Obelia oxydentata Stechow, 1914

Calder, Dale R., 2013, Some shallow-water hydroids (Cnidaria: Hydrozoa) from the central east coast of Florida, USA, Zootaxa 3648 (1), pp. 1-72 : 59

Obelia oxydentata Stechow, 1914

Fig. 16g

Obelia (?) oxydentata Stechow, 1914: 131 , fig. 7.

Obelia oxydentata .— Weiss, 1948: 158.

Type locality. Virgin Islands: St. Thomas , Charlotte Amalie ( Stechow 1914) .

Voucher material. Fort Pierce , ship canal at Link Port, 27°32’05”N, 80°20’50”W, 0.1 m, 17.ii.1991, on prop roots of Rhizophora mangle , 15° C, 22‰, collected by snorkeling, several colony fragments, up to 9 mm high, without gonophores, coll. D.R. Calder, ROMIZ B1112 .

Remarks. Specimens referred here to Obelia oxydentata Stechow, 1914 were all small (<1 cm high) with monosiphonic hydrocauli. Hydroids with the same characters have been reported elsewhere from shallow waters of the tropical and subtropical western Atlantic as O. bidentata Clark, 1875 (e.g., Bermuda: Calder 1991a; Brazil: Migotto 1996; Guadeloupe: Galea 2010). Such specimens contrast with the original descriptions of O. bidentata (colonies polysiphonic and up to 15 cm high) and its subjective synonym O. bicuspidata Clark 1875 (colonies polysiphonic and up to 8 cm high), both from temperate waters in the Long Island Sound area. While I earlier considered O. oxydentata to be conspecific with O. bidentata (e.g., Calder 1991a), it appears to be a different species. Obelia longicyatha Allman, 1877 from 90 fathoms (165 m) off Florida Reef, with small (<2.5 cm) but partly polysiphonic colonies, has also been regarded in many recent works as conspecific with O. bidentata . Comparisons are warranted to determine whether the supposedly shallow-water O. oxydentata is identical with it.

Reported distribution. Atlantic coast of Florida. Biscayne Bay ( Weiss 1948).

Western Atlantic. Florida (this report) to Brazil ( Vannucci Mendes 1946), and including the Caribbean Sea ( Stechow 1914; Fraser, 1944). Its range will likely prove to be much more extensive once it can be reliably distinguished from Obelia bidentata Clark 1875 .

Elsewhere. Tropical eastern Pacific ( Stechow 1914).

Figures

FIGURE 16. a, Clytia noliformis: hydrotheca and distal part of pedicel, ROMIZ B3984, scale equals 0.10 mm. b, Clytia noliformis: gonotheca, ROMIZ B3984, scale equals 0.10 mm. c, Clytia paulensis: part of colony with hydrotheca and pedicel, ROMIZ B1103, scale equals 0.20 mm. d, Clytia paulensis: hydrotheca and distal part of pedicel, ROMIZ B1103, scale equals 0.10 mm. e, Obelia geniculata: part of hydrocaulus with three hydrothecae, ROMIZ B1119, scale equals 0.25 mm. f, Obelia hyalina: part of colony with three hydrothecae, ROMIZ B3985, scale equals 0.25 mm. g, Obelia oxydentata: part of colony with three hydrothecae, ROMIZ B1112, scale equals 0.25 mm.