Psychropotes longicauda

The gummy squirrel, or Psychropotes longicauda, is a deep-sea cucumber from the Psychropotidae family. Adults live on the ocean floor, while the larvae drift in open water, sporting a sail-like appendage on their backs that may help them swim. Adults have eighteen short feeding tentacles, each tipped with a leathery disc edged with tiny, retractable projections. Their bodies are highly flexible, reaching 14 to 32 centimeters long, roughly cylindrical but wider and flatter near the front.

At the rear, a tail-like dorsal appendage up to 12 centimeters long may be pointed or split into two uneven tips. A double row of small tube feet runs along the underside, with a single row of larger tube feet on each side. The skin is soft and pliable; preserved specimens turn violet. Larvae have ten tentacles, are transparent with a reddish front end, and bear a single gelatinous dorsal appendage.

They can grow to at least 23 millimeters, not counting the appendage, which may be nearly as long as the body. This species is cosmopolitan in the abyssal zone, found on soft seabeds worldwide, where adults sift through sediment with their tentacles. Its eggs are the largest of any echinoderm, measuring 4.4 millimeters across. Because the larvae do not feed, the yolk sustains them for a long time, allowing wide dispersal.