Obelia spp.

Galea, Horia R., 2007, Hydroids and hydromedusae (Cnidaria: Hydrozoa) from the fjords region of southern Chile, Zootaxa 1597 (1), pp. 1-116 : 94-96

Obelia spp.

(fig. 21M, N, pl. 2M, N)

Obelia spp. Russell, 1953: 297 , figs 182–185, pl. 18 figs 1–2, pl. 19 fig. 2; Kramp, 1959: 147, fig. 184; 1961: 162; 1968: 76, fig. 200; Calder, 1971: 58, pl. 7I; Cornelius, 1975: 278; Goy et al., 1991: 112; Pagès et al., 1992: 34, fig. 37; Cornelius, 1995b: 288, fig. 67; Palma et al., 2007: 70.

Material examined. Plankton —off the Huinay Scientific Field Station, 05.ii. 2006 ( Obelia lucifera type) and 07, 08, 11.ii.2006 ( Obelia nigra type), both from hauls between 50–0 m, several medusae.

Remarks. The medusae of Obelia are derived from several distinct species of hydroids and cannot be specifically distinguished on morphologic criteria, especially when collected from plankton. Two types are actually recognized: O. lucifera and O. nigra .

Obelia lucifera is known from the plankton and was reared to maturity from both O. dichotoma and O. geniculata . It has gonads situated mid-way along the radial canals and possesses fewer than 100 marginal tentacles which are borne on pale to colorless basal bulbs ( Cornelius 1995b). O. nigra is known only from the plankton, and is probably the sexual stage of O. longissima ( Pallas, 1766) ( Cornelius 1995b) . It has gonads situated nearly at the periphery of the bell and is provided with up to 200 marginal tentacles, some of them having the marginal bulbs darkly colored ( Cornelius 1975).

The present material from Chile contains both forms of medusae. Specimens of O. nigra bearing gonads are up to 3.2 mm in diameter and have up to 113 marginal tentacles. Conversely, specimens of O. lucifera with gonads are comparatively smaller and have about 16 marginal tentacles. O. lucifera was rarely sampled from the plankton, while O. nigra was quite abundant in every catch.

Despite the presence of O. nigra in the plankton, its presumably corresponding hydroid, O. longissima , was never collected during the present study. However, south Chilean records of this hydroid are mentioned by Hartlaub (1905) and Leloup (1974). Pagès & Orejas (1999) found the hydroid of O. bidentata Clarke, 1875 in the Magellan region, but its medusa is inadequately known ( Cornelius 1995b), unless it could be related to O. nigra .

World distribution. Cosmopolitan in coastal waters, except in high Arctic and Antarctic seas ( Kramp 1959).

Records from Chile. Medusae in the present material were collected from fjord Comau. Additional records are those of Palma et al. (2007) from the southern channels (between the Gulf of Corcovado and the Pulluche-Chacabuco Channels).