Pennaria disticha Goldfuss, 1820

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 : 59-60

Pennaria disticha Goldfuss, 1820

Fig. 40 A–C

See Schuchert (2006) for a complete synonymy.

Material examined. HCUS-S 0 45 (Hydrozoa Collection, University of Salento—fauna of the Salento Peninsula).

Description (based on our own observations; Brinckmann-Voss 1970; Schuchert 2006):

Hydroid. Hydrorhiza as a network of creeping stolons; colonies erect, large, pinnate; hydrocaulus thick, often curved, monosiphonic, with monopodial growth, covered by thick perisarc, firm, smooth but annulated at more or less regular intervals, regularly distal to insertion of hydrocladia (side-branches) and hydranth pedicels; hydrocladia unbranched, originating alternately from opposite sides to form two series lying in a single plane, longest branches in the middle of the colonies, gradually decreasing in length upward and downwards; hydranths fusiform or pyriform, numerous, terminal on hydrocaulus and hydrocladia, on short pedicels; hypostome domeshaped; with a whorl of 4–6 oral capitate tentacles, up to 18 capitate tentacles scattered or in more or less regular whorls on hydranth body and one aboral whorl of up to 16 semifiliform to slightly capitate aboral tentacles; colonies gonocoric. Colours: stem dark brown to black, hydrocladia brown, fading distally to clear.

Eumedusoid: gonophores as eumedusoids, oblong, free or not, arising on short pedicels just above whorl of long filiform tentacles; 3–5 per hydranth, gonads encircling manubrium, 4 radial canals and circular canal present, 4 marginal bulbs, small velum, without ocelli, tentacles normally absent, rarely some rudiments present.

Cnidome. Stenoteles of 3–4 size classes, microbasic mastigophores with inclusion body, microbasic heteronemes without inclusion body, basitrichous isorhizas, desmonemes (polyp); stenoteles (medusoid).

Habitat type. Shallow waters with some wave action along rocky coasts ( Brinckmann-Voss 1970; Morri & Boero 1986; Puce et al. 2009).

Substrate. Stones or Balanus shells, Posidonia oceanica .

Seasonality. In the Western Mediterranean Sea (Gili 1986), Pennaria disticha occurs in June; the colonies are active from spring to fall, and they overwinter as stolons ( Brinckmann-Voss 1970; Morri & Boero 1986; this study). In Otranto has been found in November ( Piraino et al. 2013).

Reproductive period. June (Gili 1986).

Distribution. Warm waters around the world ( Rees & Thursfield 1965; Yamada 1965; Micallef & Evans 1968; Brinckmann-Voss 1970; Schmidt 1973; Cornelius 1992; Vervoort 1993; Medel & López-González 1996; Schuchert 1996, 2006; Watson 1999; Calder et al. 2003; Kirkendale & Calder 2003; Bouillon et al. 2004; Gravili et al. 2008a; Morri et al. 2009; Puce et al. 2009; Brahim et al. 2010).

Records in Salento. Rare at: S. Maria al Bagno, S.ta Caterina (Ionian Apulian coast) (this study); Porto Cesareo ( Kubota & Gravili 2011); Otranto ( Piraino et al. 2013).

Remarks. The morphological variability of this species was the main reason for its complicated taxonomic history (see Schuchert 2006); colony form can vary quite drastically depending on wave exposure ( Calder 1988; da Silveira & Migotto 1991).

References. Goldfuss (1820); Lo Bianco (1909) as P. cavolini ; Mayer (1910); Picard (1958a), Kramp (1959, 1961), Yamada (1965), Micallef & Evans (1968) all as H. disticha ; Brinckmann-Voss (1970); Rossi (1971) as H. disticha ; Schmidt (1973), Marinopoulos (1979), García Corrales & Aguirre (1985), Roca & Moreno (1985), Gili (1986), Roca (1986), Riedl (1991, García-Raso et al. (1992), Bianchi & Morri (1993) all as H. disticha ; Vervoort (1993); Astraldi et al. (1995) as H. disticha ; Chimenz-Gusso et al. (1995); Cocito et al. (1995) as H. disticha, Nicoletti & Chimenz Gusso (1995) ; Medel (1996); Medel & López-González (1996); Piraino et al. (1999) as H. disticha ; Bouillon et al. (2004); Schuchert (1996, 2006); Gravili et al. (2008a), Morri et al. (2009); Puce et al. (2009); Brahim et al. (2010) as H. disticha ; Kubota & Gravili (2011), Piraino et al. (2013).

Figures

FIGURE 40. Pennaria disticha: A, colony; B, detail of a hydranth with an almost mature female eumedusoid and several developing buds; C, eumedusoid (drawn by C. G. Di Camillo). Scale bars: A, 8.0 cm; B, C, 0.5 mm.