Clytia macrotheca

Clytia macrotheca (Perkins, 1908)

Figs. 14f, g, 15

Campanularia macrotheca Perkins, 1908: 146, pl. 3, figs. 12, 13.

not Campanularia macrotheca Leloup, 1930: 101, figs. 1–3 [invalid junior primary homonym of Campanularia macrotheca Perkins, 1908].

Laomedea macrotheca.— Leloup, 1935a: 21, fig. 8.

Type locality. USA: Florida, Dry Tortugas, Fort Jefferson, in the moat (Perkins 1908: 147).

Material examined. Sanibel Island, beach at Lighthouse Point, on stranded Thalassia, 31 August 2018, 29° C, 34‰, two colony fragments, up to 1.5 mm high, without gonothecae, coll. D. Calder, ROMIZ B4420.

Remarks. This species was originally described from the southwest coast of Florida, as Campanularia macrotheca, by Perkins (1908). The binomen Campanularia macrotheca Leloup, 1930, applied to a different species from Monaco, is an invalid junior primary homonym. Leloup’s hydroid has been taken to be conspecific with Campanularia hincksii Alder, 1856 by authors including Patriti (1970) and Cornelius (1982), and that synonymy has been adopted in WoRMS.

Perkins (1908) fully described and illustrated this hydroid, found on filamentous algae in the moat at Fort Jefferson on Garden Key in the Dry Tortugas. Amongst the material examined by him were two fertile colonies, each having a gonotheca with two well-developed medusa buds. Based on the morphology of those medusa buds, the species was justifiably reassigned to Clytia Lamouroux, 1812 by Stechow (1923b: 109). From the account of Perkins there is little doubt that a free medusa exists in Clytia macrotheca, but that stage currently remains unknown.

The hydroid of Clytia Joycei sp. nov., described immediately above, is much like that of C. macrotheca in morphology and habitat. It differs in having somewhat larger hydrothecae than those of C. macrotheca, and hydrothecal cusps that are much more deeply incised and more linguiform. Differences also exist in the size of their B-type brhabdoid nematocysts, with those of C. Joycei (15.5–18 μm long x 3.2–4.5 μm wide) being larger than those of C. macrotheca (13.5–14.8 μm long x 2.8–4.0 μm wide).

A species of very shallow waters, C. macrotheca has been recorded from various substrates including algae, other hydroids, rocks, corals, Halimeda, Rhizophora, and miscellaneous invertebrates (Perkins 1908; Leloup 1935a; Calder 1990 [1991a], 1991c; Galea 2008, 2010; Oliveira et al. 2016). Although reported infrequently, the species is now known to occur in the warm western Atlantic from Bermuda (Calder 1990 [1991a]) to the Caribbean Sea (Galea 2008, 2010), and southwards to Brazil (Oliveira et al. 2016).

Nematocysts of two categories were observed in this hydroid (Fig. 15). They were identified as A-type b-mastigophores (7.1–8.0 long x 2.0–2.3 μm wide, undischarged, n=10, ROMIZ B4420) and B-type b-mastigophores (13.5–14.8 long x 2.8–4.0 μm wide, undischarged, n=10, ROMIZ B4420).

Reported distribution. Gulf coast of Florida. Dry Tortugas, Garden Key, Fort Jefferson, on an alga (Perkins 1908: 147, as Campanularia macrotheca).—Dry Tortugas (Leloup 1935a: 21, as Laomedea macrotheca).

Elsewhere in western North Atlantic. Bonaire: Lac, Soerebon, 0.2 m, on Halecium bermudense (Leloup 1935a: 21, as Laomedea macrotheca).— Bermuda: Whalebone Bay, ledges at entrance, on algae, 1 m + Walsingham Pond, entrance of underground passage, on rock, 1 m (Calder 1990 [1991a]: 64).— Belize: Twin Cays (Calder 1991b: 223).—French Lesser Antilles: Les Saintes, Terre-de-Haut, Pompierre Bay, 15°52’25”N, 61°34’15”W, on Halimeda in seagrass meadows + Terre-de-Haut, Pain de Sucre, 15°51’45”N, 61°35’60”W, on Halimeda from rocky shore (Galea 2008: 20).—French Lesser Antilles: Guadeloupe, Grande-Terre, mangrove of Petit Canal, 16°21.891’N, 61°30.137’W, 0.5 m (Galea 2010: 4).— Cuba: Havana, coral reef system west of the city (Castellanos et al. 2018: Supplementary Table S2, as Clytia macroteca).