Last Reviewed and Updated on February 13, 2023
Comb Jellies may look like jellyfish, but they’re actually something entirely different. Let’s take a closer look at what these animals are and where they live. Read on to learn more about one of the oldest creatures on the planet, from the basics to the fun facts about comb jellies.
About Comb Jellies
Comb jellies (ctenophores) are usually small, jelly-like animals that are found in salt water. They are typically found in a variety of marine habitats, including shallow coastal waters, deep-sea environments, and pelagic zones.
There are about 100-150 validated species, and together they make up the phylum Ctenophora.
Comb jellies have a distinctive, translucent appearance and are characterized by the rows of cilia (hair-like structures) that line their bodies. The body consists of a mass of jelly (mostly water content) with a two cells thick layer on the outside plus a layer of cells lining the inner cavity. Most are radially symmetric.
These animals mostly feed on small planktonic organisms, such as copepods and larval forms of crustaceans and mollusks.
The conservation status of comb jellies varies depending on the species. Some species are considered to be abundant and not threatened, while others are considered to be at risk of extinction due to factors such as habitat destruction, overfishing, and ocean acidification.
Facts About Comb Jellies
What is unique about comb jellies? Read on and explore some of the most fascinating facts about comb jellies.
Also read: 100 weird facts about animals
1. Comb jellies are not jellyfish
Comb jellies are also commonly known as comb jellyfish, but they are not jellyfish at all. They may look like one, but they are significantly different genetically; they aren’t even as closely related. They are part of their own phylum, Ctenophora.
2. Unlike jellyfish, comb jellies don’t sting
They may look the same, but their tentacles include different structures. Jellyfish have nematocysts, and comb jellies have coloblasts. While nematocysts are used to deliver toxins into prey (or as a defense), the colloblasts found in comb jellies contain adhesives that are used to capture prey and pull it to the mouth. Colloblasts are not venomous. Thus, comb jellies don’t sting.
3. They are named cone jellies because of their cilia
Comb jellies got their name because many have comb-like rows of cilia (tiny hairlike structures) that they use for movement and to capture prey. These cilia beat in coordinated waves, creating a shimmering or iridescent effect that resembles a hair comb.
https://en.wikipedia.org/wiki/Ctenophora#/media/File:Haeckel_Ctenophorae.jpg (pod sliko Kunstformen der Natur (1904), plate 27: Ctenophorae
4. Not all comb jellies have “combs”
Comb jellies come in different shapes and sizes. For example, many adult species in the order Platyctenida lack combs.
5. Comb jellies are the largest animal that swims with the help of cilia
Comb jellies swim by using the coordinated beating of their cilia; the cilia beat in a wave-like pattern, propelling the comb jelly through the water.
Cilia are found in most types of eukaryotic cells and microorganisms known as ciliates. Comb jellies are the largest organism that uses cilia for swimming.
6. Comb jellies are hermaphrodites
Hermaphrodites are organisms that have both female and male reproductive organs and can produce gametes (reproductive cells) from both sexes.
Some comb jellies are simultaneous hermaphrodites, which means they can produce eggs and sperms at the same time, and some are sequential hermaphrodites, meaning that the sperms and eggs are produced at different stages of their lives.
7. Almost all comb jellies are predators, but some do have a parasite phase
Comb jellies are predators; they prey on microscopic organisms as well as small crustaceans.
In a few species, the juvenile comb jellies are parasitic; they live as parasites on the salps (marine invertebrates) on which adult comb jellies feed.
8. They don’t mind cannibalism
Comb jellies also eat comb jellies.
9. Smallest comb jellies are smaller than a pinhead, and the largest are about 5 ft / 1.5 m in size
The venus girdle is the largest known comb jelly; it resembles a transparent ribbon and can reach about 5 ft / 1.5 m in length.
10. Oceanic species are hard to study
Comb jellies, in general, are very fragile organisms; their fragile bodies make them very vulnerable to physical damage. The coastal species are a bit more sturdy, as they are adapted to withstand waves and swirling sediment particles; on the other hand, oceanic species are not.
Oceanic species are mainly known from photographs and aren’t (yet) heavily studied.
11. Comb jellies don’t have a brain
They are one of the few animals that don’t have a brain or a central nervous system. They do have a nerve net.
12. Most species have the ability to regenerate
Most species of comb jellies are capable of regenerating lost or damaged body parts to a certain extent. However, the extent to which comb jellies can regenerate depends on the species and the extent of the damage.
13. Some are bilumniscent
Many species of comb jellies are bioluminescent, meaning they can produce and emit light.
14. In some species, adults can shrink in size if food is scarce
As long as there is sufficient food, comb jellies can release eggs and sperm. When food becomes scarce, they first stop producing reproductive cells, and if that’s not enough, they will shrink in size until the food supply increases again.