Halecium tenellum


Scientific Name: Halecium tenellum

Phylum: Cnidaria

Class: Hydrozoa

Order: Leptothecata

Family: Haleciidae

Genus: Halecium


tenellum [Describe here as A. iricolor]

Native Distribution

Origin Realm:

Arctic, Temperate Northern Atlantic, Tropical Atlantic, Temperate South America, Temperate Northern Pacific, Central Indo-Pacific, Western Indo-Pacific, Southern Ocean

Native Region:

Origin Location:

Temperate Northern Atlantic Salcombe Bay, England (Schuchert 2001) *Type locality Gorringe Bank, Seine Bank and Ampere Bank in France. (Ramil et al. 1998) STATUS NOT STATED Tossa de Mar, Spain (Llobet et al. 1991, cited in Oliveira & Marques 2007); Sao Sebastiao, Brazil (Oliveira et al. 2006, cited in Oliveira & Marques 2007); Lacco Ameno and Prelo, Italy (Boero 1981, cited in Oliveira & Marques 2007) STATUS NOT STATED Saguenay Fjord, Southern Gaspé waters (Baie des Chaleurs, Gaspé Bay to American, Orphan and Bradelle banks; eastern boundary: eastern Bradelle valley), Prince Edward Island (from the northern tip of Miscou Island, N.B. to Cape Breton Island south of Cheticamp, including Northumberland Strait and St. George Bay to the Canso Strait causeway), Middle North Shore (from Sept-Iles to Cape Whittle, including the Mingan Islands), Westem slope of Newfoundland, including the southern part of the Strait of Belle Isle but excluding the upper 50 m in the area southwest of Newfoundland. (Estuary and gulf of Saint Lawrence, Canada) (Brunel et al. 1998) STATUS NOT STATED Sweden (multiple authors, cited in Calder 2012) STATUS NOT STATED Eastport, Maine, USA (USEPA n.d.) STATUS NOT STATED Northwest France (Cornelius 1998) STATUS NOT STATED Tossa del Mar, Spain, in the northwestern Mediterranean Sea (Llobet et al. 1991) STATUS NOT STATED Darrity's Hole, UK (Robins 1969) STATUS NOT STATED Atlantic coast of North America; Western Europe (Fraser 1931) STATUS NOT STATED West Tropical Atlantic Belize (Calder 1991) STATUS NOT STATED Bermuda (Calder 1998) STATUS NOT STATED Temperate South America Magellan area (Cantero & Carrascosa 1999) STATUS NOT STATED Temperate Northern Pacific Native in northeast Pacific (Calder et al. 2014) STATED [Japan] [Sagami Bay] Jogashima, Amadaiba, Okinose, Eboshi-iwa, Hasaki, and Suzaki. (Hirohito 1995) STATUS NOT STATED [Japan] [Izu Islands] Niijima Island and Oshima Island in Izu Islands. (Hirohito 1995) STATUS NOT STATED Northeastern and northwestern Pacific oceans (Calder et al. 2014) STATUS NOT STATED San Diego, USA (Clark 1876) STATUS NOT STATED Haida Gwaii, BC, Canada (Fraser 1936) STATUS NOT STATED Pacific coast of North America (Fraser 1931) STATUS NOT STATED Central Indo-Pacific [Japan] Ogasawara Islands. (Hirohito 1974, Kubota 1997) STATUS NOT STATED Western Indo-Pacific Indian ocean (Calder et al. 2014) STATUS NOT STATED Arctic Arctic ocean (Calder et al. 2014) STATUS NOT STATED Northern Iceland (Schuchert 2001) STATUS NOT STATED Kongsfjorden, Svalbard; bipolar distribution (Voronkov et al. 2010) STATUS NOT STATED *Noted as first record for Svalbard waters, but that it's due to insufficient sampling effort as it is common for the Arctic King Georges Sound, Port Burwell, and Richmond Gulf of Hudson Bay; Hudson Strait; Arctic regions, east of Hudson Strait (Fraser 1931) STATUS NOT STATED Southern Ocean Antarctic region (Cantero & Carrascosa 1999) STATUS NOT STATED Uncertain realm Atlantic ocean (Calder et al. 2014) STATUS NOT STATED Cosmopolitan (Schuchert 2001) STATUS NOT STATED Brazil (Kelmo et al. 2003) STATUS NOT STATED RELATED: Temperate Northern Pacific [Halecium spp.] Several species are present in the northeast Pacific, but identification is difficult (Carlton 2007) STATUS NOT STATED

