MarLIN

information on the biology of species and the ecology of habitats found around the coasts and seas of the British Isles

A hydroid (Nemertesia ramosa)

Distribution data supplied by the Ocean Biogeographic Information System (OBIS). To interrogate UK data visit the NBN Atlas.

Summary

Description

Nemertesia ramosa is a colonial hydroid that lives in small aggregations. Individual colonies consist of an upright and irregularly branched stem up to about 15 cm in height. An individual may have several other colonies attached to the stem. The main stems bear whorls of fine side branches of even length and upwardly pointing, arranged in groups of 6. The hydroid is yellow/orange in colour and is usually more pigmented than the similar Nemertesia antennina.

Recorded distribution in Britain and Ireland

Widely distributed round all British and Irish coasts.

Global distribution

In 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.

Habitat

The colonies of this species live in small aggregations, usually with several colonies attached to a single 'main' stem. The colonies are typically attached to hard substrata such as bedrock, boulders, pebbles and shells. The hydroid attaches to the substratum using hydrorhizae which form a holdfast. The species lives in slight to moderately flowing water and is intolerant of wave action. Nemertesia ramosa has very similar habitat preferences to Nemertesia antennina

Depth range

10-500

Identifying features

  • An orange-yellow hydroid or sea-fir that reaches 15 cm in height.
  • The colony consists of an upright main stem (hydrocaulus) that branches occasionally and irregularly.
  • The main stems bear fine, even length side (secondary) branches (hydrocladia) arranged in groups of six.
  • Secondary branches are whorled (3-dimensional).

Additional information

No text entered

Listed by

- none -

Further information sources

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Biology review

Taxonomy

PhylumCnidaria
ClassHydrozoa
OrderLeptothecata
FamilyPlumulariidae
GenusNemertesia
Authority(Lamarck, 1816)
Recent Synonyms

Biology

Typical abundanceHigh density
Male size rangeup to 15cm
Male size at maturity7-10cm
Female size range7-10cm
Female size at maturity
Growth formPinnate
Growth rate2.6 - 4.6cm/month
Body flexibility
Mobility
Characteristic feeding methodNon-feeding, Passive suspension feeder
Diet/food source
Typically feeds onseston
Sociability
Environmental positionEpifaunal
DependencyIndependent.
SupportsHost

See additional information

Is the species harmful?No

Biology information

Very 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.

Epizoites
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.

Habitat preferences

Physiographic preferencesOpen coast, Offshore seabed, Sea loch / Sea lough, Ria / Voe, Estuary, Enclosed coast / Embayment
Biological zone preferencesLower circalittoral, Lower infralittoral, Upper circalittoral
Substratum / habitat preferencesBedrock, Cobbles, Gravel / shingle, Large to very large boulders, Maerl, Pebbles, Small boulders
Tidal strength preferencesModerately Strong 1 to 3 knots (0.5-1.5 m/sec.), Very Weak (negligible), Weak < 1 knot (<0.5 m/sec.)
Wave exposure preferencesExtremely sheltered, Sheltered, Ultra sheltered, Very sheltered
Salinity preferencesData deficient
Depth range10-500
Other preferencesNo text entered
Migration PatternNon-migratory / resident

Habitat Information

The species is not tolerant of wave action. Where exposed to swell it is not usually found at less than 30 m. It may be found at shallower depths in sheltered locations. Some regeneration may occur from broken stems but this is generally found in few individuals.

Life history

Adult characteristics

Reproductive typeVegetative
Reproductive frequency Semelparous / monotely
Fecundity (number of eggs)11-100
Generation time<1 year
Age at maturityInsufficient information
SeasonNot relevant
Life span<1 year

Larval characteristics

Larval/propagule type-
Larval/juvenile development Lecithotrophic
Duration of larval stage< 1 day
Larval dispersal potential 10 -100 m
Larval settlement periodInsufficient information

Life history information

Very 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.

Sensitivity reviewHow is sensitivity assessed?

