Eudendrium rameum Pallas 1766

Eudendrium rameum (Pallas, 1766)

Fig. 21 A–C

See Schuchert (2008b) for a complete synonymy.

Material examined. HCUS-S 0 26 (Hydrozoa Collection, University of Salento—fauna of the Salento Peninsula).

Description (based on our own observations; Marques et al. 2000a; Schuchert 2008b, 2012):

Hydroid. Hydrorhiza root-like, creeping; colonies erect, large (up to 25 cm), usually tree-like with a thick trunk; hydrocaulus polysiphonic, branched, with thick perisarc, ringed basally on secondary branches; hydrocladia sinuous to straight; hydranths on ringed pedicels; hypostome bulbous; with 20–24 filiform tentacles in one whorl. Gonophores as fixed sporosacs, ovoid, short-stalked, borne on and below hydranths; males (up to 12 per hydranth) in a dense whorl around body of hydranth, with one to three chambers each, without terminal nematocyst clusters; females (up to 16 per hydranth) with a spadix, fertilized eggs lose spadix and become encapsulated in perisarc membrane. Colours: dark brown perisarc, hydranths pale; sporosacs yellow.

Cnidome. Heterotrichous microbasic euryteles (23x8 to 25 x8) on hypostome, hydranth and on the hydrocaulus; shaft thin, straight, occupying totally the capsule; small heterotrichous microbasic euryteles (8x 4) on tentacles and ectoderm.

Habitat type. Mostly recorded in depths from a few meters to about 100 m on hard bottoms (Christiansen 1972; Marinopoulos 1981; Piraino et al. 1999; Peña Cantero & García Carrascosa 2002; Puce et al. 2009).

Substrate. Algae, bryozoans and anthozoans, and it is used in turn as substratum by numerous species of hydroids.

Seasonality. Almost always present in the whole Mediterranean Sea (Schuchert 2008b).

Reproductive period. Fertile colonies from the Mediterranean have been found in the months January, April, September (Marques et al. 2000b; Schuchert 2008b), June–September (Bouillon et al. 2004); November (Puce et al. 2009).

Distribution. This species has been recorded in almost all oceans (Millard 1977; Marques et al. 2000a, b; Peña Cantero & García Carrascosa 2002; Schuchert 2001a, 2008b).

Records in Salento. Rare at Otranto (De Vito 2002; this study).

Remarks. This species is probably a declining one (Bouillon et al. 2004). According to Moura et al. (2008) preliminary molecular data demonstrate that the current concept of E. rameum comprises several lineages and also several species.

References. Rossi (1971), Gili (1986), Cornelius & Ryland (1990), Marinopoulos (1990, 1992), Riedl (1991), Medel & López-González (1996), Marques et al. (2000a, b), Schuchert (2001a), Peña Cantero & García Carrascosa (2002), Bouillon et al. (2004), De Vito (2002), Schuchert (2008b, 2012).