Halecium lankesteri

Remarks. Though devoid of the characteristic female gonophores and not reported yet from the tropical western Atlantic, I assign the present material to Bourne’s (1890) species, on the following arguments: the body and tentacles of polyps contain numerous zooxanthellae; the stem is monosiphonic, irregularly segmented, with internodes short and provided with boulges at their ends; the hydrothecae are slightly flaring from diaphragm to aperture, the margin is entire, not everted. Nematocysts (undischarged): large microbasic euryteles (6.8 – 7.7) × (3.1 – 3.6) µm; small microbasic mastigophores (6.0 – 6.7) × (1.7 – 1.8) µm. For a complete, recent redescription of H. lankesterii, see Schuchert (2005). The male gonothecae have been previously described by Babić (1913). The present material contains only male colonies. The gonothecae are borne on short stem apophyses. They are elongated-ovoid in shape, tapering basally, with flattened apex.

Remarks. Though sterile, the presence of numerous zooxanthellae in the coenosarc enable me to assign the present material to Alder’s (1859) species. It originates from areas with strong water movement and is mainly composed of single hydrothecate pedicels arising directly from stolon. Occasionally, the pedicels are branched once. The hydrothecae have diverging though not everted lateral walls, similar to the material described by Medel & Vervoort (2000). Renovations are often present. For a recent description of H. nanum, see Calder (1991 d). An extensive synonymy is provided by Medel & Vervoort (2000).

Distribution. Mediterranean Sea, temperate and tropical parts of the Atlantic and Pacific Oceans; for a detailed list of records, see Medel & Vervoort (2000). The Caribbean records are summarized by Calder & Kirkendale (2005). Present study Calder (1991 d) Watson (1997) Hydrotheca – height 17 – 23 28 – 38 30 – 40 – diameter at rim 133 – 165 147 – 182 130 – 160 – diameter at diaphragm 100 – 120 126 – 158 90 – 150 Hydranth – tentacle number 14 – 20 16 – 25 – Nematocysts – microbasic euryteles (9.1 – 9.6) × (4.1 – 4.7) (6.7 – 7.4) × (3.1 – 3.8) – – microbasic mastigophores (6.0 – 6.4) × (1.4 – 1.7) (5.5 – 6.2) × (1.6 – 1.9) –

Distribution. Previous records are from the Mediterranean and eastern Atlantic (Peña Cantero & García Carrascosa 2002). The present material extends the known distribution to the tropical western Atlantic. TABLE 5. Measurements of Halecium cf. lankesteri (Bourne, 1890), in µm. (1) Cited from Babiċ (1913).

Material examined. Stn. 1: 21.03.2008 — two small, sterile colonies, on Thalassia testudinum. Stn. 7: 27.03.2008 – a few small, sterile colonies, mostly stolonal, on various algae. Type locality. North-eastern Atlantic, 34 ° 48´N, 34 ° 25´W.

Material examined. Stn. 7: 27.03.2008 — two dense colonies, with both stolonal and small, erect growth forms, up to 5 mm high, with male gonophores, on algae (MHNG INVE 60983). Type localities. Plymouth, Great Britain.