Geographic Range:

-132.700012207031 -71.6000061035156, 163.400009155273 66.2000045776367 (OBIS 2015) Arctic (Calder et al. 2014) to Antarctica (Cantero & Carrascosa 1999) [France] Gorrnge Bank: 36°31.0'N, 11°34.6'W. (Ramil et al. 1998) [France] Seine Bank: 33°45.2'N, 14°21.0W. (Ramil et al. 1998) [France] Ampère Bank: 35°03.8'N, 12°55.4W. (Ramil et al. 1988)

General Diversity:


Non-native Distribution

Invasion History:

No records of invasion (Global Invasive Species Database 2015)

Non-native Region:

Not applicable

Invasion Propens:

Not applicable

Status Date Non-native:

Not applicable

Vectors and Spread

Initial Vector:


Second Vector:


Vector Details:

Introduction vector: A colony floated from Japan to USA on a floating dock (Calder et al. 2014) *Noted as already present in this area, so not an invasion, but is a possible vector to new areas

Spread Rate:

Not applicable

Date First Observed in Japan:

Not applicable

Date First Observed on West coast North America:

Not applicable


Impact in Japan:

Not applicable

Global Impact:

Not applicable


Native Temperature Regime:

Cool temperate, Mild temperate, Warm temperate, Subtropical, Tropical, See details

Native Temperature Range:

Broad temperate-tropical range in the Atlantic, Pacific, Indian, and Arctic oceans (Calder et al. 2014) [St. Lawrence estuary] Surface layer is ice-cold in the winter; surface layer summer temperatures range from 6 to greater than 20 ºC (Brunel et al. 1998)

Non-native Temperature Regime:


Non-native Temperature Range:


Native Salinity Regime:

Oligohaline, Mesohaline, Polyhaline, Euhaline

Native Salinity Range:

[St. Lawrence estuary] Surface layer in summer ranges from 0.5 to 32 ppt (Brunel et al. 1998)

Non-native Salinity Regime:


Temperature Regime Survival:

See details

Temperature Range Survival:

2.893 - 24.068 (OBIS 2015) [Kongsfjorden, Svalbard] Occurred from 0 - 3 ºC (Voronkov et al. 2010)

Temperature Regime Reproduction:


Temperature Range Reproduction:

[Tossa del Mar, Spain] Reproductively mature in February, March, and April (in 1985 and 1986; Llobet et al. 1991) [Tossa del Mar, Spain] Average sea temperatures in October, November and december are 20.9, 17.7, and 15.1ºC, respectively (SeaTemperature.org 2016b) [Malta] Fertile colonies reported from April to May (Soto Angel & Peña Cantero 2013) *samples were from Malta [Mellieha, Malta] Average sea temperatures in March, July and October are 15.3, 25.3, and 23.4ºC, respectively (SeaTemperature.org 2016) [Portofino promontory, Italy] Fertile colonies reported in January (Puce et al. 2009, cited in Soto Angel & Peña Cantero 2013) [Rapallo, Italy] Average sea temperature in January is 13.5ºC (SeaTemperature.org 2016c)

Salinity Regime Survival:

See details

Salinity Range Survival:

32.3258 - 36.395 psu (OBIS 2015) [Kongsfjorden, Svalbard] Occurred from 31 ppt to >34 ppt (Voronkov et al. 2010)

Salintiy Regime Reproduction:

Polyhaline, Euhaline

Salinity Range Reproduction:


Depth Regime:

Lower intertidal, Shallow subtidal, Deep subtidal, Bathyal

Depth Range:

