The comb jelly, aka comb jellyfish, is the largest species of jellyfish-like creatures that utilizes cilia to swim. These cilia are typically referred to as combs. While they possess the name jelly, they aren’t true jellyfish. There are 208 known species of Comb Jellies, in 66 genera, and 31 families. These fascinating critters can dwell at the surface of the water down to the crushing depths of 23,700+ feet! These creatures are plentiful and not currently listed with the IUCN. But they all face the threats of pollution and climate change.
First the Stats…
Scientific name: Ctenophora
Length: Up to 4.9 feet
Lifespan: Up to 3 years
Now on to the Facts!
1.) These jellies inhabit all the world’s oceans.
2.) Only 186 species are technically recognized.
3.) Their bodies are comprised of a mass of jelly, with a layer 2 cells thick on the outside, and another layer that lines the internal cavity.
4.) Microscopic larvae, rotifers, small crustaceans, and copepods make up the bulk of their diet. Members of the genus Haeckelia prey exclusively on jellyfish and utilize their prey’s nematocysts (stinging cells) into their own tentacles instead of colloblasts.
5.) There are juveniles of 2 species that live as parasites on the salps on which adults of their species feed.
But wait, there’s more on the comb jelly!
6.) Biologists have suggested that ctenophores make up the 2nd earliest branching animal lineage, with sponges being the sister-group to all other known multicellular animals. Other biologists propose that ctenophores emerged earlier than sponges.
7.) Ctenophores are more complex than sponges (cnidarians). However, both ctenophores and cnidarians have the following features: cells bound by inter-cell connections, carpet-like basement membranes, muscles, nervous systems, and sensory organs (in some, but not all species).
Did you know…?
Even though these creatures are soft-bodied, there have been fossil records found that date back as far as 525 million years ago!
8.) Ctenophores are differentiated from all other animals due to having colloblasts (sticky appendages that adhere to prey) although a few ctenophore species don’t have these.
9.) These ctenophores are the biggest non-colonial animals which use cilia (hairs) as their primary method of transportation.
10.) Most species possess 8 strips, coined comb rows, that run the length of their bodies and have comb-like bands of cilia, called “ctenes”, stacked along the comb rows so that when the cilia beat, each comb touches the comb below it.
But wait, there’s still more on the comb jelly!
11.) Just like cnidarians, aka jellyfish, sea anemones, etc., ctenophores’ bodies are comprised of a generally thick, jelly-like mesoglea which sits between 2 epithelia, layers of cells bound by inter-cell connections as well as by a fibrous base membrane which they secrete.
12.) The epithelia of ctenophores have 2 layers of cells rather than just 1, and some of the cells in the upper layer have several cilia per cell.
Did you know…?
The name ctenophora translates to “comb-bearing”, and hails from the Greek κτείς (stem-form κτεν-) which translates to “comb” and the Greek suffix -φορος which means “carrying”.
13.) The outer layer of the epidermis (skin) is comprised of: sensory cells; cells that secrete mucus, that protects their body; and interstitial cells, which can change into other types of cells.
14.) The outer layer also contains colloblasts that are found along the surface of tentacles and are used in capturing prey, or cells having multiple large cilia, for movement. The inner layer of their skin has a nerve net, and myoepithelial cells that serve as muscles.
15.) The internal cavity forms a mouth that can typically be closed by muscles; a pharynx (throat); a wider area in the center that serves as a stomach; and a system of internal canals.
But wait, there’s still a little more on the comb jelly!
16.) 2 of the branches of the pharynx end in anal pores.
17.) When prey is ingested, it is liquefied in the pharynx by enzymes and by muscular contractions of the pharynx. The resulting soap is guided through the canal system by the beating of the cilia, and digested by nutritive cells. The ciliary rosettes in the canals help to move nutrients to muscles in the mesoglea. Finally, anal pores eject smaller unwanted particles; however, most unused food is regurgitated by the mouth.
Did you know…?
Adults of most species can regenerate tissues that are damaged or lost, however only platyctenids reproduce by cloning, splitting off from the edges of their flat bodies portions that develop into new individuals.
18.) Running the length of their body, the outer surface has typically 8 comb rows, called swimming-plates, that are used for swimming.
19.) Some species depend on osmotic pressure to remain buoyant.
20.) Comb jellies don’t have a brain or central nervous system, but rather a subepidermal nerve net (like a cobweb) that forms a ring round the mouth and is thickest near structures like the comb rows, pharynx, tentacles, and the sensory complex furthest away from the mouth.
But wait, there’s still a bit more on the comb jelly!
21.) Some species are simultaneous hermaphrodites, which have the ability produce eggs and sperm at the same time, while others are sequential hermaphrodites (the eggs and sperm mature at different times).
22.) If food becomes scarce, they will stop producing eggs and sperm, and then they’ll shrink in size. When the food supplies return they grow back to normal size and then continue with reproduction efforts. These survival features make it possible for ctenophores to increase their populations very rapidly.
Did you know…?
The comb rows of most planktonic comb jellies produce a rainbow effect, which isn’t produced by bioluminescence but rather by the refracting of light as the combs move about.
23.) Some species of Lobata and Cydippida have a reproduction method called dissogeny; 2 sexually mature stages, 1st as a larva and later as juveniles and adults. During their time as larva they are able to release gametes periodically. After their first reproductive period is completed they won’t produce any more gametes again until later.
24.) 1 population of Mertensia ovum in the central Baltic Sea have been documented as being paedogenetic, and consist entirely of sexually mature larvae smaller than .06 inch.
25.) Most comb jellyfish that live close to the surface are predominantly lacking in color and are nearly transparent. However, some deeper-dwelling species are very pigmented.
But wait, there’s still a tad more on the comb jelly!
26.) Most deeper dwelling species are bioluminescent, but the light is typically green or blue and can only be seen in total darkness.
27.) In comb jellies, bioluminescence is produced by the activation of calcium-activated proteins called photoproteins in cells named photocytes, which are often confined to the meridional canals that underlie the 8 comb rows.
Did you know…?
When some species are disturbed, they have the ability to produce secretions (ink) that luminesce at very much the same wavelengths as their bodies do.
28.) There are currently no known freshwater ctenophores to exist. The closest they come to freshwater is brackish water (partially saline).
29.) Nearly all comb jellies are predatory, sans 1 genus that is partially parasitic.
30.) Comb jellyfish can consume up to 10 times their body weight each day in food!
But wait, we’re almost done with the comb jelly facts!
31.) Juveniles of at least a few species are able to reproduce before reaching their adult size and shape. This combination of hermaphroditism and early life stage reproduction enables small populations to grow at an incredible rate.
32.) It is believed that ctenophores might help to balance marine ecosystems by preventing an over-abundance of copepods from eating all the phytoplankton (planktonic plants), which happen to be the dominant marine producers of organic matter from non-organic ingredients.
33.) That being said though, if left unchecked or allowed to overpopulate, due in part to climate change and/or overfishing, jellies have proved themselves to be invasive and will quickly overtake a habitat.
Now a Short Comb Jelly Video!
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Some source material acquired from: Wikipedia & IUCN
Photo credit: Alexander Semenov
