Macoma balthica

Researched By	Lizzie Tyler	Data Supplied By	University of Sheffield
Refereed by	This information is not refereed.
Taxonomy
Scientific name	Macoma balthica	Common name	Baltic tellin
MCS Code	W2029	Recent Synonyms	None
Phylum	Mollusca	Subphylum
Superclass		Class	Pelecypoda
Subclass		Order	Veneroida
Suborder		Family	Tellinidae
Genus	Macoma	Species	balthica
Subspecies
Additional Information
Taxonomy References	Hayward et al., 1996, Hayward & Ryland, 1995b, Fish & Fish, 1996
General Biology
Growth form	Bivalved	Feeding method	Passive suspension feeder, Active suspension feeder, Surface deposit feeder, Sub-surface deposit feeder
Mobility/Movement	Crawler, Burrower	Environmental position	Infaunal
Typical food types	Diatoms, deposited plankton, suspended phytoplankton & detritus.	Habit	Burrow dwelling
Bioturbator		Flexibility	None (< 10 degrees)
Fragility	Intermediate	Size	Small(1-2cm)
Height	Insufficient information	Growth Rate	3 mm/year
Adult dispersal potential	100-1000m	Dependency	Independent
Sociability	Solitary
Toxic/Poisonous?	No
Additional Information	Abundance Stephen (1929) reported typical abundances of Macoma balthica from the Firth of Forth to be 0-89/m² and maximum abundance to be 288/m². Ratcliffe et al. (1981) reported adult densities in the Humber Estuary, UK, between 5,000/m² and 40,000/m² depending on time since a successful spatfall. Bonsdorff et al. (1995) reported juvenile density in the Baltic Sea following settlement to be 300,000/m² decreasing to a stable adult density of 1,000/m². Size at maturity Caddy (1967) reported Macoma balthica from the River Thames reaching maturity in their 2nd year at a size of 5-6mm, whereas in the Netherlands, first year animals larger than 4mm had developed gonads during the spawning season (Lammens, 1967). Lavoie (1970) (cited in Gilbert, 1978) reported that a population of Macoma balthica from a French estuary did not achieve sexual maturity until their second year at a mean length of 3.57mm. Given that the growth rate varies significantly between populations, Gilbert (1978) suggested that Macoma balthica may mature in its 2nd year of life regardless of size or during its first year if a certain size is achieved. Harvey & Vincent (1989), however, consider that sexual maturity is a function of size rather than age in Macoma balthica, maturation occurring when the shell reaches 6mm with corresponding ages of individuals from the same population varying between 10 and 22 months. Growth rate Gilbert (1973) reported mean annual growth rate of Macoma balthica to be 3.3mm/yr with an average length of 18-20mm for fully grown individuals. However, other studies show considerable variations in growth patterns in relation to habitat and depth. McLusky & Allan (1976) reported the maximum growth rate of Macoma balthica in the laboratory to be 1mm over an 8 month period for 5-7mm long animals maintained at 15°C and 25psu. Toxicity Macoma balthica is not normally considered to be toxic but may transfer toxicants through the food chain to predators. Macoma balthica was implicated in the Mersey bird kill in the late 1970's, owing to bioconcentration of alklyC-lead residues (Bull et al., 1983).
Biology References	Fish & Fish, 1996, Bonsdorff, 1984, Harvey & Vincent, 1989, McLusky & Allan, 1976, Brafield & Newell, 1961, Clay, 1967(b), Stephen, 1929, Gilbert, 1973, Gilbert, 1978, Caddy, 1967, Lammens, 1967, Ratcliffe et al., 1981, Bonsdorff et al., 1995, Tebble, 1976, Bull et al., 1983, Hayward & Ryland, 1990, Julie Bremner, unpub data
Distribution and Habitat
Distribution in Britain & Ireland	Common in estuarine environments around the British Isles, with the exception of the south coast.
Global distribution	Macoma balthica has an extensive geographic range that reaches from temperate to arctic coastal waters in both the North Atlantic and North Pacific oceans.
Biogeographic range	Not researched	Depth range
Migratory	Non-migratory / Resident
Distribution Additional Information	Studies have indicated that eastern and western North Atlantic populations of Macoma balthica are morphologically and genetically different from one another, and that they may have diverged as sibling species (Meehan & Carlton, 1988). Depth preferences Macoma balthica occurs in a wide depth range between the mid shore and 190m but is most abundant at moderate depths on muddy and sandy bottoms (Olafsson, 1986). However, in British waters Macoma balthica is mainly an intertidal species. Local distribution Macoma balthica is a resident species but because of near-surface habitat preference, populations may be subject to tidal re-location and scouring. Also observations of propulsion stimulus to scallops may assist in local relocation (Langston, W.J., pers. comm.)
