“Feeding requirements of white sharks may be higher than originally thought”
Hello, welcome back to the final entry on Great White Sharks blog. Last week’s topic focused on phylogenetic trees and the different traits the chosen trees observed about the Great White Shark. In order to close out our series on Great White sharks, this week I will be dissecting a scientific research paper that solely focuses on Great White Sharks. The paper being reviewed focused on the metabolic rates derived from swimming speeds to suggest the feeding requirements of Great White Sharks. This paper was an observational experiment. The scientists used a combination of estimates of swimming speeds and measurements of standard in young white sharks to estimate fuel routine metabolic rates. Simply put, they estimated the swimming speed and their averages and the measurements of the standard metabolic rate, SMR, for young white sharks in order to come up with a routine metabolic rate, RMR. An SMR refers to the minimum metabolic rate needed in order to sustain life at a specific temperature, while an RMR refers to how often an organism should be consuming food in order to keep their fuel sources up.
Research that focuses primarily on the Great White shark are space due to the fact that they live in a range, deep sea, that people can not really access that easily. Great White sharks are also very dangerous apex predators, so being able to capture a few and holding them in captivity would not only be ethically wrong but it would prove to be difficult. Apex predators are predators at the top of the food chain with little to no natural predators. This observational research paper goes into depth about how Great White Sharks time their feeding in conjunction with pinniped colonies. Pinniped colonies refer to seals, which are one of the prey of the Great White Sharks. Using one of the few research papers that focused on Great White Sharks, the authors hypothesized that the Great White Shark would not require to feed as often as others, and could in fact go for longer periods of time without feeding.
The scientists combined estimates of swimming speeds and RMR to estimate feeding requirements of Great White Sharks at an NZ fur colony in Neptune Islands, South Australia. They observed over 9,000 swim speed estimates, and when all of the data was collected what the scientists discovered was that Great White Sharks actually feed more frequently than what was previously suggested, 30kg of marine blubber for 1.5 months (44.1 days), was actually 30kg of marine blubber fro 14.8 days.
The paper was able to show the relationship between the apex predator, the Great White Shark, and their prey. Since the scientists were able to observe the feeding pattern of the Great White Sharks when they were targeting the seal colonies, they were able to not only observe the feeding intervals but the behavioral patterns that go into how the Great White Sharks decide on what to eat. Through continuous observation and data collecting they were able to hypothesize that the reason, the Great Whites were targeting one type of prey for the period they were around the Neptune Island was due to the fact that it was less energy consumptive for them to stick to preying on one type of prey as opposed to different types. They observed that the Great White Sharks also stuck to mainly targeting the newly born seals since it would be easier for them to consume the newborns due to having to exert less energy in a tussle. Their continuous watching showed them that the Great White Sharks feeding intervals and even feeding behaviors were not so random at all, and even more so it showed them some of the steps the Great White Sharks took in order to expend less energy.
As I wrap up the last blog, there are two questions I chose to answer in regard to the research paper I chose. The two questions are:
A) How are these findings unique/new/unusual?
C) How do these findings apply to broader issues in science and/or the world?
A) These findings are groundbreaking because they not only dispel the false notion about Great White Sharks and their feeding patterns and RMR, it also adds to the already minuscule amount of observational research on Great Whtie Sharks. As previously mentioned, Great White Sharks are apex predators that live at a range that we as people can not so easily get to, so the amount of research and data that is collected on them is next to nothing. Having an extra piece of data that scientists swill is able to use in the future to build even better experiments that will maybe one day lead to breakthroughs in the way that we as people understand the different ecological environments on the planet.
C) The study could be used as a tool to further understand the roles of apex predators and the effects that they have on their own ecology. The research can hopefully one day be used in the future as a blueprint in how to approach studying certain relationships in the environment particularly those of predators that we might not have that much access to.
Thank you so much for continuously coming back to my blog every week. I hope I was able to share new information about Great White Sharks with you. If you are interested in reading the full research article, it will be linked below.
Citation: Semmens, J., Payne, N., Huveneers, C. et al. Feeding requirements of white sharks may be higher than originally thought. Sci Rep 3, 1471 (2013).
