Oneirophanta mutabilis

Lore & Background

The generic name Oneirophanta is from Greek όνειρο (oneiro), 'dream', and φαίνομαι (phainomai), 'to appear', meaning 'the thing that appears as in a dream'. The specific name mutabilis is Latin for 'changeable'. This sea cucumber has an elongate body with a mouth at the anterior end of the ventral surface, surrounded by a ring of twenty tentacles of varying lengths, each tipped with eight projections. Tube feet on the ventral surface vary in number and are usually in a single row or scattered irregularly, while peg-like tube feet run along each side. The dorsal surface is dotted with papillae (conical fleshy projections with sensory tube feet at their apices) that range from 2 to 50 mm in length. The skin is rough, brittle, and somewhat transparent; preserved specimens are white, pale brown, or dark brown.

Reader's Guide

Oneirophanta mutabilis is found on the seabed at abyssal depths in most of the world's oceans, where there is little current and the temperature is permanently about 2 °C. On the Porcupine Abyssal Plain in the Atlantic Ocean, it is one of several sea cucumber species that together make up about 90% of the megafauna. It moves slowly across the sediment, ingesting it, processing it through its gut to remove nutritive organic content, and voiding the indigestible remains. Little is known of its reproduction, but its eggs are smaller than 400 μm in diameter with little nutritive tissue, suggesting some form of abbreviated development. This breeding strategy appears successful, as the species is very abundant. Its discovery during the Challenger expedition and its role as the type species of its genus make it a key reference for deep-sea holothurian studies.

Did You Know?

• Its generic name means 'the thing that appears as in a dream' in Greek.
• The species makes up part of the 90% of megafauna on the Porcupine Abyssal Plain.