Substratum preferences	Mud, Muddy sand, Sandy mud	Physiographic preferences	Ria / Voe, Estuary, Enclosed coast / Embayment
Biological zone	Upper Eulittoral, Mid Eulittoral, Lower Eulittoral	Wave exposure	Sheltered, Very Sheltered, Extremely Sheltered
Tidal stream strength/Water flow	Moderately Strong (1-3 kn), Weak (<1 kn)	Salinity	Variable (18-40 psu), Reduced (18-30 psu), Low (<18 psu)
Habitat Additional Information
AMBI Group (Borja et al., 2000)	III
Distribution References	Hayward et al., 1996, Hayward & Ryland, 1995b, Fish & Fish, 1996, Clay, 1967(b), Meehan & Carlton, 1988, Olafsson, 1986, Ratcliffe et al., 1981, Bonsdorff et al., 1995, Tebble, 1976, Picton & Costello, 1998, JNCC, 1999, Bruce et al., 1963, Hayward & Ryland, 1990, Julie Bremner, unpub data
Reproduction/Life History
Reproductive type	Gonochoristic	Developmental mechanism	Planktotrophic
Reproductive Season	Spring and autumn	Reproductive Location	Insufficient information
Reproductive frequency	Annual episodic	Regeneration potential	No
Life span	6-10 years	Age at reproductive maturity
Generation time	1-2 years	Fecundity	30000
Egg/propagule size		Fertilization type	Insufficient information
Larvae/Juveniles Larval/Juvenile dispersal potential >10km Larval settlement period Insufficient information Duration of larval stage 1-6 months
Additional Information	Life span Gilbert (1973) reviewed longevity records of Macoma balthica. Life span is typically 5-10 years but may be as long as 30 years in populations from deep, cold water. The data presented suggest that maximum size and growth rate decrease and longevity increases with increasing latitude and associated cooler temperatures. Age at maturity Caddy (1967) reported Macoma balthica from the River Thames reaching maturity in their 2nd year at a size of 5-6mm, whereas in the Netherlands, first year animals larger than 4mm had developed gonads during the spawning season (Lammens, 1967). Lavoie (1970) (cited in Gilbert, 1978) reported that a population of Macoma balthica from a French estuary did not achieve sexual maturity until their second year at a mean length of 3.57mm. Given that the growth rate varies significantly between populations, Gilbert (1978) suggested that Macoma balthica may mature in its 2nd year of life regardless of size or during its first year if a certain size is achieved. Harvey & Vincent (1989), however, consider that sexual maturity is a function of size rather than age in Macoma balthica, maturation occurring when the shell reaches 6mm with corresponding ages of individuals from the same population varying between 10 and 22 months. Gametogenesis and spawning Caddy (1967) studied gametogenesis and spawning in a population of Macoma balthica from the Thames Estuary, UK. The primary gonad passed through a male phase, maturation being achieved in the 2nd year of life. Gametogenesis was associated with a system of follicle cells which broke down as the gametes approached maturity. The arrangement of the follicle cells was characteristic of the sex. In the female, gametocytes were peripheral to the follicle cells, while in the male they were interstitial. Spermatogenesis proceeded most rapidly in the centre of the follicle, resulting in a gradient of spermatogenic stages of increasing maturity from the periphery to the centre. Spawning occurred principally in the spring and to a lesser extent in the autumn. Several spawnings were identified within a season, but repeated cycles of gametogenesis were absent. Ejection of eggs occurred from the exhalant siphon and continued for 40 minutes with brief spawning bursts at 3 minute intervals. Eggs were expelled at considerable speed to a height in the water column of approximately 8cm and settled out of suspension slowly. Females of approximately 17mm shell length were estimated to have expelled between 10,000 and 50,000 eggs.
Reproduction References	Fish & Fish, 1996, Harvey & Vincent, 1989, Gilbert, 1973, Gilbert, 1978, Caddy, 1967, Lammens, 1967, Ratcliffe et al., 1981, Bonsdorff et al., 1995, Eckert, 2003, Julie Bremner, unpub data