Amphibalanus

Classification

Phylum: Arthropoda
Subphylum: Crustacea
Class: Maxillopoda
Subclass: Thecostraca
Order: Sessilia
Family: Balanidae
Genus: Amphibalanus

Pronunciation

How to pronounce Amphibalanus: //ˌæm.faɪˈbæl.ə.nəs//

These audio files are automatically generated. While they are not always 100% accurate, they are a good starting point.

Images

Amphibalanus amphitrite 31174971 by Sam Kieschnick. Used under a CC BY 4.0 license.

Amphibalanus amphitrite 29212775 by coenobita. Used under a CC BY 4.0 license.

Amphibalanus amphitrite 19527836 by 廖榮祥. Used under a CC BY 4.0 license.

Amphibalanus amphitrite 2843548 by Even Dankowicz. Used under a CC BY 4.0 license.

Amphibalanus amphitrite 19854221 by Austin Smith. Used under a CC BY 4.0 license.

Amphibalanus amphitrite 30054748 by Jacqui Geux. Used under a CC BY 4.0 license.

Summary

Amphibalanus improvisus, also known as the bay barnacle or European acorn barnacle, is a species of acorn barnacle with a wide distribution in temperate and tropical regions. It is a filter feeder, hermaphroditic, and recognized for its smooth shelled structure.

Physical Characteristics

Amphibalanus improvisus has a smooth white or pale grey conical calcareous shell composed of six fused plates. The shell has an oval or rhombic opening at the top, which is blocked by two hinged plates. Adults typically grow to about 10 mm in diameter and 6 mm in width, though they can grow larger when densely packed. The base of the shell is characteristically grooved radially.

Identification Tips

This species can be confused with the striped barnacle (Amphibalanus amphitrite) and in European waters with the northern rock barnacle (Semibalanus balanoides) or the rock barnacle (Balanus crenatus).

Habitat

Amphibalanus improvisus is found down to a depth of about 6 metres on rocks, man-made structures, buoys, ships' hulls, shells of crabs and molluscs, and certain seaweeds. It is often found in estuaries and low salinity bays.

Distribution

Amphibalanus improvisus has a cosmopolitan distribution in the Atlantic Ocean, the Arctic Ocean, the Baltic Sea, the North Sea, the Mediterranean Sea, and the Black Sea. It has colonized parts of the Indo-Pacific and Australasia and was first recorded in the Baltic Sea in 1844.

Diet

Amphibalanus improvisus is a filter feeder, extending its six pairs of modified legs called cirri to catch plankton and other organic material.

Life Cycle

The species is hermaphroditic, with sperm transferred to a neighbouring barnacle. Eggs are fertilized and brooded, hatching into nauplius larvae that drift with currents. After six naupliar stages, the larvae become cyprid larvae and settle on a suitable surface, cementing themselves and undergoing metamorphosis into juveniles.

Reproduction

This species is hermaphroditic, and after internal fertilization of the eggs, they are brooded in the cavity of the barnacle until they hatch as nauplius larvae.

Ecosystem Role

As an invasive species, Amphibalanus improvisus competes with native organisms and can impact aquaculture by colonizing the shells of cultivated oysters and mussels.

Economic Impact

It is known to block water intake pipes in factories and power stations, creating economic challenges.