Halecium, Oken, 1815

Calder, Dale R., 2019, On a collection of hydroids (Cnidaria, Hydrozoa) from the southwest coast of Florida, USA, Zootaxa 4689 (1), pp. 1-141 : 72

Halecium sp.

Figs. 19e, f

Material examined. Southwest Florida Shelf, middle shelf west of Gasparilla Island, 26°45.86’N, 83°21.44’W, 50 m, 18 July 1981, triangle dredge, one colony fragment, 3.9 cm high, without gonophores, coll. Continental Shelf Associates, ROMIZ B1594.— Sanibel Island , beach at Lighthouse Point, 26°26’58”N, 82°01’04.5”W, detached and stranded on beach, 21 March 2018, 22° C, 34.5‰, one colony, 7 cm high, with male gonophores, coll. D. Calder, ROMIZ B4381 .

Remarks. These hydroids resemble the trophosomes of several species of Halecium Oken, 1815 that have been reported from the Gulf of Mexico ( Calder & Cairns 2009), including H. halecinum ( Linnaeus, 1758) , H. beanii ( Johnston, 1838) , H. sessile Norman, 1867 , H. macrocephalum Allman, 1877 , and H. bermudense Congdon, 1907 . In lacking female gonophores, the specimens cannot be reliably identified to species. Colonies were strongly polysiphonic, with alternate and predominantly pinnate side branches; hydranths bore 20+ tentacles and the cnidome comprised both pseudostenoteles (10.2–12.0 long x 5.4 – 7.0 μm wide) and microbasic mastigophores (ca. 6.0 long x 1.8 μm wide).

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.