Ciona intestinalis

Researched By	Angus Jackson	Data Supplied By	MarLIN
Refereed by	Dr John Bishop
Taxonomy
Scientific name	Ciona intestinalis	Common name	A sea squirt
MCS Code	ZD71	Recent Synonyms	None
Phylum	Chordata	Subphylum	Tunicata
Superclass		Class	Ascidiacea
Subclass		Order	Enterogona
Suborder		Family	Phlebobranchiata
Genus	Ciona	Species	intestinalis
Subspecies
Additional Information	Also sometimes known as a sea vase.
Taxonomy References	Svane & Havenhand, 1993, Naranjo et al., 1996, Millar, 1970, Fox, 1994(a)
General Biology
Growth form	Cylindrical	Feeding method	Active suspension feeder
Mobility/Movement	Permanent attachment	Environmental position	Epifaunal
Typical food types	Seston	Habit	Attached
Bioturbator	Not relevant	Flexibility	High (>45 degrees)
Fragility	Fragile	Size	Medium(11-20 cm)
Height	Up to 15 cm	Growth Rate	10-20 mm/month
Adult dispersal potential	None	Dependency	Independent
Sociability	Gregarious
Toxic/Poisonous?	No
Additional Information	Although not strictly gregarious, Ciona intestinalis occurs mainly in dense aggregations such that it dominates the substratum. These aggregations are believed to be caused by hydrodynamic conditions rather than some preferential selection mechanism by the larvae (Havenhand & Svane, 1991) but see Adult distribution. In Swedish shallow waters there are two distinct growth phases: in summer/autumn after settling and in spring/early summer before spawning. Growth rates have also been recorded as up to 0.7 percent of body length per day. Growth rate is dependent on temperature and body size. The species is permanently hermaphroditic so the sexes are not separate. Filter feeders including ascidians are known to be able to accumulate trace elements such as heavy metals. A detailed account of the anatomy of Ciona sp. is provided by Millar (1953).
Biology References	Robbins, 1985, Svane & Havenhand, 1993, Schmidt, 1983, Naranjo et al., 1996, Petersen et al., 1995, Millar, 1970, Fox, 1994(a), Millar, 1953
Distribution and Habitat
Distribution in Britain & Ireland	Widely distributed round British and Irish coasts.
Global distribution	Widely distributed throughout temperate regions of the world.
Biogeographic range	Not researched	Depth range	Lower shore to at least 500 m
Migratory	Non-migratory / Resident
Distribution Additional Information	Growths of the hydroid %Tubularia larynx% may greatly enhance the settlement and may be a causative factor for ascidian blooms (Schmidt, 1983). Ciona intestinalis is believed to have originated as a North Atlantic species but has spread widely through shipping to all temperate regions.
Substratum preferences	Other species (see additional information), Algae, Artificial (e.g. metal/wood/concrete), Bedrock, Large to very large boulders, Small boulders	Physiographic preferences	Open coast, Offshore seabed, Strait / sound, Sealoch, Ria / Voe, Estuary, Enclosed coast / Embayment
Biological zone	Upper Infralittoral, Lower Infralittoral, Upper Circalittoral, Lower Circalittoral	Wave exposure	Moderately Exposed, Sheltered, Very Sheltered, Extremely Sheltered, Ultra Sheltered
Tidal stream strength/Water flow	Moderately Strong (1-3 kn), Weak (<1 kn), Very Weak (negligible)	Salinity	Full (30-40 psu), Reduced (18-30 psu), Variable (18-40 psu)
Habitat Additional Information
AMBI Group (Borja et al., 2000)	III
Distribution References	Svane & Havenhand, 1993, Schmidt, 1983, Havenhand & Svane, 1991, Naranjo et al., 1996, Millar, 1970, Fox, 1994(a), Branch et al., 1994
Reproduction/Life History
Reproductive type	Permanent hermaphrodite	Developmental mechanism	Lecithotrophic, Oviparous
Reproductive Season	All year	Reproductive Location	Water column
Reproductive frequency	Annual protracted	Regeneration potential	No
Life span	1-2 years	Age at reproductive maturity	<1 year
Generation time	<1 year	Fecundity	2000-3000 eggs per spawn
Egg/propagule size	160 µm diameter	Fertilization type	External
Larvae/Juveniles Larval/Juvenile dispersal potential 100-1000m Larval settlement period Duration of larval stage 2-10 days
Additional Information	Reproductive frequency: The Plymouth Marine Fauna (Marine Biological Association, 1957) recorded Ciona intestinalis reproduction throughout the year. In more northerly populations (Sweden), gamete release peaks in May / June. In Sweden, a variety of reproductive frequencies occur. In shallower waters (0-8m) and reduced salinity (20 psu) the species tends to be semelparous whereas in deeper (15-30m), more stable waters with full salinity (30-32 psu) the species reaches larger sizes, lives longer and is more iteroparous. Adults may reach 2-3 years of age although more typically live for just one year. Spawning: Reproductive capability is size rather than age dependent. In the laboratory, settlement and spawning can be controlled by manipulation of light levels (Whittington, 1967; Woollacott, 74). Light intensity may have some role in the field but spawning and settlement may occur at any time. Whittington (1967) noted that Ciona intestinalis spawned within 4min (±2.6) of exposure to light. Therefore, light exposure may synchronize spawning in some instances, and Ciona intestinalis has been reported to spawn around dawn (Whittingham, 1967). The species is not self fertile and fertilization is external. Sperm remain viable for up to 16 hours after release in the absence of egg substances. However, in the presence of egg substances the sperms viability is reduced to 1.5 hours (Bolton & Havenhand, 1996). After release, the eggs remain viable for fertilisation for up to 30 hours. The eggs are negatively buoyant and sink in still water. They are adhesive and stick to the substratum. The eggs are about 160 microns in diameter, yolky and red or green in colour. Long tapering outer follicle cells radiate from the surface of the eggs. Eggs may be released individually or in mucus strings. The mucus strings tangle with and readily adhere to nearby adults. Dispersal: The embryonic period of development occurs over around 24 hours but is temperature dependent. The newly hatched 'tadpole' larvae may escape from the mucus strings to disperse in the plankton (40-60% of larvae) or may be retained until settlement. Retention in the mucus string may explain the dense aggregations of adults found. In the laboratory, settlement of the swimming larva may take up to six days but in the field this is usually much less (minutes or hours). Some dispersal is possible at the egg stage but most occurs during the short swimming larval stage and is, therefore, limited.
Reproduction References	Svane & Havenhand, 1993, Naranjo et al., 1996, MBA, 1957, Millar, 1953, Whittingham, 1967, Bolton & Havenhand, 1996, Yamaguchi, 1975