BIOTIC Species Information for Ciona intestinalis
Researched byAngus Jackson Data supplied byMarLIN
Refereed byDr John Bishop
Reproduction/Life History
Reproductive typePermanent hermaphrodite
Developmental mechanismLecithotrophic
Reproductive SeasonAll year Reproductive LocationWater column
Reproductive frequencyAnnual protracted Regeneration potential No
Life span1-2 years Age at reproductive maturity<1 year
Generation time<1 year Fecundity2000-3000 eggs per spawn
Egg/propagule size160 µm diameter Fertilization typeExternal
Larval/Juvenile dispersal potential100-1000m Larval settlement period
Duration of larval stage2-10 days   
Reproduction Preferences Additional InformationReproductive 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,
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