Nemertesia simplex ( Allman, 1877 )

Calder, Dale R., 2019, On a collection of hydroids (Cnidaria, Hydrozoa) from the southwest coast of Florida, USA, Zootaxa 4689 (1), pp. 1-141 : 111-112

Nemertesia simplex ( Allman, 1877)

Figs. 24d, e

Antennularia simplex Allman, 1877: 34 , pl. 21, figs. 1, 2.— Nutting, 1900: 70, pl. 9, fig. 5.

Type locality. USA: Florida, off Alligator Reef , 86 ftm (157 m) ( Allman 1877: 34, as Antennularia simplex ) .

Material examined. Southwest Florida Shelf, outer shelf NW of the Dry Tortugas, 25°16.83’N, 83°57.35’W, 127 m, 03 August 1981, triangle dredge, one colony, with stems to 14 cm high, without gonophores, coll. Continental Shelf Associates, ROMIZ B2113.

Remarks. Allman (1877) briefly described this hydroid, as Antennularia simplex , from material collected off Alligator Reef, Florida. The gonosome of the species was not observed by him, but the trophosome was said to be much like that of A. ramosa Lamarck, 1816 . Nutting (1900) provided a second account of the species based on additional specimens, and described its gonosome from fertile material. Antennularia Lamarck, 1816 is now recognized as a junior synonym of Nemertesia Lamouroux, 1812 , with the binomen N. simplex first being adopted for this species by Bedot (1912: 325).

Ramil & Vervoort (2006) provided a table of characters distinguishing this species from others in the genus, including the morphologically similar N. ramosa . Nemertesia simplex differs from that congener in having (1) hydrocauli that are monosiphonic and unbranched or slightly branched rather than polysiphonic and much branched, and (2) hydrothecal margins that usually slope at an oblique angle to the hydrocladial axis instead of being perpendicular to it ( Calder 2013: 37).

Nemertesia simplex has been reported only a few times, all from the mid- to outer continental shelf and upper continental slope of eastern North America. However, the species may not actually be especially rare. In addition to its type locality in the Straits of Florida ( Allman 1877, as Antennularia simplex , 157 m), it has been reported southwards to Cuba ( Nutting 1900, as A. simplex , 368 m) and northwards off the Atlantic coast of the United States to Florida ( Calder 2013, 65– 110 m) , to Georgia and South Carolina ( Wenner et al. 1984, 32- 69 m) , to North Carolina ( Nutting 1900, as A. simplex , 88–219 m) and to Virginia ( Nutting 1900, as A. simplex , 128–682 m) . It is reported here from the Southwest Florida Shelf northwest of the Dry Tortugas (127 m) . In their study of hard-bottom habitats off South Carolina and Georgia, Wenner et al. (1984) found N. simplex at both of their stations on the outer shelf ( OS01 , OS06) all four seasons of the year, but at one of two stations on the mid-shelf (MS06) only in autumn. Depths at the latter station (32–36 m) likely approach the upper bathymetric limit of the species. Hydroids of N. simplex were absent in samples from a second mid-shelf station (MS02, 23–29 m) , and from both inner shelf stations (IS01, 17–18 m; IS02, 17–22 m).

Reported distribution. Gulf coast of Florida. Florida Keys, off Alligator Reef, 86 ftm (157 m) ( Allman 1877: 34, as Antennularia simplex ).—Pourtalès Plateau, 70–80 ftm (128–146 m) ( Nutting 1900: 70, as Antennularia simplex ).

Elsewhere in western North Atlantic. USA: Virginia, off Cape Charles , 37°08’N, 74°36’W, 70 ftm (128 m) +

off Cape Henry, 36°41’N, 74°39’W, 373 ftm (682 m) ( Nutting 1900: 70, as Antennularia simplex ) .— USA: North Carolina, off Cape Hatteras , 35°13’N, 75°05’W, 48 ftm (88 m) + 35°02’N, 75°12’W, 120 ftm (219 m) ( Nutting 1900: 70, as Antennularia simplex ) .— Cuba: off Havana, 23°11’N, 82°20’W, 201 ftm (368 m) ( Nutting 1900: 70, as

Antennularia simplex ).— USA: South Carolina, middle (32–36 m) and outer (46–69 m) continental shelf + Georgia, outer (59–67 m) continental shelf ( Wenner et al. 1984: 21, 40) .— USA: Florida, Hoskin Reef off Vero Beach , 27°41.4’N, 79°59.1’W, 65 m ( Calder 2013: 36) .— USA: Florida, off Sebastian Inlet , 27°47.2’N, 79°57.2’W, 110– 99 m ( Calder 2013: 36) .

Figures

FIGURE 24. a, Monotheca margaretta: part of a hydrocaulus with a hydrocladium and hydrotheca, Florida Keys, Bahia Honda Channel, ROMIZ B4397. Scale equals 0.05 mm. b, Nemertesia nigra: part of hydrocaulus and proximal ends of hydrocladia, Southwest Florida Shelf, ROMIZ B2138. Scale equals 0.1 mm. c, Nemertesia nigra: part of a hydrocladium with a hydrotheca and nematothecae, Southwest Florida Shelf, ROMIZ B2138. Scale equals 0.05 mm. d, Nemertesia simplex: apophysis of hydrocaulus and proximal end of a hydrocladium, Southwest Florida Shelf, ROMIZ B2113. Scale equals 0.1 mm. e, Nemertesia simplex: part of a hydrocladium with a hydrotheca and nematothecae, Southwest Florida Shelf, ROMIZ B2113. Scale equals 0.1 mm. f, Plumularia floridana: part of a hydrocaulus with proximal end of a hydrocladium and two hydrothecae, Fort Myers Beach, ROMIZ B4399. Scale equals 0.1 mm.