On page 24, Carroll says that ice fish “[eliminated] red blood cells altogether”. This means that there is no hemoglobin because erythrocytes contain about 250 million molecules of hemoglobin each. What key roles do red blood cells have that ice fish now lost or have to make up for? Also, if there is no hemoglobin, oxygen cannot attach and be carried throughout the body. How does the ice fish make up for this substantial lack of oxygen? How does it get enough oxygen to the tail and other parts for cellular respiration to occur? How is the ice fish’s environment advantageous for obtaining oxygen?
Subscribe to:
Post Comments (Atom)
Icefish have come a long way in evolution and have completely stopped their need for the production of red blood cells. Their blood is very dilute, with only 1% cells. All of these cells are white blood cells. However, this could be looked at as a problem, because with no red blood cells or hemoglobin, how will the icefish get sufficient oxygen around its body? Hemoglobin is the binding agent to transport oxygen to the cells of the body. Being from Antarctica, these bloodless icefish live in very extreme and cold environments. Frigidly cold environments like the ones they live in, are very oxygen-rich and oxygen-solubility is higher in cold water (Carroll 24).
ReplyDeleteAlso, the icefish have developed large gills and scaleless skin with big capillaries. These are all selective advantages to delivering oxygen throughout the body with gas exchange. The gills are in a moist environment and have a large surface area, making the diffusion of oxygen easier in the cold water.
Technically, since icefish lack red blood cells and hemoglobin, you could say they were anemic. In humans, this is a problem because they can’t get sufficient oxygen to their organs. The icefish, however, have effectively adapted to live with this. Recent studies have shown advances in the information we have on curing anemia in humans. Research has been done with the genes of these icefish to learn more about the disease in humans. These genes have the potential to helping those who have this disease. The mutations from animals like this have helped humans, who look at this condition as a harmful disease.
These organisms, with their adaptations for living in a cold environment, could not survive in a warm environment like ours. They couldn’t even live in a little bit warmer of water. The icefish don’t have the heat shock response to be able to survive in a higher temperature.
The Antarctic icefish also have another condition that would be considered a disease to humans. Being benthic feeders at the bottom of the ocean, it was beneficial for these fish to not develop a swim bladder that allowed them to move up and down in the water. Instead, they only stayed at the bottom and therefore developed a “demineralized skeleton.” Soon, their skeletal system was very weak, a disease to humans called osteopenia. This is a bone condition where the bones have a very low mineral density and the skeletal system becomes weak. While being a disease for humans, this was an adaptation that occurred in the icefish because the strong skeletal system was no longer needed for the environment the icefish lived in.
http://www.physorg.com/news148753307.html597/
http://antarcticsun.usap.gov/science/contentHandler.cfm?id=1540
Red blood cells, or erythrocytes, transport oxygen and help transport carbon dioxide throughout the body. Ice fish have lost the ability to bind oxygen to hemoglobin proteins to transport oxygen throughout the body. In order to make up for this loss, Antarctic ice fish have low metabolic rate, well-perfused gills, increased blood volume, increased cardiac output, cutaneous uptake of oxygen, increased blood flow with low viscosity, enlarged capillaries, large heart, and increased skin vascularity. By having greater vessels around the skin, the ice fish have greater uptake of oxygen through the skin due to scaleless skin (Carroll 24). The body can, therefore, receive oxygen directly from the environment. Like Meagan states above, the ice fish have very dilute blood with 1% leukocytes. Due to the blood’s low viscosity, the blood can travel faster throughout the body along with greater cardiac output and the oxygen diffused into the blood can be transported to various parts of the organism more quickly for cellular respiration to occur. The ice fish’s freezing environment is advantageous for gas exchange through the skin, because the oxygen solubility is much greater in a colder environment, and gases can diffuse easily through the ice fish’s skin, since it is wet and thin. Also, the gills with large surface areas contribute to the ice fish’s gas exchange mechanism.
ReplyDeletehttp://www.pnas.org/content/94/7/3420.full.pdf+html?sid=b216d109-7ec4-4f7c-99ab-1fff2e00498a
http://www.fortunecity.com/greenfield/rattler/46/blood2.htm
In order to understand how icefish are able to survive after their loss of red blood cells, we must first understand what the role of red blood cells in most animals is. Red blood cells, or erythrocytes, are the most numerous blood cells suspended in blood plasma. The main function of erythrocytes is to transport oxygen from the alveolar capillaries of the lungs to the capillaries of working tissues and organs in order for body cells to perform cellular respiration. Their small size, biconcave shape, and lack of a nucleus allow them to have a large surface area for oxygen diffusion. Not only do they lack nuclei, but they also lack mitochondria, which means that they must generate ATP anaerobically.
