Eudendrium cf. merulum

Moura, Carlos J., 2015, The hydrozoan fauna (Cnidaria: Hydrozoa) from the peaks of the Ormonde and Gettysburg seamounts (Gorringe Bank, NE Atlantic), Zootaxa 3972 (2), pp. 148-180 : 152-154

Eudendrium cf. merulum

(figs. 2F)

Eudendrium merulum Watson, 1985: 200 , figs 53–58.— Bavestrello & Piraino, 1991: 200, figs. 2–4.— Marques et al., 2000b: 203.—Peña Cantero & García Carrascosa, 2002: 30, fig. 5a–b.— Bouillon et al., 2004: 59, fig. 35A–G. Eudendrium cf. merulum — Schuchert, 2008: 715 –719, figs. 19–20.

Material studied. Ormonde, stn 4: dense aggregations of monosiphonic, branched, tall and robust colonies (up to 7.5 cm in lenght), overgrowing sponges; epibionts: small algae; not fertile; DBUA 1513.01, Genbank accession no. KM402023 .

Remarks. The maximum size of colonies recorded was 7.5 cm. Nematocysts were found undischarged, and comprise two different size forms: small microbasic euryteles (7.5–9.5)x(3.5–4)Μm, r= 2–2.6, and large capsules on the hydranth body (14.5–16.5)x(7–8.5)Μm, r=1.7–2.1. The inconclusive taxonomic status is due to the probable cryptic biodiversity associated with this species, being doubtful whether these Gorringe specimens are conspecific with the E. merulum originally described from Australia ( Watson 1985; see Schuchert 2008). The 16S sequence obtained for this material clusters, without sequence divergence, with a Mediterranean lineage of the E. “ merulum ” complex (Schuchert, unpublished data), revealing recent gene flow between the Gorringe and Mediterranean. Furthermore, Schuchert (2008) indicates that Atlantic, Mediterranean and Black Sea populations likely correspond to three different biological species. Consequently, the Gorringe specimens of E. " merulum " can only be linked, so far, as conspecific with the Mediterranean E. " merulum " based on molecular data.

Whatsoever, these represent the deepest records of Eudendrium " cf. merulum ", previously recorded from 1 to 15 m depth ( Schuchert 2008).

Reported distribution. Eastern Atlantic.—Canary Islands, Gulf of Biscaya and English channel ( Schuchert 2008), but these records likely refer to different molecular cryptic species than the present one of the Gorringe specimens (see above; Schuchert 2008). The present account seems therefore the first for the Atlantic (and Gorringe).

Mediterranean.—Chafarinas Islands (Peña Cantero & García Carrascosa 2002); Italy ( Bavestrello & Piraino 1991; Marques et al. 2000b; Schuchert 2008; Puce et al. 2009); Croatia ( Marques et al. 2000b); Turkey: Sea of Marmara and Aegean Sea ( Marques et al. 2000b); Lebanon ( Morri et al. 2009).

Elsewhere.— Eudendrium merulum was originally described from Australia, where it is a quite rare species ( Watson 1985). Later it has also been recorded in the eastern and western Mediterranean, Black Sea, Yemen and NE Atlantic ( Bavestrello & Piraino 1991; Marques et al. 2000a, b; Schuchert 2008), but was possibly misidentified ( Schuchert 2008).