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.

Why is shark DNA so fascinating?

 

Marine scientists all over the world are using new, innovative technology to better understand sharks genetic information that can help us better understand their biology, movement, and evolution. DNA in sharks is rapidly being observed to also show migrating patterns, unique adaptations, and even susceptibility to certain diseases within a species. Marine geneticists have found that the shortfin mako has a genome almost 1.6 times bigger than our own. Other species, such as the great white have also shown a very stable genome, explaining that very little genetic mutations occur. Having a more stable genome leads to being less susceptible to diseases caused by mutations such as cancer. Sharks genomes are also being observed because of their incredible wound-healing ability. Although we have similar genome, our ability to heal isn’t quite as fast, or efficient. Through more studies, we can utilize this information to truly understand them and protect them.

    Sharks have always been so incredibly fascinating to me. Their species, adaptations, movement patterns, etc. Because of external stressors increasing, such as global warming and overfishing, it is so important we study them to learn how we can conserve and understand what makes them up. Diving into their genome could help innovate the idea of genetics itself, and how we could possibly implement that development into human research as well.

Link to article: https://saveourseas.com/worldofsharks/podcast/what-can-we-learn-from-a-sharks-dna#

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.

Sharks May be the Key to a Cure

Sharks may be the Key to a Cure

Scientists believe that sharks hold secrets to cancer and other age related diseases found in humans. Shark DNA reveals mutations that protect them from these diseases. Sharks have the ability to repair strands of their DNA in ways humans are not able to. Our genome is unstable and that leads to use acquiring these age dependent deficiencies. Currently, sharks have DNA 1.5x bigger than human DNA which obviously means they code for things we cant. This research may be the key for us to understand DNA and how it can be applied to help with our own DNA.