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Migratory Displacement

Submitted by kheredia on Thu, 11/07/2019 - 14:36

Reed warblers are night migrants, known for their incredible instinct which allows them to calculate their east-west position during the breeding season. Even in the case of displacement, these songbirds have the ability to correct their orientation. Previous research has revealed that a tiny magnetic compass is possessed by the songbirds in each eye. However, this information is not enough to explain which sensory mechanisms and cues warblers use in determining longitude. Fortunately, a key to solving this phenomena lies in a second magnetic sense, involving the ophthalmic branch of the trigeminal nerve (V1). It is speculated that V1 channels magnetic information into the brain, which has lead researchers at the University of Oldenburg to a strong hypothesis in which V1 may serve as a magnetic map and is necessary in determining a reed warbler’s east-west position.

The methods in this double blind experiment included capturing 57 Eurasian reed warblers in Rybachy and separating them into groups. Some underwent a procedure involving the severing of V1 while the other birds participated in a sham surgery. The songbirds were then displaced 1,000km eastward in Zvenigorod, and their orientation was compared before displacement in Rybachy.

The results revealed that sham sectioned bird’s orientation shifted by 49 degrees counterclockwise compared to non operated birds in Rybachy, though they did in fact correct for displacement. The V1 sectioned birds however, did not adjust for the displacement. Their orientation was considerably different in comparison. Based on these results, it was evident that V1 plays an important role in detecting longitude in the magnetic field and therefore a reed warblers sensory ability to provide map related information. This information has lead researchers closer to determining the biological function of V1 including the possibility of transmitting information through magnetoreceptors and olfactory receptors.

These implications match with the evidence that was found from this study. However, there are quite a few restrictions with this study. For example, these results cannot be applied to all birds. Migratory homing pigeons are still able to navigate despite sectioning the V1 nerve, contradictory to the results from this study with reed warblers. Thus, navigational ability involving V1 may be species dependant. In addition to this, other research involving V1 in birds is virtually useless to compare this experiment to, due to the fact that many have not been able to be replicated, resulting in a very low reliability factor. Without this, it becomes increasingly harder to find out more about the function of this nerve in birds. In addition, there may be other cues which help songbirds to correct their displacement, for example: smell.

Thankfully, unknowns and complications from this experiment like the one mentioned above serve to be quite helpful because they can always be experimented with. The possibility of olfactory senses being a major contributing factor in bird migration can be tested to determine if transmitting odor is a function of V1. Therefore one can observe whether it has impact during bird migration. Most research isn’t perfect, so these kinks in studies provide a layout for future research to take place because there is always information to be found.

Bird Flight

Submitted by kheredia on Thu, 11/07/2019 - 14:34

Bird flight is not as simple as wing-flapping and hovering above the trees. This primary mode of locomotion has evolved to possess many intricacies involving movement. Despite several studies covering migrational behavior in birds, there is little information about the aerodynamic principles and forces behind flight. This is precisely why researchers at the Department of Biology in the University of Portland have studied the mechanical power output of the pectoralis muscle in magpies, cockatiels, and doves. They hypothesized that a number of factors could contribute to the overall shape of a power curve such as morphology, wing kinematics, and ultimately flight style.

Cockatiels and doves were subjected to a variable-speed wind tunnel to measure velocity and any potential change of the pectoralis. Bone strain recordings and sonomicrometry were used to monitor tension and length of the pectoralis muscle, while work output per wing beat was calculated. 3D kinematic data was also used for analysis of mechanical movement. The data from the velocity of birds in power curves were plotted for comparison. The results revealed a significant difference in pectoralis power output and speed. The doves were found to have a higher minimum (7ms-1) and maximum (17ms-1) power output and mass specific power output compared to the cockatiels (5ms-1, 14ms-1) for most speeds. However, there was an exception at 14ms-1, which was most likely due to a trade-off in the dove’s larger wing size relative to body size. Therefore, the doves would require more power in comparison to the cockatiel’s to account for reduced maneuverability at that speed.

