Balanus crenatus
Encyclopedia
Balanus crenatus is a species
of acorn barnacle
in the Balanidae
family. It is found in the North Pacific and the North Atlantic Ocean.
species distributed in intertidal and sublittoral
zones of the North Pacific and the North Atlantic. It has a similar distribution to Balanus balanus
, a species with which it is often associated.
and the reproductive organs develop during the winter. Individuals in a group fertilise each other and, after a period of maturation, nauplii are liberated into the water. After a number of moults, the larvae settle out of the zooplankton
in about April and attach themselves to rocks and stones on the sea floor. B. crenatus is a fast growing barnacle and can grow from a length of 3 millimetre (0.118110236220472 in) to 9 mm (0.354330708661417 in) in the month of May after settling. It is fully grown by August and ready to reproduce in its first winter.
.
The main predator
is the juvenile common starfish
(Asterias rubens). Medium sized barnacles seem to be at greatest risk. Small specimens are ignored while large specimens seem able to withstand attack but in some years, the population is decimated.
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of acorn barnacle
Barnacle
A barnacle is a type of arthropod belonging to infraclass Cirripedia in the subphylum Crustacea, and is hence related to crabs and lobsters. Barnacles are exclusively marine, and tend to live in shallow and tidal waters, typically in erosive settings. They are sessile suspension feeders, and have...
in the Balanidae
Balanidae
Balanidae is a family of barnacles of the order Sessilia.- Genera :* †Alessandriella Carriol, 2001* Amphibalanus Pitombo, 2004* Arossia Newman, 1982* Austromegabalanus Newman, 1979* Balanus Da Costa, 1778* †Concavus Newman, 1982...
family. It is found in the North Pacific and the North Atlantic Ocean.
Description
The shell of B. crenatus is made of six calcareous plates and grows up to 25 millimetre (0.984251968503937 in) across. The upper edge of the plates are toothed and the shell is often tilted to one side. The opercular aperture is diamond shaped and protected by two further plates which can slide across when the animal is not feeding.Distribution
This is a borealBoreal ecosystem
The term boreal is usually applied to ecosystems localized in subarctic and subantarctic zones, although Austral is also used for the latter....
species distributed in intertidal and sublittoral
Neritic zone
The neritic zone, also called coastal waters, the coastal ocean or the sublittoral zone, is the part of the ocean extending from the low tide mark to the edge of the continental shelf, with a relatively shallow depth extending to about 200 meters...
zones of the North Pacific and the North Atlantic. It has a similar distribution to Balanus balanus
Balanus balanus
Balanus balanus is a species of acorn barnacle in the Balanidae family. It is native to the colder seas of the northern hemisphere.-Description:...
, a species with which it is often associated.
Biology
This barnacle is a hermaphroditeHermaphrodite
In biology, a hermaphrodite is an organism that has reproductive organs normally associated with both male and female sexes.Many taxonomic groups of animals do not have separate sexes. In these groups, hermaphroditism is a normal condition, enabling a form of sexual reproduction in which both...
and the reproductive organs develop during the winter. Individuals in a group fertilise each other and, after a period of maturation, nauplii are liberated into the water. After a number of moults, the larvae settle out of the zooplankton
Zooplankton
Zooplankton are heterotrophic plankton. Plankton are organisms drifting in oceans, seas, and bodies of fresh water. The word "zooplankton" is derived from the Greek zoon , meaning "animal", and , meaning "wanderer" or "drifter"...
in about April and attach themselves to rocks and stones on the sea floor. B. crenatus is a fast growing barnacle and can grow from a length of 3 millimetre (0.118110236220472 in) to 9 mm (0.354330708661417 in) in the month of May after settling. It is fully grown by August and ready to reproduce in its first winter.
Ecology
This species is mainly found in the sublittoral zone but can sometimes be found under stones or overhangs on the lower shore. It colonises pebbles, bedrock, shells and artificial structures. It is found in both calm and exposed waters and can tolerate low salinity levels and is found at depths of up to 60 metres (196.9 ft). It seems to favour habitats with strong currents and when overcrowding occurs, may be distorted to fit the space available. It is often found growing alongside another species of barnacle, Balanus balanusBalanus balanus
Balanus balanus is a species of acorn barnacle in the Balanidae family. It is native to the colder seas of the northern hemisphere.-Description:...
.
The main predator
Predation
In ecology, predation describes a biological interaction where a predator feeds on its prey . Predators may or may not kill their prey prior to feeding on them, but the act of predation always results in the death of its prey and the eventual absorption of the prey's tissue through consumption...
is the juvenile common starfish
Common starfish
The Common Starfish or Common Sea Star is the most common and familiar starfish in the north-east Atlantic. It has five arms and usually grows to between 10–30 cm across, although larger specimens are known. The Common Starfish is usually orange or brown, and sometimes violet;...
(Asterias rubens). Medium sized barnacles seem to be at greatest risk. Small specimens are ignored while large specimens seem able to withstand attack but in some years, the population is decimated.