Neopetrolisthes spp.
Flat, fan-clawed crabs hiding in anemone tentacles across the Maldives and Indonesia's Sulawesi reefs, year-round in warm water.
Look for a flat, round-bodied crab tucked right into an anemone's tentacles, rarely more than a couple of centimetres across the shell. Colour is typically mottled white or cream with brown speckling, and the two front claws are broad, flattened fans held out in front like a pair of catcher's mitts rather than pincers. It moves in short sideways shuffles and often waves those fan claws through the water to feed, which is usually the first thing that catches a diver's eye. It never strays from its host anemone, so if you see one, look for more sharing the same tentacle crown.
Spend a dive watching one and you will see it stay glued to a single anemone, shuffling around the tentacle mass and periodically sweeping its fan-shaped claws through the water to filter out passing plankton. It barely reacts to divers beyond retreating a little deeper into the tentacles if you get close with a torch or lens, making it an easy, patient macro subject. Look for it on bommies and coral heads hosting large carpet or magnificent anemones, day or night.
Those fan-shaped front claws are not for defence or fighting, they are dedicated feeding tools used to filter zooplankton straight out of the water column, a trait that separates true anemone crabs from the pincer-wielding hermit crabs often found in the same anemones.
No clear seasonal pattern shows up in the data, and with a comfortable range of roughly 26.6 to 29.5 C, these crabs sit on their host anemones on tropical reefs all year round.
Reef neighbours a diver could mistake it for. Use the identification notes above to tell them apart.
Most reliably logged in the Maldives, spread across the Northern, Southern and Central Atolls, and a strong presence through Indonesia, especially Sulawesi. The Philippines turns them up consistently too, from Luzon down through Palawan and Mindanao, with further sightings across Thailand, Australia's Queensland coast, Malaysia, Micronesia and Vietnam.
Mapping where Porcelain Anemone Crab is logged…
Best odds are in the Maldives across its Northern, Southern and Central Atolls, plus Indonesia's Sulawesi and the Philippines from Luzon to Palawan and Mindanao. Thailand, Queensland in Australia, Malaysia and Micronesia also log them regularly.
There is no strong seasonal pattern in the sightings, and the warm 26.6 to 29.5 C range they favour is present on tropical reefs year-round, so any month works.
Check any large anemone for a small, flat, cream or brown mottled crab with broad, fan-shaped front claws instead of sharp pincers. It stays put on the anemone and sweeps those claws through the water to feed.
They stay small, generally just a couple of centimetres across the shell, easy to miss unless you are looking directly into an anemone's tentacles.
Instead of grabbing food with claws like most crabs, they hold out flattened, fan-like claws and filter plankton directly from the passing current, a feeding style closer to a barnacle than a typical crab.
Site and sighting data is aggregated from diver logs, iNaturalist and GBIF. For taxonomy and conservation status:
European Green Crab
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