Turritopsis dohrnii (Weismann, 1883)

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 : 40-41

Turritopsis dohrnii (Weismann, 1883)

Fig. 26 A, B

See Schuchert (2004) for a complete synonymy.

Material examined. HCUS-S 031p and HCUS-S 031m (Hydrozoa Collection, University of Salento— fauna of the Salento Peninsula)—polyp and medusa stages.

Description (based on our own observations; Calder 1988; Schuchert 2004):

Hydroid. Colonies stolonal or erect; hydrocaulus monosiphonic in small colonies, polysiphonic in larger ones, irregularly branched, decreasing in diameter from base to distal end, covered by a firm perisarc consisting of two layers and mostly infested with detritus and algae, without annulations and terminating below hydranth base; hydrocladia adnate and parallel to hydrocaulus or to other branches for some distance before curving away at an acute angle and becoming free; hydranths terminal, fusiform and elongated, naked; hypostome conical and elongated; with 12–20 filiform tentacles scattered over distal ¾ of hydranth, proximal ones shorter than distal; medusa buds pyriform, enclosed in perisarc, arising mostly one by one on a short pedicel below hydranth. Colours: hydranths in life colourless or pinkish.

Habitat type. The hydroid is present on rocky shores, between 0 and 20 m, under overhangs constituted by either rocks or conspicuous animals ( Boero & Fresi 1986; Bavestrello et al. 1992; Peña Cantero & García Carrascosa 2002; Puce et al. 2009).

Substrate. Dorocidaris papillata (Echinodermata) , Isidella elongata (Octocorallia) , on tubes of Serpulida, sponges; algae such as Halimeda , Peyssonnelia , barnacles, bryozoans, hydrozoans, concretions on mussel.

Seasonality. In the Ligurian Sea, in March, April, June–December ( Boero & Fresi 1986), and in January–May (Puce et al. 2009); from March to December (De Vito 2006; this study) in Salento waters.

Reproductive period. In the Ligurian Sea, fertile colonies occur in July, August, October ( Boero & Fresi 1986), and in May (Puce et al. 2009); from August to October in Salento waters (De Vito 2006; this study).

Medusa. Adult. Umbrella bell-shaped to pyriform, higher than wide, 3.2 mm in diameter, up to 2.7 mm in height, mesoglea thicker at apex; manubrium cross-shaped in transverse section, large, mounted on pseudopeduncle with 4 radial canals which appears to overtop 4 compact vacuolated endodermal masses situated above digestive part of manubrium; mouth 4 lipped, with a continuous row of sessile cnidocyst clusters along margin; gonads with 4 interradial dots, arranged in 4 distinct interradial blocks, gonochoristic; with 14–32 closely spaced marginal tentacles with swollen tips; with adaxial ocelli. Colours: manubrium red, ocelli rust coloured, gonads brownish, with 4 interradial rust coloured dots.

Developmental stages. Newly released medusa with interradial pads on manubrium, vacuolated cells visible, with 8–12 marginal tentacles. Colours: pads yellow-fluorescent (paler to colourless in cultivated animals).

Cnidome. Desmonemes and microbasic euryteles.

Distribution. Western Mediterranean, Ionian Sea, Adriatic Sea ( Medel & López-González 1996; Peña Cantero & García Carrascosa 2002; Bouillon et al. 2004; Schuchert 2004; Gravili et al. 2008a; Soto Ãngel & Peña Cantero 2013). The records of T. nutricula by Schmidt (1973), Dowidar (1984), Goy et al. (1988, 1990, 1991), and Zakaria (2004) from the eastern Mediterranean do not provide sufficient data to evaluate the taxonomic status of their specimens (see Schuchert 2004).

Records in Salento. Moderately frequent at: Palude del Capitano ( Presicce 1991); Gulf of Taranto ( Denitto 1996); Otranto, Porto Cesareo (Ionian and Adriatic Seas, Apulia) ( Denitto 1996; Miglietta et al. 2000; De Vito 2006; Gravili 2006; Gravili et al. 2008a; this study); S.ta Caterina ( Denitto 1996; Andreano 2007).

Remarks. The whole life cycle was examined in the present study. This species differs mainly from Turritopis nutricula by the size of the bell, 1.8–2.7 mm for T. dohrnii to 3–6 mm for T. nutricula and by the number of tentacles 14–32 for T. dohrnii 40 to 120 for T. nutricula (Bouillon et al. 2004) . It is however not excluded that T. dohrnii and T. nutricula coexist in the Mediterranean (for more details see Bouillon et al. 2004). The medusa can metamorphose back into polyp stage (Piraino et al. 1996; Carlà et al. 2003; Schmich et al. 2007). A molecular evaluation of the species in the genus Turritopsis has been carried out by Miglietta et al. (2007).

References. Motz-Kossowska (1905) as Cordylophora Dohrni, Mayer (1910) as Dendroclava dohrnii, Hartlaub (1911) , Neppi & Stiasny (1913) as Turritopsis nutricula ; Stechow (1923); Riedl (1959), Trégouboff & Rose (1957), Balduzzi et al. (1980), Calder (1988), Piraino et al. (1996), Peña Cantero & García Carrascosa (2002), Carlà et al. (2003) all as T. nutricula ; Schuchert (2004), De Vito (2006), Gravili (2006), Gravili et al. (2008a), Puce et al. (2009).

Figures

FIGURE 26. Turritopsis dohrnii: A, hydranths with medusa buds; B, medusa (drawn by F. Boero). Scale bars: A, B, 1.0 mm.