Lytocarpia tridentata ( Versluys, 1899 )

Calder, Dale R., 2019, On a collection of hydroids (Cnidaria, Hydrozoa) from the southwest coast of Florida, USA, Zootaxa 4689 (1), pp. 1-141 : 96-97

Lytocarpia tridentata ( Versluys, 1899)

Fig. 22d

Aglaophenia tridentata Versluys, 1899: 47 , figs. 16–18.

Aglaophenia contorta Nutting, 1900: 96 , pl. 20, figs. 5–7.— Wallace, 1909: 137.

Type locality. Venezuela: Los Testigos Islands , 11 m ( Versluys 1899: 49, as Aglaophenia tridentata ) .

Material examined. Florida Keys, Bahia Honda Channel , 24°39.489’N, 81°17.198’W, 6 m, 16 June 2008, on limestone, three colony fragments, up to 14.5 cm high, with gonophores, ROMIZ B3806 .— Fort Myers Beach , stranded intertidally on detached octocoral, 16 February 2013, one colony, 2.9 cm high, without gonophores, coll. D. Calder, ROMIZ B4403 .

Remarks. Versluys (1899) provided the first account of this species, as Aglaophenia tridentata , based on sterile colonies from the Archipiélago de Los Testigos in the southeastern Caribbean Sea. It was described again by Nutting (1900), as A. contorta , from fertile specimens taken near Key West, Florida. On recognizing that hydroids in the two accounts were conspecific, Stechow (1923b) followed the Principle of Priority and adopted the senior name for the species. Totton (1926) assigned it to Thecocarpus Nutting, 1900 based on the morphology of corbulae from material collected in Brazil. With Thecocarpus now held to be a junior synonym of Lytocarpia Kirchenpauer, 1872 , the valid name of the species is Lytocarpia tridentata .

Lytocarpia tridentata is most readily distinguished by the morphology of its saddle-shaped hydrothecae. These consist of a somewhat bulbous base having an adcauline intrathecal ridge and supporting a large and projecting median inferior nematotheca, a somewhat constricted mid-region, an expanded distal end flanked by a pair of hornshaped lateral nematothecae, and a margin with three cusps, one well-developed median and two blunt laterals. Colonies are erect, with a monosiphonic and unbranched hydrocaulus reaching as much as 18 cm high ( Migotto 1996). Hydrocladia, occurring in a distal plume on larger colonies, are alternate and unbranched.

Detailed accounts of the taxonomy of this species include those of Vervoort (1968, as Aglaophenia tridentata ), and Migotto (1996, as Lytocarpia tridentata ), with the latter study based on material from Brazil. Records of L. tridentata in the tropical northwest Atlantic have been fewer in number than those to the south in Brazil ( Oliveira et al. 2016). As noted by Vervoort (1968) and confirmed by the collection data of Migotto (1996) and others, this hydroid is predominantly a species of shallow waters. Its known bathymetric range extends from the intertidal zone ( Migotto 1996) to 70 m ( Grohmann et al. 2003; Posada et al. 2010), with most reports at depths of less than 20 m.

Reported distribution. Gulf coast of Florida. Off Key West, 5½ ftm (10 m) ( Nutting 1900: 96, as Aglaophenia contorta ).—Off Marco Island, 2 ftm (4 m) ( Nutting 1900: 96, as Aglaophenia contorta ).—Dry Tortugas ( Wallace 1909: 137, as Aglaophenia contorta ).

Elsewhere in western North Atlantic. Venezuela: Los Testigos Islands, 11 m ( Versluys 1899: 49, as Aglaophenia tridentata ).— Virgin Islands of the United States: St. Thomas, Sound + Savannah Passage ( Vervoort 1968: 76, as Aglaophenia tridentata ).— Costa Rica: off Limón, 10°01’10”N, 83°04’45”W ( Kelmo & Vargas 2002: 616).— Colombia: Golfo de Salamanca, 70 m ( Posada et al. 2010: 79, as Aglaophenia tridentata ).—Caribbean Sea ( Wedler 2017b: 148, fig. 177).

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.