Nonetheless, both species exhibited a U shaped curve for their power curves. In comparison, the mechanical power curve for magpies was relatively flat. This was likely due to morphological differences. Unlike cockatiels and doves, the broad wings and long tails in magpies constrain power output, greatly increasing drag while decreasing thrust. Overall, these implications are consistent with the hypothesis of this study. Wing morphology and flight style indeed significantly alter the shape of the power curve. However, this study does have restrictions. For example, these results are species dependent. There are evident physiological and behavioral differences in birds because they have evolved to be the most fit in distinct habitats. Some species, like galliformes, do not rely much on mass specific pectoralis power output because they use flight specifically to elude from predators. In addition, the researchers failed to take into account the possibility that more than just the pectoralis muscle is responsible for power output. This study also assumed that wings are the primary source of reducing power requirements. They did not consider that the tail could also aid in work. Due to these flaws, this field of study requires more research to conclude which components are important for locomotion in birds.

In the future, any similar experiments should include a more diverse sample size, and the biologists should measure potential variables to prevent any holes or discrepancies in data. Regardless of any mistakes, the data extracted from this study will serve as a helpful guide for improving the structure of experimentation as well as getting a better look into the relationship between mechanical power output and forward velocity in birds.

Animal Locomotion Study

Submitted by kheredia on Thu, 11/07/2019 - 14:33

There are many different ways to study the locomotion of animals and humans alike; for birds, there are wind tunnels, for humans, there are treadmills, and for fish, there are swim tunnels. Jeanine M. Donley, Chugey A. Sepulveda, Peter Konstantinidis, Sven Gemballa & Robert E. Shadwick wanted to look further into the locomotion of sea animals, specifically tunas and lamnid sharks (examples would be both mako and white). The reason for their study was to determine if the morphological similarities between these two sea animals meant that their mechanical and functional design had also converged. To do this, they studied the musculature and structure of the mako shark. The scientists examined Isurus oxyrinchus, a species of shortfin mako shark. The lamnid sharks used in this study ranged from 80 to 112 cm in size. While observing the shortfin mako in a swim tunnel, the scientists were able to determine where the dorsal midline was located using digital images. The position on the midline is important because swimming modes in fishes are explained based on the proportion of the body that is used during movement of the tail, which is also known as thrust-producing movements. These modes are distinguished by different patterns of displacement. Tunas fall under the least undulatory mode, meaning the body is very rigid and the tail is the source of most movement. When studying the mako shark, it was found that they have a similar mode to the tuna due to the degree of lateral motion along the shark’s form, which was from 0.4 L to 0.8 L (L meaning total body length). Past 0.8 L, the amount of movement in the tail increases substantially. After noting the similarity between the two species, the scientists wondered if the shortening the red muscle found in the mako shark would result in a functional property found in tunas. This functional property is when the tuna uses its red muscle fiber found in the midsection/upper region of the body to propel and create thunniform kinematics in the posterior region of the body, mostly the tail. There are long tendons that link to their tail so that even the red muscle is build more interior, they can use the tendons and the tail to create the movement of the tail while keeping the rest of their body very rigid. If the shortening of the red muscles happens at the same time as the white muscle, the mako shark would swim the way most fish do; if they are not synchronized, it means the mako shark swims and propels itself in the same way a tuna fish does. Sonomicrometry and electromyography used to measure muscles lengths instantaneously during swimming sessions, both active and passive. The results showed that the shortening of red muscles was uncoupled from the other tissues, similar to tunas. The results from their study also show that mako sharks possess the same tendon structure which aids in producing thrust. The findings of this study confirm that lamnid sharks and tunas have converged on both mechanical design, as well as morphological, concluding in selection for fast and continuous locomotion. The study itself reveals more data than previously known about lamnid sharks, but because these types of sharks are large and aggressive predators, they are difficult to handle and leaves dynamic properties about their individual locomotor system unknown. Future studies could look into the reasons behind this morphological and functional conversion; the usage of certain muscles, the placement of fins, the size of fish, etc. all deserve further research.

Virtual poster

Submitted by kheredia on Thu, 11/07/2019 - 14:27


What instantly drew me into this poster other than my interest for whales was its display of the whale sighting app they were advertising inside the screen of a smartphone. Not only was there a layout of a poster, but there was a layout inside of that layout, that being, the way the app looked on the smartphone photos they provided. It added even more of a dynamic to the poster. The design of the poster was very organized and clear, with nothing too distracting other than the neon colors of the bar graph on the right side of the poster. The colors used were mostly consistent and were not hard on the eyes other than that. The color of the design had a theme and were mostly neutral colors like blue and gray theme to match the photographs of the ocean and maps they provided. The text was plain and fitting; it did not distract me. The only fault was the lack of white space. They fit a lot of information into one poster, so there was not much breathing room for space between sections.

