AP Biology class blog for discussing current research in Biology

Tag: fish

Some People Can’t Smell Stinky Fish?!

A New York Times article has just reported a new “mutant superpower.” In Iceland, a brand new genetic trait was discovered, in which 2% of the population can’t smell the stinky odor of fish. 

A study of 11,326 Icelanders was conducted, in which each participant was given six “Sniffin’ Sticks (pens imbued with synthetic odors)” of cinnamon, peppermint, banana, licorice, lemon, and fish. The participants were then asked to identify the odors based on how strong each smell was and how good each Sniffin’ Stick smelled. Across the majority, the fish was rated the lowest in pleasantness. However, a small group of people actually enjoyed the scent, noting that it smelled like caramel or even a rose. 

This small group of participants was discovered to have a genetic mutation that enables the TAAR5 gene to form. TAAR5 (Trace Amine Associated Receptor 5) aids in making proteins that recognize trimethylamine (TMA), a chemical found in rotten and fermented fish, and some bodily fluids, including sweat and urine.  TAAR5 is also a G Protein, meaning that it binds guanine nucleotides. And, like other coding proteins, TAAR5 is a quaternary structured protein that has three subunits. Because this protein is incapable of binding guanine nucleotides, it means that there will be at least one “broken” copy of the gene that codes for the inability to smell fish. 

To simplify: TAAR5 recognizes the chemical of smell in fish (TMA), however, with the mutation that prevents the TAAR5 from forming, the smell of fish (TMA) is unrecognizable.

Interestingly, research has shown that this mutation may be a reaction to the customs of Iceland and a possible next step in the evolution of the region. In Iceland, fish takes a prominent place on most menus including dishes like “rotten shark.” These cultural and possibly smelly dishes may explain why this mutation is much more prominent in Iceland compared to Sweden, Southern Europe, and Africa (where the study was repeated). Bettina Malnic, an olfaction expert at the University of Sao Paulo in Brazil, commented on the luck of the region study took place, saying, “if they hadn’t looked at this population, they might not have found the variant [of TAAR5].”

I am VERY sensitive to smell and, at the same time, a lover of sushi, so it definitely fascinates me that there are people out there who don’t have to deal with the odor of smelly fish. This mutation is definitely one I wish I obtained. What do you think about this? Do you think you could have this mutation?!


How are ocean conditions harming its animals?

A recent article written by Rachel Nuwer discusses the dangers of ocean acidification and how the ocean environment could compromise the fishes’ ability to swim and feed. The existence of one of the world’s most threatening predators is being threatened by ocean warming and acidification. Sharks might lose their place at the top of the marine food chain due to the changing ocean environment. As carbon dioxide levels rise in the ocean, it increases the acidity of the water. As this factor starts to rise, the teeth and scales of sharks may begin to damage, which compromises their ability to swim, hunt, and feed. According to research published in Scientific Reports, acid-base adjustments have proved to be the first piece of evidence of “dentical corrosion” caused by ocean acidification conditions. After investigating the impact of hypercapnia on a specific shark species and analyzing the acid-based regulation, the team concluded that the denticle corrosion could increase denticle turnover and compromise the skin and protection of the shark species.

A close up on the denticles and scales of a wild shark

The harsh conditions placed on the sharks could cause several consequences and ultimately could affect the whole ocean community. Biologist Lutz Auerswalk states that sharks could be displaced as apex predators, which could disrupt the whole food chain. In addition, great white sharks are already endangered, and these conditions could wipe them out completely, he states. Ocean research Sarika Singh and Auerswald, while studying over beers, stumbled upon a unique idea. After realizing that the high acidity of beet and many other carbonated beverages causes human teeth to erode, they wondered what effect more acidic ocean water might have on shark teeth.

Most studies on ocean acidification examine species that specifically build shells or other calcium-based structures, including corals and shellfish. Because sharks are large and challenging to work with, only a few studies have been conducted about how acidification might impact these animals. Only one paper has examined the effect of pH on sharks’ skin denticles or scales. The study used small-spotted catsharks and exposed them to different environments and filmed their swimming patterns. After analyzing a pectoral fin skin sample, they did not find a specific impact. However, the results were possible constrained by the low carbon dioxide concentration the researches used, compared with the high levels of acidity already present in many oceans.

To begin exploring this question for themselves, Auerswald and Singh conducted an experiment and focused on puff adder shy sharks, a small species that is easy to handle. They decided to investigate the acidification effects on the bigger scales. They divided the sharks into control and experimental groups and observed the results. After a few months, the electron-microscope analysis revealed that the concentrations of calcium and phosphate in the sharks’ denticles were significantly reduced. They noticed damaged scales on many of the sharks as well. Though the corroded scales might not impact their ability to hunt, for larger species such as the great white shark, scales play an essential role in hydrodynamics. Because denticles are responsible for an increase in swimming speed, damaged denticles could slow sharks down and make it more difficult for them to catch prey. Because many animals have been wiped out, we must strive to protect all the species that are deeply impacted by this condition.

