I still remember the first time I went night swimming in a quiet bay during the summer. As I moved my hands through the dark, salty water, I noticed these small, gelatinous orbs drifting by. They weren’t scary like the stinging jellyfish I had been warned about. Instead, when my dive light hit them, they pulsed with a rhythmic, rainbow-colored light that looked like a neon sign in the middle of the ocean. It felt like I was looking at a spaceship rather than an animal. These creatures are scientifically known as Ctenophora, but in Hebrew, we call them “Masrekayim,” and in English, they are commonly called Comb Jellies.
Many people mistake them for standard jellyfish because they are clear, squishy, and float in the sea. However, mistaking a comb jelly for a jellyfish is like mistaking a cat for a dog just because they both have four legs and fur. They are fundamentally different creatures with different histories, anatomies, and behaviors. Over the years, as I delved deeper into marine biology, I realized that the Masrekayim are perhaps some of the most misunderstood and evolutionarily significant animals on our planet. They are delicate, beautiful, and sometimes terrifyingly efficient hunters that have survived for hundreds of millions of years.
In this article, I want to take you on a journey beneath the waves to understand what these creatures actually are. We will explore how they move without muscles, how they hunt without stinging, and why scientists are currently fighting over where exactly they fit in the tree of life. If you have ever wondered about the glowing blobs you see in the water, or if you just love weird nature, you are in the right place.
The Magic of the Combs: Understanding the Name
The name “Masrekayim” comes from the word “Masrek,” which means “comb.” This is a direct translation of their scientific name, Ctenophora, which is Greek for “comb-bearer.” When you look at these animals closely, you will see why they earned this name. Running along the length of their oval or spherical bodies are eight distinct rows of tiny hair-like structures called cilia.
These aren’t just random hairs. They are fused together at the base to form little plates that look exactly like the teeth of a hair comb. These plates are known as “ctenes.” This is where the magic happens. Unlike jellyfish, which move by squeezing their bell-shaped bodies to push water out (jet propulsion), comb jellies do not change their body shape to move. Instead, they beat these tiny comb rows in a synchronized wave pattern.
It is a mechanical marvel. The cilia beat one after another in a coordinated rhythm, starting from the mouth and moving downward. This creates a smooth, gliding motion. In fact, Ctenophores are the largest animals on Earth that use cilia for locomotion. Usually, cilia are used by microscopic organisms, like bacteria or single-celled protozoa. To see an animal that can grow to be the size of a watermelon moving entirely by wiggling microscopic hairs is truly a biological anomaly.
The Rainbow Light Show: Bioluminescence vs. Diffraction
One of the most common questions I get when talking about these creatures is about their lights. People ask, “How do they make those rainbow colors?” There is a massive misconception here that needs clearing up. Comb jellies are famous for two different types of light, and they are not the same thing.
First, there is bioluminescence. This is when an animal creates its own light through a chemical reaction, like a firefly. Many comb jellies are indeed bioluminescent. If you disturb them in the pitch-black ocean, they will flash a bright blue or green light. This is a defense mechanism intended to startle predators or perhaps attract larger predators to eat the thing attacking the jelly. This light is internal and chemical.
However, the rainbow effect that fascinates divers during the day or under a flashlight is different. It is not bioluminescence. It is physics. When the tiny cilia in the comb rows beat rapidly, they scatter light. This is called diffraction. It is the same effect you see when light hits the back of a CD or a prism. The moving hairs break the white light from the sun or a flashlight into its component colors—red, orange, yellow, green, blue, indigo, and violet. So, when you see a “disco jelly” pulsing with rainbows, you are actually watching a living prism refracting light as it swims. It is one of the most beautiful sights in the natural world.
Safe to Touch: The Sticky Hunter
If you see a jellyfish, your instinct is to swim away because you do not want to get stung. This is a wise move for Cnidarians (true jellyfish). They possess nematocysts, which are microscopic harpoons loaded with venom. But Masrekayim are different. They branched off from the evolutionary tree long before stinging cells were invented.
