Clytia paulensis

Clytia paulensis (Vanhöffen, 1910)

Figs. 14h, i

Campanularia paulensis Vanhöffen, 1910: 298, figs. 19a, b.

Type locality. Île Saint-Paul, in the crater basin, shallow water (Vanhöffen 1910: 298).

Material examined. Southwest Florida Shelf, outer shelf northwest of the Dry Tortugas, 25°16.83’N, 83°57.35’W, 127 m, on Lafoea coalescens, 03 August 1981, triangle dredge, several colony fragments, up to 2.5 cm high, without gonophores, coll. Continental Shelf Associates, ROMIZ B1742.

Remarks. If they all belong to the same species, hydroid colonies reported under the binomen Clytia paulensis Vanhöffen, 1910 have a remarkable geographic distribution. Undescribed until its discovery just over a century ago in the crater basin of remote Île Saint-Paul in the southern Indian Ocean, the species was reported from Europe in 1919 (Stechow 1919: 45), from South Africa in 1923 (Stechow 1923a: 111), from Australia in 1924 (Stechow 1924: 69), from California in 1925 (Stechow 1925: 211), from eastern North America in 1971 (Calder 1971: 51), from Japan in 1995 (Hirohito 1995: 68), from eastern South America in 1997 (Grohmann et al. 1997: 231; Genzano & Zamponi 1997: 291; but not C. paulensis in Blanco 1968), and from western South America in 2007 (Galea 2007: 90). A report of the hydroid from the Antarctic (Naumov & Stepanjants 1972, as Obelia paulensis) is likely to have been based on a different species. Of particular interest, however, was the discovery of specimens in collections at the Natural History Museum, London, collected in 1899 by E.T. Browne from Devon, England (Cornelius 1982: 90; 1995b: 260). Those hydroids were not recognized as C. paulensis until 1978.

Given initial misgivings about the identity of hydroids from Chesapeake Bay as C. paulensis, specimens were compared with colonies of the species from South Africa provided by N.A.H. Millard (Calder 1971). Overlap was found in length and width measurements of pedicels, hydrothecae, and gonothecae in materials from the two regions. American specimens tended to have about one less marginal cusp, but that apparent difference was considered unimportant taxonomically and the two populations were taken to be conspecific. While hydrothecae of C. paulensis somewhat resemble those of Obelia bidentata Clark, 1875 and O. oxydentata Stechow, 1914 in having bimucronate marginal cusps, the colony form of the species differs in being mostly stolonal rather than erect with a distinct and regularly sympodial hydrocaulus. Measurements of hydrothecae and pedicels of specimens from southwest Florida, examined here, fell within or close to the range of specimens from Virginia and South Africa.

Clytia paulensis as generally conceived is a species of warm-temperate to tropical regions (Cornelius 1982, 1995b; Medel & Vervoort 2000; Peña Cantero & García Carrascosa 2002). Its reported distribution in the western North Atlantic, from the mid-Atlantic states of the USA (Calder 1971) to the Caribbean Sea (Calder 1991b; Calder & Kirkendale 2005), coincides with that concept. In Chesapeake Bay, at the northern end of its range on this coast, the species is active only during the warmer months of the year (May to November) (Calder 1990). Previous records from the Gulf of Mexico include those of Defenbaugh & Hopkins (1973) from Texas, Mendoza-Becerril et al. (2018b) from Mexico, and Castellanos et al. (2018) from the north coast of Cuba. This is the first account of it from the Gulf coast of Florida. Clytia paulensis has been reported from Brazil and Argentina in the western South Atlantic (Oliveira et al. 2016). Clytia longitheca Fraser, 1914, reported from British Columbia, Canada, to Oaxaca, Mexico (Fraser 1946 [1947 a]), appears to be essentially indistinguishable from C. paulensis (Calder 1971; Peña Cantero & García Carrascosa 2002; Calder & Choong 2018).

Specimens examined here were found, as epizoites on the hydroid Lafoea coalescens, at a depth of 127 m. Hydrothecae were quite varied in size, as apparent from Figs. 14h and i. Clytia paulensis appears to be eurybathic, with a reported depth range from the intertidal zone to 4751 m (Cornelius 1995b; Fernandez & Marques 2018). Other hydroids are a frequent substrate of the species (Peña Cantero & García Carrascosa 2002), although those authors also mentioned reports of it from polychaete tubes, bryozoans, ascidians, mollusc shells, algae, sea grasses, stones, and anthozoans. Stechow (1923b) included a record of the species from spines of an echinoid, and specimens from Chesapeake Bay were found on sponges, hydroids, polychaete tubes, and mollusc shells (Calder 1971).

The medusa stage of C. paulensis is as yet unknown (Cornelius 1982, 1995b).

Reported distribution. Gulf coast of Florida. First record.

Elsewhere in western North Atlantic. USA: Virginia, York River (Tue Marsh Light; Ellen Island; off VEPCO power plant at Yorktown; Gloucester Point; Pages Rock) + James River (Old Point Comfort; Hampton Flats; Newport News Bar; Hampton Roads Middle Ground) + Chesapeake Bay (Chesapeake Bay Bridge-Tunnel, mid-span) (Calder 1971: 51).— USA: Texas, off Galveston (Defenbaugh & Hopkins 1973: 80, as Clytia longitheca).— USA: Georgia, outer continental shelf, 59–67 m (Wenner et al. 1983: 39).— Belize: Twin Cays (Calder 1991b: 223).— USA: South Carolina estuaries, Bulls Bay + Prices Creek + St. Helena Sound + Port Royal Sound (Calder & Hester 1978: 90).— Bermuda: Challenger Bank (Calder 2000: 1134).— Panama: Colón, Fort Sherman dock, wood, 09°22’12”N, 79°56’59”W, 0-2 m (Calder & Kirkendale 2005: 486).— USA: Florida, Off St. Lucie Inlet, 27°10.8’N, 80°00.8’W, 44 m (Calder 2013: 57).— Mexico: Alacranes Reef, on sponges, soft corals (Mendoza-Becerril et al. 2018b: 131).— Cuba: Havana, coral reef system west of the city (Castellanos et al. 2018: Supplementary Table S 2).