Hello, welcome back to another week of Great White Shark topics. The previous blog focused on the fuel economy of sharks, their metabolic rates, and how it helps them adapt to their environment. This week we will be talking about phylogenetic trees and how the Great white shark fits into them. Phylogenetic trees are diagrams that represent evolutionary relationships amongst organisms. Today we will be looking at a few phylogenetic trees and discussing their relationships with the Great White Shark and the trait of focus for the tree. The first tree we will be analyzing is:
Phylogenetic Tree 1
From: de Bellard, Maria. (2016). Myelin in Cartilaginous Fish. Brain Research. 1641. 10.1016/j.brainres.2016.01.013. https://www.researchgate.net/figure/Phylogeny-of-myelin-from-chondrichthyes-perspective-The-phylogenetic-tree-summarizes-the_fig4_290624062
This phylogenetic tree is first broken into two main categories, Gnathostomes, and Agnathans. Agnathans are jawless organisms while Gnathostomes are organisms with jaws. The two categories are further divided into Cyclostomes (Agnatha), Chondrichthyans, Actinopterygians, and Sarcopterygians, which are all Gnathostomes. If we look for sharks on the tree, we will see that they are under the category of Chondrichythians. The name Chondrichthyans means cartilaginous fish. Sharks are not the only members of the class Chondrichthyans, chimera, rays, and skates also fall under the same class. However sharks, skates and rays belong under Elasmobranches, while chimeras belong to the subclass Holoesteans. One of the differences between the subclasses is that Elasmobranches, do not have an operculum, gill covering, while Holeseans do, to be put simply. Both subclasses also have a different amount of gills and their embryonic development is different.
Now that you have a bit of backstory to Class and subclasses, let’s focus on the intended topic of the phylogenetic tree. The tree talks about the evolution of myelin proteins. Myelin proteins help with lining the axons of nerves in order for propagated signals to travel faster and main the same strength of the original signal. Understanding how these proteins evolved in these classes can further help scientists understand the nervous systems in them and how their sensory systems work.
The second phylogenetic tree we will be looking at is:
Phylogenetic Tree 2
This phylogenetic tree in comparison to the first phylogenetic tree focuses on elasmobranch adaptations that help with wound healing. For more context I will be adding the graph shown below:
Phylogeny tree 1 and Phylogeny tree 2 are different in the sense that tree 2 did not start from a broad class and work its way into subclasses, it more so shows different Elasmobranchii, while tree one shows the relationships all the way from jaws to how they have different embryonic development. Phylogenetic tree 2 is more finely focus on different Elasmobranchii as opposed to tree 1 which shows broad relationships between different classes and how they deviated in time. Looking at evolutionary changes in animals not only from a physical sense, but a molecular sense could potentially lead to even more understanding of these animals and maybe one day even greater scientific discovery that humans could use to adapt for our benefit.
Thank you once again for showing up and engaging with this weeks’ topic. Can you think of any other traits that phylogenetic trees, can and should focus on? Thank you for reading and see you on the next blog.
Hello, welcome back to another week at my blog. I hope all is well. The topic of discussion last week centered on the Great White Shark’s dermal denticles, their origin, and how they help the Great White Shark in its natural habitat. Today’s topic will be focused more so on an aspect of the Great White Shark that can not be physically seen with the naked eye. Great White sharks are known to be warm-bodied, however, have you ever asked yourself if their temperature is at a constant level or if they are able to thermoregulation? Simply put, Great White Sharks are not able to thermoregulation however, scientists have found that they do something else as a response to their environment.
When studying animals, whether they are marine or terrestrial, and their energy input vs. output, scientists tend to look at their Basal Metabolic Rate or BMR. BMR is the minimal rate of energy expenditure necessary for an organism to maintain life processes. For the longest time, though other species of sharks were able to be held in captivity and studied, the Great White had not had its BMR studied due to the fact that they do not cope well in captivity. It was not until the 1st of July 1979, when a fisheries scientist by the name of Frank Carey was able to follow and study a Great White’s BMR and how their body temperature would react in response. Carey and some of his colleagues heard about Great White sharks in a town nearby that were in the area due to a carcass of a large whale. They organized an expedition and were able to tag one of the sharks in order to study them. One of the things discovered was that the muscles of the Great White are indeed warm and they would, later on, be the first to demonstrate endothermy in this species.
