Lovenella gracilis Clarke, 1882

Gravili, Cinzia, Vito, Doris De, Camillo, Cristina Gioia Di, Martell, Luis, Piraino, Stefano & Boero, Ferdinando, 2015, The non-Siphonophoran Hydrozoa (Cnidaria) of Salento, Italy with notes on their life-cycles: an illustrated guide, Zootaxa 3908 (1), pp. 1-187 : 119-120

Lovenella gracilis Clarke, 1882

Fig. 84 A, B

See Calder (1971) for a complete synonymy.

Material examined. HCUS-S 0 92 (Hydrozoa Collection, University of Salento—fauna of the Salento Peninsula)—polyp stage.

Description (based on our own observations; Calder 1971):

Hydroid. Hydrorhiza creeping, as an assemble of stolons; colonies erect; hydrocaulus monosiphonic, unbranched or slightly branched, divided into internodes by septa at more or less regular intervals, annulations on the hydranth pedicels and at base of the hydrocauli; hydranth with 14 or more tentacles, no intertentacular web; hydrothecae alternate, on short pedicels, diaphragm thin, operculum a folded continuation of the hydrothecal wall, lacking hinge-like base, with about 8 facets when folded. Gonothecae clavate, truncate terminally, borne near the base of hydrothecal pedicels, several medusa buds in each.

Habitat type and substrate. Usually recorded on Agardhiella tenera , Zostera marina , Sertularia argentea , shells of Crassostrea virginica and Crepidula fornicata ( Calder 1971) .

Seasonality. February (De Vito 2006; this study) in Salento waters; May (for a review see Bouillon et al. 2004).

Reproductive period. Unknown in the Mediterranean Sea.

Medusa. Adult. Umbrella hemispherical, about 2.1 mm wide and 1.1 mm high; manubrium urn-shaped; mouth with 4 simple lips; 4 radial canals and circular canal narrow; gonads oval, at midway of radial canals length; velum wide; oldest specimens with 21 marginal tentacles; each marginal tentacle with 1 pair of lateral cirri; 33 statocysts. Colours: gonads, tentacle bulbs and manubrium pale straw-coloured.

Developmental stages. At liberation, medusa 0.45–0.50 mm high, 0.50–0.55 mm wide; medusae hemispherical with flattened sides.

Cnidome. Basitrichous haplonemes, microbasic mastigophores.

Distribution. Atlantic, Mediterranean (Huvé 1952; Calder 1971; Bouillon et al. 2004).

Records in Salento. Moderately frequent at Otranto (De Vito 2006; Gravili 2006; Gravili et al. 2008a; this study).

Remarks. Diagnosis taken from Calder (1971) and based on raised material from polyp colonies. In the Mediterranean, only juvenile medusae and hydroids are known. Gonothecae and medusae not seen in this study.

References. Huvé (1952a, b), Picard (1958a) as Dipleuron gracile ; Calder (1971, 1991), Bouillon et al. (2004), De Vito (2006), Gravili (2006), Gravili et al. (2008a).

Figures

FIGURE 84. Lovenella gracilis: A, portion of a colony; B, medusa (A, B redrawn and modified after Calder 1971 by C. G. Di Camillo). Scale bars: A, B, 1.0 mm.