Semibalanus balanoides
| Semibalanus balanoides | |
|---|---|
 |
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| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Subphylum: | Crustacea |
| Class: | Maxillopoda |
| Infraclass: | Cirripedia |
| Order: | Sessilia |
| Family: | Archaeobalanidae |
| Genus: | Semibalanus |
| Species: | S. balanoides |
| Binomial name | |
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Semibalanus balanoides (Linnaeus, 1767) |
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| Synonyms | |
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Balanus balanoides Linnaeus, 1767 |
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| External identifiers for Semibalanus balanoides | |
|---|---|
| Encyclopedia of Life | 336009 |
| ITIS | 89687 |
| NCBI | 94630 |
| WoRMS | 106210 |
| Also found in: ARKive, MarLIN, ADW | |
Balanus balanoides Linnaeus, 1767
Semibalanus balanoides is a common and widespread boreo-arctic species of acorn barnacle. It is common on rocks and other substrates in the intertidal zone of north-western Europe and both coasts of North America.
Adult S. balanoides grow up to 15 millimetres (0.6 in) in diameter, and are sessile, living attached to rocks and other solid substrates. They have six greyish wall plates surrounding a diamond-shaped operculum. The base of the shell is membranous in Semibalanus, unlike other barnacles which have calcified bases. When the tide rises to cover the barnacles, the operculum opens, and feathery cirri (modified thoracic appendages) are extended into the water to filter food from the seawater. When the tide falls, the operculum closes again to prevent desiccation; the reduction from the primitive condition of eight wall plates to six is believed to decrease water loss even further by reducing the number of sutures through which water can escape.
S. balanoides is found in the intertidal zone in the world's northern oceans. Its distribution is limited in the north by the extent of the pack-ice and in the south by increasing temperature which prevents maturation of gametes. The mean monthly temperature of the sea must drop below 7.2 °C (45.0 °F) for it to breed.
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