Salmacis sphaeroides

Identification: its shape ranges from oval to conical. The almost cloudy-white test is 5 to 8 cm across and covered with many short (1 to 1.5 cm), spade-like spines, broader and flatter near the oral side. The spines are white with maroon bands, all maroon, or green and maroon; Reef Life Survey describes a brown-green test with red-and-white banded spines.

In the wild it ranges from China to the Solomon Islands and Australia, Singapore and the Johor Strait, from 0 to 90 m (124 m according to SeaLifeBase), mostly in shallow seagrass beds and muddy sublittoral zones, sometimes on reefs. It covers itself with debris or shells as camouflage. It eats algae, bryozoans, seaweed and detritus, swallows loose sediment and scrapes films off hard surfaces. In the Gulf of Thailand a study watched it attack two burrowing urchins (Brissus latecarinatus and Lovenia elongata), stripping their spines before eating their organs; it also eats water hyacinth, sea pens, jellyfish and other urchins, including its own species.

Reproduction: in the laboratory, larvae from artificial fertilisation feed on single-celled algae from day 2 and are ready to metamorphose after 35 days at 24 °C. In 2024 a Chinese team described full rearing from larva to broodstock (harvested at about 71 mm) and presented it as a good aquaculture candidate. It is served in seafood restaurants in Hong Kong.

Status: it has not been evaluated by the IUCN and is not CITES-listed. None of the sources consulted documents keeping it in an aquarium.