THE ANIMAL FILES

Deep-water redfish (sea cucumber)

Actinopyga echinites

The name says “redfish”; the animal is a sea cucumber.

Actinopyga echinites is a brown sea cucumber of tropical Indo-Pacific coasts. Its body is arched above and flatter below, with a rough surface often carrying grains of sand.[1]

Follow the evidence ↓
Deep-water redfish (sea cucumber)
Image: François Michonneau · Commons · CC BY 3.0
Animal group
Sea cucumber, not fish[1]
Skin support
Microscopic rod-shaped spicules[1]
Habitat
Shallow reef flats, lagoons and seagrass beds[1]

A leathery surface with tiny supports

Papillae make the skin rough, while microscopic spicules reinforce it. The brown upper surface and orange-brown underside differ in colour. External texture and internal support describe different scales of the same body wall.[1]

The ends are not identical

The body widens in the middle and narrows toward each end. Around the anus are five pale tooth-like structures. These belong to the rear opening and should not be mistaken for feeding teeth in a mouth.[1]

A shallow-water animal

Despite the English name “deep-water redfish”, the species is recorded on shallow seabeds, including reef flats, lagoons, rubble and seagrass meadows. A common name is less reliable than habitat observations for locating an animal.[1]

A COMMON MIX-UP

Is this a deep-sea fish?

No. It is a sea cucumber recorded in shallow tropical coastal habitats.[1]

TRY A LITTLE REASONING

Why inspect where the tooth-like structures occur?

Reveal the explanation

Their position around the anus distinguishes them from mouthparts and prevents a misleading feeding interpretation.[1]

Sources & editorial notes

Adapted and translated from the cited Wikipedia revisions, with source-linked reasoning. Image credit and licence are listed separately above.

Adapted and translated from Wikipedia contributors; exact revisions are linked below. CC BY-SA 4.0

  1. Wikipedia contributors — Deep-water redfish (sea cucumber) (fixed revision; adapted and translated)
  2. NCBI Taxonomy — Actinopyga echinites (identity and classification)

Last fact check:

One discovery leads to another

Green sea urchinA spiny adult begins as a swimmer.Strongylocentrotus droebachiensis ↗Common starfishA small opening can turn into a meal.Asterias rubens ↗Brook lampreyTeeth appear just when eating ends.Lampetra planeri ↗