BIOTIC Species Information for Corbula gibba
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Researched byLizzie Tyler Data supplied byUniversity of Sheffield
Refereed byThis information is not refereed.
Taxonomy
Scientific nameCorbula gibba Common nameBasket shell
MCS CodeW2157 Recent SynonymsNone

PhylumMollusca Subphylum
Superclass ClassPelecypoda
Subclass OrderMyoida
SuborderMyina FamilyCorbulidae
GenusCorbula Speciesgibba
Subspecies   

Additional InformationNo text entered
Taxonomy References Hayward et al., 1996, Hayward & Ryland, 1995b, Tebble, 1976,
General Biology
Growth formBivalved
Feeding methodPassive suspension feeder
Active suspension feeder
Mobility/MovementBurrower
Environmental positionInfaunal
Typical food typesPhytoplankton, diatoms and bacteria. HabitFree living
Bioturbator FlexibilityNone (< 10 degrees)
FragilityIntermediate SizeSmall(1-2cm)
HeightInsufficient information Growth RateSee additional information
Adult dispersal potential100-1000m DependencyIndependent
SociabilityGregarious
Toxic/Poisonous?No
General Biology Additional InformationGrowth
Corbula gibba is a small bivalve mollusc. The growth rate of Corbula gibba is rapid during the first few months of its juvenile stage although it is very slow in adults (Jensen, 1990). In Nissum Bredning, Denmark the growth of juvenile Corbula gibba was rapid during their first two months (July-August) but leveled off in September and October at lengths ranging from 2.9-3.5 mm (Jensen, 1988). Thus juvenile Corbula gibba reached a size of 3 mm within the first 1-2 months after settling (Jensen, 1990). The absolute growth rate for that period was about 0.03 mm/day and remained constant until the end of August. No further growth was observed in September and October (Jensen, 1988). One year after juvenile settlement, specimens reached a mean size of 6 -7 mm. In the Limfjord (Denmark) it was suggested that the variation in growth rates was caused by variable frequencies of wind induced resuspension of settled organic matter. In the Limfjord wind speeds above Beaufort force 8 caused mixing of the water column and probably resuspension of bottom material in 1986. These conditions probably favour Corbula gibba as it is one of the most efficient bivalve particle feeders (Kiøboe & Mohlenberg, 1981). In 1985 the wind speeds never exceeded force 8 and no mixing was observed. This resulted in lower abundances of Corbula gibba and slower growth rates (Jensen, 1990).

Slower growth rates have been recorded in the Danish Sound where it took a population of Corbula gibba seven months to reach a mean size of 1.1 mm (Muss, 1973). Whereas in Port Erin on the Isle of Man it took one year for a population of juveniles to reach a mean size of 4 mm (Jones, 1956, Jensen, 1990). Jones (1956) also reported that the specimens of Corbula gibba on the Isle of Man had a modal length of 2.25 mm. Jensen (1990) suggested that the higher growth rates in the 1990's in Danish waters could be the result of specific events such as eutrophication. However, in Nissum Bredning no specimens were found over two years old in 1990. The size of Corbula gibba around the British Isles ranged from 0.5 mm in length to 1.2 cm in the 1940's (Yonge, 1946), and in Australian waters it can reach sizes up to 1.5 cm (CRIMP, 2000).

Abundance
Corbula gibba is often found in very large numbers and is often abundant in eutrophic areas (Pearson & Rosenberg, 1978). Corbula gibba are known to occur in enormous numbers, for instance 7450/m², at certain localities in the Atlantic (Healy & Lamprell, 1996). In the Limfjord, sampling of Corbula gibba was carried out at monthly intervals from April 1986 to May 1988. Ten samples were taken with a HAPS-corer (0.014 m²) and sieved over a 1 mm sieve (Jensen, 1990). The density for Corbula gibba ranged from 9,000 to around 53,000 per m². Newly settled Corbula gibba ranged from 30,000 and 67,000 individuals per m² (Jensen, 1988). In Pula Harbour in the Northern Adriatic, Corbula gibba was found at densities ranging from 33 -121 individuals / 0.2 m² (Hrs-Brenko, 1981). Corbula gibba is also found in Australia, outside of its native range, at densities of up to 250/m² in Port Philip Bay (CRIMP, 2000).

Biomass / Production
During 1974-1984 nitrogen concentration and primary production of specimens of Corbula gibba in Nissum Bredning increased from 50-100 % and 200-300 %. The production (P) of Corbula gibba is generally high. Productivity was measured over two years and ranged from 0.7-72 g AFDW (ash free dry weight) m²/ yr. with an average of 26.8g AFDW m² / yr. in Nissum Bredning. The production / biomass ratio was amongst the highest recorded with a mean P / B of 4:2 per year (Jensen, 1990).

