Cuttlefish Ink: The Secret to Outsmarting Sharks

         Cuttlefish have an escape plan when they are approached by predators, they release a cloud of dark ink. While the ink does help hide them, it also has a strong odor that drives sharks away. The chemicals that give blood a strong scent to sharks is weaker than the ink.  One of the main elements that make up the ink is melanin, it sticks really well to the smell receptors in sharks. Researchers looked deeper into the genetics behind how sharks sense of smell works. They gathered genetic data on three shark species - the cloudy catshark, small-spotted catshark, and great white shark, this would model the shapes of 146 different odor receptors. Sharks have 45 smell receptor genes which is not a lot compared to mammals who have somewhere around 850. What that means for the sharks is that they can detect fewer types of odors but are very sensitive to the ones they actually can smell. When scientists modeled how melanin interacts with these smell receptors, they found that it binds really tightly to the receptor. Because sharks are already sensitive to scents the ink is very overwhelming for them driving them away. The melanin's ability to bind so tightly to the receptors is why the sharks react more to the ink than the metallic smell of blood. 

    I think this article is a very interesting example of how evolution can improve the survival skills of animals. Its amazing that a fish that is on the smaller side can get sharks to leave an area because of the ink's odor. I never realized scientist could just make models of smell receptors using the genetic information from different types of sharks to demonstrate how certain component impact the sharks behavior. In this case it was melanin which i also learned gives the black color to the ink. This article kept me very engaged because of the way they connected animal behavior with genetics. It made me realize that something as simple as ink can be a product of natural selection. 

A Shark Divide

 A recent Forbes article, titled "Three Sharks, Three Fates: The Genetic Divide Of Great Whites" by marine scientist and science communicator Melissa Cristina Marquez covers new research published by scientific journal Current Biology. Researchers Isabel Wagner, Irina Smolina, Martina E.L. Koop, etc. took genetic samples of 89 different Great White Sharks, then categorized the sharks by genetic similarity.

It turns out that Great White Sharks are genetically divided into three lineages: North Atlantic, North Pacific, and Indo-Pacific. These lines rarely mix due to habitat isolation. Specifically, ocean currents keep these groups of sharks apart in different ocean basins. Yet, interbreeding is still possible. The researchers also bring into question the possibility of sharks inheriting roaming behavior, a possible reason why different shark lineages may also stay on their respective areas.

This divide, however, presents a problem for the species in that depletion of one group could not be replenished by another. Marquez mentions that the genetic divide puts the Great White Shark in real danger of extinction, especially combined with other threats, such as pollution or poaching.

Could the three different lineages of the Great White Sharks evolve into completely new species, with their own separate niches? It is possible, but unlikely that we would see it anytime soon. Or, could there only be one lineage that survives? As of now, the possibilities for where this genetic division might go are practically endless. What may be be most likely (and most cynical to reason) is that human-caused habitat destruction and poaching may result in all three lineage's deaths. Evolution is happening now, all around us, and with us. It's hard to tell what direction it may go.

Pondering aside, I would like to do more research on each type of lineage. Different lineages concentrated in each area might indicate differences in each type of shark. That could mean differences in diet, physical appearance, or it could just be genetic differences. Either way, I would like to know.

ARTICLES:

https://www.forbes.com/sites/melissacristinamarquez/2024/11/08/three-sharks-three-fates-the-genetic-divide-of-great-whites/

https://www.sciencedirect.com/science/article/pii/S0960982224008601?dgcid=coauthor

https://www.britannica.com/science/ocean-basin

https://bio.libretexts.org/Bookshelves/Introductory_and_General_Biology/Map%3A_Raven_Biology_12th_Edition/22%3A_The_Origin_of_Species/22.01%3A_The_Nature_of_Species_and_the_Biological_Species_Concept/22.1.02%3A_Formation_of_New_Species/22.1.2.2%3A_Reproductive_Isolation#:~:text=In%20some%20cases%2C%20populations%20of,now%20reproductively%20and%20genetically%20independent.

Scientists just mapped the great white shark's genome

A recent discovery made by scientists may provide clues on how to heal wounds and fight cancer.  Theses scientists have been working to map the Great White shark genome and have finally succeeded.  While mapping the genome, they found some interesting things such as "jumping genes" and genes that balance them out.  These genes copy themselves and insert themselves into different parts of the genome.  However, instead of becoming unstable and increasing errors and damage to the coding, the sharks have these stabilizing genes that help it stay stable.  This type of instability is common with cancer and age-related disease.  They believe that with a better understanding of these genes that they could create better way to fight cancer, age-related diseases and heal wounds.

Longevity Clues Tucked in Great White Shark Genome

In a recent article on "TheScientist," the great white shark is discussed, as new discoveries have suggested its DNA being linked to wound healing, cancer protection, and a long life. The great white shark has almost double the amount of chromosome pairs as humans do with a total of 41 pairs. A research team analyzed and sequenced the entire genome and came across very interesting results. They found specific genetic changes/adaptations that have contributed to the species' success on Earth for such a long time. These genetic changes include DNA repair, damage response and tolerance, and wound healing including, blood clotting agents and proteins to produce new flesh. Due to sharks being so large in size and having a long lifespan, they should theoretically, have more time and cells for oncogenic mutations to develop. With this new data, researchers were able to conclude that the organim's genetic adaptations have helped put them at a lower rate of developing cancer. The researchers hope that fully understanding these genes that protect the sharks from cancer, could be used to benefit humans. 

 

I found this article to be extremely interesting as it discusses that more research could lead to human benefits. If the great white shark's DNA can be used to cure cancer or prevent it in humans, that would be a major breakthrough discovery that would really change the world.