Convergent evolution in the mechanical design of lamnid sharks

Submitted by kheredia on Thu, 10/31/2019 - 11:00

The driver of evolutionary change is natural selection, a process where communities thrive or perish depending on the environmental conditions. Despite the unique traits that darwinism has brought, these evolved bodily functions are not exclusive to one species. Lamnid sharks and tunas are an example of two species thought to have independently evolved similar traits. However, there is little data regarding the mechanisms behind their convergent evolution. Under these circumstances, researchers have investigated the evolutionary relationship between mako sharks, Isurus oxyrinchus, and tunas’ swift, continual movement and morphological design. They also compared swimming kinematics, and muscular function to determine this. When exposed to a controlled swim tunnel, scientists observed how both species concentrate movement in their posterior, more specifically, the caudal region of the tail.

Results showed that mechanistically, allowing the mid-body to become virtually stiff and focusing muscle activation in the rear has evolutionarily allowed these fish to become more energy efficient. Because the tuna and shark resemble one another in their structural design, both are able to swim for longer periods of time compared to other fish, without the cost of travel. The important feature in tunas which allow this specialized movement is the physical uncoupling of the red and white muscle when in motion. In other species, the muscles act synchronously. This thunniform-like mobility in tuna was tested for similarity in mako shark via sonomicrometry, by shortening the muscle during passive and active swimming in the hopes to detect uncoupling. Throughout active swimming, they recorded asymmetrical muscle activity. There was a delay in red muscle strain compared to white muscle. This confirmed that red muscle was in fact uncoupled, supporting the claim that tunas and mako’s are evolutionarily similar. This is also indicative of strong posterior movement. The analogous relationship between the two species was supported morphologically as well. Elongated tendons were measured in both fish. Its association with the red muscle creates a system which allows the transfer of great power from the anterior of the animals’ to the posterior.

However, the driving force behind the system was found in the hypaxial lateral tendons in sharks, whereas the tuna’s primary source of transmission is located in the horizontal septum of the tendon. Despite this regional difference, the study overall was representative of a phenomenal evolutionary relationship between two separate species; though it does have its complications. Studying animals such as sharks without sedation can serve to be quite difficult. These predators pose great danger to the handlers, so precautions must be taken and some methods may be carried out quickly; resulting in fewer studies and limiting the amount of information available to others. To avoid potential risks in the future, studying the similar, less harmful tuna in the place of lamnidae can be useful.

A future experiment may include a common ancestor of the tuna to study the mechanisms in which they diverged. This will help map out the history of how tunas were able to develop different characteristics over time, and eventually become similar to the mako shark.


Submitted by kheredia on Thu, 10/31/2019 - 10:57

Gene duplication is a mechanism where genetic material is essentially generated and copied in a region of DNA. A regulatory mutation is a mutation that affects the spatial or temporal regulation of the gene without causing an entire loss of the gene product. Lastly, coding sequence mutations are changes in the coding sequence that can have different outcomes in expressivity like nonsense or missense mutations.

These three factors combined aided the use of a snake's venom to evolve into what it is today: from defensin genes that are used for different basic tasks like fighting infections in the pancreas, to today’s cromatine genes that encode the venom molecules and are used for attacking and destroying muscles. These changes did not alter the universal product of the gene, but in turn changed the way the genes were communicating. By sequencing genes from different snakes and mapping them out in an evolutionary tree, scientist Fry, colleagues compared the relationship of defensive and cromatine genes and found out that they are closely related. In newer generations that inherited the defensive gene, gene duplication took place for this change to occur.

There may have been an accidental duplication of a gene in which in turn would spark a new gene recruitment. Regulatory gene mutations would occur because gene recruitment now took place, helping change the gene’s functions through mutations: one of these copies would now be able to produce proteins in a venom gland. At the DNA level, a type of mutation could have occurred at the coding sequence by changing the amino acids, which, for this example, could have changed the expression of a gene from being a defensin gene to cromatine even by one difference in sequencing. Having these factors repeatedly happen over and over again in snakes eventually gave rise to a new family of venom producing genes.

