Gymnangium sinuosum (Fraser, 1925)

Calder, Dale R., 2019, On a collection of hydroids (Cnidaria, Hydrozoa) from the southwest coast of Florida, USA, Zootaxa 4689 (1), pp. 1-141 : 95-96

Gymnangium sinuosum (Fraser, 1925)

Fig. 22c

Halicornaria sinuosa Fraser, 1925: 171 , figs. 7A–C.

Aglaophenia (?) allmani .— Leloup, 1935a: 57 [part] [not Macrorhynchia allmani ( Nutting, 1900) ].

not Halicornaria sinuosa .— Leloup, 1937: 110, fig. 13 [= Gymnangium speciosum ( Allman, 1877) ].

Halicornaria hians var. balei .— Van Gemerden-Hoogeveen, 1965: 70, figs 39–41 [not Gymnangium hians balei (Marktanner- Turneretscher, 1890).

Gymnangium sinuosum .— Bogle, 1975: 271, figs. 23A, B.

Type locality. USA: Florida, Gulf Stream off Cape Florida, 2-1/ 8 miles (3.4 km) SSE of Fowey Rocks Lighthouse, 45 ftm (82 m) (Fraser 1925: 172, as Halicornaria sinuosa ) .

Material examined. Southwest Florida Shelf, middle shelf west of North Naples, 26°16’15”N, 83°47’00”W, 76 m, 04 November 1980, one fragment, 4.0 cm high, plus broken stem, without gonophores, coll. Continental Shelf Associates, ROMIZ B2203.

Remarks. Gymnangium sinuosum (Fraser, 1925) has been discussed in detail elsewhere ( Bogle 1975; Calder 1997; Ansín Agís et al. 2001). While much like the essentially sympatric G. speciosum ( Allman, 1877) , the two have been distinguished to date mainly on the basis of a single morphological character. The hydrothecal margin in G. sinuosum has a single embayment on each side rather than two. According to Bogle (1975), the length of the median inferior nematotheca is much less variable in G. sinuosum as well. Although she examined material of both species (including type specimens) and considered them to be distinct, examination of the two morphotypes using molecular methods would nevertheless be worthwhile. Hydroids conforming to the concepts of G. allmani ( Marktanner-Turneretscher, 1890) and G. longicaudum ( Nutting, 1900) , species or putative species from the Caribbean Sea with particularly long median inferior nematothecae, might well be included in any such studies.

As noted earlier ( Bogle 1975; Calder 1997; Ansín Agís et al. 2001), part of the material assigned to Gymnangium speciosum by Nutting (1900, as Halicornaria speciosa ), specifically that from the Straits of Florida south of Carysfort Reef (25°05’N, 80°15’W), is referable instead to G. sinuosum . In addition, part of the material identified as Aglaophenia (?) allmani by Leloup (1935a), namely several colonies in collection No. 71, Sta. 210 from the Dry Tortugas, was assigned by Van Gemerden-Hoogeveen (1965: 79) to Halicornaria hians var. balei ( Marktanner-Turneretscher, 1890) . From her description and illustrations (figs. 39–41), however, it is clear that they are referable to G. sinuosum ( Bogle 1975; Calder 1997). Finally, as apparent from his illustration, Leloup’s (1937, fig. 13) record of Halicornaria sinuosa (= G. sinuosum ) from shelf waters off Tampa Bay is based on a misidentification of G. speciosum ( Bogle 1975; Calder 1997).

The name Halicornaria Allman, 1874a , sometimes applied to this genus in the past, is a junior synonym of Gymnangium Hincks, 1874 ( Stechow 1921b; Calder 1997, 2013). Evidence now exists for subdivision of Gymnangium into two taxa. Ronowicz et al. (2017) studied nine species assigned to the genus from the Indian Ocean, utilizing both morphological and molecular methods. In addition to maintenance of Gymnangium , their results support recognition of Taxella Allman, 1874b , long held to be its congener. As for G. sinuosum , the species studied here, it remains in Gymnangium . From current knowledge of this hydroid and its distribution, it is another species typical of shelf waters in the warm western Atlantic.

Reported distribution. Gulf coast of Florida. Dry Tortugas, 27 ft (8 m) ( Leloup 1935a: 57, as Aglaophenia (?) allmani ; Van Gemerden-Hoogeveen 1965: 70, as Halicornaria hians var. balei ).—Straits of Florida, E of Alligator Reef, 24°51’N, 80°35’W, 64–69 m ( Bogle 1975: 272).

Elsewhere in western North Atlantic. USA: Florida, Straits of Florida, 25°05’N, 80°15’W, south of Carysfort Reef, 56 ftm (102 m) ( Nutting 1900: 127, as Halicornaria speciosa ; Bogle 1975: 271).— USA: Florida, Gulf Stream off Cape Florida, 2-1/ 8 miles (3.4 km) SSE of Fowey Rocks Lighthouse, 45 ftm (82 m) (Fraser 1925: 172, as Halicornaria sinuosa ; Bogle 1975: 271, syntypes).— USA: Florida, Straits of Florida, E of Cape Florida, 25°43’N, 80°04’W– 25°44’N, 80°04’W, 137–174 m ( Bogle 1975: 271).— USA: South Carolina, inner (17–18 m), middle (32–36 m) and outer (46–69 m) continental shelf + Georgia, inner (17–22 m) and middle (23–29 m) continental shelf ( Wenner et al. 1984: 21, 40).— Bermuda: 2.5 km E of St. David’s Lighthouse, 85 m (Calder 1997: 43).

Figures

FIGURE 22. a, Aglaophenia dubia: part of a hydrocladium with two hydrothecae, Southwest Florida Shelf, ROMIZ B2147. Scale equals 0.1 mm. b, Aglaophenia latecarinata: part of a hydrocladium with three hydrothecae, Fort Myers Beach, ROMIZ B4402. Scale equals 0.1 mm. c, Gymnangium sinuosum: part of a hydrocladium with one hydrotheca, Southwest Florida Shelf, ROMIZ B2203. Scale equals 0.1 mm. d, Lytocarpia tridentata: part of a hydrocladium with two hydrothecae, Florida Keys, Bahia Honda Channel, ROMIZ B3806. Scale equals 0.1 mm. e, Macrorhynchia allmani: part of a hydrocladium with two hydrothecae, Southwest Florida Shelf, ROMIZ B2187. Scale equals 0.1 mm. f, Macrorhynchia philippina: part of a hydrocladium with two hydrothecae, Sanibel Island, ROMIZ B4405. Scale equals 0.1 mm.