Eudendrium?cyathiferum Jäderholm, 1904

Watson, Jeanette W., 2003, Deep-water hydroids (Hydrozoa: Leptolida) from Macquarie Island, Memoirs of Museum Victoria 60 (2), pp. 151-180 : 153

Eudendrium?cyathiferum Jäderholm

Figures 2A–D

Eudendrium cyathiferum Jäderholm, 1904: 11 .— Jäderholm, 1905: 10, pl. 4 figs 1–3.— Bedot, 1925: 184.— Stepanjants, 1979: 18, pl. 1 fig. 13.— Marques et al., 2000: 92, fig. 42.

Material examined. Stn 120, NMV F91307, colony 50 mm high, attached to fragment of calcareous bryozoan, specimen alcohol preserved. Stn 122, TM K2769, four colonies, the largest 90 mm high and 50 mm wide, attached to a dead solitary coral, Caryophyllia sp. , specimen alcohol preserved.

Description. Colonies arborescent with thick, heavily fascicled main stems up to 3 mm wide at base; hydrorhiza a mass of stolons entwining substrate, becoming erect as polysiphonic tubes of stem. Branching twiggy, in many orders, almost in one plane, polysiphonic tubes running almost to tips of branches but ultimate branches and branchlets (pedicels) monosiphonic, given off from within the mass of tubes. Pedicels short, arising more or less alternately from branches, with up to 10 clear basal corrugations, remainder of pedicel more or less rugose. No hydranths present on pedicels.

Several clusters of female gonophores on colony from stn 122; 6– 10 immature gonophores in cluster completely replacing a hydranth, clusters seated on short, corrugated pedicels; gonophore encircled by a large spadix shed as gonophore matures; a single mature gonophore ovoid, borne on a slender peduncle with dish-shaped distal end, gonophore at this stage 0.4 mm long and 0.25 mm wide, enclosed in a distinct transparent pellicle, containing 6–8 developing ova.

No nematocysts seen on gonophores; a few undischarged euryteles present in coenosarc of stems; capsule small, droplet shaped, 8 X 4.5 µm.

Colour. Fascicled stems and branches shining brown, fading to yellowish on monosiphonic branches; gonophores were probably creamy-pink.

Distribution. Previously recorded from South Georgia ( Jäderholm, 1905; Stepanjants, 1979) but now known to have a wider distribution in deep subantarctic and Patagonian waters (A. Marques, pers. comm.).

Remarks. There are two differences between the present specimen and available published and unpublished descriptions of E. cyathiferum . These are: (i) the length of the peduncle of the nearly mature gonophore; and (ii) the presence of only one size of eurytele in the cnidome.

Three species of Eudendrium with pedunculate (i.e. secondary pedicellate) female gonophores are known: E. cyathiferum , E. vervoorti Marques and Migotto, 1998 and E. glomeratum Picard, 1951 (see Marques et al., 2000). E. glomeratum was rejected as it is a temperate to tropical species ( Watson, 1999), E. vervoorti is discounted because of the small size of the colony and the fact that the developing female gonophore lacks an encircling spadix. Although the “golf-tee” peduncle supporting the nearly mature female gonophore of the present specimen is typical of E. cyathiferum it is, however, somewhat longer and slenderer than that shown in a photomicrograph of the type specimen ( Marques et al., 2000).

The cnidome of the holotype specimen of E. cyathiferum contains two size classes of euryteles, the smaller associated with the hydrocaulus and the larger with the gonophore (A. Marques, pers. comm.). In view of the limited amount of present material available for study it could not be ascertained if large nematocysts are always absent from the gonophore. The few nematocysts in the coenosarc are similar in size to those in the hydrocaulus of the holotype.

For the above reasons, together with the fact that the colonies are smaller than previously reported for E. cyathiferum , the present specimens are doubtfully referred to that species.

Figures

Figures 2A–D. Eudendrium?cyathiferum. A, female colony, stn 122. B, cluster of immature female gonophores on colony. C, mature female gonophores with ova from same colony. D, undischarged eurytele from coenosarc of branch. Scale bar: A, 50 mm; B, C, 0.5 mm; D, 10 µm.