Tunicates: The Ocean's Shape-Shifting Blobs That Are Secretly Your Cousins

The Plot Twist You Never Saw Coming

Imagine finding out that the weird, squishy blob stuck to a dock piling is more closely related to you than it is to the clams living next to it. Welcome to the mind-bending world of tunicates—animals that start life with a backbone and end it as living water filters. They're the ocean's greatest identity crisis, and they're about to make you question everything you thought you knew about evolution.

What in the World is a Tunicate?

The Basics: Living Brita Filters of the Sea

Tunicates, also called sea squirts (because they squirt water when you poke them—science is fun), are marine animals that look like translucent bags, psychedelic blobs, or alien fruit, depending on the species. They belong to the phylum Chordata, which means—plot twist—they're more closely related to humans than to any other invertebrate in the ocean.

The Name Game

The name "tunicate" comes from their unique outer covering called a tunic, made of a substance called tunicin. Here's where it gets weird: tunicin is chemically similar to cellulose, the stuff that makes up plant cell walls. These animals are literally wearing plant-like suits. It's like finding out your leather jacket is actually made of lettuce.

The Most Epic Glow-Down in Nature

From Swimming Scholar to Sedentary Blob

Baby tunicates (larvae) are overachievers. They have:

• A notochord (primitive backbone)

• A hollow nerve cord

• A tail for swimming

• Eye spots for detecting light

• A primitive brain

• All the hallmarks of a chordate

Then, in the greatest academic burnout story ever told, they find a nice rock, glue their heads to it, and proceed to absorb their own brain, tail, and notochord. They literally eat their own nervous system and become a filter-feeding blob. It's like going from Harvard valedictorian to professional couch potato, except it's their actual life strategy.

The Reverse Metamorphosis

While butterflies famously transform from crawling caterpillars to flying beauties, tunicates do the opposite—they go from mobile, complex larvae to stationary, simplified adults. Scientists call this "retrogressive metamorphosis," which is a fancy way of saying "evolution's biggest downgrade."

The Tunicate Family Reunion: Meet the Weird Relatives

Sea Squirts: The Classic Model

These are your standard tunicates—blob-shaped, attached to surfaces, and living their best filter-feeding life. They come in colors that would make a rainbow jealous: electric blue, neon orange, deep purple, and translucent clear.

Salps: The Jet-Powered Jellies

Salps are the rebels of the tunicate world. Instead of settling down, they spend their entire lives floating in the open ocean, jet-propelling themselves by pumping water. They can form chains hundreds of feet long, creating living subway trains in the sea.

Pyrosomes: The Fire Bodies

Pyrosomes are colonial tunicates that form tubes up to 60 feet long—imagine a giant gummy worm made of thousands of tiny individuals. They're also bioluminescent, glowing with an eerie blue-green light that earned them the name "fire bodies." Divers have reported swimming through these glowing giants, which must be like passing through a living, breathing aurora.

Larvaceans: The Snot Palace Architects

These tiny tunicates build elaborate mucus houses around themselves—yes, snot palaces—that can be 10 times their body size. They use these structures to filter food, and when the house gets clogged, they abandon it and build a new one. It's like having a disposable mansion made of boogers.

Superpowers That Put Comic Books to Shame

Regeneration: The Ultimate Healing Factor

Some tunicates can regenerate their entire body from just a small fragment. Cut them in half? You get two tunicates. It's like having Wolverine's healing factor turned up to 11. Scientists are studying this ability for potential applications in human medicine and regenerative therapy.

Blood That Breaks Chemistry Rules

Certain tunicates have blood containing vanadium concentrations 10 million times higher than the surrounding seawater. Vanadium is a metal used in steel production. These creatures are literally heavy metal, concentrating elements in ways that would kill most other organisms. Scientists still aren't entirely sure why they do this—it's one of marine biology's enduring mysteries.

The Cellulose Surprise

Remember that plant-like tunic? Tunicates are the only animals known to produce cellulose. This discovery has led to research into sustainable materials and biofuels, because these blob creatures might hold the key to eco-friendly plastics.

Tunicates: The Ocean's Overachieving Janitors

Filter Feeding Champions

A single sea squirt can filter up to 170 liters of seawater per day—that's about 45 gallons. They're living water purifiers, removing bacteria, phytoplankton, and organic particles. Without tunicates, our oceans would be much murkier and less healthy.

The Carbon Capture Experts

Salps and other pelagic tunicates play a crucial role in the ocean's carbon cycle. They eat carbon-containing phytoplankton at the surface, then their fecal pellets sink rapidly to the deep ocean, effectively removing carbon from the atmosphere. They're nature's carbon sequestration system, fighting climate change one poop at a time.

