BIOTIC Species Information for Nemertesia ramosa
Researched byAngus Jackson Data supplied byMarLIN
Refereed byDr Rob Hughes
Scientific nameNemertesia ramosa Common nameA hydroid
MCS CodeD466 Recent SynonymsNone

PhylumCnidaria Subphylum
SuperclassHydrozoa ClassLeptolida
SubclassLeptothecatae OrderConica
SuborderPlumulariida FamilyPlumulariidae
GenusNemertesia Speciesramosa

Additional InformationNo text entered
Taxonomy References Howson & Picton, 1997, Hayward & Ryland, 1995b, Hughes, 1977, Ansín Agís et al., 2001, Picton & Morrow, 2004,
General Biology
Growth formPinnate
Feeding methodPassive suspension feeder
Mobility/MovementPermanent attachment
Environmental positionEpifaunal
Typical food typesSuspended particulates HabitAttached
BioturbatorNot relevant FlexibilityHigh (>45 degrees)
FragilityFragile SizeMedium(11-20 cm)
HeightUp to 15 cm Growth Rate2.6 - 4.6 cm/month
Adult dispersal potentialNone DependencyIndependent
General Biology Additional InformationVery little information is directly available on Nemertesia ramosa. Completion of most of the fields has been done through extrapolation from the very similar species Nemertesia antennina.

The main stems of Nemertesia ramosa branch occasionally whereas those of Nemertesia antennina do not. The size at maturity for Nemertesia ramosa (a smaller species) may be less than that for Nemertesia antennina. Growth rates for Nemertesia ramosa may also be lower than those recorded for Nemertesia antennina. Growth rates are highest in the summer and lowest in the winter. An individual planula larva gives rise to a colony (sometimes referred to as an individual). These colonies (individuals) are gregarious. The feeding polyps of this species are too large to be withdrawn into the protective theca. Nemertesia ramosa is fed on by a variety of sea slugs including Doto fragilis, Doto cuspidata, Lomanotus genei, and by the sea spider Endeis spinosa.

Ansín Agís et al (2001) list the following species as epibionts on Nemertesia ramosa: Plumularia setacea, Clytia gracilis, Clytia hemisphaerica, Scalpellum scalpellum, Antennella secundaria, Aglaopheria tubulifera, Plumularia setacea, Obelia bidentata, Camapnularia hincksii, Zygophylax biarmata, Filellum serratum and Modeeria rotunda.
Biology References Hayward & Ryland, 1995b, Hughes, 1977, Gili & Hughes, 1995, Hughes, 1978, Gili & Hughes, 1995, Ansín Agís et al., 2001,
Distribution and Habitat
Distribution in Britain & IrelandWidely distributed round all British and Irish coasts.
Global distributionIn the North Atlantic; from Iceland down to north-west Africa. In the Mediterranean; the Straight of Gibraltar, some parts of the Spanish coast, Israel and Italy. In the Indian Ocean; coasts of South Africa and Mozambique.
Biogeographic rangeNot researched Depth range10-500 m
MigratoryNon-migratory / Resident   
Distribution Additional Information

Substratum preferencesBedrock
Large to very large boulders
Small boulders
Gravel / shingle
Physiographic preferencesOpen coast
Offshore seabed
Ria / Voe
Enclosed coast / Embayment
Biological zoneLower Infralittoral
Upper Circalittoral
Lower Circalittoral
Wave exposureSheltered
Very Sheltered
Extremely Sheltered
Ultra Sheltered
Tidal stream strength/Water flowModerately Strong (1-3 kn)
Weak (<1 kn)
Very Weak (negligible)
SalinityInsufficient information
Habitat Preferences Additional InformationThis species is not tolerant of wave action. Where exposed to swell it is not usually found at less than 30 m depth. It may be found at shallower depths in sheltered locations.
Distribution References Hayward & Ryland, 1995b, Hughes, 1977, Jones, 1951, Ansín Agís et al., 2001,
Reproduction/Life History
Reproductive typeVegetative
Developmental mechanismLecithotrophic
Reproductive SeasonFebruary - September Reproductive LocationAs adult
Reproductive frequencySemelparous Regeneration potential No
Life span<1 year Age at reproductive maturityInsufficient information
Generation time<1 year FecundityInsufficient information
Egg/propagule sizeInsufficient information Fertilization typeInternal
Larval/Juvenile dispersal potential10-100m Larval settlement periodInsufficient information
Duration of larval stage<1 day   
Reproduction Preferences Additional InformationVery little information is directly available on Nemertesia ramosa. Completion of most of the fields has been done through extrapolation from the very similar species Nemertesia antennina from Hughes (1977).
  • Males and females are separate but similar, differentiation being possible through the colour of the reproductive tissues, females being orange (yolk) and males white.
  • Allocation of reproductive frequency is difficult. An individual colony will only reproduce once during its 4-5 month lifespan but this reproductive effort is probably spread over an extended period rather than a short episode. In Nemertesia ramosa, gonothecae have been observed in all months of the year with the exception of January, October, November and December (Ansín Agíl et al., 2001).
  • Information on fecundity is sparse and has only been recorded for Nemertesia antennina as mean length of reproductive areas in relation to total length. Recorded values are only an estimate.
  • The planula larvae are released from the gonothecae and drop off the end of the hydrocladium. They settle and metamorphose at between 12-24 hours. This is the only mobile stage in the life cycle of Nemertesia antennina and therefore very important for dispersal.
  • Dispersal distance is dependent on current speed, turbulence and the height at which the larvae are released but in Torbay, the distance is thought to be between 5 and 50m.
  • The dense larva reduces sinking rates by producing a mucous thread (without the thread the larvae sink at 5mm per second in still water).
  • Once the larva lands on the seabed, further dispersal is limited to crawling although this probably last for no more than 1-2 hours. Crawling speeds may reach up to 5mm per minute on smooth surfaces so the planula larvae will probably not move further than 1-2 m before settlement.
  • Some regeneration may occur from broken stems but this is generally found in few individuals.
Reproduction References Hughes, 1977, Gili & Hughes, 1995, Gili & Hughes, 1995, Ansín Agís et al., 2001,
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