Halecium fjordlandicum Galea, 2007

Galea, Horia R. & Schories, Dirk, 2012, Some hydrozoans (Cnidaria) from Central Chile and the Strait of Magellan, Zootaxa 3296, pp. 19-67 : 33-34

Halecium fjordlandicum Galea, 2007

(pl. 3C, fig. 3A–F)

Halecium fjordlandicum Galea, 2007: 56 , fig. 13A–D, pl. 2C–I.

Material examined. Stn. CMZ — 13.vii.2010, S01 (40 m): several stems, up to 4.3 cm high, on worm tube, most of them bearing male gonothecae (MHNG-INVE-79615); S0 2 (20 m): several stems and fragments, up to 4.0 cm high, epizoic on gorgonian, most of them bearing female gonothecae (MHNG-INVE-79613); 18.vii.2010, S06 (30–50 m): several male and female stems on a fragment of dead gorgonian (MHNG-INVE-79614). Stn. YBU — 20.vi.2010, S04 (20 m): several stems, up to 4.5 cm high, on dead gorgonian, richly bearing female gonothecae; S06 (20 m): several stems, up to ca. 7 cm high, richly bearing female gonothecae, epizoic on dead gorgonian (MHNG-INVE-79612); 12.vii.2010, S04 (45 m): two sterile, badly-preserved, 5 cm high stems, with no coenosarc left; 26.iv.2011, S03 (20 m): four stems, 5.5–8.2 cm high, all bearing male gonothecae; S08 (20 m): a small (0.7 cm high), sterile colony epizoic on stem of unidentifiable hydroid.

Remarks. The largest colonies are polysiphonic. Stems are occasionally and rather irregularly branched, with up to 3rd order branching. Cladia exhibit a tendency to a pinnate arrangement (pl. 3C). The present material is mostly fertile and allows both male and female gonothecae to be described. Individual stems are monoecious. In sample S06 from Stn. CMZ, male and female stems co-occur on the same fragment of dead gorgonian, but the latter is heavily overgrown by additional epizoic fauna, making it impossible to ascertain whether the colonies of both sexes arise from the same stolon.

Gonothecae of both sexes are given off from below the first hydrophores, more rarely from the secondary ones. Male gonothecae are club-shaped and borne on short, annular pedicels; they are 1060–1315 µm long and 200–230 µm wide in middle region; lumen of gonotheca is almost completely filled with developing mass of spermatocytes. Female gonothecae are kidney-shaped, 1165–1280 µm long, 410–450 µm wide in middle region, slightly compressed laterally, "dorsal" side broadly rounded, "frontal" side provided with twin hydrothecae in middle region, from which spring two normally-developed hydranths. Below the level of twin hydrothecae, the gonotheca is conical and tapers gradually, ending in a short, annular pedicel; above, the gonotheca is narrower frontally but significantly widens dorsally, as seen in fig. 3C.

Twin hydrothecae face upwards and resemble the number 8 when seen from above; there is no transverse wall separating thecal pairs except for a rather prominent, frontal perisarcal carina, which plunges for some distance into the lumen of gonotheca (fig. 3D). These hydrothecae are 20–25 µm deep and 120–130 µm wide at aperture (measurements taken in lateral view). There are 5– 8 eggs per gonotheca, occurring in a chain following the curve of the gonothecal wall; eggs are spherical and 220–230 µm in diameter. The whole mass of eggs is surrounded by a sac-shaped, thin membrane. This membrane is especially apparent in spent gonothecae, in which the imprint of the chain of eggs is retained. Extremities of this membrane are fixed following a line of desmocytes to the anterior and posterior walls of the bipartite hydrotheca.

Distribution in Chile. Present knowledge indicates that the species is probably endemic to the Northen Patagonian zone, and occurs from the Reloncaví Sound (present study) to Magdalena Island ( Galea et al. 2009).

PLATE 3. A, B: Halecium pallens Jäderholm, 1904 —colonies in situ. C: Halecium fjordlandicum Galea, 2007 —typical shape of a colony. D: Sertularella antarctica Hartlaub, 1901 —four stems showing their characteristic mode of branching. E: Sertularella curvitheca sp. nov. —colony in situ. F: Sertularella ? implexa ( Allman, 1888) —two colonies. Scale bars: 1 cm (C, D, F).