Molgula manhattensis

Researched By	Dr Keith Hiscock	Data Supplied By	MarLIN
Refereed by	This information is not refereed.
Taxonomy
Scientific name	Molgula manhattensis	Common name	Sea grapes
MCS Code	ZD151	Recent Synonyms	None
Phylum	Chordata	Subphylum	Tunicata
Superclass		Class	Ascidiacea
Subclass		Order	Pleurogona
Suborder	Stolidobranchiata	Family	Molgulidae
Genus	Molgula	Species	mahattensis
Subspecies
Additional Information	Several species had, until recently, been included in Molgula manhattensis: Molgula simplex Alder & Hancock, 1870; Molgula siphonata Alder 1850; Molgula socialis Alder 1848, and Molgula tubifera Orstedt 1844 (Connor & Picton in Howson & Picton, 1997). Separation for the purpose of this review has not been carried out as it is uncertain to what extent authors of papers have worked with Molgula manhattensis sensu stricto. It also seems (Kott 1976 quoted in Kott 1985) that the eastern Atlantic species may be Molgula tubifera and that Molgula manhattensis occurs on the Atlantic coast of North America from Maine to Lousiana. Nevertheless, the Species Directory (Howson & Picton, 1997) lists Molgula manhattensis for Britain and Ireland and so no change in name is suggested here.
Taxonomy References	Millar, 1970, Howson & Picton, 1997, Kott, 1985
General Biology
Growth form	Globose	Feeding method	Active suspension feeder
Mobility/Movement	Permanent attachment	Environmental position	Epibenthic
Typical food types	Plankton	Habit	Attached
Bioturbator	Not relevant	Flexibility	Low (10-45 degrees)
Fragility	Fragile	Size	Small(1-2cm)
Height	Up to 3 cm	Growth Rate	Insufficient information
Adult dispersal potential	None	Dependency	Independent
Sociability	Gregarious
Toxic/Poisonous?	No
Additional Information	Molgula manhattensis typically lives on hard substrata including artificial substrata. Molgula manhattensis sensu stricto (see taxonomy page) occurs especially in ports and harbours (Connor & Picton in Howson & Picton, 1997).
Biology References
Distribution and Habitat
Distribution in Britain & Ireland	Distributed all around Britain and Ireland but no records from the east basin of the Irish Sea.
Global distribution	In the north Atlantic, extending from the White Sea and North Cape to Portugal and, on the American coast from Maine to the Gulf of Mexico (Berrill 1950). Since the early 1970's at least, it has been present in the western Pacific (Tokioka & Kado 1972).
Biogeographic range	Not researched	Depth range	Littoral to 90 m
Migratory	Non-migratory / Resident
Distribution Additional Information	Identifying the distribution of Molgula manhattensis is confused by taxonomic problems (see taxonomy page). Although indicated as a native species, the author of this review suggests that it is possible that Molgula manhattensis is an early 'import' from North America as it settles on the hull of ships and could have been transported on wooden sailing ships at a very early stage in north Atlantic crossings. Van Name (1945), quoted in Kott (1985), noted that Molgula manhattensis occurred in salinities equivalent to 20 to 36 psu.
Substratum preferences	Seagrass, Bedrock, Large to very large boulders, Small boulders, Cobbles	Physiographic preferences	Ria / Voe, Estuary, Enclosed coast / Embayment
Biological zone	Lower Infralittoral, Upper Circalittoral, Lower Circalittoral	Wave exposure	Exposed, Moderately Exposed, Sheltered, Very Sheltered, Extremely Sheltered
Tidal stream strength/Water flow	Moderately Strong (1-3 kn), Weak (<1 kn), Very Weak (negligible)	Salinity	Variable (18-40 psu), Full (30-40 psu)
Habitat Additional Information
AMBI Group (Borja et al., 2000)	I
Distribution References	Tokioka & Kado, 1972, Millar, 1970, Howson & Picton, 1997, Berril, 1950, Kott, 1985
Reproduction/Life History
Reproductive type	Gonochoristic	Developmental mechanism	Oviparous
Reproductive Season	Insufficient information	Reproductive Location	Insufficient information
Reproductive frequency	Annual protracted	Regeneration potential	No
Life span	Insufficient information	Age at reproductive maturity	Insufficient information
Generation time	<1 year	Fecundity	Insufficient information
Egg/propagule size	Insufficient information	Fertilization type	Insufficient information
Larvae/Juveniles Larval/Juvenile dispersal potential 1km-10km Larval settlement period Insufficient information Duration of larval stage <1 day
Additional Information	Berrill (1931) noted that Molgula tubifera (possibly a synonym of Molgula manhattensis) collected from the Salcombe Estuary and Millbay Docks in Plymouth were oviparous and had a tadpole larva that developed outside of the body. The tadpole developed and hatched in about 10 hours at a temperature of 18°C and the tadpole larva settled after a further one to 10 hours. Samples were collected in spring and summer and it seems likely that time of reproduction is for an extended time and certainly during summer. Berrill (1931) further describes the larval biology of Molgula manhattensis from North America and notes much the same development as in Molgula tubulifera.
Reproduction References	Berril, 1950, Berrill, 1931