Instead of stinging, comb jellies stick. They possess specialized cells called colloblasts. You can think of these cells as spring-loaded glue grenades. When a small prey item, like a copepod or a fish larva, brushes against the tentacles of a comb jelly, these colloblasts burst open and release a sticky, adhesive thread. The prey gets glued to the tentacle. The comb jelly then spins its body or retracts its tentacle to wipe the food into its mouth.
From a human perspective, this is great news. You can hold a comb jelly in your hand without fear. The sticky cells are designed for microscopic plankton, not human skin, so you won’t feel a thing. I have handled many of them during dives to move them out of the way or to show them to students. They feel like firm gelatin, wet and fragile. However, you must be gentle. Because they rely on water pressure to hold their shape, they can fall apart easily if removed from the water or handled roughly.
The Voracious Appetite and the Black Sea Crisis
While they are harmless to humans, comb jellies are absolute nightmares for plankton and fish larvae. They are voracious predators. Some species can expand their stomachs to hold prey larger than themselves. Because they swim continuously to keep from sinking, they are constantly filtering water and capturing food.
This efficiency can sometimes cause massive ecological problems. The most famous example of this occurred in the 1980s involving a species called Mnemiopsis leidyi, or the Sea Walnut. This species is native to the Atlantic coast of the Americas, where its population is kept in check by natural predators. However, massive cargo ships often take in ballast water (water used to stabilize the ship) in one port and dump it in another.
In the early 80s, a ship likely took in water near the United States and dumped it into the Black Sea. That water contained the larvae of the Sea Walnut. The Black Sea had plenty of food and, crucially, no natural predators for this jelly. The result was catastrophic. The comb jellies reproduced at an insane rate. They ate all the zooplankton, which is the food for small fish like anchovies. Then, they ate the anchovy eggs and larvae.
The local fishery collapsed. Fishermen lost their livelihoods, and the ecosystem was on the brink of total death. It was a stark lesson in how delicate nature is. The solution came, ironically, in the form of another invasion. Another comb jelly, Beroe ovata, was accidentally introduced later on. Beroe ovata is a specialized hunter that only eats other comb jellies. It ate the Sea Walnuts, the plankton population recovered, and the fish returned. It was a rare case where two wrongs essentially made a right, but it serves as a warning about the impact of these unassuming creatures.
Evolutionary Puzzles: Are They the First Animals?
For decades, biology textbooks taught us that sponges (Porifera) were the first animals to branch off the evolutionary tree. Sponges are very simple; they have no neurons, no muscles, and no gut. It made sense that they came first, and everything else evolved later.
However, recent genetic studies on Ctenophores have thrown a wrench into this theory. Some genomic data suggests that Ctenophores might actually be the oldest sister group to all other animals, essentially “older” than sponges in the lineage split. This is confusing because comb jellies have a nervous system, muscles, and a complex gut, while sponges do not.
If Ctenophores came first, it implies one of two wild theories. One, that the common ancestor of all animals was complex and sponges “devolved” or lost their complexity over time. Or two, that the nervous system evolved twice independently—once in Ctenophores and once in the ancestors of humans and other animals.
Their nervous system is indeed weird. It doesn’t use the same chemical messengers (neurotransmitters) in the same way we do. They have a “nerve net” rather than a brain. This makes them a focal point for evolutionary biologists trying to understand how thinking and sensing began on Earth. Every time we study them, we find they break the rules we thought we knew.
Regeneration and Immortality
Another fascinating aspect of the Masrekayim is their ability to heal. If a comb jelly is cut in half, it can often regenerate the missing parts. This is a common trait in simple marine organisms, but the comb jelly takes it a step further. There is a fascinating behavior observed in the larval stages of some ctenophores. If the conditions are bad—say, there isn’t enough food—they can actually shrink. They reverse their growth until conditions improve.
