Amphinema rollinsi, Widmer, Chad L., 2007

Widmer, Chad L., 2007, The hydroid and medusa of Amphinema rollinsi (Cnidaria: Hydrozoa), a new species of pandeid from the Monterey Bay Submarine Canyon, USA, Zootaxa 1595, pp. 53-59 : 54-56

Amphinema rollinsi , sp. n.

( Figs. 1 – 2 )

Type material: Holotype: one mature female medusa, released 15 January 2007 from paratype hydroid listed below and raised under laboratory conditions at the Monterey Bay Aquarium, Monterey, California; preserved in 70% ethanol; California Academy of Sciences, CASIZ no. 174847.

Paratypes: one immature female medusa, released 17 January 2007 from paratype hydroid under laboratory conditions at the Monterey Bay Aquarium, Monterey, California; preserved in 70% ethanol; California Academy of Sciences, CASIZ no. 174848. A single hydroid colony, collected 25 October 2006, growing on PVC pipe emplaced in Monterey Bay Submarine Canyon (N 36° 46. 2931; W 122° 4. 9568) on 25 May 2006, depth 1016m; California Academy of Sciences, CASIZ no. 174847.

Etymology. The species is named in honor of Henry Rollins, artist, activist, and philosopher. It is the best way I know to thank him for his much appreciated and noble United Service Organizations (USO) service.

Description (from living material). Hydroid colonies stolonal or with upright, monosiphonic hydrocauli, arising from a creeping hydrorhiza. Single hydranths arising from hydrocaulus on simple short pedicels lacking distinct basal annulations. Paratype hydrocaulus 9.5mm tall before preservation, bearing very short, irregularly-spaced pedicels with terminal hydranths ( Fig. 1 A). Hydranths also present on creeping hydrorhizae, each with a single whorl of 8–12 mildly amphicoronate filiform tentacles, each tentacle with a small terminal cap ( Fig. 1 B) not formed by a concentration of cnidocysts. Hydranths with cylindrical columns about 475µm long, 100µm wide; hypostomes bluntly conical, with simple circular mouths. Undisturbed hydranths bending slowly from side to side; disturbed hydranths bending to one side or the other, but not the same way each time. Tentacles sometimes contracted but never retracted inside perisarcal tubes. Medusa buds ( Fig. 1 C) arising singly from short pedicels (about 175µm long) on upright hydrocauli. Medusa buds usually about 600µm long, 425µm wide.

Newly released medusae dome shaped, about 1.5mm tall, 1.0mm wide, with a distinct, well-developed, thin apical projection ( Fig. 2 A); apical projection accounting for about ¼ total bell height, uniform in width, ending in a bluntly rounded point; mesoglea thin; exumbrella evenly covered with nematocysts; gastric peduncle absent; manubrium flask-shaped, cruciform in cross-section; mouth with prominent recurved lips; gonads not apparent in newly released specimens; radial canals four, simple; ring canal tubular; velum narrow. Medusae with two long, opposite, perradial marginal tentacles with elongated conical bulbs, and with two perradial and four interradial tentaculae that were all alike. Ocelli and marginal warts absent. Apical chamber shaped like two cones with bases placed together, resulting in two pointed ends, one end pointing toward and extending into the apical process and the other end pointing toward the mouth ( Figure 2 A, B).

Medusae maturing in about three weeks under laboratory conditions, retaining both the same domeshaped bell and thin, elongated and bluntly rounded apical process as in newly released medusae. In mature medusae the two perradial tentacles continued to elongate but all tentaculae remained short. Holotype medusa mature, 2.35mm tall, 1.45mm wide before preservation. Manubrium flask-shaped, about 25% as long as total length of bell. Gonads adradial, in form of simple regions on the either side of radial canals, not extending past upper half of manubrium. Eggs of female medusae bright red, circular, ranging in size from 175–200µm. Male medusae not observed.

Figures

FIGURE 1. Hydroid of Amphinema rollinsi, sp. n.: A. Upright hydrocaulus. B. Mature hydranth. C. Medusa bud nearly ready for release. Scale bar A = 5 mm. Scale bars B and C = 500 µm.

FIGURE 2. Medusae of Amphinema rollinsi, sp. n. A. Newly released medusa. B. Mature female medusa. Scale bars = 1 mm.