Halecium tenellum Hincks, 1861

Calder, Dale R., 2019, On a collection of hydroids (Cnidaria, Hydrozoa) from the southwest coast of Florida, USA, Zootaxa 4689 (1), pp. 1-141 : 71

Halecium tenellum Hincks, 1861

Figs. 19c, d

Halecium tenellum Hincks, 1861: 252 , pl. 6, figs. 1–4.— Clarke, 1879: 244.—Leloup, 1935: 9; 1937: 96.— Fraser, 1944: 201.

Type locality. UK: Devon, Salcombe Bay (Hincks 1961: 252) .

Material examined. Southwest Florida Shelf, middle shelf west of North Naples, 26°16’15”N, 83°47’00”W, 76.2 m, 04 November 1980, one colony fragment, 4 mm high, without gonophores, coll. Continental Shelf Associates, ROMIZ B4379.— Southwest Florida Shelf, middle shelf west of North Naples , 26°16.72’N, 83°46.82’W, 83 m, 24 July 1981, otter trawl, on Acryptolaria longitheca , one colony, 2 mm high, without gonophores, coll. Continental Shelf Associates, ROMIZ B4380 .

Remarks. Originally described by Hincks (1861) from Salcombe Bay, England, Halecium tenellum has been widely regarded as a virtually cosmopolitan species (Calder 1990 [1991a]; Cornelius 1995; Medel & Vervoort 2000; Schuchert 2001). Given current uncertainty over identifications of this hydroid from high latitudes (Calder 1990 [1991a]; Schuchert 2001; 2005), reports of it from Arctic and subarctic waters of Canada (Verrill, 1879: 152; Fraser 1922: 5, 1931: 481, 1933: 564) have been excluded from distribution records given below. Reports from the boreal western Atlantic have been included, although it is questionable whether they too are reliable. Notwithstanding its type locality in southern England, most collections of H. tenellum in the northeastern Atlantic have been to the south of the British Isles ( Medel & Vervoort 2000).As stated in previous work (Calder 1990 [1991a]; 2013), H. tenellum is believed to be a species occurring mostly in temperate and tropical waters. In the western South Atlantic, it has been reported as far south as Brazil and Argentina ( Oliveira et al. 2016). Its bathymetric range, according to Oliveira et al., extends from the intertidal zone to 835 m. However, records of the species cited below have predominantly been from neritic bottoms. Specimens from the Southwest Florida Shelf examined here fall within that zone.

The two colonies of H. tenellum reported above (ROMIZ B4379, ROMIZ B4380) were sterile. Several earlier accounts of the species from the tropical and warm-temperate western North Atlantic were also based on sterile hydroids ( Fraser 1912b; Leloup 1935, 1937; Calder 1990 [1991a], 2013; Galea 2010; Castellanos et al. 2018). Other reports of H. tenellum exist from the region ( Clarke 1879; Fraser 1944, 1947b; Cain 1972; Wedler 1975; Calder & Hester 1978; Wenner et al. 1984; Wedler & Larson 1986; Calder 1991b, 2000; Calder & Kirkendale 2005; Castellanos et al. 2011), but no indication was given in them of the reproductive state of the specimens. While fertile colonies were mentioned by Bennitt (1922) in material from Bermuda, they were neither described nor illustrated by him.

In hydroids currently assigned to the genus Halecium Oken, 1815 , morphological characters of the female gonothecae are of critical importance in species identification. Those of H. halecinum ( Linnaeus, 1758) , type species of the genus, are irregularly obovate with a tubular and distolateral aperture at the end of a chimney-like tube for one or more gonothecal hydranths. By contrast, those of H. tenellum , as described by Cornelius (1975b; 1995b) and others, are much different in shape, being ovate, laterally flattened, and with a simple terminal aperture. Gonophoral hydranths are absent. The possible taxonomic significance of this difference, at the generic level, warrants exploration ( Calder 2017: 47).

Medel & Vervoort (2000) provided a detailed synonymy of H. tenellum , along with worldwide records of the species. A substantial recent literature on the species from South America has been cited by Oliveira et al. (2016).

Reported distribution. Gulf coast of Florida. SW Florida Shelf, W of the Dry Tortugas, 24°34’N, 83°16’W, 36 ftm (66 m) ( Clarke 1879: 244).—Dry Tortugas, 27 ft (8 m), on pebbles (Leloup 1935: 10).—Off Tampa Bay, 7–10 miles (11–16 km) offshore, 8–10 ftm (15–18 m) ( Leloup 1937: 96).—Tampa Bay ( Fraser 1944: 203).

