“…and today we’re talking about an active kid that grows into a lazy adult. But more on that later.”
A tiny tadpole freely glides along ocean currents, going where it wills, seeking its thrills. The ocean is its oyster. But when a larva is on an adventure, it dreams of home, and when it’s home, it dreams no more. The Gold-Mouth Sea Squirt seeks a throne on which to rest forever–
No more to roam through Life, Death, and Taxonomy.
Description of the Gold-Mouth Sea Squirt
- Picture a hollow, urn-shaped blob that looks like my first-grade attempt at pottery—kinda lumpy and very proud of it.
- Vibrant paint job of white with purple and orange splotches, like my kids’ table after paint day.
- Two siphons sticking out—one on top, one on the side
- The inside edge of those siphons glows a gold-yellow, hence the name
- Skin’s got that tunicate toughness—think leathery but slimy.
- No hair, no fur, just a slick, sessile vibe
Measure Up
Welcome to the beloved Measure Up segment. The official listener’s favorite part of the show! The part of the show when we present the animal’s size and dimension in relatable terms through a quiz that’s fun for the whole family. It’s also the part of the show that’s introduced by you when you send in audio of yourself saying, singing, or chittering the words Measure Up into ldtaxonomy at gmail dot com.
Tadpole length
0.5 to 2 millimeters (500 to 2,000 micrometers)
- 1.6 billion go into the length of the great barrier reef
- 84,496 go into the Jeddah Flagpole in Saudi Arabia
- 140 go into a standard fork
Adult Length
5 to 15 centimeters (50 to 150 millimeters, or roughly 2 to 6 inches)
- 45,000 go into Kjeragbolten
- 450,000 go into the width of Spotted Lake
- 20,000 go into Vĩnh Nghiêm Pagoda
Fast Facts about the Gold-Mouth Sea Squirt
- Range: Hanging out in the tropical eastern Indian Ocean and western Pacific—think Philippines, Indonesia, and northern Australia.
- Habitat: Sticks to coral reefs and rocky surfaces between 16 and 164 feet deep (5-50 meters)
- Diet: Omnivorous filter fiend—slurps up phytoplankton, zooplankton, bacteria, and whatever else floats by, like the ocean’s least picky eater.
- Behavior: It’s sessile, meaning that once it picks a spot as an adult, it’s not moving. It’s already RSVP’d “no” to everything.
- Mating: These weirdos are hermaphrodites, so they’ve got all the parts to go solo or with a buddy—eggs and sperm just float out and hope for the best.
- Lifespan: No hard data, but tunicates like these probably live a few years.
- Predators: Nudibranchs, flatworms, and fish think they’re a snack, but good luck biting into that leathery hide without a side of regret.
- Sounds: Silent as the grave—unless you count the faint whoosh of water getting sucked and squirted, which I’m calling the sea’s lamest ASMR.
The gold-mouth sea squirt (*Polycarpa aurata*) has been studied for its potential to produce bioactive compounds with medical applications. Research has identified several classes of compounds from this species with promising antimicrobial, antitumor, antioxidant, and anti-inflammatory properties.
Major Fact: Cesassionist
This sea squirt goes through a dramatic metamorphosis from a free-swimming, tadpole-like larva to a sessile adult.
The process also reduces its brain function.
(Brain is a strong word. More like brain-like nervous structure.)
In its larval stage, the gold-mouth sea squirt has a tail, a primitive notochord (a precursor to a spine), and a cerebral ganglion—a simple cluster of nerve cells that functions like a rudimentary brain, enabling it to swim and respond to its environment.
This larva actively searches for a suitable surface to settle on, using light and gravity cues. Once it finds a spot, it attaches head-first, and over the course of hours to days, it undergoes a radical makeover: the tail and notochord are reabsorbed, the body reshapes into the urn-like adult form, and the cerebral ganglion largely degenerates.
As an adult, it no longer needs to move, so it trades mobility and that brain-like structure for a life of filter-feeding through its golden siphons.
This process is intriguing because it’s almost like the animal “chooses” to abandon a more complex, mobile existence for a simpler, stationary one—a rare evolutionary pivot. Tunicates like the gold-mouth sea squirt are also among our closest invertebrate relatives, sharing a distant ancestor with vertebrates, and this larval stage hints at that connection with its notochord and nervous system.
The idea of an organism essentially dismantling its own “brain” to adapt to a new lifestyle is a striking example of nature’s adaptability and efficiency.
Ending: So pick your lifetime squatting spot, put on your clown makeup, and become simpler in your old age like the gold mouth sea squirt here in LDT.