Respiration
Laboratory studies have shown that Corbula gibba are able to survive long periods at near anoxic conditions. After 57 days, 9 out of 14 specimens survived 10 -11°C and oxygen levels of 0.18 to 0.37 mg oxygen per dm³ (Christensen, 1970).

Burrowing
Corbula gibba is a shallow burrowing bivalve with very short siphons (Yonge & Thompson, 1976). When placed on their normal substratum, individuals extrude their thin long foot to a distance that may exceed the length of its shell (Yonge, 1946). The process of burrowing is very slow. For example, an individual 1 cm long took about 30 minutes to burrow below the surface. This is slow when compared to other bivalve species, for example Abra alba that can disappear below the surface in less than a minute. It is the stout rounded shell that makes slow progress into the substratum, whereas Abra alba has a much flattened shell and foot therefore slides quickly into the substrata (Yonge, 1946).

Predators
Corbula gibba is consumed by gastropods, crustaceans, fish and echinoderms. Predators of Corbula gibba include the necklace shell Natica poliana (Jones, 1956), the sand star Astropecten irregularis (Christensen, 1970), the brittle star Ophiura texturata, the common starfish Asterias rubens, the common shore crab Carcinus maenas and the brown shrimp Crangon crangon (Jensen, 1988).

Non-native species
In Australia, Corbula gibba is an alien species and a pest (CRIMP, 2000). Corbula gibba is now widespread and highly abundant in Port Phillip Bay (Australia) (Talman, 1998; cited in Talman & Keough, 2001). Corbula gibba might affect endemic Australian species via habitat modification, predation on planktonic larvae, and competition. It also possesses a number of characteristics that may give it a competitive advantage over Australian endemic species, such as the capacity for fast growth and the ability to tolerate a wide range of environmental conditions including anoxia and eutrophication (Jensen, 1990; Talman & Keough, 2001). Concern has arisen in Australia regarding the impact of Corbula gibba on the commercial scallop Pecten fumatus. Corbula gibba and Pecten fumatus overlap in distribution, and as suspension feeders, it has been suggested that they utilize similar food and therefore may be competing for space and food (Talman & Keough, 2001). It was found that ambient densities of Corbula gibba had a significant impact on the size and growth of the native juvenile Pecten fumatus but not on mortality rates (Talman & Keough, 2001). Scallops in the presence of Corbula gibba had shells that were, on average, 35% lighter, 24% smaller and exhibited 54% less growth (based on caging experiments) (Talman, 2000: cited in NIMPIS, 2002). As a result of these concerns Australian authorities have developed new methods to control the spread of Corbula gibba. However, measures such as dredging / beam trawling / mopping, changing salinity and oxygen deprivation have all proved relatively unsuccessful (McEnnulty et al., 2001a).

Biology References Jensen, 1990, Rasmussen, 1973, Lauckner, 1983, Jensen, 1988, CRIMP, 2000, Kiørboe & Møhlenberg, 1981, Hrs-Brenko, 1981, Yonge, 1946, Jones, 1956, Yonge & Thompson, 1976, Muus, 1973, Pearson & Rosenberg, 1978, Talman & Keough, 2001, Christensen, 1970, McEnnulty et al., 2001a, NIMPIS, 2002, Healy & Lamprell, 1996, Hayward & Ryland, 1990,
Distribution and Habitat
Distribution in Britain & IrelandCommon and widespread on all British coasts. The species is probably more widespread than mapped but records are not readily available.
Global distributionCorbula gibba is distributed from the Norwegian Sea south to the Iberian Peninsula, into the Mediterranean and Black Seas, and along the coast of West Africa to Angola.
Biogeographic rangeNot researched Depth range
MigratoryNon-migratory / Resident   
Distribution Additional Information

Global distribution
Corbula gibba has spread and outside its native range. This species and its larvae can survive long periods in ballast water and can generate heavy or at least significant populations in foreign harbours. It is most likely that the presence of larvae in ballast water has resulted in the introduction of Corbula gibba into Australian waters in Port Phillip Bay (McEnnulty et al., 2001b). Its occurrence in Port Phillip was the first documented record of the species outside its area of natural distribution (Talman & Keough, 2001). The clam has subsequently been found in Portland, Western Port Bay in Victoria, Devonport and the D'Entrecasteaux Channel in Tasmania (CRIMP, 2000).

Substrata
Corbula gibba is specialized for life in a substratum of muddy sand mixed with larger pieces of gravel and stone that are necessary for the planting of its single byssus thread (Yonge, 1946). This preference for muddy substrata was reported by Jones (1956). Jones (1956) recorded significant differences in the numbers of Corbula gibba between two sites in Port Erin on the Isle of Man. Higher numbers of Corbula gibba were recorded in areas of coarse muddy sand. In an area only 1/2 mile seawards from the previous site the sediments were fine and the numbers of Corbula gibba present were low (Jones, 1956). In the Adriatic Corbula gibba was completely absent in clean, sandy bottoms as it prefers some mud (Hrs-Brenko, 1981).

