Halecium

Galea, Horia R., 2010, Notes on a small collection of thecate hydroids (Cnidaria: Hydrozoa) from Tristan da Cunha, south Atlantic, Zootaxa 2336, pp. 1-18 : 4

Halecium sp.

( fig. 3 C)

Material examined. Stn. I10, 28.xi.2007: several sterile stems off barnacles.

Description. A small colony composed of minute (165–410 µm high), unbranched stems annulated throughout; hydrotheca 25–30 µm deep, diameter 115–125 µm at aperture, 60–70 µm at base; margin flaring and much everted; 1–4 renovations occasionally present. Gonothecae not found.

Remarks. This species is unidentifiable in the absence of (female) gonothecae. It resembles H. diminutivum Fraser, 1940 and the small, unbranched stems of both H. corrugatum Nutting, 1899 , and specimens likely incorrectly assigned to H. annulatum Torrey, 1902 by Jäderholm (1920)1.

Figures

FIGURE 3. A and B: Filellum sp. (material from station Stn. I 10) – portion of colony (A); hydrotheca (B). C: Halecium sp. – four erect stems. D: Halecium cf. beanii (Johnston, 1838) – fragment of monosiphonic part of stem with origin of a side branch. E and F: Halecium cf. delicatulum (Coughtrey, 1876), morphotype 1 – portion of stem (E); hydrotheca (F). G to P: Halecium? delicatulum (Coughtrey, 1876), morphotype 2 (part) – whole colony on piece of alga (G); cross section through the stolon (H); basal part of stem (I); portion of colony (J); various branching patterns (K – M); fragment of stem showing internodes (N); various shapes of primary hydrophores (O); gonotheca arising from primary hydrophore (P). Scale bars: 50 µm (H); 100 µm (F); 200 µm (B, F, O); 300 µm (A, E, I, P); 400 µm (D, K, L, M); 500 µm (N); 2 mm (J); 1 cm (G).