Stauridiosarsia ophiogaster ( Haeckel, 1879 )

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 : 56-57

Stauridiosarsia ophiogaster ( Haeckel, 1879)

Fig. 38 A, B

See Nawrocki et al. (2010) and Schuchert (2010) for a complete synonymy.

Material examined. HCUS-S 0 43 (Hydrozoa Collection, University of Salento—fauna of the Salento Peninsula)—polyp stage.

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

Hydroid. Hydrorhiza as creeping, ramified tubules; colonies stolonal, up to 4 mm high; hydrocaulus generally unbranched or branched once, covered by thin, smooth perisarc that widens distally allowing the basal part of hydranth to retract into this enlargement; hydranth clavate to cylindrical; hypostome, large and rounded, ectoderm of hypostome differentiating into a well developed cap of glandular cells; with 10–18 capitate tentacles in one oral whorl of 4 tentacles and below them lower capitate tentacles scattered or in indistinct whorls; with one aboral whorl of 2–6 filiform tentacles (often reduced or absent); medusa buds developing in 2–3 clusters below the capitate tentacles and above filiform tentacles, 2–6 buds per cluster.

Habitat type. Rocky infralittoral zone (depth-range: 0–50) ( Brinckmann-Voss 1970; Boero & Fresi 1986; Schuchert 2001b).

Substrate. Algae, bryozoans, barnacles, mussels.

Seasonality. From February to May, scarce from June to January ( Brinckmann-Voss 1970) in the Tyrrhenian Sea; from October to May ( Boero & Fresi 1986) in the Ligurian Sea; from October to February, May, August (De Vito 2006; this study) in Salento waters.

Reproductive period. April–May ( Brinckmann-Voss 1970); February–March ( Boero & Fresi 1986); April ( Goy 1997); January (De Vito 2006; this study).

Medusa. Adult. Umbrella bell-shaped, 4–5.5 mm high, 1.5 times higher than wide, mesoglea unevenly thick, becoming gradually thicker from margin towards top, at apex 3 times as thick as lateral walls, with distinct rounded apical chamber; manubrium with a long thin serpentine proximal part and a broader distal (oral) extremity, very long, up to 3 times the umbrella height; mouth simple, tubular; 4 narrow radial canals and circular canal; gonads distributed in 2–9 broad rings, encircling completely manubrium leaving upper third free, most distal one covering the distal swollen part; relaxed velum spanning half to two-fifths of radius; 4 marginal bulbs, rather flat, with cnidocyst pads, bulb cavity egg-shaped; circular canal entering bulbs adaxially; each marginal bulb with one very long and thin tentacle, length up to 5 times umbrella height, with numerous, irregularly distributed cnidocyst clusters and a small terminal cluster; with an abaxial ocellus on each marginal bulb. Colours: ocelli black-brown, bulbs and apical chamber yellowish brown or reddish yellow.

Developmental stages. The newly released medusae have 8 distinct, broad, adradial rows of spherical exumbrellar nematocysts, tentacles bear 18 and more nematocyst clusters.

Cnidome. Stenoteles (polyp); stenoteles and rarely a few isorhizas along the radial canals (medusa) ( Bouillon 1971).

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. Rare at: Grotta del Ciolo (Denitto et al. 2007); Otranto (De Vito 2006; Gravili 2006; Gravili et al. 2008a; Piraino et al. 2013; this study).

Remarks. Only the hydroid stage and the new born medusa were seen in the present study. The adult medusa of S. ophiogaster is not easily distinguishable from D. reesi (see Brinckmann-Voss 1970; Schuchert 2001b). This species was previously included in the genus Dipurena (see Nawrocki et al. 2010 and Schuchert 2010).

References. Mayer (1910) as Slabberia ophiogaster, Hartlaub (1917) , Trégouboff & Rose (1957), Picard (1958a) as S. ophiogaster, Kramp (1959, 1961 ), Brinckmann-Voss (1970, 1987) as S. ophiogaster, Goy (1973, 1997 ); Boero (1981c) as Sarsia ophiogaster ; Lakkis & Zeidane (1985); Boero & Fresi (1986) as S. ophiogaster ; Goy et al. (1988, 1990, 1991), Medel & López-González (1996), Buecher & Gibbons (1999), Piraino et al. (1999) as S. ophiogaster, Schuchert (2001b, 2010 , 2012), Bouillon et al. (2004) as D. ophiogaster, Touzri et al. (2004) , De Vito (2006), Gravili (2006), Denitto et al. (2007), Galea (2007), Gravili et al. (2008a), Piraino et al. (2013).

Figures

FIGURE 38. Stauridiosarsia ophiogaster: A, hydranth with medusa buds; B, medusa (A drawn by F. Boero; B drawn by C. G. Di Camillo). Scale bars: A, 0.1 mm; B, 2.0 mm.