Sampled at 0 - 1066 m (OBIS 2015) Infralittoral (0 - 20m) and circalittoral (20 - 200 m) (Brunel et al. 1998) Sampled from 0 - 25 m, 26 - 100 m, 101 - 200 m, 201 - 500 m (Calder 1998) Found at 15-20 fathoms and 40 fathoms (Fraser 1931) Sampled at 60 fathoms; on rock at low tide; at 15 - 18 fathoms; and at 30 fathoms (Fraser 1936) Collected from 10 m depth (Llobet et al. 1991) Sampled at 28 m depth (Robins 1969) Sampled from littoral to 700 m depth (Voronkov et al. 2010) [Mediterranean] Found from 0.5 - 200 m (Soto Angel & Peña Cantero 2013) [France] Gorrnge Bank: 54-62m (Ramil et al. 1998) [France] Seine Bank: 165m. (Ramil et al. 1998) [France] Ampère Bank: 225-280m. (Ramil et al. 1988) [Japan] Ogasawara Islands: Intertidal zone to several meters. (Kubota 1997) [Japan] Many points in Sagami Bay: 18-92m. (Hirohito 1995)

Non-native Salinity Range:

Native Abundance:

Common, Few


Fertilization Mode:

See details

Reproduction Mode:

Gonochoristic/ dioecious

Spawning Type:


Development Mode:

Lecithotrophic planktonic larva (non-feeding)

Asexual Reproduction:

See details

Reproduction Details:

RELATED: [Obelia sp. as a representative example of class Hydrozoa] Medusae have separate sexes. Males release sperm; eggs are fertilized while still in the gonads. Planula lavae (Kozloff 1990) *Note: entered as lecithotrophic because planula larvae are non-feeding and planktonic; other sources for Obelia spp. contradict where eggs are fertilized (see two Obelia entries) [Hydroids] Rapidly colonize through asexual proliferation (Denny & Gaines 2007)

Adult Mobility:


Adult Mobility Details:

RELATED: [Hydroids] Sessile (Denny & Gaines 2007)

Maturity Size:


Maturity Age:


Reproduction Lifespan:




Broods per Year:


Reproduction Cues:


Reproduction Time:

[Northwest Mediterranean] Reproductively mature in February, March, and April (in 1985 and 1986; Llobet et al. 1991) [Mediterranean] Fertile colonies reported from April to May (Soto Angel & Peña Cantero 2013) and in January (Puce et al. 2009, cited in Soto Angel & Peña Cantero 2013)



Egg Size:


Egg Duration:


Early Life Growth Rate:


Adult Growth Rate:


Population Growth Rate:


Population Variablity:

Collected year round from Tassa del Mar, Spain, but is scarce in summer (Llobet et al. 1991)



Rocky subtidal, SAV, Macroalgal beds, Coralline algae, Fouling, Mangrove, Flotsam, Other

Habitat Type:

Epibenthic, Epizoic, Epiphytic


Rock, Biogenic, Artificial substrate



Habitat Expansion:


Habitat Details:

Found on Hypnea musciformis (Oliveira et al. 2006, cited in Oliveira & Marques 2007); and on Posidonia oceanica (Boero 1981, cited in Oliveira & Marques 2007) Attached to barnacles on a floating dock (tsumani debris) (Calder et al. 2014) Parasitic on Bimeria, found on wharf piles (Clark 1876) On red mangrove, Rhizophora mangle, and wooden test panels (Calder 1991) Found on Laminaria washed up in Wakeham Bay (Fraser 1931) Sampled on rock and in a tow net (Fraser 1936) Colonies present on the alga Halimeda tuna. frequently grows over other hydroids, bryozoa and coralline algae(Llobet et al. 1991) Epizoic on Cellaria sp., on a boulder (Robins 1969) Found on bedrock with some kelp; very exposed to waves; strong current without silt (Voronkov et al. 2010) Epibiotic on algae, hydrozoans, bryozoans, and other invertebrates; sampled from Eudendrium sp. 2 (Soto Angel & Peña Cantero 2013) Epibiotic on algae, hydrozoans, bryozoans, and other invertebrates; sampled from Eudendrium sp. 2 (Soto Angel & Peña Cantero 2013, Yamada M 1988) Found on axis and branches of Eudendrium sp. at Seine Bank and on Sertularella ellisii at Amère Bank, France. (Ramil et al. 1998)

Trophic Level:

