Marine life  /  Sea urchins  /  Collector urchin
Reviewed 2026-09-06
Species entry

Collector urchin

Tripneustes gratilla

A short-spined urchin that covers itself in weed and shell, common in seagrass.

Size
Test to about 12 cm
Depth
0–25 m
Habitat
Seagrass, shallow sand and rubble
Active
Day and night
Range
Indo-Pacific
Rarity
Lembeh Strait
1 star of 5, found on most dives
SP-01
collector urchin · full body · habitat
4:3 · min 2400px

A round urchin with a test to about 12 cm, dark purple-black to brown with narrow pale bands of tube feet radiating over it, and covered in short spines rarely more than a centimetre or two long, most often white but sometimes orange or dark. It is nearly always carrying something, pieces of seagrass, shell, weed or plastic held over the upper surface by the tube feet, which is where the common name comes from. At a distance a loaded Tripneustes and a loaded flower urchin Toxopneustes pileolus have much the same size and outline. Close up they do not: the flower urchin’s surface is covered in stalked pedicellariae that look like small flowers, with the spines almost hidden between them, while here the short spines are what the surface is made of.

It grazes seagrass and algae, occurs in seagrass beds and on shallow sand and rubble, and can be dense enough over a small area to strip a patch of seagrass down to the sediment. It is one of the region’s food urchins, taken for its roe in the Philippines and Indonesia, so numbers close to settlements say as much about collecting as about the habitat.

Recorded from the shallows to about 25 m.

Where to find:

LocationRarity Best monthsDepthHabitat
Lembeh Strait Indonesia editorial estimate
1 star of 5, found on most dives
Year-round
0–25 m
Seagrass, shallow sand and rubble
Dauin & Dumaguete Philippines editorial estimate
1 star of 5, found on most dives
Year-round
0–25 m
Seagrass and sand
Anilao Philippines editorial estimate
2 stars of 5, usually seen in a week
Year-round
1–25 m
Rubble and shallow sand
Bali Indonesia editorial estimate
2 stars of 5, usually seen in a week
Year-round
1–25 m
Rubble and seagrass
Papua New Guinea Papua New Guinea editorial estimate
2 stars of 5, usually seen in a week
Year-round
0–25 m
Seagrass and rubble

Ratings are per location: 1 means found on most dives that look for it, 5 means a handful of records. Where enough dives have been logged the figure is calculated from them; otherwise it is an editorial estimate, and says so. We publish habitat and destination, not the dive site.

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