The non-Siphonophoran Hydrozoa (Cnidaria) of Salento, Italy with notes on their life-cycles: an illustrated guide Author Gravili, Cinzia Author Vito, Doris De Author Camillo, Cristina Gioia Di Author Martell, Luis Author Piraino, Stefano Author Boero, Ferdinando text Zootaxa 2015 3908 1 1 187 journal article 42365 10.11646/zootaxa.3908.1.1 6f1d1977-6b97-4789-828c-76ed250cf1ae 1175-5326 242729 D6AD2B49-170B-4D9C-84AA-DBE0FEEAD8BE Halecium tenellum Hincks, 1861 Fig. 67 A–C See Peña Cantero & García Carrascosa (2002) for a complete synonymy. FIGURE 67. Halecium tenellum : A , part of stem; B , female gonophore; C , male gonophore (B, C same scale bar) (A drawn by C.G. Di Camillo; B, C redrawn and modified after Millard 1975 by C.G. Di Camillo). Scale bars: A, 0.1 mm; B, C, 0.5 mm. Material examined. HCUS-S 0 74 (Hydrozoa Collection, University of Salento—fauna of the Salento Peninsula). Description (based on our own observations; Peña Cantero & García Carrascosa 2002 ): Hydroid. Hydrorhiza stolonal, colonies erect; hydrocauli very thin and delicate, monosiphonic, up to 20 mm high, irregularly branched, internodes long, in a zigzag arrangement, separated by transverse nodes; hydrocladia may originate from hydrothecal base; hydrothecae shallow, walls widening from base to top giving a wide aperture, rim everted and curved outwards, borne laterally at upper part of internodes, alternate and provided with a well developed hydrophore, secondary hydrothecae provided with hydrophore, may arise from primary hydrothecae. Gonothecae: male gonothecae ovate and flattened, female similar but slightly larger and broader. Cnidome. Microbasic euryteles and mastigophores. Habitat type . Eurybathic species that has been found from 0.5 to 200 m depth ( Marinopoulos 1979 ; Boero & Fresi 1986 ). Substrate. Algae, hydroids, concretions, Posidonia , bryozoans, polychaete tubes, anthozoans, sponge. Seasonality. April ( Picard 1955 ; Gili 1986), May (Medel et al . 1998), and October–March, July ( Boero & Fresi 1986 ) in the western Mediterranean; June, July (De Vito 2006; this study) in Salento waters. Reproductive period. April ( Picard 1955 ; Gili 1986) and May (Medel et al . 1998) in the western Mediterranean. Distribution. Cosmopolitan species present in the eastern and western Atlantic, Mediterranean, Indo-Pacific, Arctic, Antarctic ( Broch 1918 in part as Halecium textum ; Stepan’yants 1979; Ramil & Vervoort 1992; Medel & López-González 1996 ; Medel et al . 1998; Peña Cantero & García Carrascosa 2002 ; Bouillon et al. 2004; Gravili et al . 2008a ; Soto Ãngel & Peña Cantero 2013 ). Records in Salento. Rare at Otranto (De Vito 2006; Gravili 2006; Gravili et al . 2008a ; this study). Remarks. It is not always easy to distinguish the European Halecium species H. mediterraneum , H. labrosum , and H. tenellum (for details see Schuchert 2005b ). The distinctive characteristics of H. tenellum are that the colonies are more gracile , non-polysiphonic and smaller than those of the other two species, with internodes more elongate, strongly arranged in a zigzag manner. References. Motz-Kossowska (1911) , Broch (1912 , 1933 ), Stechow (1919) , Leloup (1934) , Picard (1958a) , Rossi (1961) , Patriti (1970) , Boero (1981a , b ), Fresi et al. (1982) , Boero & Fresi (1986) , Gili (1986), Llobet et al. (1986 , 1991 ), Llobet i Nadal (1987) , Ramil & Vervoort (1992), Medel & López-González (1996) , Migotto (1996) , Medel et al. (1998), Piraino et al . (1999) , Medel & Vervoort (2000) , Peña Cantero & García Carrascosa (2002) , Bouillon et al. (2004), De Vito (2006), Gravili (2006), Gravili et al . (2008a) , Puce et al . (2009).