The deep sea is a mysterious dark void untouched by humans. There a lots of fascinating creatures in it, but a lot of them follow a similar trend. A lot of animals in the deep grow to be much, much larger than their shallow water counterparts. This phenomenon is called deep sea gigantism.
Why does it happen? There are many explanations that try to answer this question. One is that the lack of gravity and because of the pressure in the deep ocean, the animals can sustain much larger bodies without being weighed down or hindered. There are two main laws that try to explain deep sea gigantism: Kleiber's law and Bergman's law. Kleibers law proposes that larger animals are much more efficient due to how the circulatory system and blood vessels work. This makes their metabolisms much slower, because surface area increases more slowly than volume does. Slow metabolisms are great in the deep because food is so rare. Bergman's law is that sea animals size tends to increase when temperature gets lower. This helps with keeping warm, and it works because the deep sea is incredibly cold due to the lack of sunlight. Personally, I think that Bergman's law makes more sense, as there have been examples of gigantism happening in shallow but cold Antarctic waters.
One example of deep sea gigantism are amphipods. These disgusting little buggers are normally a tiny 8 milimeters in shallow water, but in the deep the become giants. 10,000 meters underwater, you can find the 34 centimeter long supergiant isopod gorging on dead animals. Another example are squid. On the surface, most squid aren't that large, but if you go down, you can find the colossal squid. These behemoths weigh a whopping 700 kilograms and are 15 meters long. They hold the record for largest invertabrate and largest eyes of any animal. Another bizarre squid species is the magnapinna, a type of squid that has large fins and even longer tentacles that they hold perfectly straight down. The reason they hold their tentacles like that is to filter out plankton in the water below while not being seen.
- Image Credit to NOAA
Even though deep sea gigantism is more common in invertebrates due to them not needing bones, there are some vertabrate giants too. One example are sleeper sharks, a group of deep sea sharks that can grow to massive sizes. One such species of sleeper shark is the greenland shark, which can grow a massive 7 meters in length. These sharks move very slowly and have very slow metabolisms, letting them live to over 300 years old.
- Image Credit to National Geographic
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