BIOTIC Species Information for Molgula manhattensis
Researched byDr Keith Hiscock Data supplied byMarLIN
Refereed byThis information is not refereed.
Scientific nameMolgula manhattensis Common nameSea grapes
MCS CodeZD151 Recent SynonymsNone

PhylumChordata SubphylumTunicata
Superclass ClassAscidiacea
Subclass OrderPleurogona
SuborderStolidobranchiata FamilyMolgulidae
GenusMolgula Speciesmahattensis

Additional InformationSeveral 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 formGlobose
Feeding methodActive suspension feeder
Mobility/MovementPermanent attachment
Environmental positionEpibenthic
Typical food typesPlankton HabitAttached
BioturbatorNot relevant FlexibilityLow (10-45 degrees)
FragilityFragile SizeSmall(1-2cm)
HeightUp to 3 cm Growth RateInsufficient information
Adult dispersal potentialNone DependencyIndependent
General Biology Additional InformationMolgula 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 & IrelandDistributed all around Britain and Ireland but no records from the east basin of the Irish Sea.
Global distributionIn 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 rangeNot researched Depth rangeLittoral to 90 m
MigratoryNon-migratory / Resident   
Distribution Additional InformationIdentifying 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 preferencesSeagrass
Large to very large boulders
Small boulders
Physiographic preferencesRia / Voe
Enclosed coast / Embayment
Biological zoneLower Infralittoral
Upper Circalittoral
Lower Circalittoral
Wave exposureExposed
Moderately Exposed
Very Sheltered
Extremely Sheltered
Tidal stream strength/Water flowModerately Strong (1-3 kn)
Weak (<1 kn)
Very Weak (negligible)
SalinityVariable (18-40 psu)
Full (30-40 psu)
Habitat Preferences Additional Information
Distribution References Tokioka & Kado, 1972, Millar, 1970, Howson & Picton, 1997, Berril, 1950, Kott, 1985,
Reproduction/Life History
Reproductive typeGonochoristic
Developmental mechanismOviparous
Reproductive SeasonInsufficient information Reproductive LocationInsufficient information
Reproductive frequencyAnnual protracted Regeneration potential No
Life spanInsufficient information Age at reproductive maturityInsufficient information
Generation time<1 year FecundityInsufficient information
Egg/propagule sizeInsufficient information Fertilization typeInsufficient information
Larval/Juvenile dispersal potential1km-10km Larval settlement periodInsufficient information
Duration of larval stage<1 day   
Reproduction Preferences Additional InformationBerrill (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,
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