Longest bioluminescent salp

Salps (also called thaliaceans) are tiny marine invertebrates that aggregate together to yield much bigger colonial "super-organisms". The longest salp super-organism, containing thousands of tiny individual salps known as zooids, is that of the giant fire salp (Pyrostremma spinosum), a pelagic species that is bioluminescent, hence its name. The colony takes the form of an enormous hollow tube, free-floating and curved, measuring 20–30 m (65 ft 7 in–98 ft 5 in) long and up to 1.2 m (3 ft 11 in) across at its open posterior end, tapering to a much narrower, closed anterior end. When touched, this spectacular-looking structure glows a brilliant white colour, which it can sustain for some time. Moreover, its zooids communicate with each other via this bioluminescence, their emitted light travelling through the colony in waves with each individual zooid producing light that can be seen from several metres away. If attacked by predators such as sea turtles, however, they turn pink and the tube sinks to greater depths. Examples of their tubular super-organism have been filmed on several occasions, especially in waters off mainland Australia, Tasmania and New Zealand.

Found in marine waters worldwide, the giant fire salp exists at depths of 460–3,000 m (1,510–9,850 ft), and its super-organism's thousands of individual zooids, both on its tube's outer surface and on its inner surface, obtain their nutrients by filter-feeding. Despite its extraordinary size and appearance, therefore, the giant fire salp's tubular super-organism is entirely harmless.