Gymnangium speciosum ( Allman, 1877 )

Calder, Dale R., 2013, Some shallow-water hydroids (Cnidaria: Hydrozoa) from the central east coast of Florida, USA, Zootaxa 3648 (1), pp. 1-72 : 49-50

Gymnangium speciosum ( Allman, 1877)

Fig. 14e

Halicornaria speciosa Allman, 1877: 54 , pl. 34, figs. 1–5.

not Halicornaria speciosa . — Nutting, 1900: 127 (part) [= Gymnangium sinuosum ( Fraser, 1925) ].

Gymnangium speciosum .— Humann, 1992: 69, middle photograph.— Humann & DeLoach, 2002: 69, middle photograph.

Type locality. Bahamas: Double-Headed Shot Key ( Allman 1877: 55) .

Voucher material. West Palm Beach, on reef seaward of the Breakers Hotel, 45 feet (13.7 m), January 1991, SCUBA, fragments of one dead colony, c. 19.5 cm high, with empty gonothecae, coll. P. Humann, ROMIZ B1131.

Remarks. This species was originally described by Allman (1877) as Halicornaria speciosa . Halicornaria Allman, 1874 was widely used as a generic name until it was a shown to be a junior synonym of Gymnangium Hincks, 1874 by Stechow (1921b). He noted that Allman’s (1874) account of Halicornaria appeared in April 1874, whereas its subjective synonym Gymnangium was made available by Hincks (1874) earlier that year (February). Moreover, the name Halicornaria Allman, 1874 is now known to be an invalid junior homonym of Halicornaria Hincks, 1865 ( Calder 1997) . The status of the senior homonym is discussed above under Halopteris carinata Allman, 1877 . Although the name Gymnangium is now well-established, the genus-group it represents is thought to be polyphyletic ( Leclère et al. 2007).

Of the four putatively valid species of Gymnangium in the tropical western Atlantic, G. speciosa differs from G. arcuatum ( Lamouroux, 1816) in having unbranched colonies and in possessing an intrathecal septum, from G. longicaudum ( Nutting, 1900) in having median inferior nematothecae that extend a relatively short distance beyond the hydrothecal rim instead of well beyond it, and from G. sinuosum ( Fraser, 1925) in having two embayments on each side of the hydrothecal rim instead of one. More detailed accounts of these species are given by Bogle (1975) and Calder (1997).

Nutting’s (1900) report of this species (as Halicornaria speciosa ) from Albatross Station 2640 (25°05’N, 80°15’W) south of Carysfort Reef, Florida, was assigned instead to Gymnangium sinuosum by Bogle (1975: 271) after an examination of Nutting’s specimens (USNM 18703, 18704). The misidentified record was repeated in Fraser (1944).

The photograph of Gymnangium speciosum in Humann (1992) and Humann & DeLoach (2002) shows the same colony examined here.

Reported distribution. Atlantic coast of Florida. Off West Palm Beach ( Humann 1992; Humann & DeLoach 2002).

Western Atlantic. Southeastern Florida, Bahamas, Gulf of Mexico, and Arrowsmith Bank in the northwestern Caribbean Sea ( Bogle 1975) to Barbados ( Fraser 1944) and Colombia ( Wedler 1975). The species is also known from Bermuda ( Calder 1997).

Figures

FIGURE 14. a, Aglaophenia dubia: part of a hydrocladium with two hydrothecae, ROMIZ B1125, scale equals 0.10 mm. b, Aglaophenia latecarinata: part of a hydrocladium with two hydrothecae, ROMIZ B1086, scale equals 0.10 mm. c, Aglaophenia rhynchocarpa: part of a hydrocladium with two hydrothecae, ROMIZ B1083, scale equals 0.10 mm. d, Aglaophenia trifida: part of a hydrocladium with three hydrothecae, ROMIZ B1086, scale equals 0.10 mm. e, Gymnangium speciosum: part of a hydrocladium with three hydrothecae, ROMIZ B1131, scale equals 0.20 mm. f, Macrorhynchia allmani: part of a hydrocladium with two hydrothecae, ROMIZ B3982, scale equals 0.10 mm. g, Macrorhynchia clarkei: part of a hydrocladium with two hydrothecae, ROMIZ B1129, scale equals 0.10 mm. h, Macrorhynchia clarkei: a single phylactogonium from a pseudocorbula, ROMIZ B1129, scale equals 0.25 mm. i, Macrorhynchia philippina: part of a hydrocladium with three hydrothecae, ROMIZ B1092. Scale equals 0.10 mm.