Hydractinia aggregata Fraser, 1911

Calder, Dale R. & Choong, Henry H. C., 2018, Names of hydroids (Cnidaria, Hydrozoa) established by Charles McLean Fraser (1872 - 1946), excluding those from Allan Hancock Expeditions, Zootaxa 4487 (1), pp. 1-83: 14

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Hydractinia aggregata Fraser, 1911


Hydractinia aggregata Fraser, 1911 

Hydractinia aggregata Fraser, 1911: 25  , pl. 2, figs. 1–4.

Syntypes. USNM 71134View Materials: USA, Washington, San Juan Islands , 1904, three colonies on empty gastropod shells, coll. H. Moon; ethanol. 

Lectotype, by present designation. USNM 71134View Materials: USA, Washington, San Juan Islands , 1904, one colony on an empty gastropod shell, in good condition, with gonozooids and gonophores, coll. H. Moon; ethanol. 

Paralectotypes. USNM 1458915View Materials: USA, Washington, San Juan Islands , 1904, two colonies on empty gastropod shells, one colony, in fair condition, with gonophores, one colony, in poor condition, without gonophores, coll. H. Moon; ethanol. 

Type locality. USA: Washington, San Juan Archipelago ( Fraser 1911). 

Current status. Valid.

Remarks. Fraser (1911) described Hydractinia aggregata  based on collections from two localities on the west coast of North America ( Canada: Departure Bay; USA: San Juan Archipelago). One of these, made available to him by C.C. Nutting at the University of Iowa, had been collected in the San Juan Archipelago by H. Moon. The Nutting collections at Iowa were eventually deposited in the NMNHAbout NMNH ( Calder 2004), and material of H. aggregata  from one of the original localities at that museum ( USNMAbout USNM 71134), listed above, is taken here to be a syntype. The three specimens (“specimen count: 1 ca.”) are not recorded as type material in the current online database of that museum but are considered so here. Material of H. aggregata  from another of the two original type localities (Departure Bay, British Columbia), likely collected by Fraser himself, exists on a slide in the Fraser Hydroid Collection at the RBCMAbout RBCM ( BCPMAbout BCPM 976-00206-001). However, we were unable to determine the date of its collection and could not confirm that it was a syntype. Other collections of the species in the Fraser Collection are non-types ( BCPMAbout BCPM 976-00203-001: Departure Bay, channel N of Inskip Rock and Jesse Island, 18 April 1912, 9– 22 m; BCPMAbout BCPM 976-00204-001: N of Jesse Island, 10 July 1912, 27 m; BCPMAbout BCPM 976-00205-001 and BCPMAbout BCPM 976-00205-002: Departure Bay, S of Jesse and Brandon Islands, 17 September 1912, 18– 37 m; BCPMAbout BCPM 976-00207-001: Horswell Channel, near Clarke Rock, 0 2 November 1912, 15– 37 m; BCPMAbout BCPM 976-00208-001: Horswell Channel, between Horswell Rock and Clarke Rock, 25 July 1913, 27–55 fm; BCPMAbout BCPM 976-00209-001: S of Mudge Island, 21 August 1912, 22– 37 m; BCPMAbout BCPM 976-00210-001: Friday Harbor, 25 July 1912; BCPMAbout BCPM 976-00211-001: SW arm Tasoo Harbour, 0 7 June 1935, 18- 46 m; BCPMAbout BCPM 976-00212-001: Rose Spit, 0 6 September 1935).

The best colony of the syntype series, covering most of a relatively small gastropod shell, is designated here as the lectotype ( USNMAbout USNM 71134). The remaining two colonies are paralectotypes ( USNMAbout USNM 1458915).

Hydractinia aggregata  was found on gastropod shells occupied by hermit crabs ( Fraser 1911). Gastrozooids and gonozooids, but not dactylozooids, were observed. The species is apparently common in the Strait of Georgia ( Fraser 1914a, 1937a, 1947a).


Smithsonian Institution, National Museum of Natural History


Smithsonian Institution, National Museum of Natural History


Royal British Columbia Museum


British Columbia Provincial Museum














Hydractinia aggregata Fraser, 1911

Calder, Dale R. & Choong, Henry H. C. 2018


Hydractinia aggregata

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