Halopteris catharina (Johnston, 1833)

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 : 101-102

Halopteris catharina (Johnston, 1833)

Fig. 71 A–D

See Schuchert (1997) for a complete synonymy.

Material examined. HCUS-S 0 78 (Hydrozoa Collection, University of Salento—fauna of the Salento Peninsula).

Description (based on our own observations; Schuchert 1997):

Hydroid. Hydrorhiza as branched stolons; colonies pinnate, up to 40 mm high; hydrocauli monosiphonic, unbranched, basal part composed of several segments bearing 2 longitudinal rows of nematothecae, nodes transverse, remaining stem axis heteromerously segmented by alternating oblique and transverse nodes; hydrocladia opposite, borne laterally below hydrothecae, on long stem apophyses, hydrothecate segments with one hydrotheca and 5 nematothecae, one median inferior and 2 pairs of lateral ones, non-hydrothecate segments with 1–4 nematothecae, hydrocladia with a first athecate segment, remaining segments as in the main axis, but nonhydrothecate ones with 1–2 nematothecae; hydrothecae cup-shaped, walls straight almost parallel, in the middle of the internode, 1/2 adnate, rim smooth, aperture at 45º from the axis; nematothecae all two-chambered and movable, upper chamber with a deep embayment, outer pair of lateral nematothecae reaching the rim or slightly beyond it, on long apophyses, inner pair at base of those apophyses. Gonothecae of both sexes on the same plume, developing on main segments below hydrotheca of stem and hydrocladia, female ones cylindrical, somewhat flattened, narrowed at base, with 2 nematothecae, truncated distally, with annular thickening and lid, basal pedicel with 2 segments, male ones smaller and elongated. Colour: all tissues colourless.

Cnidome. Microbasic mastigophores.

Habitat type. Rocky, depth range down to 412 m (Gili et al. 1989; Ramil & Vervoort 1992).

Substrate. Terebellid tubes, Ascidiacea, algae, hydroids.

Seasonality. January–April, June–August, December (Gili 1986) in the western Mediterranean; October (De Vito 2006; this study) in Salento waters.

Reproductive period. March, June (Gili 1986) in the western Mediterranean Sea.

Distribution. Temperate and southern-boreal regions of the eastern and western sides of the Atlantic, Mediterranean (Ramil & Vervoort 1992; Medel & López-González 1996; Schuchert 1997; Bouillon et al. 2004; Gravili et al. 2008a; Bianchi et al. 2011).

Records in Salento. Rare at Otranto (De Vito 2006; Gravili 2006; Gravili et al. 2008a; this study).

Remarks. Halopteris catharina is easily recognisable for its rather distinct plumose habit with opposite hydrocladia, but it can also occur in forms differing from the typical plumose stems. Therefore, population genetic methods are needed for correct identification (for more details see Thorpe et al. 1992).

References. Russell (1957), Picard (1958a), Gili (1986), Ramil & Vervoort (1992), Medel & López-González (1996), Schuchert (1997), Ansín Agís et al. (2001), Bouillon et al. (2004), Morri & Bianchi (1999), Morri et al. (1999), De Vito (2006), Gravili (2006), Gravili et al. (2008a), Bianchi et al. (2011).

Figures

FIGURE 71. Halopteris catharina: A, normal plumose colony; B, part of caulus with opposite branched hydrocladia; C, part of hydrocladium with main segment and intersegment; D, gonothecae: left female, right male (redrawn and modified after Schuchert 1997 by C. G. Di Camillo). Scale bars: A, 5.0 mm; B, 0.5 mm; C, D, 0.2 mm.