Eudendrium vaginatum Allman, 1863

Calder, Dale R., 2017, Additions to the hydroids (Cnidaria, Hydrozoa) of the Bay of Fundy, northeastern North America, with a checklist of species reported from the region, Zootaxa 4256 (1), pp. 1-86 : 37-38

Eudendrium vaginatum Allman, 1863

Figs. 13 e, f, 16

Eudendrium vaginatum Allman, 1863: 10 .

Type locality. UK : Shetland, tidepools at extreme low water spring ( Allman 1863).

Material examined. NS: Sandy Cove, Digby County, south side, 22.vii.1970, one colony, 2.3 cm high, without gonophores, coll. J.S. Bleakney, SNM HYD- 001053 .

Description. Colony erect, bristly, bushy, stiff, 2.3 cm high, arising from a dense network of creeping hydrorhizal tubes. Tubes of hydrorhiza contorted but not annulated. Hydrocaulus polysiphonic over proximal region, base covered with a tangle of stolons and with numerous short, twisted branches and pedicels lacking hydranths; hydrocaulus becoming monosiphonic distally, curved and irregularly branched; branches frequent, of different lengths, some of them rebranched, bent upwards at insertion with hydrocaulus, resembling an old stovepipe entering a chimney. One of two hydrocauli, and several branches, with clear signs of renovation. Ultimate branchlets of varied length, resembling hydrocaulus and branches but shorter and usually more slender. Perisarc over most of colony quite thick and rusty-brown, thinner and honey-coloured in younger parts, covering all parts of colony up to a filmy envelope resembling a pseudohydrotheca over proximal half of each hydranth; all parts of hydrocaulus, branches, and ultimate branchlets distinctly, closely, regularly, and strikingly annulated. Hydranths not well-preserved in examined colony but apparently cup-shaped, about 0.5 mm long from base to tip of hypostome, 0.35 mm wide at level of tentacles; perisarc groove indistinct in present material; hypostome knobshaped. Tentacles filiform, in one whorl, about 18 in number. Nematophores absent. Nematocysts comprising small microbasic euryteles and complementary large microbasic euryteles, the latter on hypostome and scattered on trunk of hydranth.

Gonophores not seen.

Cnidome ( Fig. 16 )

Hydranths—

small microbasic euryteles (n = 10): 6.7–7.1 µm long × 2.8–3.2 µm wide (undischarged)

large microbasic euryteles (n = 10): 21.0–23.0 µm long × 8.7–10.0 µm wide (undischarged)

Remarks. Allman (1863) described Eudendrium vaginatum from Shetland, UK, based on sterile colonies found in rock pools at extreme low water on a spring tide during August 1862. The species was not illustrated until later, in his monograph on gymnoblastic hydroids ( Allman 1872). A combination of several trophosomal characters appear to distinguish the species, with perisarc being deeply and regularly annulated throughout, with hydranths having a perisarc groove that is usually located some distance up the hydranth column, and with hydranths partially enclosed within a pseudohydrotheca. The proximal end of polysiphonic stems may be overgrown by a convoluted mass of tubes, creating a bark-like covering. The nematocyst complement consists of small and large microbasic euryteles, the latter having a small coil in the shaft at the distal end of the capsule ( Schuchert 2008b). Hydranths are vermilion in colour ( Allman 1863), and the perisarc is deep reddish-brown ( Allman 1872), at least in older parts.

In re-describing the species, Schuchert was unable to locate Allman’s type material, but little doubt exists about its identity. Eudendrium annulatum Norman, 1864 has sometimes been included or questionably included in the synonymy of E. vaginatum (e.g., Cornelius 1995a: 292; Marques, Mergner et al. 2000: 107), but evidence exists for recognizing both as valid ( Schuchert 2008b). In E. annulatum , the perisarc is incompletely annulated, and annulations are much less pronounced. Material examined and illustrated by Marques, Mergner et al., and attributed to E. vaginatum , is a mix of the two species. Recent synonymy lists are given by Schuchert (2008b) and Antsulevich (2015).

Gonophores were absent in the colony examined here ( SNM HYD- 001053 ). According to Schuchert (2008b, 2012), reproductive hydranths vary from normal to somewhat atrophied. Male gonophores are are two-chambered, with more than 10 on a given hydranth. Female gonophores have an unbranched spadix, with six or more of them appearing on a hydranth. Ripe embryos become encapsulated in perisarc and may occur down the hydranth pedicel.

The cnidome of Eudendrium vaginatum from the Bay of Fundy included both small and large microbasic euryteles. Undischarged capsules of large euryteles are distinctive in having a small loop in the shaft near the distal end of the capsule ( Fig. 16 c), as noted above for the species. The sizes of nematocysts observed here, in preserved material, are similar to those recorded by Schuchert (2008b).

This is the first record of Eudendrium vaginatum from the Bay of Fundy. Reliable identifications of the species exist to the north in Newfoundland and western Greenland ( Leloup 1939; Schuchert 2008b). To the south, an identification of E. vaginatum from the coast of Maine by Berrill (1952) appears to be correct, and Fraser (1944) reported it from Quicks Hole, west of Martha’s Vineyard , Massachusetts . Most records of the species have been from boreal waters of the eastern North Atlantic . Although considered to be an Arctic to northern boreal species by Schuchert (2008b), he believed that records of it from Alaska and elsewhere in the North Pacific needed verification. Its distribution in that region, according to Antsulevich (2015), is from the Bering Sea and the Sea of Okhotsk to Japan and Alaska . Fraser (1937, 1947a) included a record of it from the coast of Oregon. The bathymetric range of E. vaginatum is reported to be 0–180 m ( Schuchert 2008b; Antsulevich 2015).

Recorded distribution. Bay of Fundy: recorded for the first time.

Eastern North America: Hudson Strait ( Fraser 1931) and Greenland ( Schuchert 2008b) to Boothbay Harbor, Maine ( Berrill 1952), and possibly to Quicks Hole, Massachusetts ( Fraser 1944).

Elsewhere: northeastern North Atlantic from the White Sea, Norway, Jan Mayen Island, Svalbard, and Iceland to the Shetland Islands ( Schuchert 2008b; Ronowicz et al. 2013; Antsulevich 2015) ; North Pacific from the Bering Sea to Japan ( Antsulevich 2015); possibly from Alaska to Oregon ( Fraser 1937). Records of the species from the North Pacific by Nutting (1901b), Stechow (1913) and Fraser (1937) were considered questionable by Schuchert (2008b).

Figures

FIGURE 13. Filiferan hydroids, continued. a, Hydractinia symbiolongicarpus, part of colony with gastrozooid, gonozooid with female gonophores, spine, and dactylozooid, ROMIZ B 643. Scale equals 0.25 mm. b, Eudendrium bleakneyi, sp. nov., hydranth, holotype, ROMIZ B 1473. Scale equals 0.1 mm. c, Eudendrium bleakneyi, female gonophores, paratype, ROMIZ B 1381. Scale equals 0.1 mm. d, Eudendrium bleakneyi, male gonophores, holotype, ROMIZ B 1473. Scale equals 0.1 mm. e, Eudendrium vaginatum, part of a stem with hydranth pedicels, SNM HYD- 001053. Scale equals 0.5 mm. f, Eudendrium vaginatum, tip of a pedicel with hydranth, bent over, SNM HYD- 001053. Scale equals 0.2 mm.

FIGURE 16. Eudendrium vaginatum, nematocysts, SNM HYD- 001053. a, small microbasic eurytele, from hydranth. b, small microbasic eurytele, from hydranth, discharged. c, large microbasic eurytele, from hydranth.