Gene duplication and crotamine

Submitted by kheredia on Thu, 10/31/2019 - 10:53

Gene duplication, regulatory mutations, and the coding sequence all play different but important roles in the evolution of venom. Gene duplication, which is a mechanism where genetic material is generated/duplicated, and this area of DNA contains a gene. This event allows one copy to continue with the original function of said gene, while the other copy has the ability to evolve into something else. A regulatory mutation affects the temporal or spatial regulation without causing a complete loss of the gene product. This basically means that the mutation can change the different tissues the gene is expressed in, without losing the purpose/function of the gene itself. A coding sequence mutation is when a base is changed within the amino acid, and this can cause either a nonsense or a missense mutation (can change the whole amino acid or just the base).

Gene duplication plays a role in the evolution of crotamine because after the defensins evolved from a common ancestor and was inherited between many animals, including snakes, the extra copies of this gene created by gene duplication allowed the defensins to become more specialized. In the case of these snakes, the specialization was for attacking different pathogens found in the pancreas. This duplication, according to Fry, began to change the actual shape of the protein (after many duplications). A new shape meant a new function, which leads us from defensins to crotamine. The regulatory mutation changed the location of where the protein was being produced (from the pancreas, to the mouth). This mutation played a huge role in the usage of this gene. With a gene that damaged muscles instead of pathogens, found in a place crucial for killing prey it could easily used to incapacitate and kill the desired prey. As for the coding sequence mutation, a simple change of one amino acid could cause a cascade of other elements that led to crotamine as a deadly, venomous, protein. This type of mutation could explain how ancient venom is, especially in certain snakes that are deemed non poisonous. Meaning that a coding sequence mutation could’ve caused earlier ancestors to produce crotamine. This, along with gene duplication and regulatory mutation, played big roles in the evolution of crotamine, from defensins.

Fish Locomotion

Submitted by kheredia on Thu, 10/31/2019 - 10:49

A variety of mechanisms allow fish to propel themselves through an ever-changing environment. Locomotor techniques such as wave-like motions are currently being researched, and with the help of recent technological advances, can now be examined in greater detail. In this article, George V. Lauder of Harvard University observed how morphological differences in fish, and the basic commonalities of swimming has become better understood. He viewed new approaches in kinematics, hydromatics and robotic studies of undulatory fish.

Lauder emphasized that not all fish use their fins the same way, because variations in their body shape make them complex. Stingrays are a unique example of this. Their flexible bodies and expanded pectoral fins help increase amplitude and lift. A study Lauder reviewed about center of mass dynamics (COM) went further in detail. Scientists compared a bluegill, clown knifefish, and an eel during surge and sway-like undulatory motion. The results from this study revealed that sway increased as speed increased. Researchers also observed that sway displacement was largest in eels. Lauder expressed that this particular experiment on COM was vital for understanding how physique affects aquatic propulsion, especially because COM research is lacking. He also notes that fish are able to alter the surface area of their fins. This helps them maneuver through difficult areas. In addition to kinematics, Lauder discussed a shark study which implemented a new hydromatic strategy by using 3D reconstructions of bonnethead sharks.

The experiment tested whether shark skin denticles have an effect on performance. Scientists 3D printed two bonnethead sharks, with and without denticles. When placed under appropriate swimming conditions, they discovered that intact surface skin increased the shark’s speed by 12.3%. This suggested that denticles can reduce drag, therefore improving performance. Biomimetics are an alternative to studying animals like the sharks in this study, because it is both harmless and safe for all that are involved.

Consequently, this has lead scientists to widen their range of research with recent advances in fish robotics. These realistic representations help researchers learn more about fish dynamics in an interactive way. Scientists manipulate variables, and even expose mimetic fish to several different conditions, without the limitations that might occur using live fish. Lauder analyzed an experiment which focused on modifying robotic fin supports to determine which level of stiffness corresponded with maximum performance.

Based on the results, the scientists in this study confirmed that a complex relationship between stiffness and flapping existed. As it turned out, optimal stiffness is based on the frequency of flapping. Constantly altering the shape of their fins allows fish to relax or stiffen their flippers and yield maximum performance with many different speeds. Despite the benefits, Lauder noted that physical models are still imitations and do not yet fully replicate the animals they represent. Even so, employing robotics in research is a safe and favorable alternative for animals that might be harmed for the sake of research. Evidently, these new techniques are incredibly helpful for understanding fish biology and provide innumerable opportunities for future research.

