Invertebrates
Pyrosome
Pyrosoma spp. · also called sea pickle
Drifting through open water, a pyrosome colony glows faintly at the slightest disturbance, its hollow, tube-shaped body made up not of one single animal but thousands of genetically identical individuals, each pumping water in perfect coordination to keep the whole structure gently moving forward.
Overview
Pyrosomes, genus Pyrosoma, are colonial, bioluminescent tunicates found drifting through tropical and temperate open ocean waters worldwide. Their thousands-strong clone colonies and hollow, glowing, tube-shaped bodies make them one of the more genuinely strange animal groups in the open ocean.
One structure, thousands of individuals
Unlike most animals built from a single connected body, a pyrosome exists as a true cooperative, with every part of its glowing tube made from separate, genetically identical organisms acting together as if they were one.
Status
Not Evaluated — no formal conservation assessment completed, with population numbers known to fluctuate unpredictably across its wide oceanic range.
Pyrosome: common questions
Is a pyrosome a single animal or many animals?
A pyrosome is not a single organism but a colony made up of thousands of tiny genetically identical individuals called zooids, each fused together and functioning collectively as one larger structure, making it more accurate to think of a pyrosome as a cooperative colony rather than one individual creature.
Why does the pyrosome glow?
A pyrosome produces bioluminescent light in response to stimulation such as touch or nearby movement, an ability directly reflected in its name, which derives from Greek words meaning fire body, and this glow can sometimes ripple visibly across the entire colony as individual zooids respond in sequence.
How big can a pyrosome colony get?
Some pyrosome colonies can grow to a considerable size, with certain reported specimens large enough that a diver could swim directly through the hollow centre of the tube-shaped colony, a striking scale for a structure made up entirely of tiny individual clone organisms working together.
How does a pyrosome move through the water?
The individual zooids making up a pyrosome colony coordinate their water-pumping activity, drawing water in through numerous small openings and expelling it through the open end of the tube-shaped structure, and this combined pumping action allows the entire colony to move gradually through the water.