Eudendrium sp. 1

Calder, Dale R., 2010, Some anthoathecate hydroids and limnopolyps (Cnidaria, Hydrozoa) from the Hawaiian archipelago 2590, Zootaxa 2590 (1), pp. 1-91 : 42

Eudendrium sp. 1

Figs. 28 , 29

Eudendrium rameum .— Nutting, 1905: 939 [not Eudendrium rameum ( Pallas, 1766) ].

Material examined. Kauai: Albatross Stn. 4135, off Wailua, 22.076389º N, 159.323611º W, 1.viii.1902, 411– 538 m, two colony fragments, to 6.8 cm high, hydranths in poor condition, apparently without gonophores (colonies possibly dry at some time), labelled Eudendrium rameum, USNM 22223.–Maui: Albatross Stn. 4077, NE of Kahului Harbor, 21.016667º N, 156.404167º W, 21.vii.1902, 181– 194 m, one colony, in fragments, largest fragment 3.5 cm high, with numerous hydranths in rather poor condition, with female gonophores, labelled Eudendrium rameum, USNM 22267.–Niihoa: Albatross Stn. 4150, 23.1º N, 161.9º W, 5.viii.1902, 130- 293 m, four colony fragments, to 5.8 cm high, one with female gonophores, labelled Eudendrium arbuscula, USNM 22270.

Description. Colonies erect, up to 6.8 cm high, broken off near base, densely branched in one plane, dendritic, branching irregular proximally, more or less regular and alternate distally. Hydrocaulus strongly polysiphonic, up to 2 mm thick basally, irregularly twisted or curved; largest branches resembling hydrocaulus; ultimate branches much more slender, monosiphonic or weakly polysiphonic basally, hydranth-bearing branchlets monosiphonic. Perisarc in older parts of colony thick, brown to light brown in colour, becoming thinner and golden to almost glassy, terminating at base of hydranths; annulated at bases of ultimate branches and branchlets, smooth or with scattered wrinkles elsewhere. Hydranths small, about 0.3 mm long, with a single whorl of about 22 filiform tentacles, otherwise too poorly preserved to adequately describe.

Gonophores fixed sporosacs. Female gonophores occurring at distal end of branchlet, sometimes associated with a partially atrophied hydranth with a cluster of stubby tentacles and lacking a hypostome; spadix unbranched, curving over egg, 1–3 gonophores per branchlet; male gonophores not seen.

Remarks. Nutting (1905) identified this hydroid as Eudendrium rameum ( Pallas, 1766) . Like that species, colonies from Hawaii are robust, strongly polysiphonic, and profusely branched, but the identification seems uncertain. The specimens also resemble Eudendrium arbuscula Wright, 1859a in colony form, and a colony from Niihoa in NMNH collections (USNM 22270) is labelled and catalogued as such. Given the poor condition of the hydranths, the absence of male gonophores, inadequate knowledge of the cnidome, and the remoteness of Hawaii from the predominantly eastern North Atlantic distribution of E. arbuscula , identification of present material to that species on current evidence seems questionable.

Reported distribution. Hawaii. Albatross Stn. 4077, “off … Maui, 99 fathoms” (181 m); Albatross Stn. 4135, off … Kauai, 225 fathoms” (411 m) ( Nutting 1905, as Eudendrium rameum ) .

Figures

FIGURE 28. Eudendrium sp. 1: part of hydrocaulus bearing a hydranth and a blastostyle with female gonophores, USNM 22270. Scale equals 0.5 mm.