Avenging Lamarck: The Epigenetics of a Fish

The laughingstock of biology classrooms everywhere, the footnote to Charles Darwin and his widely acclaimed theory of natural selection, the scientist who has caused many a biology student to stop and wonder why he or she should even know his name, Jean Baptiste Lamarck has gotten a bad rap among student’s across the country. Predicting that evolution in species resulted from individual species adapting to their environment and morphing their bodies to better survive and reproduce, passing their adapted traits to their offspring, Lamarck has been criticized by students everywhere for simply not being correct. However, he wasn’t entirely wrong. Recent research conducted in the Gulf of St. Lawerence off the Labrador Peninsula has revealed that skate fish  in the area have developed differences in terms of size from other skate fish because individual organisms are able to turn on and off select genes.

The ability to turn on and off certain genes in organisms based on environmental conditions and pass those changes to offspring is called epigenetics. Epigenetics allows individual organisms to change their traits slightly to adapt to their environment. Where evolution by natural selection takes millions of years and results in the evolution of populations on a macro scale rather than individual organisms, epigenetic changes are much quicker.

Researchers were attracted to studying the winter skate fish in this bay because though the fish lies all along the North American coast, in this bay, the fish tends to be significantly smaller than other members of its species. Scientists attribute this to the warm water in this shallow water area which makes smaller organisms more likely to survive and reproduce.

However, DNA tests showed that significant changes in the genome of the fish weren’t what made them smaller, indicating it wasn’t Darwinian natural selection that dominated this process. The researchers discovered that the fish could turn on and off certain pieces of DNA in individual organisms to better adapt to the environment. Thus, the fish are able to adapt more quickly to changes in temperature than other organisms that rely solely on natural selection for changes to their traits.

Thus, Lamarck wasn’t entirely wrong all along (just mostly!).

The researchers hope this new information will help with conservation efforts and will give more insight into how species adapt to climate change.

So, do we owe Lamarck an apology? How can conservationists use this information to draw more interest to their goal?

Proteins Keeping Fishes Alive



Words To Know:

notothenoids: the arctic ice fish

practical application: how organisms adapt through natural selection

superheating: solid is above its melting point but does not actually it to melt at this point


     Fish in Antarctica have been forced to evolve natural antifreeze proteins to stay alive.  These proteins are mainly found in the notothenoid fishes, which are found in freezing temperatures. Arthur DeVries discovered these fish, their ice- binding-proteins and also figured out how they work in the 1960s . The proteins bind to small crystals and also protect cells by binding to their cell membranes. They are anti-freezing proteins that allow fish to survive and adapt to harsh and cold conditions of arctic waters.

Recent Discoveries:

          Paul Cziko, among other researchers in the United States and New Zealand, published in The Proceedings of the National Academy of Sciences that these ‘anti freeze’ proteins’ are also ‘anti melting’. Cziko and his team wanted to understand the antifreeze ability and examined if an anti-freeze protein (that was attached to an ice crystal inside the fish) would melt when the temperature rose. Instead, they found that the ice crystals did not melt. Ice above the melting is point is considered superheated. Cziko’s research basically says that even when it is way past its melting point, the ice (that’s latched on to the protein) still stays frozen inside the fish. These ‘anti-freezing’ proteins are also ‘anti-melting’ proteins that cause ice crystals to accumulate in the fish’s body.

The study shows evolution, not practical application, and this is a typical case of ‘evolutionary trade off’. There are difficulties that get solved, but there’s also a price to pay. Cziko’s research has not indicated any unfavorable effect due to the crystals, but the crystals could potentially block up the blood vessels of the fish and provoke an inflammatory reaction.

Personal Statement: 

      Personally, I really liked the NY Times article. I actually didn’t realize that we had to find additional articles until I re-read the assignment sheet. I found other articles because I was genuinely curious as to how this worked and came about. I was initially attracted to the word ‘protein’ in the article’ title -since it relates to what we are learning in class- but stayed because of the evolutionary aspect. It has always been hard for me to think of evolution as something. It is such a difficult-to-grasp concept since you can’t really see it happening . But, in some way- this made me think that I did see evolution. Instead of making me think of evolution as a concept or theory that I learn at school, it made me think of it as a reality, and as something that actually happens.     

Original Article:

Additional Article:

Additional Article:

From Fin to Foot

It is widely understood in the scientific community that, at some point, life evolved from aquatic to terrestrial. In that evolution, at some point fish must have evolved into amphibians. The question of this evolutionary jump still remains a mystery, but the discovery of a new fossil has shed new light on the issue, filling in some of the many gaps in this evolutionary story. This new fossil, discovered in Canada was of the Tiktaalik, a proto-amphibian of the Devonian period. Although this species was not necessarily a new find, it was a complete fossil. Prior to the discovery of this specific fossil scientists only had the front half of the Tiktaalik fossil, and as such could only speculate about its back half. The accepted evolutionary story at the time was that front legs developed first as the power behind walking on land, with back legs functioning only as weak supports. However, this new fossil was fully complete and showed a highly developed pair of back legs with a very developed pelvis, quite unlike any found. Although the bones in the fishes back leg were not as complicated as those of modern amphibians, they were far more advanced than the average fish of the time and more advanced than the widely accepted belief of the scientific community had suggested. This Tiktaalik fossil discovered by Dr. Neil Shubin, has fascinated the scientific community, as it is a great example of a creature exhibiting a myriad of evolutionary changes. Although the bone structure development here still favors the fin, there is astounding development in both the fore and hind legs that show that mark this creature as a key link between aquatic and terrestrial life.