Climate change in Beluga whales

Submitted by kheredia on Tue, 10/29/2019 - 16:36

Climate change can create a cascade of effects throughout entire ecosystems. In marine life, communities that rely heavily on biotic and abiotic factors have experienced the effects of rising temperatures in the ocean. Warming of the sea can be detrimental to life in the future, especially for migrants like beluga whales whose habitat is surrounded by seasonally-ice covered waters. This is why researchers have conducted a study spanning over 30 years to collect data and determine if the ever changing sea ice has had an impact on their migrational behavior. From 1974-2014, scientists followed four traditional migratory routes in beluga whales between wintering and summer  areas of the Alaskan and Canadian arctic.

The methods used to monitor the population included genetic data and harvesting data from whale sightings. Tissue samples from a total of 978 whales were collected and DNA was extracted from each sample and screened. Ariel surveys were taken by native hunters and field biologists which determined the annual arrival times during migration. Lastly, ice conditions were examined through passive microwave-derived sea-ice concentration (SIC). Based on the reports, it was revealed that beluga whales migrated to the Chukchi Sea each summer with its peak population in June at Kotzebue Sound, located in the Arctic.

The results from the SIC demonstrated that the varying sea ice conditions, (5.2% in 1997 vs. 83.7% in 2006), did not affect the times that the distinct populations arrived. However, after the year 1983, the occurrence of beluga whales at this location diminished quite dramatically despite two exceptions in 1996 and 2007. Genetic analysis determined that at one point, in 2007, 90% of the whale migrants to Kotzebue sound had been males, thus, suggesting a link between sea ice conditions and migratory behavior which caused them to alter their course. This phenomena also suggests that changes in the ecosystem may affect gender differently. During the years where sea-ice levels were low, orca whales were able to easily maneuver themselves into the Chukchi Sea. This resulted in an increase in predation, which may have been a contributing factor for evasive shifts in beluga migratory patterns.

The data collected from this study indeed proposed a relationship between ice levels and beluga whale migration, though the research may have been flawed. There most definitely are variables that could have skewed the results that was determined. For example, relying on whale sightings alone does not seem to be a strong enough resource for tracking. There should have been another method used to monitor movement: like attaching a gps tracking device to the mammal. In addition to this, it can be difficult to consistently measure sea-ice conditions that vary considerably throughout the year especially if they are due to underlying factors, which may need more research in the future to eliminate these possibilities.

This study was specifically chosen because of its relation to climate change and as an effort to shine some light on future conservation efforts. If the ocean temperature continues to rise and potentially even affect prey availability for beluga whales, it can pose a huge threat for them in the future. Hopefully soon they receive the rightful attention and action will be taken to conserve, and protect this species.


Autopolyploidy vs. Allopolyploidy

Submitted by kheredia on Tue, 10/29/2019 - 16:33

One important difference between allopolyploidy and autopolyploidy is how they come to be. Meaning, an allopolyploid individual is made when two parent individuals come together with a different number of their pairs of chromosomes (one gamete has 3, the other 2) to form a hybrid that cannot produce viable gametes. An autopolyploid individual happens when the chromosomes of the diploid parent individual go through a meiotic error which causes the chromosomes to divide incorrectly, resulting in gametes having a full set of chromosomes as well (2n). Another major difference between allo- and autopolyploidy is the fact that one could have the opportunity to produce viable gametes with another in its species, while the other self-fertilizes. Allopolyploid hybrids can go through a duplication event and ‘accidentally’ double the number of the chromosomes they have, which allows them to produce sexually again, and meiosis can proceed normally.

Allopolyploid individuals cannot reproduce easily with the two species that made it (similar to autopolyploidy) but can mate and produce viable gametes with another of its species, unlike autopolyploidy, where there is just one parent involved. A third important difference between allo- and autopolyploidy is the amount of genetic variation in each. Because there is only one parent involved for autopolyploidization, there is a small amount of genetic variance within the offspring. But, this is not the case for allopolyploidization. Two species can create a large amount of the allopolyploid hybrids, which can then interbreed between each other. This different origins of the hybrid creates more genetic variation, which allows for natural selection to create more fit hybrids as the generations continue. 



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