Psychropotes

Psychropotes is a genus of sea cucumbers belonging to the family Psychropotidae. These animals can swim, but only when they choose to—it is not a constant ability.

As adults, members of this genus are roughly cylindrical and range in color from red to violet. They have a sail-like structure that helps them swim during their larval stage, but this appendage is no longer needed once they mature.

The larvae are benthopelagic, meaning they live and swim near the seafloor, using that sail to move. Researchers are still unsure what purpose the appendage serves in the fully grown sea cucumber. Larvae are transparent and can reach about 2 centimeters in length.

The genus includes the following species: Psychropotes belyaevi, Psychropotes depressa, Psychropotes dubiosa, Psychropotes dyscrita, Psychropotes fuscopurpurea, Psychropotes hyalinus, Psychropotes longicauda, Psychropotes loveni, Psychropotes minuta, Psychropotes mirabilis, Psychropotes monstrosa, Psychropotes moskalevi, Psychropotes pawsoni, Psychropotes raripes, Psychropotes scotiae, Psychropotes semperiana, Psychropotes verrucicaudatus, Psychropotes verrucosa, and Psychropotes xenochromata.