Eudendrium Ehrenberg, 1834

Calder, Dale R., 2010, Some anthoathecate hydroids and limnopolyps (Cnidaria, Hydrozoa) from the Hawaiian archipelago 2590, Zootaxa 2590 (1), pp. 1-91 : 38-39

Genus Eudendrium Ehrenberg, 1834

Eudendrium Ehrenberg, 1834: 319 .

Type species. Tubularia ramosa Linnaeus, 1758 [ Eudendrium ramosum ], by subsequent designation by Allman (1872).

Diagnosis. Eudendriid hydroids with hydranths having a relatively short calyx; tentacles filiform, varied in number but usually fewer than 35, in one whorl.

Remarks. The hydrozoan genus Eudendrium Ehrenberg, 1834 is distinctive morphologically and welldefined taxonomically, but identification of the numerous species assigned to it can be decidedly difficult. A number of them were founded on the basis of taxonomically unreliable characters and on incomplete specimens, and are of doubtful validity. The extent of morphological similarity among species of the genus further complicates the taxonomy of the group ( Watson 1985). Significant phenotypic variation also exists in certain species of Eudendrium , and the existence of sibling species is possible ( Oliveira et al. 2000). Characters currently considered important in distinguishing species of the genus include reproductive structures, fate of reproductive hydranths, and nematocyst complement (cnidome), in addition to general morphology ( Watson 1985; Calder 1988; Marques, Mergner et al. 2000, Marques, Peña Cantero et al. 2000; Schuchert 2008b). A detailed discussion of the utility of the cnidome in the taxonomy of Eudendrium , together with the morphology, size, location, and relative abundance of nematocyst categories present, was given by Watson (1985). Given the importance of gonophore morphology in the taxonomy of the group, identification of sterile material by traditional means may in many cases be all but impossible.

Colony size in species of Eudendrium varies from about 0.5 cm high in E. fragile Motz-Kossowska, 1905 (= E. album Nutting, 1896 : see Schuchert 2008b) to as much as 30 cm high in E. rameum ( Pallas, 1766) ( Oliveira et al. 2000) . Eudendriids are often relatively large and conspicuous. Major contemporary reviews of species include works by Watson (1985) on 17 species from Australia, by Marques, Mergner et al. (2000) on 25 species from various locations representing all oceans, by Marques, Peña Cantero et al. (2000) on 13 species from the Mediterranean Sea, and by Schuchert (2008b) on 20 species known from European waters.

Earlier nomenclatural threats to the familiar name Eudendrium by Thoa Lamouroux, 1816 and Fistulana O. F. Müller, 1776a have been removed, as discussed earlier ( Calder 1988).