Suspension feeder

Trophic Details:

RELATED: [Hydroids] Suspension-feeding or carnivorous (Denny & Gaines 2007) [Obelia sp. as a representative example of class Hydrozoa] Suitable food organisms are imobilized by nematocysts after touching one or more tentacles, then the tentacles bring the food to the mouth (Kozloff 1990)

Forage Mode:


Forage Details:

RELATED: [Hydroids] They consume completely small animals like small crustacea, mollusc, annelida and juvenile fish. (Uchida 1961)

Natural Control:

RELATED: PREDATION [Hydroids] [Predation] Hydranths may be eaten by nudibranchs, pyconogonids, fish, and the polychaete Procerastea halleziana (Denny & Gaines 2007) PARASITES [Hydroids] [Parasites] Pycnogonid larvae may parasitize and develop in hydranths (Denny & Gaines 2007)

Associated Species:

RELATED: SYMBIONTS [Hydroids] [Symbionts] Act as microhabitats for many other species, including other hydroids, gammarid amphiods, and mussel recruits (Denny & Gaines 2007) PARASITES [Hydroids] [Parasites] Pycnogonid larvae may parasitize and develop in hydranths (Denny & Gaines 2007)

References and Notes


Brunel P, Bossé L, Lamarche G (1998) Catalogue of the Marine Invertebrates of the Estuary and Gulf of Saint Lawrence. Can. Spec. Publ. Fish. Aquat. Sci. 126. www.dfo-mpo.gc.ca/Library/223686.pdf Calder DR (1991) Associations between hydroid species assemblages and substrate types in the mangal at Twin Cays, Belize. Canadian Journal of Zoology 69(8): 2067-2074. www.nrcresearchpress.com/doi/abs/10.1139/z91-288 Calder DR (1998) Hydroid diversity and species composition along a gradient from shallow waters to deep sea around Bermuda. Deep Sea Research Part I: Oceanographic Research Papers 45(11): 1843-1860. www.sciencedirect.com/science/article/pii/S0967063798000442 Calder DR (2012) On a collection of hydroids (Cnidaria, Hydrozoa, Hydroidolina) from the west coast of Sweden, with a checklist of species from the region. Zootaxa 3171: 1-77. www.mapress.com/zootaxa/2012/f/zt03171p077.pdf Calder DR, Choong HHC, Carlton JT, Chapman JW, Miller JA, Geller J (2014) Hydroids (Cnidaria: Hydrozoa) from Japanese tsunami marine debris washing ashore in the northwestern United States. Aquatic Invasions 9(4): 425-440. http://www.researchgate.net/publication/267394881_Calder_D.R._Choong_H.H.C._Carlton_J.T._Chapman_J.W._Miller_J.A._and_Geller_J._2014._Hydroids_%28Cnidaria_Hydrozoa%29_from_Japanese_tsunami_marine_debris_washing_ashore_in_the_northwestern_United_States._Aquatic_Invasions_9_425-440 Cantero ALP & Carrascosa AMG (1999) Biogeographical distribution of the benthic thecate hydroids collected during the Spanish Antartida 8611 expedition and comparison between Antarctic and Magellan benthic hydroid faunas. Scientia Marina 63(S1): 209-218. scientiamarina.revistas.csic.es/index.php/scientiamarina/article/viewArticle/905 Carlton JT (2007) The Light and Smith manual: intertidal invertebrates from central California to Oregon. London, England: University of California Press, Ltd Clark SF (1876) The Hydroids of the Pacific coast of the United States, south of Vancouver Island, with a report upon those in the Museum of Yale College. Proceedings of the California academy of Natural Sciences 3: 249-264. https://books.google.ca/books?id=cttCAQAAMAAJ&printsec=frontcover&source=gbs_ge_summary_r&cad=0#v=onepage&q&f=false Cornelius PFS (1998) Taxonomic characters from the hydranths of live thecate hydroids: European Haleciidae (Cnidaria: Leptothecatae). Zoologische