This image of the Tiktaalik shows an artists representation of the creature before its powerful hind were discovered

Fish Schooling Not Nurture, But Nature

Recent research done by by biologist’s Catherine Peichel and Clifford Tabin show that the complex actions that are required by fish that travel in Schools. Fish that travel in schools do so to better protect themselves from predators, but swimming in a school requires an enormous amount of synchronization in body patterns and the ability to the change with water currents and other environmental changes. The first study conducted by Peichel in which she gathered Sticklebacks that were prone to joining schools and those that were not, showed differences in certain genetic regions. This suggests that the act of traveling in a school is not stored in memory, but is stored in their genetic make up. Research done by Tabin suggests that the eyes are  a huge part of Schooling. He found that blind Sticklebacks dwell deep underwater in solitude while the others travel in their schools. This research relates to whether Humans are driven to stay in packs and be around each other because of these certain genetic regions, or whether we as people were brought up this way.




Guts or Glory?

According to Aristotle, what separates man from beasts is his ability to reason. Humans have this luxury because of their large brains, but it comes at a price; guts! Scientists have long imagined that big brains come with an evolutionary cost and up until a recent study, it was all theory.

A Swedish team of researchers, led by Niclas Kolm decided to put this theory, known as the “expensive tissue hypothesis”, to the test. The hypothesis basically states that there is a trade-off between the demands of the brain and the demands of other organs. So, to prove this theory, the team selectively bred common guppies to produce bigger (or smaller) brains. They were able to produce brains that were as much as 9.3 percent larger. The bigger brained fish tended to have smaller guts, as well as produce fewer offspring.

The experiment tested 48 guppies using an underwater arithmetic test to see if the guppies (with large brains) possessed greater cerebral capabilities. It worked! The “smart” fish were more successful at learning and recognizing geometric shapes, that were on a door, in order to get to the food on the other side.

Where these “brainy” fish lost ground, was in the gut division. Males were found to have a 20 precent decrease and females an 8 percent decrease in gut size. Brainier fish(females) were found to produce 19 percent less offspring than the smaller brained fish. This evidence implies that larger brains may be the cause of smaller broods.

Even though the evidence pretty clearly supports the “expensive tissue hypothesis”, Kolm and his team have not completely ruled out the “genetic mechanism for the trade-off”. It is not obvious whether small guts or big brains develop first.

Guppy Love!

Tiger Guppy (domesticated)- CC licensed photo by Leonard Paguia

Guppies (those small, colorful freshwater fish that everyone loves to keep in their fish tanks) have been evolving in the wild for more than 500,000 years, yet one feature has remained constant over all that time. Research conducted by UCLA Biologists has shown that the orange spot found on the wild male guppy has remained not simply the same color, but the same hue of orange since near the beginning of this fish’s existence. The reason for all this effort? That particular shade of orange is the one that female guppies prefer. What is so fascinating about this to biologists is that it proves that evolution is not simply an organisms adaptations to be better suited to its environment.

The two pigments that, when combined, allow a male to have an orange-colored spot are carotenoids (taken in by the guppies through food) and drosopterins (synthesized by the guppies). A higher percentage of carotenoids would make a guppy’s spot appear more yellow, and a higher percentage of drosopterins would make the spot appear more red.

Now one would think that, in order to conserve energy and be able to function more efficiently, a male guppy that had an abundance of carotenoids in its diet would not waste energy on synthesizing drosopterins as it would not need them to have a brightly colored spot. Conversely, one would think that in order to maintain a bright and noticeable spot, a guppy that did not have a lot of carotenoids in its diet would synthesize more drosopterins. However, this is not the case.

As the type and availability of food for male guppies has varied as a result of both time and location (guppies are native to both trinidad and venezuela) they have evolved to match the levels of carotenoids and drosopterins to produce that orange that the females are so attracted to, even if it comes at a high energy cost, or the spot must be more dull to produce the correct shade.

Although we all understand that reproduction is the ultimate goal of all organisms, what these guppies have done over the past half a million years is still not evolution in the way that many of us think about it. What has happened with a great many organisms is that they adapt in ways that make it more easy for them to survive and then these traits become attractive to the opposite sex because their presence indicates that that individual will produce offspring that will also be better suited for its environment. Here, however, male guppies have striven to remain attractive to their mates even when this comes at a high energy cost for many. As a result, the females have not had to change their taste in mates, and the males have been forced to continue playing to their preferences, or risk not reproducing.

Can you think of any other organisms that have adapted to be attractive to mates even when it made them less suited for their environment?

For further reading on the actual experiment conducted by UCLA biologists click here


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