During the experiment, the shark’s muscle temperature deviated, and slowly responded to changes in the water temperature. As the Great White Shark dove deeper into the water, the temperature of the water dropped. As the water temperature dropped, the shark’s muscles began to cool, however, it was not thermoregulation, because the change occurred slowly and several hours after the shark had dove deeper. Meaning that as the shark cooled off it would be releasing heat but the heat release was actually significantly lower than expected which was later on then attribute to the rete mirable. The rete mirable is a complex of arteries and veins that uses countercurrent blood flow to act as a countercurrent exchanger.
The experiment demonstrated that Great White sharks are excellent energy metabolizers. “if the animal were perfectly insulated, the production of metabolic heat would cause its temperature to rise; the rate of temperature increase would be directly related to metabolism. The shark, of course, was not perfectly insulated, and thus its body temperature was the result of a dynamic equilibrium between heat production and heat loss ” (ReefQuest Centre for Shark Research).
Due to their managing of energy Great White sharks do not need to feed as often as other animals, though they feed more regularly than thought before. The latest study done by Semmens et al shows that the feeding gap for Great White sharks is about 14.8 days, meaning that Great White sharks are able to greatly space out their refeeding window. Which if you think about it is absolutely amazing that they can not only go so long without feeding but that their energy expenditure is well maintained and balanced. Shown below is a graph of the results from the mentioned study.
Movements, swimming speeds and metabolic rates of a white shark.
(a) 3.5 h track from a 3.5 m male white shark at the Neptune Islands fur seal colony, Australia, determined by a radio-acoustic positioning system. Inset. a white shark Carcharodon carcharias at the Neptune Islands. (b) Swimming speeds (U, TLs−1) were calculated from locations made at ≤5 s intervals in (a) and used to estimate routine metabolic rate (RMR) (MO2, gO2h−1 as per the figure axis label) (see Materials and Methods for details).
Studying how exactly Great White sharks’ bodies adapt to their surroundings without thermoregulation, and their energy consumption to expenditure ratio can be further studied by scientists in order to maybe one day create technology that would mirror not only energy input to energy output but also to the longevity of the periods of refueling. Perhaps using the research scientist will someday be able to create even better diving suits that mimic the shark’s temperature response in order for us as people to be able to go to even deeper depths of the ocean.
As the blog comes to an end for this week, I leave you with a question: What are some other ideas that you can come up with that scientist could possibly create from studying the fuel economy of the Great White shark and their gradual temperature change? Take your time to ponder and I hope to see you next week for a new topic.
Welcome back to another week on my Great White Shark blog. Last week I introduced the Great White Shark to you all. This week I will be focusing on one interesting anatomical feature that Great White Sharks possess, known as dermal denticles. Dermal denticles are flat rough v-shaped scales that line the bodies of Great White Sharks. The word dermal refers to the skin while denticles refer to the word teeth, which has given them the moniker of skin teeth. Dermal denticles act as a form of defense and hydrodynamics for the Great White shark. What do I mean by that? When people think of the Great White shark, some words that come to mind might include, strong, fast, predatory, ect. Dermal denticles are present on the shark as a form of defense and protection. Even rubbing against the denticles can cause tears in the skin. “The dentine layer of dermal denticles is composed of a hard, crystalline mineral called apatite, embedded in a soft protein, our old friend collagen. Due to their microstructure, dermal denticles are about as hard as granite and as strong as steel.” ( Center for Shark Research). In regards to hydrostatics, dermal denticles help in reducing the amount of drag that Great White Sharks might experience when swimming. They also help with canceling noise so that the shark can be stealthy when hunting its prey. In fact, dermal denticles functions are so impressive swimwear companies have taken to imitating the patterns for professional swimmers and divers. So I know what you are thinking, “What exactly is so unique about a defense mechanism such as this? Yes, it is impressive, but other animals have defense mechanisms as well.”
