Atys semistriatus
A small sand-dwelling sea slug logged uncommonly at Saipan and Xiaoliuqiu, on warm reefs between 24 and 30 C year-round.
A small, inflated shell-bearing sea slug with a smooth, glossy bubble-shaped shell patterned in irregular brown or grey bands that vary a lot from one individual to the next, hence the name. The soft body extends past the shell as a fleshy headshield used for ploughing through sand. Look for it low on the reef, half-buried or crawling across sand and rubble patches rather than out on open coral.
Divers find it moving slowly over sand and rubble patches, often near the base of the reef where it ploughs through the substrate hunting for small prey. It shows no reaction to divers beyond continuing its slow crawl, and it is easiest to spot with a careful eye or a dive light angled low across the sand during the day.
Like other bubble snails in the Haminoeidae family, it hunts by burrowing through sand and swallowing small invertebrates whole, using its fleshy headshield almost like a shovel.
No clear season shows up in the sighting data, and its comfort range of roughly 24 to 30 C spans tropical reefs all year, so any month is fair game at these sites.
Reef neighbours a diver could mistake it for. Use the identification notes above to tell them apart.
Most reliably logged around Saipan in the Northern Mariana Islands, with a second strong cluster at Xiaoliuqiu in Taiwan. Single sightings also come from Bali in Indonesia and Western Australia, so it turns up across a wide swathe of the western Pacific and Indian Ocean on the right sandy habitat.
Mapping where Variably Banded Bubble is logged…
It is most often logged around Saipan in the Northern Mariana Islands and at Xiaoliuqiu in Taiwan, with occasional sightings in Bali, Indonesia and Western Australia. Look on sandy or rubble patches near the reef base rather than on the coral itself.
There is no strong seasonal pattern in the sighting data, and it tolerates a wide warm-water range of about 24 to 30 C, so it can turn up on any dive at these sites throughout the year.
Look for a small, glossy, inflated shell with irregular brown or grey banding that varies between individuals, carried on a soft body crawling slowly over sand or rubble. It stays low on the reef and does not swim in open water.
Exact size data is not confirmed for this species, but like most Atys bubble snails it is small, generally only a couple of centimetres long, making it an easy one to overlook on a sandy bottom.
It burrows through sand using a fleshy headshield extension of its body, effectively ploughing the substrate to find and swallow small invertebrate prey whole rather than grazing like many other reef slugs.
Site and sighting data is aggregated from diver logs, iNaturalist and GBIF. For taxonomy and conservation status:
Elysia Timida
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