Physical pressures

 IntoleranceRecoverabilitySensitivityEvidence/Confidence
High Moderate Moderate Low
This species is permanently fixed to the substratum so substratum loss would cause death. See information on recoverability below.
Intermediate Very high Low Low
Nemertesia ramosa is an upright hydroid with a height of up to 15 cm. The colony structure is fairly tough and flexible. Smothering with 5 cm of sediment may cover over some individuals, others may just have the lower section of the main stem covered. Hughes (1977) found that maturing hydroids that had been smothered with detritus and silt lost most of the hydrocladia and hydranths. After one month, the hydroids were seen to have recovered but although neither the growth rate nor the reproductive potential appeared to have been affected, the viability of the planulae may have been affected. Therefore, an intolerance of intermediate has been recorded.
Intermediate Immediate Very Low Low
Nemertesia ramosa is a passive suspension feeder, extracting seston from the water column. Increased siltation may clog up the feeding apparatus, requiring energetic expenditure to clear. Recovery from the energetic expenditure of clearing the feeding apparatus is likely to take only a few days.
No information
High Moderate Moderate Low
The species is entirely sub-tidal and typically found below 10 m unless in very sheltered areas. Exposure to desiccating influences will probably cause death. See information on recoverability below.
High Moderate Moderate Low
The species is entirely sub-tidal and typically found below 10m unless in very sheltered areas. Emergence for an hour will probably cause death. See information on recoverability below.
No information
Intermediate High Low Low
The species lives in very weak to moderate water flows. Increases above this may provide more food but may also prevent the individual hydranths of the colony from remaining extended and feeding therefore, an intolerance of intermediate has been recorded.
No information
No information No information No information Not relevant
Insufficient
information
No information
Tolerant Not relevant Not sensitive Low
The species probably has very limited facility for visual perception. It occurs down to depths of 500 m so attenuation of light is probably of little importance.
No information
High Moderate Moderate Low
The species is intolerant of high wave exposure and so is only found in sheltered areas. Increases in wave exposure above the preferred limits is likely to cause death, either through physical damage or prevention of feeding. See information on recoverability below.
No information
Tolerant Not relevant Not sensitive High
The species is likely to have limited facility for detecting noise.
Tolerant Not relevant Not sensitive High
The species probably has very limited facility for visual perception. It occurs down to depths of 500 m. Visual disturbance is probably of little importance.
Intermediate High Low Low
Although the species is quite flexible and robust, abrasion may cause displacement, physical damage to the colonies or death. For example, erect epifauna have been reported to be particularly vulnerable to damage by fishing gear. For example, Magorrian & Service (1998) reported that trawling for queen scallops resulted in removal of emergent epifauna and damage to horse mussel beds in Strangford Lough. They suggested that the emergent epifauna were more intolerant than the horse mussels themselves and reflected early signs of damage (Service & Magorrian, 1997; Magorrian & Service, 1998; Service 1998). Veale et al., 2000 reported that the abundance, biomass and production of epifaunal assemblages decreased with increasing fishing effort. Therefore, a passing scallop dredge is likely to damage or remove a proportion of the population and an intolerance of intermediate has been recorded.
Hydroids can regenerate from fragments, form resting stages and have considerable powers of repair (see Gili & Hughes, 1995). In a study of the long term effects of scallop dredging in the Irish Sea, Bradshaw et al. (2002) noted that the tough stemmed hydroids Nemertesia spp. increased in abundance, presumably because of their powers of regeneration, good local recruitment and ability to colonize newly exposed substratum quickly. Therefore, recoverability has been reported as high.
High Moderate Moderate Low
The colonies of this species are permanently attached either to the substratum or to other colonies. On displacement individual colonies would be unable to re-attach and therefore an intolerance of high has been recorded. See information on recoverability below.

Chemical pressures

 IntoleranceRecoverabilitySensitivityEvidence/Confidence
No information No information No information Not relevant
Insufficient
information
Heavy metal contamination
No information No information No information Not relevant
Insufficient
information
Hydrocarbon contamination
No information No information No information Not relevant
Insufficient
information
Radionuclide contamination
No information No information No information Not relevant
Insufficient
information
Changes in nutrient levels
No information No information No information Not relevant
Insufficient
information
No information No information No information Not relevant
Insufficient
information
No information
No information No information No information Not relevant
Cole et al. (1999) suggest possible adverse effects on marine species below 4 mg/l and probable adverse effects below 2mg/l. However, there is no information about Nemertesia ramosa tolerance to changes in oxygenation.