Well, dermal denticles are regenerative. In fact, all Great White Shark teeth are regenerative. Scientists have now discovered that the way that the dermal denticles regenerate is not random they couldn’t be. The teeth in sharks mouths are controlled by several genes that allow their regenerative properties. Scientists have found that dermal denticles also have genes that control their regenerative properties. Though they are both teeth, dermal denticles and mouth teeth are not the same regenerative wise. In fact, dermal denticles share a more similar regenerative pattern to chick feathers than to teeth regeneration. Their patterns during regeneration are also not random. Scientists have found that dermal denticles are formed by molecular signals that later on form the patterns on the Great White shark.
Though dermal denticles are a unique feature in sharks and some rays, researchers have found that the genes that make and pattern all vertebrate skin appendages, like feathers and hair share a common ancestry with those of dermal denticles. In fact researchers now dermal denticles, skin teeth, evolved first before oral teeth. They were first there as a form of protection but then evolved to a form for acquiring food. The core genes that make a pattern all vertebrate skin appendages, from denticles to feathers and hair, share a common ancestry.
I hope this blog post taught you something new about Great White Sharks. I hope you enjoyed the topic, and see you again on my next post.
Embedded below is a video on shark denticles. Enjoy.
The image below is of dermal denticles that line the shark’s head.
The class Chondrichthyes belong to the Phylum Chordata. Chondrichthyes is a class that contains cartilaginous fishes. The animals in this class are jawed vertebrates that have paired fins, paired nares, a two-chambered hear, scales, and a skeleton composed up of cartilage, and a pair of nostrils. Due to their skeleton being made of cartilage, it is very flexible. This blog will be focusing on one of it’s most famous animals. Based on the description I gave can you guess which animal we will be focusing on?………..
SHARKS !!! Great White sharks to be specific, belong to the Kingdom Animalia, Phylum Chordata, Subphylum Vertebrata, and Class Chondrichthyes and are known as Carcharodon carcharias.
Ask yourself, what exactly do you know about Great White Sharks? I know that what I knew I gathered from movies, the Animal Planet or the news. Prior to researching sharks, I will admit that I held and still hold a bit of a prejudiced view. My limited interactions with the subject of sharks have all mostly been negative. When I think of the word shark, I think of a strong, vicious, and agile predator. The word tends to have a negative connotation when I hear it. The only “good” thought I had of sharks was when I played my Shark Tales video game.
In essence, sharks get a very bad reputation with people. Most people see them as a sort of scary entity that only wreaks havoc and eats surfers’ limbs. However, through this blog, I would love to show that though there are merits in the fear that shark produces in people’s minds, sharks also play an important role in their environment.
When looking at sharks have you ever thought how exactly they are able to maneuver so well in water? Though they are quite large and appear menacing, if they are not agile they will not be able to catch their prey or will easily fall prey to another animal. Depending on the type of shark, they can be found in either shallow coastal regions or deep waters on the ocean floors. The presence of sharks in the ecosystem serves as a regulator of other animals. Without sharks being present in their respective environments as a predator to other predators, the population of predators would vastly increase, and deplete the amount of prey in the ocean, which would, in turn, affect the marine life and ocean itself. Though scary, sharks play a very important role in the marine ecosystem.
Since they are instrumental to the health of the ocean, sharks have to be swift, agile and coordinated in order to keep order in the sea. Sharks are able to swim by moving their heads side to side in the water and use their fins to stabilize and steer themselves. Located on sharks are different kinds of fins that help them function and navigate in the water. For example, their dorsal fins, located on their back help keep sharks from rolling over. Depending on the species will determine the amount of dorsal fins present.
On the side of the sharks is a different type of fin known as the pectoral fin. Pectoral fins are used for steering and help the shark stay lifted in the water. Pectoral fins also help with stabilizing the big body of the sharks. The last two types of fins are the anal and caudal fin. The anal fin is found on the underside of the shark and used for stabilization. Anal fins are not found on all sharks. The final type of fins is the caudal fin which is composed of a top and bottom part. The caudal fin helps with propelling the shark through the water.
This was just a brief synopsis of how sharks are able to maneuver in the ocean. Please come back and join me next time when I speak in depth about any unique anatomical features they possess. I am hoping that by reading my blog, I am able to make people reconsider their prejudice in regards to sharks. Thank you and see you again soon.