By Mario Meouchi | Staff Writer

     Evolution is the phenomenon in which new traits, aspects, and even species emerge. This has given rise to a wide range of animals, ranging from the beautiful butterfly and the elegant peacock to the many monsters of the deep waters. Deep-sea gigantism is a phenomenon in which deep-sea creatures tend to be larger than those found in the shallow parts of the water.  The tricky nature of accessing the deep sea makes this weird phenomenon an obscure topic, but some explanations have still risen. 

     First, let’s discuss the nature of the deep ocean. It’s a cold environment, with an average temperature of around 4°C, as this is the temperature in which water is the densest. Food is very scarce, the majority of it being in the form of marine snow, a rain of particulate organic matter, bearing barely anything of value after its trip down from the upper layers. It’s a dark and lonely environment, predators have a harder time finding prey to feast on. On top of all of that, we can only imagine the crushing pressures created by thousands of meters of water pressing down on you. How do animals adapt to such harsh and extreme conditions?

     Pressure isn’t as much of a problem, as deep-sea creatures are largely made up of water, the same substance all around them. Gravity is non-restrictive, as the creatures of the world of the three-dimensional ocean are suspended in this large reservoir of liquid. Then, we resort to three rules to explain deep-sea gigantism: Kleiber’s rule, Bergman’s rule, and the Island rule. 

     Kleiber’s rule states that the bigger an animal is, the more efficient it tends to be. Comparing the efficiency of the metabolism of a whale to that of small fish, whales make better use of their food. This comes down to the area to volume ratio. Small animals have a high surface area compared to their volume, while bigger animals’ surface area may be higher, their volume increases much faster, thus decreasing the aforementioned ratio. A lower ratio correlates to a lower level of heat loss to the surrounding cold water via conduction, thus a lower amount of heat needed to be replaced via the metabolism, which in turn significantly decreases the amount of food required to sustain oneself. Larger animals can also consume larger prey, have bigger reserves, and go for longer without eating while searching for more prey or simply a mate.

     Bergman’s rule dictates that animals living in cold conditions tend to be large. Cells will grow in size, and the fact that deep waters contain high levels of oxygen helps that growth. Those larger cells will have a slower metabolism, leading to them looking to live in slow motion as well as having longer lifespans than their shallow counterparts.

     The Island Rule is the rule in which small organisms may grow to large sizes on isolated islands. The ocean would be similar in its limited resources, isolation from the rest of the ocean and low predation. Marine biological diversity was already high, but it saw a boom after the impact of the meteor that caused the extinction of the dinosaurs. With the surface being a treacherous place to be, fishes went deeper and were forced to adapt. 

     One of the most famous examples of such fauna would be the squid. Squids typically do not exceed much more than half a meter in length, however both the colossal squid and giant squid dwarf that by having an average length of 10m and 11m respectively. Another would be sea spiders that normally are about 1 mm in size, whereas sea spiders coming from deep waters have been observed to grow to a meter tall. 

     While it may seem to be counter-intuitive at times, nature works in mysterious and creative ways. Although we might expect animals to shrink under the immense pressure of the deep sea, instead, we see quite the opposite. The large size of these sea creatures can only be explained using three rules. Through the Kleiber, Bergman’s, and the Island rules, one can learn that only through the perfect mix of heat and energy preservation, cell expansion, and oxygen-rich environments can such massive bodies exist and continue to have a large advantage over smaller creatures. Thus, deep-sea gigantism is all but an illogical phenomenon.