Fig. 6d
Halecium tenellum Hincks, 1861b: 252, pl. 6, figs. 1–4.— Jones, 2002: 216.
Type locality. UK: Devon, Salcombe Bay (Hincks 1961b).
Voucher material. Jeff’s Reef off Fort Pierce, 27°32.8’N, 79°58.8’W, 80 m, 15.iv.1977, Johnson-Sea-Link, JSL 2184- A, diver lockout, one colony, 1.3 cm high, without gonophores, coll. F. Stanton, ROMIZ B1105.
Remarks. The morphology of the hydroid examined here approaches accounts of Halecium delicatulum Coughtrey, 1876 (type locality: Upper Harbour, Dunedin, New Zealand) and H. mediterraneum Weismann, 1883 (type locality: Naples, Italy) in having typically long primary hydrophores. However, no pseudodiaphragm such as that often reported in both of those species (e.g., Schuchert 2005) was present in hydrophores of the colony from Florida. It was also small (1.3 cm high) and its hydrocaulus monosiphonic except at the base, as is typical of Halecium tenellum Hincks, 1861b.
In the western North Atlantic, Fraser (1944) included distribution records of Halecium tenellum from Hudson Strait to the Caribbean Sea. At least some reports of the species from high latitudes have been based on misidentifications (Hamond 1957; Cornelius 1975; Calder 1991a; Schuchert 2005). The species is more likely restricted to temperate and tropical waters. An extensive list of literature pertaining to H. tenellum was given by Medel & Vervoort (2000).
Reported distribution. Atlantic coast of Florida. Biscayne Bay (Jones 2002).
Western Atlantic. Possibly from southern New England (Fraser 1944) to Argentina (Oliveira et al. submitted), including Bermuda (Calder 1991a), the Gulf of Mexico (Calder & Cairns 2009), and the Caribbean Sea (Galea 2010).
Elsewhere. Considered a cosmopolitan species by Medel & Vervoort (2000), but see Remarks above.