Hydractinia apicata (Kramp, 1959)

Buecher, Emmanuelle, Goy, Jacqueline, J, Mark & Gibbons, 2005, Hydromedusae of the Agulhas Current, African Invertebrates 46, pp. 27-69 : 40

Hydractinia apicata (Kramp, 1959)

Podocoryne apicata: Kramp 1959 c: 228 , fig. 5; 1961: 67; 1968: 28, fig. 71.

Hydractinia apicata: Bouillon & Boero 2000 b: 89 .

Description: Single specimen. Essentially conical, bell-shaped umbrella, slightly taller than broad, with slight apical projection; 1.5 mm in height. Exumbrella surface smooth. Mesoglea thickish. Velum narrow. Peripheral canal and four narrow, unbranched radial canals present; one centripetal canal in each quadrant, may reach to manubrium; without apical canal. Four tentacles arising from umbrella margin at position of radial canals; arising from pronounced swollen bulbs, long, solid. Secondary tentacles absent. Manubrium barrel-shaped, extending to half bell depth. Mouth simple, with four small but elongated lips; with gastric peduncle of variable length. Four gonads, small, interradial, on manubrium, not extending along radial canals; without transverse folds. Material examined: H5015.

Comments: Hydroids of the genus Hydractinia may reproduce by fixed sporosacs, eumedusoids or free medusae. This variability in the mode of reproduction is similarly reflected in the variability of medusoid morphology. 15 species of free medusae are recognised as valid by Bouillon and Boero (2000 b), which can be separated by a combination of characters including; mouth and stomach shape, the degree of branching of the mouth ‘arms’, and the number and relative size/s of marginal tentacles and their bulbs. A number of other features are either present or absent, including, an apical process, a gastric peduncle and ocelli (colour and size also important diagnostic features). Only one other species, H. carnea ( Sars, 1846) , has been recovered from the west Indian Ocean (Bouillon 1978 b) and this is characterised by the absence of an apical projection, a flask-shaped manubrium, 4–8 marginal tentacles, four capitate oral tentacles and no centripetal canals. A number of benthic polyps with fixed sporosacs are also recognised from the region (see e.g. Millard 1975).

Distribution: Tropical Indo-West Pacific. Previously collected by Bouillon (1978 b) from around the Seychelles and in the Mozambique Channel. Neritic.