Balanus crenatus

Researched By	Nicola White	Data Supplied By	MarLIN
Refereed by	Prof. Alan J. Southward
Taxonomy
Scientific name	Balanus crenatus	Common name	An acorn barnacle
MCS Code	R77	Recent Synonyms	None
Phylum	Crustacea	Subphylum
Superclass		Class	Maxillopoda
Subclass	Cirripedia	Order	Thoracica
Suborder	Balanomorpha	Family	Balanidae
Genus	Balanus	Species	crenatus
Subspecies
Additional Information	No text entered
Taxonomy References	Rainbow, 1984, Bassindale, 1964
General Biology
Growth form	Conical	Feeding method	Passive suspension feeder, Active suspension feeder
Mobility/Movement	Permanent attachment	Environmental position	Epifaunal, Epilithic
Typical food types	Zooplankton and other organic particles of a suitable size, such as detritus and phytoplankton.	Habit	Attached
Bioturbator	Not relevant	Flexibility	None (< 10 degrees)
Fragility	Robust	Size	Small(1-2cm)
Height	Insufficient information	Growth Rate	4.4 mm/month
Adult dispersal potential	None	Dependency	Independent
Sociability	Gregarious
Toxic/Poisonous?	No
Additional Information	Balanus crenatus has a calcareous base, while Semibalanus balanoides has a membranous base. Feeding Balanus crenatus feeds by extending thoracic appendages called cirri out from the shell to filter zooplankton from the water. In the absence of any current, the barnacle rhythmically beats the cirri. When a current is present Balanus crenatus holds the cirri fully extended in the current flow. Barnacles feed most during spring and autumn when plankton levels are highest. Little if any feeding takes place during winter, when barnacles rely on stored food reserves. Feeding rate is important in determining the rate of growth. Moulting Barnacles need to moult in order to grow. Frequency of moulting is determined by feeding rate and temperature. Moulting does not take place during winter when phytoplankton levels and temperatures are low. Size: Balanus crenatus is hermaphroditic and grows up to 25mm in diameter.
Biology References	Rainbow, 1984, Barnes et al., 1963, Bassindale, 1964
Distribution and Habitat
Distribution in Britain & Ireland	All coasts of Britain & Ireland, and offshore in the North Sea and Celtic Sea.
Global distribution	Northeast Atlantic from the Arctic to the west coast of France as far south as Bordeaux; east and west coasts of North America and Japan.
Biogeographic range	Not researched	Depth range	Insufficient information
Migratory	Non-migratory / Resident
Distribution Additional Information	Balanus crenatus is a widespread species that occurs at quite high latitudes in the Arctic. It colonizes a wide range of substrata, attaching to any hard substrata, molluscs and their dead shells (Southward, pers. comm.), often as an initial colonizing species. Densely packed colonies occur particularly in areas exposed to strong tidal streams where few other epifauna survive. It can also be found attached to carapaces of the Norway lobster or Dublin Bay prawn (Nephrops norvegicus) and other crustaceans. Balanus crenatus may have been misidentified as Solidobalanus fallax in shallow waters lying to the south of the UK. The deep water record of Gruvel (noted in Southward, 1998) is an error (Southward, pers. comm.). Balanus crenatus and Solidobalanus fallaxcolonize different substrates and also occur in different temperatures. Solidobalanus fallax occurs in warmer water on shells, false corals, seaweeds and other soft substrata, including plastic bags and synthetic netting (Southward, pers. comm.).
Substratum preferences	Bedrock, Artificial (e.g. metal/wood/concrete), Cobbles, Gravel / shingle, Large to very large boulders, Pebbles, Small boulders	Physiographic preferences	Open coast, Offshore seabed, Strait / sound, Sealoch, Ria / Voe, Estuary, Enclosed coast / Embayment
Biological zone	Lower Eulittoral, Sublittoral Fringe, Upper Infralittoral, Lower Infralittoral	Wave exposure	Extremely Exposed, Very Exposed, Exposed, Moderately Exposed, Sheltered, Very Sheltered, Extremely Sheltered
Tidal stream strength/Water flow	Very Strong (>6 kn), Strong (3-6 kn), Moderately Strong (1-3 kn), Weak (<1 kn), Very Weak (negligible)	Salinity	Full (30-40 psu), Reduced (18-30 psu), Variable (18-40 psu), Low (<18 psu)
Habitat Additional Information
Distribution References	Rainbow, 1984, Barnes, 1953, Barnes et al., 1963, JNCC, 1999, Bassindale, 1964, Southward, 1998
Reproduction/Life History
Reproductive type	Permanent hermaphrodite	Developmental mechanism	Planktotrophic, Lecithotrophic
Reproductive Season	February to September	Reproductive Location	As adult
Reproductive frequency	Annual episodic	Regeneration potential	No
Life span	1-2 years	Age at reproductive maturity	<1 year
Generation time	<1 year	Fecundity	Insufficient information
Egg/propagule size	Insufficient information	Fertilization type
Larvae/Juveniles Larval/Juvenile dispersal potential >10km Larval settlement period Insufficient information Duration of larval stage 11-30 days
Additional Information	Balanus crenatus is an obligate cross-fertilizing hermaphrodite. Nauplii larvae are released from the barnacle between February and September, with peaks in April and late summer when phytoplankton levels are highest. However, release is not synchronised with the spring algal bloom, unlike Semibalanus balanoides. Nauplii larvae are planktotrophic and develop in the surface waters. They pass through six nauplii stages before eventually developing into a cyprid larva. Cyprid larvae are specialised for settlement. They drift and swim in the plankton before selecting a suitable substratum for settlement and metamorphosis. Peak settlement occurs in April and declines until October. Metamorphosis usually takes place within 24 hours of settlement. Barnacles grow rapidly except in winter. April-settled individuals may release larvae the same July and reach full size before their first winter. Individuals that settled later reach maximum size by the end of spring the following year (Rainbow, 1984). Balanus crenatus has a life span of 18 months (Barnes & Powell, 1953). Growth rate varies greatly with the degree of current flow and the presence of silt. Balanus crenatus populations attached to Nephrops norvegicus grew only 2mm in 4 months, whereas populations on rafts grew at 0.2mm per day. This reduction in growth in epizoic populations is attributed to the higher presence of silt and reduction in water currents (Barnes & Bagenal, 1951).
Reproduction References	Rainbow, 1984, Barnes & Powell, 1953, Barnes & Bagenal, 1951