Lafoea intorta, Calder, 2013

Calder, Dale R., 2013, Some shallow-water hydroids (Cnidaria: Hydrozoa) from the central east coast of Florida, USA, Zootaxa 3648 (1), pp. 1-72 : 15-17

Lafoea intorta , sp. nov.

Figs. 2e, f , 3 , 4

? Lafoea gracillima .— Clarke, 1879: 243.— Fraser 1944: 225 [part]. Type material. Holotype: off St. Lucie Inlet, 27°11.8’N, 79°57.3’W, 87 m, 04.x.1986, Johnson-Sea-Link, J028/ JSL 2132, one colony, 2.5 cm high, without coppiniae, coll. R. Roesch, ROMIZ B1098.

Etymology. The specific name intorta is taken from the Latin word for “twisted” or “tangled,” in reference to the bushy and tangled appearance of the hydroid colony.

Description. Colony erect, profusely tangled, about 3 cm high, arising from a creeping and somewhat wrinkled hydrorhiza, comprising several hydrocauli. Larger hydrocauli polysiphonic throughout most of length, becoming progressively more slender distally, monosiphonic at distal end, irregularly branched; larger branches resembling hydrocauli, polysiphonic except at extremities; smaller and younger branches monosiphonic throughout; perisarc of stem and branches thickest basally, thinning out distally. Hydrothecal pedicels 130–210 µm in length, sometimes almost straight but usually with a curve or loose twist basally, diameter of pedicels 60–70 µm and remaining nearly uniform throughout length, arising directly from all sides of hydrocaulus and branches, never adnate basally, most given off at an angle of 45 degrees or more from stem and branches. Hydrothecae deeply conical and with smooth walls, sometimes nearly symmetrical but more often somewhat curved with abcauline wall less convex than adcauline side, length abcauline wall 380–500 µm, length adcauline wall 420–550 µm; base of hydrotheca with an irregular whorl of punctae just above a filmy diaphragm, then merging almost imperceptibly with pedicel; diameter across diaphragm 65–85 µm; hydrothecal margin entire, distinctly everted, occasionally renovated in older parts of colony; orifice round, 150–165 µm in diameter, without an operculum. Nematothecae absent. Hydranths with about 12 filiform tentacles.

Gonophores not seen.

Nematocysts ( Fig. 4 ): microbasic mastigophores (5.5–6.4 µm long x 2.1–2.6 µm wide; n = 10), abundant on tentacles; holotrichous isorhizas (23.2–24.5 µm long x 9.0–10.0 µm wide; n = 10), common on hydranth body and in coenosarc. Identifications of nematocyst categories are tentative; discharged threads were too indistinct in ethanol-preserved material for certain designation.

Remarks. The warm-water Lafoea intorta , sp. nov., resembles Lafoea dumosa ( Fleming, 1820) , L. fruticosa (M. Sars, 1850) , and L. gracillima ( Alder, 1856) , cold-water species found at higher latitudes or at greater depths further south. While species of Lafoea Lamouroux, 1821 are difficult to identify because of their morphological variability, and their taxonomy is therefore unsettled, material examined here can nevertheless be distinguished from each of these putative species. In L. intorta , pedicels are longer and more obviously twisted than those of L. dumosa , a species with hydrothecae that appear almost sessile. Conversely, its pedicels are shorter and have fewer twists than in either L. fruticosa or L. gracillima . Unlike in L. gracillima , its hydrothecae are deep-cone-shaped rather than decidedly narrow and cylindrical, and the hydrothecal margin is distinctly flared instead of straight or slightly flared. Hydrothecae of L. intorta are smaller than those of L. dumosa and L. fruticosa . A filmy, vestigial diaphragm was observed in some of the empty hydrothecae ( Fig. 3b ), a structure said to be absent in the genus ( Millard 1975; Cornelius 1995a; Bouillon et al. 2006).

On biogeographic grounds, material identified as Lafoea gracillima by Clarke (1879) from shelf waters of southwest Florida and by Fraser (1944) from northwest of the Dry Tortugas (Florida) may have been L. intorta . Existence of the Arctic-boreal species L. gracillima in the subtropical southeastern Gulf of Mexico where these sites are located is improbable. A colony identified as Lafoea fruticulosa (sic) by Wenner et al. (1984) from a reef on the outer continental shelf off Charleston, South Carolina (32°29.5’N, 78°49.5’W, 50 m, 5.v.1981, R/V Dolphin, Cerame-Vivas dredge, without gonophores, ROMIZ B1916) was re-examined here and found to be identical with L. intorta . That specimen is designated here as a paratype of the species.

The cnidome of Lafoea intorta includes what are believed to be microbasic mastigophores and holotrichous isorhizas. Other nematocyst categories were observed as well, but it was unclear whether they were part of the cnidome or simply exogenous ones. Study material long preserved in alcohol rendered nematocyst examination difficult.

Reported distribution. South Carolina ( Wenner et al. 1984, as Lafoea fruticulosa ) to the central east coast of Florida (this study).

Figures

FIGURE 2. a, Lovenella grandis: hydrocaulus with two hydrothecae and a gonotheca, ROMIZ B1076, scale equals 0.5 mm. b, Lovenella grandis: hydrocaulus with pedicel and hydrotheca, ROMIZ B1076, scale equals 0.25 mm. c, Plicatotheca anitae: part of hydrocaulus with two hydrothecae, ROMIZ B1072, scale equals 0.25 mm. d, Plicatotheca anitae: gonotheca, ROMIZ B1072, scale equals 0.25 mm. e, Lafoea intorta, sp. nov.: part of hydrocaulus with five hydrothecae, ROMIZ B1098, scale equals 0.25 mm. f, Lafoea intorta, sp. nov.: part of hydrocaulus with a hydrotheca, ROMIZ B1098, scale equals 0.10 mm.

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 4. Lafoea intorta, sp. nov., nematocysts, ROMIZ B1098: a, microbasic mastigophores, from tentacle; b, holotrichous isorhiza, from hydranth; c, holotrichous isorhiza, partially discharged.