Comb Jellyfish

Jellyfish are some of the most fascinating ocean creatures. The comb jellyfish is named for the plates that surround its center and look like combs as it moves through the water. These combs are actually cilia, small projections of their bodies that they use to push themselves around the ocean. These jellyfish belong to a different phylum than other jellyfish. Even though they share a name and have many similar characteristics, they are not closely related. The comb jellyfish is the largest animal that uses cilia to move around, giving them a unique appearance.

Comb Jellyfish Facts

• Comb jellyfish are the common name given to the Ctenophora phylum.
• These jellyfish are the largest animals that use cilia to move around.
• Because of their interesting appearance and propulsion in the water, they are popular in large aquariums.
• Jellyfish do not have any bones, shells, or other heavy structures in their bodies. They are lightweight and around 95% water.
• Some species of comb jellies have been observed eating their own larvae, particularly when other food sources are scarce.

Classification and Scientific Name

Comb jellyfish are actually an entire phylum known as Ctenophora with between 100 and 150 named species, depending on the source. Comb jellyfish are known for their cilia, which look like combs. Some of these species live in the deep ocean, and not very much is known about them. Others were given multiple names when they were first discovered until researchers later realized that they were actually the same species.

Now, Ctenophora is divided into two classes. Tentaculata have tentacles that extend behind their jelly bodies. Comb jellyfish without tentacles are called Nuda. Some are large while others are very small. The Tentaculata are further divided into six orders based on the shape of their bodies, as well as how flat they are, the types of tentacles, and other distinguishing features. There are fewer species within the Nuda class, which only has one order, one family, and two genera.

Other jellyfish belong to the Cnidaria phylum, along with sea anemones and coral. They have some different features that separate them from comb jellyfish. These include the way that they find and eat prey, as well as some aspects of their appearance.

Appearance

Other than the comb-like cilia that give them their name, comb jellyfish vary a lot in size and shape. Smaller species are less than half an inch long, while the largest can grow up to 5 feet. All of them have some features in common, including the cilia arranged on the outside of their bodies that they use to move through the water.

Both true jellyfish and comb jellyfish have two primary layers of cells—an outer layer (ectoderm) and an inner layer (endoderm) — with a gelatinous layer (mesoglea) in between. However, the structure and composition of these layers differ between the two groups.

The cilia on the outside are arranged in eight rows. These are easy to spot and make them really interesting to watch. Large aquariums, such as the Monterey Bay Aquarium, have amazing jellyfish exhibits. Their tanks are backlit to show off the moving rows of cilia. The jellyfish create a mesmerizing ripple effect that visitors really love to watch. While the rainbow effect seen on their cilia is caused by light diffraction, many comb jellyfish species are also capable of true bioluminescence, producing their own light in addition to reflecting ambient light.

Distribution, Population, and Habitat

Ctenophora species live in salt water, except for a few isolated instances where they were transported to lakes and brackish water unintentionally. They can live near the shore or in deep water, although the same species are not suited to both environments. Comb jellyfish that live in shallower water are prepared for strong tides that can move them around. They tend to have lighter and even see-through pigmentation. Deepwater comb jellyfish are more likely to have bold colors. One of the most striking species is the tortuga red. This jellyfish has a dark red body with tentacles on the back.

Comb jellyfish are most common in the Atlantic Ocean and can be found near the eastern side of North and South America. They have expanded to other areas, although they do not often fare as well or develop large populations in these non-native habitats. They can be more plentiful during different times of the year, especially in coastal areas.

Predators and Prey

Some other ocean animals eat comb jellyfish, although they have to eat quite a few to get any sort of sustenance. Because jellyfish are mostly water, they don’t fill up predators quickly. Jellyfish often eat other jellyfish, and you can even see Ctenophora eating other Ctenophora. One study of comb jellyfish in the Baltic Sea found that they ate their young when they didn’t have other nutrients available in their environment. In fact, scientists believed that they intentionally reproduced to create a source of food.

All species of comb jellyfish eat other ocean animals, such as zooplankton, krill, fish larvae, and even other jellyfish. The species with tentacles use them to trap other creatures. But comb jellyfish do not sting like jellyfish that belong to the Cnidaria phylum. Instead, they capture their dinner with their tentacles, which have a sticky substance that physically sticks to their prey.

Reproduction and Lifespan

Most comb jellyfish are hermaphroditic, possessing both male and female reproductive organs, and many are capable of self-fertilization, though some species may require cross-fertilization. Spawning typically happens at night when the surrounding water cools. The temperature of the seawater signals that it is time to release the eggs. They lay up to 8,000 eggs. After they hatch, the young immediately start eating and growing. In less than two weeks, they are able to lay their own eggs, and the cycle begins again.

Because they grow and reproduce so quickly and in such large quantities, you may suddenly see a big boom in their population. Like many similar sea creatures, they need a certain environment in order to spawn. When these conditions occur, the population can seem to explode overnight.

Fishing and Cooking

Unlike other jellyfish, comb jellyfish do not sting and are not dangerous to humans, but that doesn’t mean that they are a common dish. However, in areas where they are common, they have become a part of the local cuisine. They are often salted or served alongside cold, pickled salads, such as kimchi.

Comb Jellyfish Population

The population varies based on location and species. They are very plentiful in the western Atlantic Ocean. They tend to live closer to the surface and are commonly seen in bays and near the coasts. However, some species live in the deep ocean, but these are a bit harder to find and study. Comb jellyfish break apart when they come out of the water. You probably won’t see them intact washed up on the beach, as you may with other jellyfish.