Preference for coarse muddy sand has also been seen in Port Philip Bay where Corbula gibba are rarely found in sediments that contain less than 10% mud (<63 µm). Below 15% mud there was a strong relationship between the percentage mud and the abundance of Corbula gibba (Parry & Cohen, 2001). Above 15 % mud there was no significant relationship between the abundance of Corbula gibba and percentage mud in the finer sediments (Parry & Cohen, 2001).

Water quality
Hrs-Brenko (1981) suggested that Corbula gibba thrives in eutrophic waters.

Salinity range
Corbula gibba has been recorded at the following salinities, 26 - 39 ppt in Port Phillip Bay (Talman, 2000: cited in NIMPIS, 2002), 28 - 34 ppt in Limfjord, Denmark, (Jensen, 1990), 27 - 32 ppt in Nissum Bredning, Denmark (Jensen, 1988) and 8.2-38.6 ppt in Elefsis Bay, Greece (Theodorou, 1994).


Substratum preferencesMixed
Muddy gravel
Muddy sand
Sandy mud
Gravel / shingle
Physiographic preferencesOpen coast
Offshore seabed
Strait / sound
Estuary
Enclosed coast / Embayment
Biological zoneLower Eulittoral
Sublittoral Fringe
Upper Infralittoral
Lower Infralittoral
Upper Circalittoral
Lower Circalittoral
Wave exposureVery Exposed
Exposed
Moderately Exposed
Sheltered
Very Sheltered
Tidal stream strength/Water flowStrong (3-6 kn)
Moderately Strong (1-3 kn)
Weak (<1 kn)
Very Weak (negligible)
SalinityReduced (18-30 psu)
Variable (18-40 psu)
See additional Information
Full (30-40 psu)
Habitat Preferences Additional Information
Distribution References Hayward et al., 1996, Hayward & Ryland, 1995b, Tebble, 1976, Hrs-Brenko, 1981, Yonge, 1946, McEnnulty et al., 2001b, Jones, 1956, Parry & Cohen, 2001, NIMPIS, 2002, NBN, 2002, JNCC, 1999, Picton & Costello, 1998, Hayward & Ryland, 1990,
Reproduction/Life History
Reproductive typeGonochoristic
Developmental mechanismPlanktotrophic
Reproductive SeasonSummer - Autumn Reproductive LocationInsufficient information
Reproductive frequencyAnnual protracted Regeneration potential No
Life span1-2 years Age at reproductive maturity
Generation timeSee additional information Fecundity
Egg/propagule size Fertilization typeInsufficient information
Larvae/Juveniles
Larval/Juvenile dispersal potentialInsufficient information Larval settlement periodInsufficient information
Duration of larval stage   
Reproduction Preferences Additional InformationReproduction
Yonge (1946) determined that Corbula gibba was dioecious with no evidence of a sex change. When the gonads of Corbula gibba are maturing it is easy to distinguish between males and females. Males have white testes whereas females have pink ovaries (Yonge, 1946).
Reproduction and spawning generally occur during summer and autumn. Yonge (1946), observed that during early August the male gonads were filling but were not yet ripe and that the testes had developed further than the ovaries. There were however, no active sperm present. In late August, it was noted that in female Corbula gibba the ovaries were filling. No ripe sperm was found until the middle of September. By the end of September the male and female specimens were ripe. The ripe females had relatively large yolky eggs and ripe males had very active sperm (Yonge, 1946).

Fosshagen, (1965; cited in Muss, 1973) found larvae of Corbula gibba in plankton from October - November and once again from January - February and suggested that it was possible for large individuals to spawn during the autumn.
Larval Settling Time
The settling time of Corbula gibba larvae is variable depending on location and may take several months (Jensen, 1988). In Danish waters settlement occurred in August. (Jensen, 1988) states that the settlement of Corbula gibba is very distinct with very few specimens below 2 mm in size during the month of September in Limjford. The recruitment of Corbula gibba was achieved within one week after settlement (Jensen, 1988). However, high moralities of newly settled individuals occurred during the first month of settling. It was suggested that this was may be due to predation from epibenthic predators. Low and constant mortality occurred during the winter months with decreases in abundance again in spring and early summer. It was suggested that these observation could be due to the weakened conditions in the bivalves that had spawned (Jensen, 1988).
Longevity
Jensen (1990) suggested that the life span of Corbula gibba seems to be shorter at 1 -2 years in Nissum Bredning than in the first part of this century when individuals had a life span of 5 -6 years with a maximum size of 12 mm (Jensen 1919: cited in Jensen, 1990).
Reproduction References Jensen, 1990, Jensen, 1988, Yonge, 1946, Muus, 1973, Eckert, 2003,
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