even with tremendous hair loss that they become basically unrecognizable.

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An example of one of these detrimental winter ticks, a female engorged in size with blood and larvae, ready to reproduce .

But How Can This Be Stopped?

Currently, researchers are offering a multitude of solutions to help save these wonderful species from these terrifying parasites, as Swantje says that “They have huge cultural and nutritional value to our First Nations, And when moose forage in wetlands, they help release nutrients into the environment and make them available to other plants and organisms, studies have shown”, one solution can even be seen here. One possibility is to continuously treat half of the moose with anti-parasite gel and pills that make attached ticks drop from their bodies in order to isolate specifically what the ticks do and don’t do to harm these moose. The other possibility is a highly unlikely one, hunt the moose. Researcher Peter Pekins suggests that “issuing more moose-hunting permits in strategically selected areas” could essentially starve out the ticks in certain areas, yet it is argued that this would only benefit the environment short term, as the climate will continue to warm leading to the growth of more and more ticks.

Who know, if this isn’t stopped soon, ticks will continue to grow in population and maybe even take down us humans! Save the moose (and the caribou)!

We used to be shrews!?!

Ever think where did we come from?  Well, one answer to that could be evolution. While it is not yet a proven fact, it is a theory that shows promise to be true.

http://www.flickr.com/photos/usfws_pacificsw/5665647177/

Experts on the matter of evolution “recorded 4,500 physical traits for 86 mammalian species, including 40 that are now extinct.”  Using this information in tandem with DNA samples, the experts were able to figure out the probable start of placental mammals.  One of the findings was that the rise of placental mammals came after the dinosaurs had become extinct.  This was an earlier hypothesis that was now confirmed. The death of the Dinosaurs would allow for mammals to fill the top of the food chain where the dinosaurs once stood.  Less competition makes it easier to rise to the top.  Dr. Jonathan Bloch, who works at the Florida museum of Natural history, said “This gives us a new perspective of how major change can influence the history of life, like the extinction of the dinosaurs. This was a major event in Earth’s history that potentially then results in setting the framework for the entire ordinal diversification of mammals, including our own very distant ancestors.”

I think this is incredibly cool how all species could be related to one primal and ancient ancestor.  It shows how we are all linked in some way.

What do you guys think on the matter?

 

http://www.guardian.co.uk/science/2013/feb/07/ancestor-humans-mammals-insect-eater

 

Love Hormone: From Maternal Love to Romantic Attachment to Basic Survival Need

Photo Credit: Roberto Pagani

Introduction

The hormone oxytocin, known as the Love Hormone and sometimes the Cuddle Hormone, is responsible for a plethora of emotional and nervous responses in our bodies. It is a hormone exclusively found in mammals. It causes maternal bonds to form between mothers and their children along with romantic bonds to form between monogamous pairs. Oxytocin controls many social responses that aid bonding and even cause us to feel sympathy. Oxytocin is also known for its ability to cause subjects to feel content, reduce anxiety, and feel calm and secure around one’s mate. The presence of oxytocin is a basic survival adaptation for mammals because it causes them to trust members outside the family unit and therefore permits mating to occur among unrelated members of the same species, thus creating a healthier, more diverse gene pool.

Maternal Love

It’s not surprising that oxytocin is only present in mammals. After all, it controls the release of milk to the nipples during lactation, helps dilate the cervix and trigger labor, and aids formation of bonds between members of species that are vital to the survival of many mammals. One particular bond that oxytocin helps initially form is that between mother

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and offspring. However, one study found that oxytocin levels are higher when first creating a maternal bond than once the bond has been made, therefore oxytocin begins the maternal behavior in the mother, but does not solely maintain it. Researchers have also found that the higher level of oxytocin in mothers during pregnancy, the stronger the bond between mother and child will be once the baby is born and the more maternal the mother will act towards the baby.

Romantic Attachment

Oxytocin is also responsible for causing romantic attachment to form between a monogamous pair. Oxytocin is the cause of the anxiety a person feels when they have been separated from the one they love or, more specifically, have been monogamously paired with. When a monogamous pair is with each other, oxytocin is released. This release causes them to feel content, happier, relaxed, and trusting: basic components of “feeling in love”. However, when the pair is separated for a prolonged period of time, separation anxiety kicks in because the oxytocin which was keeping stress levels low before is no longer being release. Large amounts of oxytocin are released during sexual intercourse and orgasm, hence its name “the love hormone”. Therefore, habitual sexual intercourse between a monogamous pair works to strengthen the romantic bond and causes heightened separation anxiety.

Mammalian Evolutionary Benefits of Oxytocin

The presence of oxytocin is a basic survival adaptation for mammals because it causes stress levels to fall and trust levels to rise, thus it creates the proper conditions for bonding between non-family members or in other words, strangers who they’re instinctually wired to avoid. The social bonding between non-family members aided and maintained by oxytocin is the psychological strategy which enables humans to override our neophobia and to mate with and create a strong, life-long bond with a complete stranger. Mating with non-family members is fundamental to a species survival because it creates a healthier, more diverse gene pool. On top of social bonding that leads to mating, the maternal instincts and maternal bonds are increased by higher levels of oxytocin. The presence of oxytocin in mother is vital for mammalian survival because they have evolved to care for our young and provide them with milk and protection until they are old enough to fend for themselves. Without the oxytocin present during labor, mammals wouldn’t have maternal instincts when offspring is born, the dilation of the cervix would become impaired, milk would not be let down to the nipples during lactation (so there would be no lactation), and mothers wouldn’t have the strong bonds or urges to care for their young.

 

My Opinion and Conclusion

We know that oxytocin causes romantic bonds to form between monogamous humans and causes us to feel sympathy, but what about animals? The “Love Hormone” is known to form maternal bonds between rat mothers and their young and even helps rats form life long monogamous mating bonds. Is it possible that if oxytocin forms bonds and causes sympathy in humans and also causes pair bonding between animals that it could also cause animals such as rats to feel sympathy? Evidence of this would be groundbreaking because it would prove that animals are capable of feeling emotions previously thought to be solely possessed by humans.

 

For More:

http://www.biomedcentral.com/1745-0179/content/2/1/28#B14

http://jn.physiology.org/content/94/1/327.long

http://www.springerlink.com/content/m761t10000r382q5/

http://www.annualreviews.org/doi/abs/10.1146/annurev.neuro.27.070203.144148?url_ver=Z39.88-2003&rfr_dat=cr_pub%3Dpubmed&rfr_id=ori%3Arid%3Acrossref.org&journalCode=neuro

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2953948/?tool=pmcentrez