Macrorhynchia allmani ( Nutting, 1900 )

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

Macrorhynchia allmani ( Nutting, 1900)

Fig. 14f

Aglaophenia ramosa Allman, 1877: 39 , pl. 23, figs. 1–4 [permanently invalid junior secondary homonym of Aglaophenia ramosa ( Busk, 1852) ; replaced before 1961 by a substitute name in current use (ICZN Art. 59.3)].

Aglaophenia allmani Nutting, 1900: 100 , pl. 22, figs. 2–3 [replacement name for Aglaophenia ramosa Allman, 1877 ].

Type locality. USA: Florida, “ Florida reef, from a depth of from 2 to 3 fathoms” (3.7–5.5 m) ( Allman 1877: 40, as Aglaophenia ramosa ) .

Voucher material. Bethel Shoal off Vero Beach, 27°42.6’N, 80°06.8’W, 24 m, on shell fragments, 18.ii.1976, Johnson-Sea-Link, JSL 328, diver lockout, three cormoids, up to 4.2 cm high, without gonothecae, coll. S. Nelson, ROMIZ B3982 .

Remarks. Fully-developed colonies of Macrorhynchia allmani Nutting, 1900 reach as much as 28 cm high ( Calder 1997). Those examined here were much smaller, but they otherwise correspond in morphology with earlier accounts of the species.

Macrorhynchia allmani resembles the sympatric M. clarkei Nutting, 1900 , and the two have sometimes been confused, as noted earlier ( Calder 1997). The most obvious difference between them macroscopically is colour, with colonies of M. allmani appearing brownish and those of M. clarkei black. Microscopically, hydrocladial internodes of M. allmani usually have two internal perisarcal ridges while those of M. clarkei have only one. Other differences are reported in remarks on the latter species immediately below.

Reproductive structures of this species have yet to be described. In their absence, M. allmani is referred to the aglaopheniid genus Macrorhynchia Kirchenpauer 1872 based on trophosomal characters identified by Bogle (1975) and reiterated by Calder (1997). As in that genus, the hydrocaulus is polysiphonic and repeatedly branched, cauline nematothecae are large and triangular, median inferior nematothecae are largely adnate to the abcauline hydrothecal wall, and hydrothecae are of moderate depth. Wedler (2004) described gonophores in a hydroid identified as this species, but in my opinion his specimens are referable to M. furcata ( Nutting, 1900) instead. Lateral nematothecae visible in his Fig. 3c are forked, as in that species.

Reported distribution. Atlantic coast of Florida. First record.

Western Atlantic. Continental shelf of South Carolina and Georgia ( Wenner et al. 1984, as Aglaophenia allmani ) to Brazil (Oliveira et al. submitted) including Bermuda ( Calder 1997), the Gulf of Mexico ( Calder & Cairns 2009), and the Caribbean Sea ( Vervoort 1968, as Aglaophenia (?) allmani ).

Figures

FIGURE 3. Lafoea intorta, sp. nov.: a, part of hydrocaulus with two hydrothecae, ROMIZ B1098; b, hydrotheca, with diaphragm marked by an arrow, ROMIZ B1098.

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.