Barnacles

From Arctic Bioscan Wiki

Barnacles — Class Cirripedia

Barnacles
Barnacle.png
Balanus sp., also known as acorn barnacles, are found in the Arctic.
Scientific classification
Kingdom:
Animalia
Phylum:
Arthropoda
Subphylum:
Crustacea
Class:
Maxillopoda
Subclass:
Thecostraca
Infraclass:
Cirripedia

Arctic_Life | ← More Animals | ← More Invertebrates | ← More Molluscs

Until 1830, when their larval stages were discovered, cirripeds or "barnacles" were classified as molluscs. However, these creatures are now known to be a diverse group of marine crustaceans that settle on structures including shells, rocks, wharves, boats, and even whales! Four barnacle species inhabit the Arctic Ocean, all of which belong to the genus Balanus.

General Information and Anatomy

A nauplius larva: a baby barnacle.

Barnacles exhibit a diverse array of body forms and range in length from a few millimetres to 70 cm. Some are parasitic, burrowing into other animals, and some do not even have a shell. Those found in the Arctic have four to six "plates," secreted by the underlying body wall, that overlap and interlock to create a shell that resembles an igloo. Their shell remains open at the top, but can be sealed off with a four-plated "lid." The animal is attached at its base by a single plate that is cemented to the substrate. Barnacles feed by opening their "lid" and extending their branched arms into the surrounding environment to trap small organisms and detritus. Barnacles also utilize this "lid" during harsh environmental conditions, such as lowered salinities or exposure during low tide - they are able to draw their body and arms deep within their shell and close the "lid" to protect their soft tissues.

Behaviour and Distribution

Arctic barnacles have both male and female reproductive parts. Reproduction is accomplished when an individual unfurls its penis and directly inserts it into the female reproductive organ of another barnacle. Their eggs range in diameter from 0.1 to 0.5 mm and are brooded. In the Arctic, release of larvae is triggered by the presence of abundant food in the water column.

Barnacle eggs hatch into planktonic nauplius larvae, that have a single eye at the front of their head and three pairs of appendages that are used for swimming. Additional appendages and trunk segments appear as the barnacle grows, and individuals eventually settle out of the water column and attach their bodies permanently to the substrate.

External resources

Name ID
NCBI Taxonomy 6675
WikiSpecies Cirripedia
Wikipedia Barnacle
iNaturalist Cirripedia
BOLD 27882

References