Biological pressures

 IntoleranceRecoverabilitySensitivityEvidence/Confidence
No information No information No information Not relevant
Insufficient
information
No information No information No information Not relevant
Insufficient
information
Not relevant Not relevant Not relevant Low
It is highly unlikely that the species would be extracted for any reason.
Tolerant Not relevant Not sensitive Low
Nemertesia ramosa has no known obligate relationships.

Additional information

Recoverability
Detailed information on reproduction in this species is not known although fecundity is not particularly high. The larvae of Nemertesia ramosa are passive drifters, quite dense and have limited dispersal potential, dependent on water flow rates near the seabed. In a study of the long term effects of scallop dredging in the Irish Sea, Bradshaw et al. (2002) noted that Nemertesia spp. increased in abundance, presumably because of their powers of regeneration, good local recruitment and ability to colonize newly exposed substratum quickly. In Nemertesia antennina, reproduction occurs regularly, there being three generations per year. The presence of adults stimulate larval settlement therefore if any adults remain, reproduction is likely to result in local recruitment.

Importance review

Policy/legislation

- no data -

Status

Non-native

Importance information

In Torbay, Nemertesia antennina, a similar species, has been recorded as hosting more than 150 epizoic species, most of which are not present on other local substrata.

Bibliography

  1. Ansín Agís, J., Ramil, F. & Vervoort, W., 2001. Atlantic Leptolida (Hydrozoa, Cnidaria) of the families Aglaopheniidae, Halopterididae, Kirchenpaueriidae and Plumulariidae collected during the CANCAP and Mauritania-II expeditions of the National Museum of Natural History, Leiden, the Netherlands. Zoologische Verhandelingen, no. 233, 268 pp.

  2. Bradshaw, C., Veale, L.O., Hill, A.S. & Brand, A.R., 2002. The role of scallop-dredge disturbance in long-term changes in Irish Sea benthic communities: a re-analysis of an historical dataset. Journal of Sea Research, 47, 161-184.

  3. Gili, J-M. & Hughes, R.G., 1995. The ecology of marine benthic hydroids. Oceanography and Marine Biology: an Annual Review, 33, 351-426.

  4. Hayward, P.J. & Ryland, J.S. (ed.) 1995b. Handbook of the marine fauna of North-West Europe. Oxford: Oxford University Press.

  5. Howson, C.M. & Picton, B.E., 1997. The species directory of the marine fauna and flora of the British Isles and surrounding seas. Belfast: Ulster Museum. [Ulster Museum publication, no. 276.]

  6. Hughes, R.G., 1977. Aspects of the biology and life-history of Nemertesia antennina (L.) (Hydrozoa: Plumulariidae). Journal of the Marine Biological Association of the United Kingdom, 57, 641-657.

  7. Hughes, R.G., 1978. Life-histories and abundance of epizoites of the hydroid Nemertesia antennina (L.) Journal of the Marine Biological Association of the United Kingdom, 58, 313-332.

  8. Jones, N.S., 1951. The bottom fauna of the south of the Isle of Man. Journal of Animal Ecology, 20, 132-144.

  9. Magorrian, B.H. & Service, M., 1998. Analysis of underwater visual data to identify the impact of physical disturbance on horse mussel (Modiolus modiolus) beds. Marine Pollution Bulletin, 36, 354-359.

  10. Picton, B.E. & Morrow, C.C., 2004. Nemertesia ramosa Lamouroux, 1816. http://www.habitas.org.uk/marinelife/species.asp?item=D5990, 2004-09-14

  11. Service, M. & Magorrian, B.H., 1997. The extent and temporal variation of disturbance to epibenthic communities in Strangford Lough, Northern Ireland. Journal of the Marine Biological Association of the United Kingdom, 77, 1151-1164.

  12. Service, M., 1998. Recovery of benthic communities in Strangford Lough following changes in fishing practice. ICES Council Meeting Paper, CM 1998/V.6, 13pp., Copenhagen: International Council for the Exploration of the Sea (ICES).

Citation

This review can be cited as:

Jackson, A. 2004. Nemertesia ramosa A hydroid. In Tyler-Walters H. and Hiscock K. (eds) Marine Life Information Network: Biology and Sensitivity Key Information Reviews, [on-line]. Plymouth: Marine Biological Association of the United Kingdom. Available from: http://www.marlin.ac.uk/species/detail/1318

Last Updated: 15/09/2004