''Balanus crenatus'' is a
species
In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...
of acorn
barnacle
A barnacle is a type of arthropod constituting the subclass 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 eros ...
in the
Balanidae
The Balanidae comprise a family of barnacles of the order Balanomorpha. As a result of research published in 2021 by Chan et al., the members of the family Archaeobalanidae were merged with this family.
Genera
These genera belong to the family B ...
family. It is found in the
North Pacific
The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the continen ...
and the
North Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the "Old World" of Africa, Europe an ...
.
Description
The shell of ''B. crenatus'' is made of six calcareous plates and grows up to 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
boreal
Boreal may refer to:
Climatology and geography
*Boreal (age), the first climatic phase of the Blytt-Sernander sequence of northern Europe, during the Holocene epoch
*Boreal climate, a climate characterized by long winters and short, cool to mild ...
species distributed in
intertidal
The intertidal zone, also known as the foreshore, is the area above water level at low tide and underwater at high tide (in other words, the area within the tidal range). This area can include several types of Marine habitat, habitats with var ...
and
sublittoral
The littoral zone or nearshore is the part of a sea, lake, or river that is close to the shore. In coastal ecology, the littoral zone includes the intertidal zone extending from the high water mark (which is rarely inundated), to coastal areas ...
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.
Biology
This barnacle is a
hermaphrodite
In reproductive biology, a hermaphrodite () is an organism that has both kinds of reproductive organs and can produce both gametes associated with male and female sexes.
Many Taxonomy (biology), taxonomic groups of animals (mostly invertebrate ...
and the reproductive organs develop during the winter. Individuals in a group fertilise each other and, after a period of maturation,
nauplii
Nauplius, Nauplia or Nauplios , may refer to :
Greece-related
* Nauplius (mythology), in Greek mythology, the son of Poseidon and Amymone, the father of Palamedes, and also the name of an Argonaut
* Nauplia
Nafplio ( ell, Ναύπλιο) is a ...
are liberated into the water. After a number of moults, the larvae settle out of the
zooplankton
Zooplankton are the animal component of the planktonic community ("zoo" comes from the Greek word for ''animal''). Plankton are aquatic organisms that are unable to swim effectively against currents, and consequently drift or are carried along by ...
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 to 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 . 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 balanus''.][
The main ]predator
Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill th ...
is the juvenile common starfish
The common starfish, common sea star or sugar starfish (''Asterias rubens'') is the most common and familiar starfish in the north-east Atlantic. Belonging to the family Asteriidae, it has five arms and usually grows to between 10–30 c ...
(''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.
References
{{Taxonbar, from=Q542791
Barnacles
Crustaceans described in 1789