The Evolutionary Plot Twist That Changes Everything

Your 550-Million-Year-Old Cousin

Genetic studies have confirmed that tunicates are our closest invertebrate relatives. Somewhere around 550 million years ago, our ancestors and theirs parted ways. While our lineage kept the backbone and ran with it, theirs decided that was overrated and went for the sedentary lifestyle instead.

The Missing Link That Isn't Missing

Tunicates provide crucial evidence for how vertebrates evolved. Their larvae show us what our ancient ancestors might have looked like—small, tadpole-like creatures swimming in prehistoric seas. Every time you see a sea squirt, you're looking at a living fossil that chose a different evolutionary path.

Tunicates in Human Culture: From Dinner Plate to Laboratory

The Delicacy Dilemma

In Korea, Japan, and parts of the Mediterranean, certain tunicates are considered delicacies. In Korea, Halocynthia roretzi (called meongge) is eaten raw and is said to taste like "rubber dipped in ammonia"—which is certainly one way to describe a flavor. It's an acquired taste that most people never actually acquire.

Medical Marvels in the Making

Tunicates are producing compounds that might save human lives:

• Ecteinascidin 743: A compound from the tunicate Ecteinascidia turbinata is used in cancer treatment

• Anti-inflammatory compounds: Being studied for treating arthritis and other conditions

• Antiviral substances: Show promise against certain viruses

• Regeneration factors: Could revolutionize wound healing and organ regeneration

The Invasion of the Blob Creatures

Invasive Species Extraordinaire

Some tunicates are too successful for their own good. Species like Didemnum vexillum form massive mats that smother everything in their path, covering shellfish beds, docks, and boat hulls. They're like the kudzu of the sea, except squishier and harder to remove.

The Biofouling Nightmare

Tunicates cost the shipping industry millions of dollars annually by growing on boat hulls, increasing drag and fuel consumption. They're so good at attaching to surfaces that researchers are studying their adhesives for potential applications—because if you can't beat them, learn from them.

Climate Change and the Tunicate Takeover

Winners in a Warming World?

Some tunicate species thrive in warmer waters and lower pH conditions—exactly what climate change is creating. While coral reefs struggle, certain tunicates are expanding their range and abundance. It's possible we're heading toward a future ocean dominated by these blob creatures.

The Jelly Ocean Hypothesis

Scientists worry about a potential "jellification" of the oceans, where gelatinous creatures like tunicates and jellyfish replace fish. It's not exactly the underwater world we imagined, but it might be the one we get if current trends continue.

Why You Should Care About Sea Squirts

The Canaries in the Ocean Coal Mine

Tunicates are excellent bioindicators—their presence, absence, or abundance tells us about water quality and ecosystem health. They're sensitive to pollution but resilient to other changes, making them perfect for monitoring environmental conditions.

The Biomimicry Goldmine

Engineers and designers are studying tunicates for:

• Self-cleaning surfaces inspired by their tunics

• Efficient water filtration systems

• Biodegradable plastics from tunicin

• Underwater adhesives that work in saltwater

• Regenerative medicine applications

The Future is Squishy

What We're Still Learning

Every year, scientists discover new tunicate species and new things about known species. Recent discoveries include:

• Deep-sea tunicates that glow in patterns we're just beginning to decode

• Colonial species with specialized individuals like a miniature society

• Chemical communication systems we're only starting to understand

The Questions That Keep Scientists Up at Night

• Why do some tunicates concentrate heavy metals?

• How exactly do they regenerate entire bodies?

• What triggers the dramatic metamorphosis from larva to adult?

• Could their regeneration abilities be transferred to other organisms?

The Last Squirt: Embracing Our Blob Relatives

Tunicates force us to confront our assumptions about intelligence, complexity, and success in evolution. They start with all the equipment for an active, complex life, then choose to become stationary filter feeders. And it works brilliantly for them.

In a world obsessed with constant growth and complexity, tunicates offer a different model: sometimes the smartest move is to simplify, attach yourself to something solid, and let the current bring dinner to you. They've survived mass extinctions, climate changes, and predators for over 500 million years by perfecting the art of being a blob.

The next time you're near the ocean and see what looks like a squishy, unimpressive blob attached to a rock or dock, take a moment to appreciate it. You're looking at a relative—a very distant cousin who took a radically different approach to life. While you kept your backbone and your brain, they traded theirs for the ability to filter-feed, regenerate, and produce chemicals that might one day save your life.

Tunicates prove that in evolution, there's no single path to success. Sometimes the winners are the ones who look like losers, the complex creatures that choose simplicity, the swimmers who decide to settle down. They're nature's reminder that being a highly successful blob is still being highly successful—even if you did eat your own brain to get there.