Synthecium evansi (Ellis and Solander, 1786)

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 : 137-138

Synthecium evansi (Ellis and Solander, 1786)

Fig. 98 A–C

See Peña Cantero & García Carrascosa (2002) for a complete synonymy.

Material examined. HCUS-S 105 (Hydrozoa Collection, University of Salento—fauna of the Salento Peninsula).

Description (based on our own observations; Ramil & Vervoort 1992; Cornelius 1995; Peña Cantero & García Carrascosa 2002):

Hydroid. Hydrorhiza as strong, thick stolons; colonies erect, pinnate; hydrocaulus monosiphonic, up to 100 mm high, perisarc thick in old colonies, divided into thecate internodes by distinct or indistinct transverse nodes, except in the most basal part; hydrocladia opposite, in the same plane, similar in structure to hydrocaulus; hydrothecae lateral and opposite, one to two pairs per internode, cylindrical, distal part curving outwards, adcauline wall 2/3 adnate to the axis, rim even, circular, renovation of the margin very frequent. Gonothecae growing out the hydrothecal aperture, fusiform, pointed apically, with deep transversal ridges. Colour: colonies dark-blue.

Cnidome. Microbasic mastigophores.

Habitat type. Eurybathic species, in the Mediterranean it has been found in the depth range 2–250 m ( Marinopoulos 1981; Boero & Fresi 1986).

Substrate. Algae, sponges, Posidonia , hydrozoans, mollusc shells, bio-concretions, rock; this species is also substratum for other hydroids.

Seasonality. October–March ( Boero & Fresi 1986) in the Ligurian Sea; present throughout all the year in Salento waters (De Vito 2006; this study).

Reproductive period. July, September ( Gili 1982, 1986; De Vito 2006; this study), October–November ( Boero & Fresi 1986; De Vito 2006; this study), and December (this study) in several localities of the Mediterranean Sea.

Distribution. Mediterranean and eastern Atlantic (Strait of Gibraltar and Canary Islands) ( Izquierdo et al. 1986; Ramil & Vervoort 1992; Medel & López-González 1996; Peña Cantero & García Carrascosa 2002; Bouillon et al. 2004; Gravili et al. 2008a; Soto Ãngel & Peña Cantero 2013).

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

Remarks. In this species there is considerable variability in the shape of the hydrothecae through the varied length of the free portion of the hydrotheca, the degree of curvature, the shape of the abcauline hydrothecal wall and the total depth of the hydrotheca (Ramil & Vervoort 1992).

References. Stechow (1919, 1923), Picard (1951a, 1958a), Relini Orsi et al. (1977), Gili (1982, 1986), Izquierdo et al. (1986), Roca (1986, 1989), Boero & Fresi (1986), Ramil & Vervoort (1992), Medel & López- González (1996), Piraino et al. (1999), Peña Cantero & García Carrascosa (2002), Bouillon et al. (2004), Di Camillo et al. (2005); De Vito (2006), Gravili (2006), Gravili et al. (2008a).

Figures

FIGURE 98. Synthecium evansi: A, fertile colony; B, part of colony showing hydrocladium with secondary ramification; C, gonotheca (A, C drawn by L. Basso; B drawn by C. G. Di Camillo). Scale bars: A, 2.0 mm; B, C, 1.0 mm.