Furthermore, recent research has discovered that some species have a “transient anus.” For a long time, it was thought that simple jellies had one opening that served as both mouth and anus. You eat, you digest, and you spit the waste back out the mouth. We now know that Ctenophores have small pores on the opposite end of the body that can open to release waste and then disappear or close tightly. This is a crucial evolutionary step toward the “through-gut” digestive system that humans have.
Where to Find Them
You don’t need a submarine to see Ctenophores. While many strange red and black species live in the deep abyss, many common species live in shallow coastal waters. If you live near the ocean, go to a dock or pier at night. Bring a strong flashlight and shine it down into the water.
Look for small, walnut-sized shapes or long, ribbon-like transparent belts. The ribbon-like ones, such as the Venus Girdle (Cestum veneris), can grow up to a meter long and snake through the water like a shimmering dragon. The most common coastal ones, usually Pleurobrachia (Sea Gooseberries), look like clear marbles with two long, trailing tentacles.
They are present in almost every ocean in the world, from the freezing waters of the Arctic to the warm tropics. They are a vital part of the food web, serving as food for sea turtles, large fish, and even other jellyfish.
Why Should We Care?
You might ask why it is important for the average person to know about Masrekayim. Aside from their beauty, they are indicators of ocean health. Because they reproduce so fast, a sudden bloom of comb jellies can tell us that something is out of balance in the water—perhaps the water is getting warmer, or overfishing has removed their competitors.
They are also a reminder of how much we still have to learn. We explore outer space with fervor, yet right here in our oceans, we have creatures with alien nervous systems and rainbow lights that we are just barely beginning to understand. They challenge our definitions of what an animal is and how life evolved.
Conclusion
The world of the Masrekayim, or Ctenophora, is a blend of delicate beauty and ruthless survival. These creatures, with their shimmering comb rows and sticky tentacles, have drifted through our oceans for hundreds of millions of years, long before the dinosaurs walked the earth. They are not jellyfish; they are something entirely their own—a unique branch on the tree of life that offers us clues about the origins of the nervous system and the resilience of nature.
From the invasive struggles in the Black Sea to the peaceful, light-scattering dance they perform in tide pools, comb jellies are a testament to the diversity of life. Next time you are by the sea, take a moment to look closer at the water. You might just spot a flash of rainbow light, a tiny, silent signal from one of the ocean’s oldest and most fascinating residents. They remind us that there is still magic to be found in the natural world, provided we take the time to look for it.
Frequently Asked Questions (FAQ)
Q1: Do comb jellies (Masrekayim) sting humans?
No, they do not sting. Unlike true jellyfish, comb jellies lack stinging cells (cnidocytes). Instead, they have sticky cells called colloblasts used to capture small plankton. They are completely safe for humans to touch.
Q2: Why do comb jellies glow with rainbow colors?
The rainbow effect seen on the sides of comb jellies is usually not produced by the animal itself but is a physical phenomenon called diffraction. The tiny hair-like cilia beat so fast that they scatter ambient light into a spectrum of colors. However, some species can also produce a blue or green bioluminescent glow in the dark.
Q3: Are comb jellies related to jellyfish?
They are distantly related but belong to a completely different phylum. Jellyfish are in the phylum Cnidaria, while comb jellies are in the phylum Ctenophora. They look similar due to “convergent evolution,” where unrelated animals develop similar traits to survive in the same environment.
Q4: What do comb jellies eat?
They are carnivorous predators. Their diet consists mainly of zooplankton, fish larvae, copepods, and sometimes other comb jellies.
Q5: Can I keep a comb jelly in an aquarium?
It is very difficult to keep them in a home aquarium. They require a specialized tank called a “kreisel tank” that rotates water gently to keep them from touching the walls or corners, which can damage their delicate bodies. They also require massive amounts of live food.
Q6: Are Ctenophores invasive?
Some species can be. The most famous example is Mnemiopsis leidyi, which was accidentally introduced to the Black Sea and caused a collapse of the local anchovy fishery by eating all the food.
