Halecium petrosum Stechow, 1919,

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: 93-94

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Halecium petrosum Stechow, 1919


Halecium petrosum Stechow, 1919 

Fig. 65View FIGURE 65 A –D

See Schuchert (2005 b) for a complete synonymy.

Material examined. HCUS-S 0 72 (Hydrozoa Collection, University of Salento—fauna of the Salento Peninsula). Description (based on our own observations; Schuchert 2005 b):

Hydroid. Colonies erect; hydrocauli stiff, monosiphonic, up to 35 mm, with a thick perisarc; hydrocladia alternate, laterally at the end of each internode; hydrothecae sessile, but adcauline wall not adnate to the axis, walls gradually widening distally, rim not flared, hydrothecal renovations frequent, secondary hydrophore large and with undulated perisarc. Gonothecae: female gonothecae ovoid to spherical, big, aperture apical with 2 hydranths, borne on hydrorhiza or on hydrocauli, male gonothecae sac-shaped, elongated, arising from inside of the hydrotheca or below it.

Cnidome. Atrichous isorhizas.

Habitat type. Littoral and shelf species, but absent from the shallowest infralittoral ( Peña Cantero & García Carrascosa 2002; Schuchert 2005 b).

Substrate. Algae, other hydroids, Posidonia oceanica  , anthozoans, incrusting sponge.

Seasonality. Always present in the western Mediterranean ( Llobet i Nadal 1987; Llobet et al. 1991); April, August (De Vito 2006; this study) in Salento waters.

Reproductive period. August ( Motz-Kossowska 1911; De Vito 2006; this study); September ( Llobet et al. 1991; Coma et al. 1992); October ( Stechow 1923; Llobet i Nadal 1987; Llobet et al. 1991; Coma et al. 1992); November ( Llobet i Nadal 1987) in the Mediterranean Sea.

Distribution. Endemic to the Mediterranean ( Medel & López-González 1996; Bouillon et al. 2004; Schuchert 2005 b; Gravili et al. 2008 a; Morri et al. 2009).

Records in Salento. Rare at: Otranto (De Vito 2006; Gravili 2006; Gravili et al. 2008 a; this study); La Strea (Porto Cesareo) ( Ventura 2011).

Remarks. Motz-Kossowska (1911) identified abundant material from Banyuls as Halecium robustum Pieper, 1884  . Female gonothecae of Motz-Kossowska’s material differed from typical H. lankesterii  , and for this reason Stechow (1919) attributed it to a new species with the name Halecium petrosum  .

References. Motz-Kossowska (1911) as H. robustum  ; Stechow (1919, 1923), Leloup (1934), Picard (1951 a, 1958 a), Rossi (1961), Llobet et al. (1986, 1991), Llobet i Nadal (1987), García-Carrascosa (1981), Llobet i Nidal (1987), Coma et al. (1992), Medel & López-González (1996), Peña Cantero & García Carrascosa (2002), Bouillon et al. (2004), Schuchert (2005 b), De Vito (2006), Gravili et al. (2008 a), Morri et al. (2009), Puce et al. (2009), Ventura (2011).