Outer-hermit sea anemone (Calliactis polypus)
Source-cited species reference: taxonomy from WoRMS, biology from SeaLifeBase, occurrence map from GBIF, description from Wikipedia.
Last updated
Diego Delso · via Wikipedia: Calliactis polypus · CC BY-SA 4.0
Calliactis polypus is a species of sea anemone in the family Hormathiidae. It is usually found living on the surface of a sea snail shell in which a hermit crab is living.
Scientific classification
- KingdomAnimalia
- PhylumCnidaria
- SubphylumAnthozoa
- ClassHexacorallia
- OrderActiniaria
- FamilyHormathiidae
- GenusCalliactis
- SpeciesCalliactis polypus
Named by (Forsskål, 1775)
Close relatives
Other species of Calliactis with a Codexery entry.
- 'Parasitic' anemone (Calliactis parasitica) Calliactis parasitica
- Hermit anemone Calliactis tricolor
Sources: Wikipedia taxobox: Calliactis polypus (CC BY-SA 4.0) · order, family and genus agree with WoRMS AphiaID 220515 (CC BY 4.0)
Where the outer-hermit sea anemone (calliactis polypus) has been recorded
Each dot is a place where the species has been observed and reported (413 records, half-degree grid) — not a modelled range. 35 inland records left out (institution coordinates).
Map: drawn by Codexery. Data: GBIF occurrence search (records CC0 / CC BY) · Natural Earth basemap (public domain) · place coordinates: Wikipedia (CC BY-SA 4.0)
Classification (WoRMS)
Full classification as recorded by WoRMS: Kingdom: Animalia · Phylum: Cnidaria · Class: Hexacorallia · Order: Actiniaria · Family: Hormathiidae · Genus: Calliactis.
Accepted name: Calliactis polypus · Authority: (Forsskål, 1775) · Taxonomic status: accepted · AphiaID: 220515.
Synonyms and superseded combinations recorded for this taxon: Actinia decorata Couthouy in Dana, 1846; Actinia polypus; Adamsia decorata; Adamsia miriam Haddon & Shackleton, 1893; Calliactis decorata (Drayton in Dana, 1849); Calliactis miriam Haddon & Shackleton, 1893; Cribrina (Tristemma) polypus Ehrenberg; Priapus polypus Forsskål, 1775.
Source: World Register of Marine Species (WoRMS) — https://www.marinespecies.org/aphia.php?p=taxdetails&id=220515 (CC BY 4.0). Accessed 2026-09-25.
Biology and life history (SeaLifeBase)
Measured values published by SeaLifeBase for Calliactis polypus. Only fields the database actually holds for this species are shown; these are database values, not aquarium guidance.
Depth range: 0–638 m · Habitat zone: sessile.
Source: SeaLifeBase species summary (SpecCode 42338) — https://www.sealifebase.se/summary/Calliactis-polypus.html (CC BY-NC 3.0 — non-commercial use only). Accessed 2026-09-25.
Distribution and occurrence records (GBIF)
413 georeferenced occurrence records for Calliactis polypus are published through GBIF from 48 countries or marine areas. The map above plots 136 distinct locations from a sample of 413 records, omitting 35 inland records that carry an institution's coordinates rather than a collection site; it shows where the species has been observed and reported, not a modelled range.
Most records by country or area: United States of America (98); Australia (70); Philippines (45); Korea, Republic of (29); French Polynesia (28); Egypt (14); New Caledonia (13); Indonesia (11); Tanzania, United Republic of (11); Japan (10); Oman (8); Mexico (7); Ecuador (5); South Africa (5); Mozambique (4).
Marine regions with a valid WoRMS distribution record: Mozambican Exclusive Economic Zone; Indo-West Pacific; Red Sea; Gulf of Mexico; Marshall Islands Exclusive Economic Zone; Philippine Exclusive Economic Zone; United States Exclusive Economic Zone; French Polynesian Exclusive Economic Zone; Ecuadorean Exclusive Economic Zone; Djiboutian Exclusive Economic Zone; Cape Verdean Exclusive Economic Zone; Tanzanian Exclusive Economic Zone; Japanese Exclusive Economic Zone; Gulf of California; Andaman Sea; Pacific Coast of Costa Rica.
Source: GBIF Occurrence Search (taxonKey 10570072) — https://www.gbif.org/occurrence/search?taxon_key=10570072&has_coordinate=true (records CC0 / CC BY); WoRMS distribution records (MarineRegions) — https://www.marinespecies.org/aphia.php?p=taxdetails&id=220515 (CC BY 4.0); Natural Earth 110m basemap — https://www.naturalearthdata.com/ (public domain). Accessed 2026-09-25.
Description and natural history (Wikipedia)
C. polypus can grow up to 8 cm (3 in) long. Several anemones can grow on one shell.
The base is wide with wavy edges and pink striations and flares out over the shell surface. The column is wider at the base than further up and has pale brown and white patches and longitudinal striations. The oral disc has several whorls of long brownish translucent tentacles with paler bases surrounding the mouth.
C. polypus is found in the Indo-Pacific area and the Red Sea. It lives in the neritic zone at depths down to about 25 metres (80 ft).
C. polypus lives as a commensal with several species of hermit crab including Dardanus gemmatus. The anemone shows no inclination to attach itself to a gastropod shell with or without a hermit crab.
However the crab shows great interest in the anemone and taps and massages the base of the column with its legs until the anemone relaxes and the pedal disc becomes detached. The crab then picks up the anemone and holds it against the shell in which it is living. Both the pedal disc and the tentacles are very sticky and either can quickly form a firm attachment to the shell.
Source: Wikipedia: Calliactis polypus — https://en.wikipedia.org/wiki/Calliactis_polypus (CC BY-SA 4.0). Accessed 2026-09-25.
Sources
Compiled from Wikipedia and the sources listed below. Text from Wikipedia is available under CC BY-SA 4.0; this entry is adapted from it.
- Wikipedia: Calliactis polypus (CC BY-SA 4.0).
- Classification: the source article's taxobox; order, family and genus checked against WoRMS, the World Register of Marine Species (CC BY 4.0).
- Occurrence records: GBIF (CC0 / CC BY). Basemap: Natural Earth (public domain).
- Biology values: SeaLifeBase species summary (CC BY-NC 3.0, non-commercial).
- Word definitions: the , each quoted from its Wikipedia article.
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