Sea Turtles – BioQuakes

Water makes up 71% of our planet while only around 3.5% of the total water on. Earth is fresh. While there is plenty of water around, many animals can’t even drink it. For humans, consuming salt water disrupts cellular processes. Cells try to balance osmotic pressure, and end up losing more water, leading to dehydration. Our kidneys also work to filter out the excess salts, but the high rapid intake of seawater overwhelms our body’s ability to eliminate it. However, marine animals, like the sea turtle, have evolved to live in salty environments. Although sea turtles can process and get rid of the salt from their bodies, they are not too different from humans when it comes to the intake of salt water. You may think how is a sea turtle similar to us? Well Sea turtles have less salt inside their bodies than the ocean around them, and their kidneys can’t make saltier urine than their blood. In order to survive they need less salt in their bodies than their surroundings. The turtles are able to keep the salt from going through its skin because their skin is so tough. Some marine animals are able to regulate their water intake through the food they eat, like in the case of whales, but this does not work for the sea turtle. The main food source for many sea turtles are jellyfish. If you think about the jellyfish, they really dont have much to them. If you had to guess that sea turtles have to eat a lot of jellyfish to get the energy they need you would be right. Jellyfish are 96% water, and 4% salt, which makes them salty just like the ocean. Less than 1% of the jellyfish is used for food. This causes the sea turtle to take in a lot of salt along with its meal. Imagine having more salt than food on your plate! How would you handle the intake of all that salt?

Sea turtles use salt glands to shed out the salt they intake. The salt glands take up a large part of the head region, primarily around its eyes. The glands transport the salt from the turtle’s bloodstream and concentrate it into a salty solution, which is then excreted through the turtle’s tear ducts. Specifically the leatherback sea turtle cries around 8 liters (2 gallons) of tears every hour. Yes, it sounds sad, but sea turtles cry out salt everyday. This process is very important in maintaining sea turtles internal salt balance and allows them to survive in salty environments.

In our AP Biology class, we learned about osmosis which is, the movement of water across a permeable membrane to equalize solute concentrations. The process of a turtle’s regulation of its bodys salt concentration is related to the topic of osmosis. In the case of sea turtles, their bodies must manage the osmotic challenge of living in a salty ocean environment. The process of the turtle using its salt glands involves the movement of water. This process involves moving water to dilute the excess salt, and is a form of osmosis that helps the turtles maintain their internal salt balance despite the high-salt surroundings. As we learned, animals can not have salt water surrounding their cells because it will cause the cells to become severely hypertonic, meaning the cell will completely shrivel up since the water went from a high concentration of water inside the cell to the low concentration of water surrounding it.

Process of osmosis: water going from high to low concentration

Sea Turtles are one of the most fascinating creatures in the world. When snorkeling in the middle of the Caribbean you hope and pray that you get to swim along with one of these wonderful creatures. But little did you know, they have millions of years of history hidden within their shells. Currently, only 7 species of sea turtles are alive, among the seven are those in the genus Lepidochelys: the olive ridley and the Kemp’s ridley. These two species are some of the most popular in the Caribbean Sea yet we know so little about their history. Until…

A group of paleontologists found remains of a turtle shell in 2015 in the Chagres Formation on Panama’s Caribbean coast. This turtle shell happened to be 6 million years old and it represents the oldest known fossil evidence of Lepidochelys turtles.

When analyzing the fossil, the scientists discovered preserved bone cells called osteocytes. These bone cells are the most abundant in the vertebrates and have nucleus-like structures. To test for genetic material the group used DAPI, a blue-fluorescent DNA stain. The test was successful and they were amazed because this was the first time DNA remains have been found in a fossilized turtle that is millions of years old. Not only does this discovery bring understanding to the biodiversity present in Panama millions of years ago, but it also brings a whole new topic of molecular paleontology.

Molecular paleontology is a study of ancient and prehistoric biomatter including proteins, carbohydrates, lipids, and DNA that can sometimes be extracted from fossils. The understanding of how these complex molecules such as DNA and proteins can be preserved in fossils will continue to help scientists now to understand how soft tissues can be preserved over time. In Unit 1 of AP Bio, we are introduced to DNA. DNA is a fascinating molecule that carries most of the genetic instructions used in the growth, development, functioning, and reproduction of all known living organisms and many viruses. It is composed of two long strands forming a double helix structure. Each strand is made up of nucleotides, which consist of three components: Deoxyribose Sugar which makes up the backbone, a Phosphate group that contributes to the backbone structure, and a Nitrogenous base whose sequence encodes genetic information. At this point you may be thinking, why is this turtle so special? Can’t they find DNA in every fossil? Well, you would be shocked; before the discovery of DNA in this 6 million-year-old turtle, scientists were simply amazed by discoveries of DNA over 1 million years old. This is because DNA consists of sequences of base pairs that are chemically linked along the sides of a double-helix structure, resembling a twisting ladder. Being an organic substance, the constituent parts of this helical structure can deteriorate naturally over time. In the absence of active cellular processes within a living organism to repair and replicate DNA, it can degrade relatively quickly, rendering its components meaningless. Although DNA is plentiful and easily obtainable from living organisms, the task of retrieving viable DNA becomes increasingly challenging with extinct organisms, especially the further back in time they lived. All of these reasons indicate why this singular turtle fossil has more to tell about our genetic code than the millions of other fossils we have found over millions of years. Before reading these articles I had never understood how we were able to learn so much about animals and their ways of life just by a single fossil. But this discovery begs the question of why the DNA was able to survive so long within the shell of a turtle and not in the million of other animals around the world?

BioQuakes

AP Biology class blog for discussing current research in Biology

Tag: Sea Turtles

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