Verhandelingen 323(7): 79-97. www.repository.naturalis.nl/record/317662 Denny MW & Gaines SD (2007) Encyclopedia of Tidepools and Rocky Shores. Berkeley and Los Angeles, California: University of California Press Fraser CM (1931) BIOLOGICAL AND OCEANOGRAPHIC CONDITIONS IN HUDSON BAY 3. HYDROIDS OF HUDSON BAY AND HUDSON STRAIT. Contributions to Canadian Biology and Fisheries 6(1): 475-481. www.nrcresearchpress.com/doi/abs/10.1139/f31-025 Fraser CM (1936) Hydroid distribution in the vicinity of the Queen Charlotte Islands. The Candian Field-Naturalist 50: 122-126. www.biodiversitylibrary.org/item/89296#page/156/mode/thumb Global Invasive Species Database. http://www.issg.org/database/species/search.asp?sts=tss&st=tss&fr=1&x=37&y=15&li=7&tn=Halecium+tenellum&lang=EN Access date: 25-11-2015 Hirohito (1974) Some hydrozoans of the Bonin Islands. Biological Laboratory Imperial Household, Tokyo: 55pp. Hirohito (1995) The Hydroids of Sagami Bay II. Biological Laboratory Imperial Household, Tokyo: 355pp Kelmo F, Attrill MJ, Jones MB (2003) Effects of the 1997–1998 El Niño on the cnidarian community of a high turbidity coral reef system (northern Bahia, Brazil). Coral Reefs 22(4): 541-550. link.springer.com/article/10.1007/s00338-003-0343-0 Kozloff EN (1990) Invertebrates. Philadelphia, PA: Saunders College Publishing Kubota S (1997) Athecate and Thecate hydropolyps from the Bonin Islands, Japan. Nanki-Seibutsu 39: 149-150. (in Japanese) Llobet I, Gili JM, Hughes RG (1991) Horizontal, vertical and seasonal distributions of epiphytic hydrozoa on the alga Halimeda tuna in the Northwestern Mediterranean Sea. Marine Biology 110(1): 151-159. link.springer.com/article/10.1007/BF01313102 OBIS. Ocean Biogeographic Information System. http://iobis.org/mapper/ Access date: 25-11-2015 Oliveira OMP & Marques AC (2007) Epiphytic hydroids (Hydrozoa: Anthoathecata and Leptothecata) of the World. Checklist 3(1): 21-38. Ramil F, Wervoort W, Ansín JA (1988) Report on the Haleciidae and Plumularioidea (Cnidaria, Hydrozoa) collected by the French SEAMOUNT 1 expedition. Zoologische Verhandelingen (Leiden) 322: 1-42. http://repository.naturalis.nl/document/149163 Robins MW (1969) The marine flora and fauna of the Isles of Scilly Cnidaria and Ctenophora, Journal of Natural History 3(3): 329-343. www.tandfonline.com/doi/abs/10.1080/00222936900770291 Schuchert P (2001) Hydroids of Greenland and Iceland (Cnidaria, Hydrozoa). Meddeleelser om Gronland, Bioscience 53(1): 1-184. www.researchgate.net/publication/229439253_Hydroids_of_Greenland_and_Iceland_%28Cnidaria_Hydrozoa%29 SeaTemperature.org. Malta. http://www.seatemperature.org/europe/malta/mellieha-august.htm Access date: 29-08-2016 SeaTemperature.org b. Tossa de Mar, Spain. http://www.seatemperature.org/europe/spain/tossa-de-mar-august.htm Access date: 29-08-2016 SeaTemperature.org c. Tossa de Mar, Spain. http://www.seatemperature.org/europe/italy/rapallo-august.htm Access date: 30-08-2016 Soto Angel JJ & Peña Cantero AL (2013) Shallow-water benthic hydroids from the Maltese Islands (Central Mediterranean). Marine Ecology 34(s1): 177-196. onlinelibrary.wiley.com/doi/10.1111/maec.12035/full Uchida T (1961) Coelenterata. In: Animal systematics. Uchida T (ed.) Nakayama-shoten Co. Ltd., Tokyo: 55-204. (in Japanese) (USEPA) US Environmental Protection Agency (n.d.) 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Hirohito (1974) Some hydrozoans of the Bonin Islands. Biological Laboratory Imperial Household, Tokyo : 55pp.