Bougainvillia muscus (Allman, 1863)

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 : 9-10

Bougainvillia muscus (Allman, 1863)

Fig. 2 A–C

See Schuchert (2007) for a complete synonymy.

Material examined. HCUS-S 0 0 1 and HCUS-S 0 0 2 (Hydrozoa Collection, University of Salento—fauna of the Salento Peninsula)—polyp stage.

Description (based on our observations; Edwards 1966a; Schuchert 2007, 2012):

Hydroid. Hydrorhiza as an irregular network of tubular stolons from which hydrocauli arise; colony erect; hydrocauli mono- or polysiphonic, irregularly branching and variable in growth and form from dwarf, monosiphonic and little-branched to tall, polysiphonic and tree-like; perisarc of hydrocauli and hydrocladia often covered by detritus, corrugated at base of hydrocladia and thinning out over hydranths forming a pseudohydrotheca; hydranths cylindrical to fusiform, terminal on hydrocauli and hydrocladia; hypostome short and conical; with up to 20 amphicoronate filiform tentacles; pseudohydrotheca thin, much variable in development, from usually present in natural populations to absent in cultivated animals. Medusa buds covered by periderm, arising singly or in groups on hydrocladia just below hydranths, on moderately long stalks. Colours: hydranths pink, red, orange, or greyish purple; colour depends on food items.

Habitat type. B. muscus hydroids usually occur under wave-sheltered conditions, often in slightly reduced salinity and also harbours, on a wide variety of substrata, from the surface to 100 m, but it has also been found in deeper waters ( Schuchert 2012).

Substrate. Posidonia oceanica leaves and rhizomes, Zostera leaves, Sargassum , Cystoseira , bryozoans, algae, hydroids, mussels, polychaete tubes, barnacles, man-made objects.

Seasonality. In the Ligurian Sea the species was recorded all year ( Boero & Fresi 1986) and from January to May and November to December (Puce et al. 2009). In Salento, the species was observed in February and November (this study).

Reproductive period. May in the Ligurian Sea ( Boero & Fresi 1986), January ( Galea 2007) along the Mediterranean French coast, from spring to autumn (Schuchert 2007) in European temperate waters.

Medusa. Adult. Umbrella globular, 2.0–3.5 mm wide and high; mesoglea thick; manubrium bulbous, half of subumbrellar height, sometimes on a short peduncle; oral tentacles long, branching 1–2 (rarely 3–4) times; 4 interradial gonads on manubrium, globular in females and prolonged along sides of radial canals in males; mature eggs covered with a layer of cnidocysts (microbasic euryteles); marginal bulbs small, each bearing 3–5 (rarely 6–9) long marginal tentacles; 2 round ocelli situated adaxially on each marginal bulb near the origin of tentacles. Colours: marginal bulbs and stomach reddish brown, red or yellowish; sometimes with greenish tinge, depends on food items; ocelli red or black in colour.

Developmental stages. Newly released medusa with globular umbrella, jelly uniformly thin, with a few nematocysts on exumbrella; manubrium not mounted on a gastric peduncle; 4 unbranched oral tentacles; small not developed oogonia can be seen on the manubrium of females; 2 tentacles and 2 ocelli per marginal bulb. Colours: ocelli red or black.

Cnidome. Microbasic euryteles and desmonemes (hydroids and medusae).

Distribution. A widely distributed species, probably also due to anthropogenic activity, recorded in Atlantic, Indo-Pacific, Mediterranean, and Arctic waters ( Bonnevie 1901; Vervoort 1946; Rees 1952; Patriti 1970; Christiansen 1972; Millard 1975; Hirohito 1988; Schönborn et al. 1993; Medel & López-González 1996; Schuchert 1996, 2001a, 2007; Peña Cantero & García Carrascosa 2002; Bouillon et al. 2004; Gravili et al. 2008a).

Records in Salento. Hydroid moderately frequent at Otranto (De Vito 2006; Gravili 2006; Gravili et al. 2008a).

Remarks. B. muscus is a very variable species in both stages of the life cycle. Earlier authors attempted to assign the several forms to different species (see Schuchert 2007). Only the hydroid stage and the new born medusa were seen in the present study.

References. Schneider (1898), Babic (1910), Broch (1912, 1933), Picard & Le Roch (1949), Russell (1953, 1970), Trégouboff & Rose (1957), Vucetic (1957), Picard (1958a), Kramp (1961), Vannucci & Rees (1961), Edwards (1966a), Rossi (1971), Boero (1981a), Maluquer (1985), Riedl (1991), Schuchert (1996, 2007, 2012), Morri & Bianchi (1999), Peña Cantero & García Carrascosa (2002), Bouillon et al. (2004), De Vito (2006), Gravili (2006), Galea (2007), Çinar et al. (2008), Gravili et al. (2008a), Puce et al. (2009).

Figures

FIGURE 2. Bougainvillia muscus: A, colony; B, fragment of a colony with medusa buds; C, mature medusa (A, C drawn by C. G. Di Camillo; B, redrawn and modified after Leloup 1952 by C. G. Di Camillo). Scale bars: A, B, 0.5 mm; C, 1.0 mm.