Elsewhere in western North Atlantic. USA: Maine, Casco Bay, 8–34 ftm (15–62 m) ( Verrill 1874c: 364).— USA: Massachusetts, Cashes Ledge, 52–90 ftm (95–165 m) ( Verrill 1875a: 414).— Canada: Nova Scotia, NE Georges Bank, 41°25’N, 66°24.8’W, 50 ftm (91 m) ( Smith & Harger, 1875: 7).— USA: Massachusetts, Woods Hole ( Nutting 1901: 357).— Canada: Quebec, Gaspé ( Stafford, 1912a: 59; 1912b: 73).— Canada: New Brunswick, St. Andrews ( Stafford, 1912b: 73).— Canada: Quebec, Seven Islands (Sept-Îles) ( Stafford 1912b: 73).— USA: North Carolina, Beaufort area ( Fraser 1912b: 369).— Canada: Nova Scotia, Canso Banks, 50 ftm (91 m), on ascidian stalks ( Fraser, 1913: 169).— Canada: New Brunswick, from N end of Campobello Island to head of Passamaquoddy Bay ( Fraser, 1918: 353).— Canada: Nova Scotia, Brier Island ( Fraser, 1918: 353).— Canada: Quebec, Seven Islands (Sept-Îles) ( Fraser, 1918: 353).— Canada: Newfoundland and Labrador, Bay of Islands ( Fraser, 1918: 353).— Bermuda: Som- erset Bridge, on Sargassum ( Bennitt 1922: 246) .— Canada: New Brunswick, Miramichi River estuary, outside Portage and Fox islands, 15–40 m ( Fraser 1926: 210).— USA: Maine, Mount Desert region, shore to 330 feet (101 m) ( Procter 1933: 119).— Bonaire: Zuidpunt, on stranded algae + Lac, mouth, 1 m, on detached algae + Lac, Soerebon, 0.8 m (Leloup 1935: 10).— Curaçao: Boca Grandi, on stranded Sargassum (Leloup 1935: 10) .— USA: Maine, Casco Bay, 21 ftm (38 m) ( Fraser 1944: 202).— USA: off Cape Cod, 41°41’N, 69°47’W, 18 ftm (33 m) ( Fraser 1944: 203).— USA: Massachusetts, 5¾ miles (9 km) off Chatham Light, 14 ftm (26 m) ( Fraser 1944: 203).— USA: Massachusetts, 11.5 miles (19 km) off Cape Cod Light, 28 ftm (51 m) ( Fraser 1944: 203).— Venezuela: off Isla Tortuga, 2–5 ftm (4–9 m) ( Fraser 1947b: 9).— Colombia: Santa Marta area, rocky littoral ( Wedler 1975: 334, as “ H. tenellum (?)”).— Canada: Quebec, Saguenay Fjord (Fjord de Saguenay) ( Brunel, 1970: 18; Drainville et al., 1978: 9).— USA: North Carolina, Lithothamnion reef S of Cape Lookout ( Cain 1972: 80).— USA: South Carolina, Prices Creek ( Calder & Hester 1978: 90).— USA: South Carolina, inner (17–18 m), middle (32–36 m) and outer (46–69 m) continental shelf + Georgia, inner (17–22 m), middle (23–29 m) and outer (59–67 m) continental shelf ( Wenner et al. 1984: 20, 39).— USA: South Carolina, Beaufort River, oyster reefs ( Fox & Ruppert 1985: 211).— Virgin Islands of the United States: St. Croix, on algae ( Wedler & Larson 1986: 91).— Bermuda: Argus (=Plantagenet) Bank, on Argus Tower, 20 m (Calder 1990 [1991a]: 23).— Belize: Twin Cays ( Calder 1991b: 223).— Bermuda: Challenger Bank + Argus (=Plantagenet) Bank ( Calder 2000: 1133).— Panama: Galeta, STRI Galeta Laboratory, dock, 09°24’08”N, 79°51’39”W, 0-2 m ( Calder & Kirkendale 2005: 481).— Canada: Nova Scotia, Western Bank ( Henry et al. 2006: 68).—French Lesser Antilles: Guadeloupe, Grande-Terre, Grotte aux Barracudas, 16°27.343’N, 61°32.244’W, 21 m, on Sertularella diaphana + Pointe Plate , 16°27.220’N, 61°32.128’W, 15–20 m, on Thyroscyphus marginatus + Les Ancres , 16°27.002’N, 61°32.320’W, 15–18 m, on Sertularella diaphana ( Galea 2010: 11) .— Cuba: Golfo de Batabanó, Cayería San Felipe, Cayo Real + Arrecife Punta Francés, Boya 5 (Castellanos et al. 2011: 14).—French Lesser Antilles: Martinique ( Galea 2013: 49).— USA: Florida, Jeff’s Reef off Fort Pierce, 27°32.8’N, 79°58.8’W, 80 m ( Calder 2013: 22).— Cuba: Havana, coral reef system west of the city (Castellanos et al. 2018: Supplementary Table S2).— Panama: Bocas del Toro area, vicinity of Manuguar Cay ( Miglietta et al. 2018b: 108).

Figures

FIGURE 19. a, Halecium lightbourni: part of hydrocaulus with hydrothecae, Fort Myers Beach, ROMIZ B4377. Scale equals 0.1 mm. b, Halecium nanum: stolon with hydrocaulus and two hydrothecae, Sanibel Island, ROMIZ B4378. Scale equals 0.05 mm. c, Halecium tenellum: part of colony with a hydrotheca, Southwest Florida Shelf, ROMIZ B4379. Scale equals 0.05 mm. d, Halecium tenellum: part of colony with renovated hydrothecae, Southwest Florida Shelf, ROMIZ B4379. Scale equals 0.2 mm. e, Halecium sp.: part of a branch with three hydrothecae, Sanibel Island, ROMIZ B4381. Scale equals 0.1 mm. f, Halecium sp.: part of a branch with a hydrotheca, Southwest Florida Shelf, ROMIZ B1594. Scale equals 0.1 mm. g, Nemalecium lighti: part of colony with five hydrothecae, Fort Myers Beach, ROMIZ B4419. Scale equals 0.2 mm. h, Nemalecium lighti: two internodes, with hydrothecae, Fort Myers Beach, ROMIZ B4419. Scale equals 0.1 mm. i, Thyroscyphus marginatus: part of colony with three hydrothecae, Sanibel Island, ROMIZ B4382. Scale equals 0.5 mm. j, Thyroscyphus marginatus: hydrotheca, Sanibel Island, ROMIZ B4382. Scale equals 0.2 mm. k, Thyroscyphus ramosus: part of colony with three hydrothecae, Sanibel Island, ROMIZ B4385. Scale equals 0.5 mm. l, Thyroscyphus ramosus: hydrotheca, Sanibel Island, ROMIZ B4385. Scale equals 0.2 mm.