Sea apple

Lore & Background

Sea apples are holothuroids, sharing many physical characteristics with other sea cucumbers. Their ovate body can grow up to 7.8 inches long, with a central mouth surrounded by feathery tentacles. They have rows of tube feet for movement and adhesion. The Australian species has a primarily purple body, red feet, and purple and white tentacles. Sea apples feed primarily on plankton, filtering it from the water with their tentacles, usually at night to avoid predators.

Reader's Guide

Sea apples are notable for their vivid appearance and defensive adaptations. When disturbed, they can eviscerate their internal organs or release the toxic saponin holuthurin into the water. They can also swell to nearly double their size by consuming seawater, allowing them to be carried by currents to new areas. In captivity, sea apples are often desired for marine aquariums due to their appearance, but they face challenges such as starvation from low plankton levels and harassment from other tank inhabitants like hermit crabs and fish. Their toxin release can poison other aquarium species, contributing to their rarity in home tanks.

Did You Know?

• Sea apples can release a toxic saponin called holothurin into the water as a defense mechanism.
• When threatened, they can swell to nearly double their original size by consuming seawater.
• The Australian species has a primarily purple body, red feet, and purple and white tentacles.
• Sea apples often starve in aquariums because plankton levels are lower than in their natural habitat.