Amphinema, Haeckel, 1879

Calder, Dale R., 2019, On a collection of hydroids (Cnidaria, Hydrozoa) from the southwest coast of Florida, USA, Zootaxa 4689 (1), pp. 1-141 : 23-24

Amphinema sp.

Fig. 2f, g , 4

Material examined. Naples ( FL), Doctors Pass, north jetty, channel side, on stolonal bryozoan on boulder,

26°10’29.14”N, 81°48’53.45”W, ELWS, 06 December 2017, one stolonal colony, 2 mm high, without gonophores, coll. D. Calder, ROMIZ B4337 .— Captiva Island , Turner Beach, on jetty , 26°28’57.3”N, 82°11’02.8”W, on rocks at low tide, 01 March 2018, several colony fragments, up to 4 mm high, without gonophores, coll. D. Calder, ROMIZ B4338 .

Remarks. While these hydroids have been assigned to Amphinema Haeckel, 1879 (family Pandeidae Haeckel, 1879 ), no gonophores were present in the examined specimens. Their trophosomes resemble those of species such as A. dinema ( Péron & Lesueur, 1810) and A. rugosum ( Mayer, 1900a) , whose medusa stages have been reported from the southeastern Gulf of Mexico ( Mayer 1910a; Segura-Puertas et al. 2009), but these sterile specimens cannot be confirmed as conspecific with either one from current evidence. The cnidome comprised the usual categories of nematocysts found in pandeids and bougainvilliids, namely desmonemes (3.2 – 3.8 long x 1.7 – 2.2 μm wide, undischarged, n=10, ROMIZ B4338) and microbasic euryteles (6.2 – 7.1 long x 1.9 – 2.2 μm wide, undischarged, n=10, ROMIZ B4338). In size and shape, the euryteles approached those of A. dinema ( Péron & Lesueur, 1810) as described by Russell (1938), and those of both A. dinema and A. rugosum as described by Schuchert (1996). Most notably, they were longer and much more slender than those of the bougainvilliid Bougainvillia rugosa from the study area. Nevertheless, life cycle or molecular studies of conspecifics from the study area are needed to resolve the specific identity of this hydrozoan.

Figures

FIGURE 2. a, Bimeria humilis: colony with two hydranths, Fort Myers Beach, ROMIZ B4330. Scale equals 0.2 mm. b, Bougainvillia rugosa: part of colony with hydranth and medusa bud, Sanibel Island, ROMIZ B4333. Scale equals 0.2 mm. c, Bougainvillia rugosa: newly liberated medusa from same hydroid, ROMIZ B4333. Scale equals 0.1 mm. d, Bougainvillia rugosa: 3-day-old laboratory-raised medusa from same hydroid, ROMIZ B4333. Scale equals 0.1 mm. e, Calyptospadix cerulea: part of hydrocaulus with branches, pedicels, hydranths, and a female gonophore, Caloosahatchee River at Fort Myers, ROMIZ B4340. Scale equals 0.3 mm. f, Amphinema sp.: hydranth and pedicel, Captiva Island, ROMIZ B4338. Scale equals 0.2 mm. g, Amphinema sp.: hydranth and pedicel, Captiva Island, ROMIZ B4338. h, Eudendrium carneum: hydranth and pedicel, Sanibel Island, ROMIZ B4343. Scale equals 0.2 mm. i, Eudendrium carneum: part of female colony with encapsulated embryos, Sanibel Island, ROMIZ B4344. Scale equals 0.4 mm.

FIGURE 4. Amphinema sp.: nematocysts of hydroid stage, ROMIZ B4338. a, desmoneme. b, heterotrichous microbasic euryteles.