Pyrosomes are cylindrical or cone-shaped colonies made up of hundreds to thousands of individuals, known as zooids. Colonies range in size from less than one centimeter to several metres in length.
Pyrosomes and salps are pelagic (free-swimming) tunicates or sea squirts. All species are open ocean animals that rarely come close to shore, and all are colonial, although many salps can also be solitary.
The team on this dive are extremely experienced, with over 20,000 dives around the world logged between them, but no-one had ever seen a pyrosome before!
Pyrosomes get their name (Pyro = fire + soma = body) from their ability to emit light (bioluminescence) – colonies can glow or flash light at night, particularly if touched.