ReplyDeleteThe reason why erythrocytes lack nuclei and mitochondria is that they have more room for respiratory pigments, which are special proteins that transport oxygen in blood. Some respiratory pigments, such as hemocyanin, are dissolved in blood. However, hemoglobin, which is the respiratory pigment of vertebrates, is found in red blood cells. Hemoglobin has quaternary protein structure and is made up of four polypeptide subunits. Each subunit contains a cofactor (non-protein chemical compound needed for proper protein function) called a heme group. Each heme group contains a porphyrin ring encircling an iron atom, which is able to bind with oxygen. Therefore, each hemoglobin molecule is able to bind with four oxygen molecules.
Hemoglobin binds reversibly to oxygen, meaning that it can load oxygen in the alveolar capillaries and release them in other body parts. This works by cooperativity of the four polypeptide subunits. When oxygen binds to the iron atom of one subunit, the binding induces the other three subunits to change shape, which allows them to have a higher affinity for oxygen. However, when one subunit releases their oxygen molecule, the other three subunits change their shape, which allows them to have a lower affinity for oxygen. The affinity for oxygen of hemoglobin can be shown in an oxygen dissociation curve, which shows that hemoglobin usually uptakes oxygen molecules when there is a high partial pressure of oxygen (such as in the lungs) and releases them when there is a low partial pressure of oxygen (such as in tissues that are working hard).
Since icefish do not have red blood cells, and therefore don’t have hemoglobin, they must transport oxygen that is dissolved in the blood plasma. Even though this is much less efficient than using respiratory pigments such as hemoglobin, their environment and their anatomical adaptations has allowed them to survive with much less oxygen than most other animals, as described by Meagan’s and Amie’s posts.
Sources:
Campbell – Chapter 42 p.883 and p.894-895
As the icefish gradually “lost” their hemoglobin molecules, it would seem impossible for them to survive because they would have very limited ability to transport oxygen to the major organs and muscles. However, when putting their environmental factors into perspective, one would see that since cold water has a greater affinity for oxygen, the amount of dissolved O2 in the water would be more than enough for the icefish to survive on. Since they also developed extra large gills and a larger heart, the dissolved O2 can simply be transported in the blood plasma, thereby not needing any hemoglobin. Looking at a biological stand point, the icefish's evolution of getting rid of red blood cells and developing methods of directly absorbing O2 from the environment is advantageous because it allows them to survive in such cold temperatures, which gives them protection from some predators and allow them to make home of a hostile habitat so that they can survive and reproduce.
ReplyDeleteSo to answer you question, the icefish now do not have a specific function, or any function for that matter, of its 1% red blood cells like Meagan ad pointed out. Therefore, the oxygen needed for cell respiration can simply be supplied by the high concentration of dissolved O2 in the surroundings. Finally, since the icefish live in subzero waters, blood plasma with more red blood cells would be harder to pump, thereby creating unnecessary stress on the organism’s cardiovascular system. Therefore, it would be very advantages for the icefish to evolve a less dense blood plasma with little to no red blood cells so that nutrients can be pumped easier while the oxygen requirements are still met.
Sources:
http://www.physorg.com/news148753307.html597/
http://www.fortunecity.com/greenfield/rattler/46/blood2.htm
http://antarcticsun.usap.gov/science/contentHandler.cfm?id=1540
Ice fish are discussed in the beginning of the novel by Carroll and show how incredible species can be. The most interesting feature of the ice fish is its lack of re blood cells and hemoglobin. This is something that has never been seen before in any vertebrate. With the discovery of the ice fish was the discovery of something never before seen.
ReplyDeleteHemoglobin is a protein that is found in red blood cells. Hemoglobin is made up of two alpha and two beta proteins and has 4 sites where oxygen is carried on from the lungs to vital target organs. With the lack of hemoglobin there is the inability for the ice fish to carry oxygen through the bloodstream to vital organs. This is important because oxygen is used in creating energy for the body to use. Interestingly the lack of red blood cells and hemoglobin make the blood of the ice fish are more fluid. This allows the ice fish to save energy that would have been used in pumping blood throughout their body.
To adapt to this lack of hemoglobin, the ice fish have gills of large surface area that are able to diffuse more oxygen into their body. They also are able to diffuse oxygen through their skin, which allows almost their entire body to receive oxygen.
The fossilization of the hemoglobin gene is able to occur because of the environment that the ice fish live in. The ice fish is able to live in waters that are so cold they can freeze the blood of other fish. This is a reason for the adaptation that has occurred in the lack of red blood cells. Also water that is of a lower temperature is more oxygen rich and so just with diffusion the ice fish is able to receive more oxygen. For these reasons the fossilization of the hemoglobin gene was advantageous to the ice fish in its environment.
http://sickle.bwh.harvard.edu/hemoglobin.html
http://www.eurekalert.org/multimedia/pub/3289.php
http://blogs.reuters.com/environment/2009/02/16/antarctic-ice-fish-redefines-cold-blooded/