Discover What Lives at the Bottom of the Gulf of Mexico and Feasts on Dead Animals

When animals die in the sea, their dead bodies sink to the seafloor. These lifeless bodies don’t break down right away because the rate of decomposition is much slower in water. You might expect to see the remains of dead organisms weeks after they sink to the bottom, but this is not the case. Like vultures waiting around to feed on land animals when they die, there are sea scavengers too. They feed on dead organisms at a relatively fast rate, leaving little to nothing behind. The Gulf of Mexico has bottom-dwelling scavengers like this that live on the seafloor and feed on dead animals. 

One of the most significant scavengers that exist on the deep gulf’s sea floor is the giant isopod. This post details all you need to know about this bottom-dweller called the giant isopod. Let’s dive right in!

What Are Giant Isopods?

The giant isopod is one of the many bizarre organisms that live at the bottom of the Gulf of Mexico. It is a sizable arthropod related to decapods (shrimp and crabs). It is also a close relative of Armadillidium, a genus of terrestrial crustaceans commonly known as pillbugs. 

The giant isopod belongs to the order Isopoda, a diverse group of crustaceans that includes woodlice and other related organisms. Any of the 20 large isopod species in the Bathynomus genus can be referred to as a giant isopod. 

Bathynomus giganteus is the largest of all giant isopod species and most likely the largest of all isopods in the world. They can be found in some of the major oceans of the world, where they scavenge the deep waters for food. Due to their carnivorous nature, they are also capable of attacking fish caught in commercial trawls. 

What Does A Giant Isopod Look Like?

The giant isopod looks like a big woodlouse. The size of many species within the Bathynomus genus ranges from 3.1 to 19.7 inches. For Bathynomus giganteus, the size range is typically between 7.5 and 14.2 inches. The largest giant isopod ever found was about 20 inches long, although there are unconfirmed sightings of a 30-inch-long isopod. They are mostly pinkish, pale lilac, or brown in color.

The outer part of the entire body is covered in a multi-segmented hard shell (exoskeleton) for protection and flexibility. Like a typical arthropod, its body is sectioned into the head (cephalon), thorax (pereon), and abdomen (pleon). The organism has two pairs of antennae, one pair being longer than the other. Isopods use their antennae and compound eyes to detect their environment. 

This crustacean has seven pairs of legs for movement on the seafloor. The first set of appendages is designed in such a way that it can be used to actively direct food into the organism’s mouth. The abdomen is divided into five segments, each containing a pair of pleopods (swimmerets). These pleopods and the fan-like tail allow the isopod to swim gracefully in the waters of the Gulf of Mexico and other locations where it lives. Apart from swimming, the pleopods also work with the flat gill-like structures known as rami to aid the isopod’s respiration.

Even though they are very similar, the male individual can still be distinguished from the females based on a couple of morphological features. You can see these differences on the underside of the species with the help of a magnifying glass. The segment plates of male isopods have a pointed arch shape, while those of females have a rectangular shape. The last pair of appendages in the males also appear to be longer than those of the females.

What Do Giant Isopods Feed On?

Giant isopods are creatures that feed on the dead, decaying bodies of animals in the ocean. These animals, also known as bottom carrion feeders, often have limited access to food resources on the seafloor. As a result, they may go long periods without finding a meal. For giant isopods, these periods of starvation can last for several years.

These big arthropods have a slow metabolic rate and can survive for years without food. A giant isopod in captivity could live for five years without food! Due to their deep-sea habitat, these bottom dwellers must be able to wait for food to come to them.

Giant isopods are dependent on food particles that fall from shallower waters. These particles, known as “falling marine snow,” often appear as white flakes by the time they reach the sea bottom. The “snow” may consist of crab flesh and marine worms, among other animal debris. Occasionally, giant isopods may be lucky enough to get big food in the form of dead whales and other large animals. 

In an experiment to demonstrate how the giant isopods that live at the bottom of the Gulf of Mexico feed, scientists dropped three dead reptiles in the water. In the 2019 experiment, the scientists recorded the isopods in action. The video showed how the deep-sea dwellers decimated the carcass within a short time. The creatures used their powerful mandibles to tear away at the tough flesh of the alligators, feeding quickly until they could barely move. 

Behavior and Adaptation of the Scavenger That Lives at the Bottom of the Gulf of Mexico

The reason why giant isopods grow to be extremely big is still a topic for debate. Some suggest that their lack of predators may contribute to their size, but the more probable explanation is the theory of deep-sea gigantism. According to this theory, certain deep-sea dwellers tend to grow larger than their shallow-water counterparts of the same species. Since pressure increases with depth, deep-sea gigantism is a mechanism that allows the giant isopod to cope with the enormous pressure that bombards its body at such great depths.

Thanks to its flexible exoskeleton, a giant isopod can curl up and look like a ball when threatened. Woodlice show this defense mechanism as well. It protects the soft, vulnerable underside from predators and leaves only the outer, tough exoskeleton exposed. 

Since the food supply in the deep sea environment is limited, it is not much of a surprise that the species always go on a feeding frenzy anytime they find food. They stuff in so much food at a go that they can hardly move. 

Another way giant isopods cope with the sparse supply of food is by constantly staying in semi-hibernation. When they are in this state, their metabolism is slower, and they rarely move around to conserve energy. 

How Do Giant Isopods Reproduce?

Giant isopods reproduce sexually. The female lays eggs and waits for fertilization by the males. The female giant isopod has about 30 unfertilized eggs kept in a pouch (marsupium) on its underside. The male carries two distinct sexual organs on its underside. Usually, the male deposits its sperm into the female right after she molts. The process is easier at this point because the body is softer. 

The female keeps the fertilized eggs in the marsupium until they hatch. The offspring come out fully developed as miniature giant isopods (manca). The only body part lacking in juveniles is the last pair of appendages.

Conclusion

Giant isopods, which are crustaceans that live at the bottom of the Gulf of Mexico, are considered pricey due to their scarcity and the difficulty of breeding them in captivity. In Taiwan, they are considered a delicacy and are often boiled and served with rice. Some people claim that they taste similar to shrimp or crabs. They are not typically aggressive towards humans and can be kept as pets, but they can inflict painful bites if they are mishandled. Even if you can’t dive to the depths of the Gulf of Mexico, where giant isopods are found, you may be able to see them on display in some aquariums.

Up Next 

• What Lives At The Bottom of The Mississippi River?
• Discover Why Scientists Are Dropping Dead Alligators into the Gulf of Mexico
• What Lives At The Bottom of Lake Superior?

The photo featured at the top of this post is © iStock.com/LindaZ