Slabberia halterata Forbes, 1846

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 : 55-56

Slabberia halterata Forbes, 1846

Fig. 37 A–C

See Schuchert (2001b, 2010) for a complete synonymy.

Material examined. HCUS-S 0 42 (Hydrozoa Collection, University of Salento—fauna of the Salento Peninsula)—polyp stage.

Description (based on our own observations; Brinckmann-Voss 1970 as Sarsia halterata ; Schuchert 2001b as Dipurena halterata, 2010 , 2012):

Hydroid. Hydrorhiza embedded in sponges, only the most distal part of the hydrocaulus and the hydranth emerging; colonies stolonal; hydrocaulus unbranched, covered by smooth perisarc up to halfway of its length; hydranths clavate to cylindrical; hypostome rounded, ectoderm of hypostome differentiating into a well developed button of mucous gland cells; with up to 24 identical capitate tentacles distributed in an oral whorl of 4–5 tentacles and irregularly scattered tentacles along the body, without filiform tentacles; medusa buds in one to several whorls borne in middle of hydranth, 1–10 per hydranth.

Habitat type. Embedded in sponges (depth range: 0–30) ( Brinckmann-Voss 1970; Boero & Fresi 1986 as S. halterata ).

Substrate. Petrosia dura , Spirastrella cunctatrix , Chondrilla nucula (sponges).

Seasonality. March, May–October, December in the British waters (see Russell 1953 as D. halterata ); from January to June in the Ligurian Sea ( Boero & Fresi 1986); from January to June, and September (De Vito 2006; this study) in Salento waters.

Reproductive period. In the western Mediterranean Sea, fertile colonies occur from April to June ( Boero & Fresi 1986), and April ( Goy 1997); in Salento waters (De Vito 2006; this study) in April.

Medusa. Adult. Umbrella bell shaped, up to 6 mm wide, 8 mm high, with globular apical chamber; manubrium with a long serpentine proximal part and a swollen distal part, 2–3 times longer than umbrella height; mouth simple, circular; middle part of radial canals with linear swellings; gonads in 2 or more rings, leaving upper third of manubrium free; 4 tentacular marginal bulbs, prominent; one tentacle on each marginal bulb, of uniform diameter, smooth for most of their length, each with large terminal cnidocyst knob and 3 to 6 distinct rings of cnidocysts just above; each marginal bulb with an abaxial ocellus. Colours: bulbs and terminal tentacular clusters orange to brown, apical knob red to green.

Developmental stages. Newly released medusa 1.1–1.3 mm wide and 1.5–1.6 mm high, exumbrella with interradial furrows and a few scattered nematocysts; radial canals narrow; tentacles with a large spherical terminal nematocyst cluster, some smaller clusters on the distal half of the tentacles; with ocelli. Colour: ocelli dark-red.

Cnidome. Stenoteles and basitrichous isorhizas (polyp); stenoteles, isorhizas and desmonemes (medusa).

Distribution. Atlantic, Indo-Pacific, Mediterranean ( Brinckmann-Voss 1970; Medel & López-González 1996; Schuchert 2001b; Bouillon et al. 2004; Gravili et al. 2008a).

Records in Salento. Common at: Torre dell’Inserraglio ( Presicce 1991); La Strea ( Miglietta et al. 2000 as D. halterata ); Otranto (De Vito 2006; Gravili 2006; Gravili et al. 2008a; this study). Other Apulian records: Gargano ( Fraschetti et al. 2002).

Remarks. Only the hydroid stage and the new born medusa were seen in the present study. Exhaustive taxonomic histories of this species are reported by Russell (1953) and Schuchert (2001b).

References. Hadzi (1911); Rees (1939), Trégouboff & Rose (1957) both as D. halterata ; Picard (1958a) as S. halterata ; Kramp (1959, 1961) as D. halterata ; Brinckmann-Voss (1970); Rossi (1971) as Syncoryne halterata ; Bouillon (1971), Boero & Fresi (1986), Benović & Lučić (1996), Medel & López-González (1996), Miglietta et al. (2000) all as D. halterata ; Schuchert (2001b as D. halterata, 2010 , 2012); Fraschetti et al. (2002), Bouillon et al. (2004), Milos & Malej (2005), De Vito (2006), Gravili (2006), Gravili et al. (2008a) all as D. halterata .

Figures

FIGURE 37. Slabberia halterata: A, hydroid colony in a sponge; B, hydranth with medusa buds; C, adult medusa (A and B same scale bar) (A, B drawn by F. Boero; C drawn by C. G. Di Camillo). Scale bars: A, B, 1.0 mm; C, 4.0 mm.