Clytia hummelincki (Leloup, 1935)

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 : 143-145

Clytia hummelincki (Leloup, 1935)

Fig. 102 A–F

See Calder (1991) for a complete synonymy.

Material examined. HCUS-S 109p and HCUS-S 109m (Hydrozoa Collection, University of Salento—fauna of the Salento Peninsula)—polyp and medusa stages.

Description (based on our own observations; Gravili et al. 2008b):

Hydroid. Hydrorhiza reticular and anastomosed; colony stolonal; pedicels long, with several distal annulations (generally three) and four proximal ones, sub-hydrothecal spherule present, diaphragm oblique; hydranth with peduncled hypostome; with 22 amphicoronate filiform tentacles; hydrotheca short and wide, about 0.35 mm high, 0.30 mm wide, hydrothecal rim smooth. Gonothecae sessile to shortly stalked, truncate, tapering below, 0.8 mm in height and 0.28 mm maximum diameter, with 2 basal annulations, borne on hydrorhiza, only one medusa bud per gonotheca.

Habitat type and substrate. Sea urchin barrens (depth: 0.5– 1 m) ( Gravili et al. 2008b).

Medusa. Adult. Bell almost spherical, 2.52 mm in diameter and 2.03 mm high; mouth quadratic, with 4 large ondulate lobes; 4 male oval gonads in the upper side of radial canals; 8 marginal bulbs; 8 statocysts along circular canal.

Developmental stages. Newly released with bell almost spherical, 1.24 mm in diameter, 0.85 mm high; manubrium 0.27 mm long; mouth quadratic, with 4 lobes; 4 radial canals; gonads absent; velum about 0.16 mm wide; 8 marginal bulbs (4 large, pyriform, perradial and tentacular ones; 4 small, rounded and interradial); tentacular tips clavate; 8 statocysts along circular canal, with one statolith each.

Cnidome. Small microbasic b-mastigophores on both tentacles and hydranth body (polyp); atrichous isorhizas, microbasic mastigophores, on tentacles and manubrium (medusa).

Seasonality. June–October (De Vito 2006; Gravili et al. 2008b; this study) in Salento waters.

Reproductive period. August, September in Salento waters (De Vito 2006; Gravili et al. 2008b; this study).

Distribution. Circumtropical (West Indies, Gulf of Mexico, Ghana, South Africa, Papua New Guinea, Bermuda, Brazil, Indonesia, Galapagos Islands, and the Mediterranean) (Bouillon et al. 2004; Boero et al. 2005; Gravili et al. 2008a, b; Gravili et al. 2010; Occhipinti-Ambrogi et al. 2011).

Records in Salento. Common at: Torre Lapillo, S.ta Caterina ( Andreano 2007; Gravili et al. 2008b); Sant'Andrea, S. Emiliano, Marina di Andrano, Tricase, Tiggiano, Gagliano, S. Maria di Leuca, Torre Suda, Porto Racale, Isola di S. Andrea, Grotta Corvine, Punta Longa, S. Isidoro, Porto Cesareo, Isola della Malva ( Gravili et al. 2008b); Otranto (De Vito 2006; Gravili 2006; Gravili et al. 2008a, b; Piraino et al. 2013; this study).

Remarks. The whole life cycle was examined in the present study. C. hummelincki is a successful invader frequent in shallow sea urchin barrens, where it forms a ‘belt’ ( Gravili et al. 2008b). The present description, and that reported by Gravili et al. (2008b) do not cover the whole development of the medusa, since complete gonad maturation and spawning were not observed. Indeed, the medusae do not grow easily under laboratory conditions and, probably, their natural diet has much different requirements than what is available in an Artemia -based diet.

References. Millard (1975); Cornelius (1982) as Laomedea ; Calder (1991), Boero et al. (1997b), Boero (2002), Bouillon et al. (2004), Boero et al. (2005), De Vito (2006), Gravili (2006), Gravili et al. (2008a, b), Gravili et al. (2010), Occhipinti-Ambrogi et al. (2011), Piraino et al. (2013).

Figures

FIGURE 102. Clytia hummelincki: A, colony with gonotheca; B, gonotheca with a medusa-bud; C, newly liberated medusa; D, 11 - day-old medusa; E, 15 - day-old medusa, enlargement of tentacled and atentacled bulbs, and statocysts; F, male mature medusa (modified after Gravili et al. 2008). Scale bars: A, 0.5 mm; B, C, D, 1.0 mm; F, 2.0 mm.