Halecium

? Halecium reflexum — Vervoort, 1968: 9, fig. 1.

Description. Colonies dwarf, stolonal, with primary hydrophores arising at more or less regular intervals from creeping hydrorhiza. Hydrophores of variable length, with conspicuous bulge basally above insertion on stolon; lateral walls smooth, gradually diverging from base towards distal end. Perisarc transparent. Hydrotheca shallow to moderately deep, margin widely flaring; a ring of desmocytes above diaphragm. Some primary hydrophores with one lateral branch, arising just below primary hydrotheca. Hydrothecae generally renovated several times; secondary hydrophores with or without basal bulge, the following ones gradually shorter and with nearly parallel sides. Hydranths large, with 18 – 21 tentacles; zooxanthellae absent from coenosarc. Gonothecae not seen. Nematocysts (undischarged capsules): microbasic euryteles (8.6 – 9.0) × (3.7 – 4.0) µm; microbasic mastigophores (5.4 – 5.8) × (1.4 – 1.6) µm.

Remarks. The Caribbean material assigned to H. reflexum Stechow, 1919 by Vervoort (1968) appears very similar to ours, in the following respects: the colonies are generally stolonal, with occasional small, sparingly branched stems; the primary hydrophores are provided basally with “ a few undulations of the periderm ”; the hydrothecae have widely flaring margins. Halecium reflexum has so far been recorded from the Mediterranean only, and differs morphologically from the Caribbean material in the structure of the stem, which is composed of an alternation of hydrothecate and ahydrothecate segments, both with bulges at their ends. Additionally, the perisarc is undulated nearly throughout.

Distribution. Known only from the Caribbean: St. Thomas (Vervoort 1968), Guadeloupe (present study).

Material examined. Stn. 2: 22.01.2008 — several hydrothecae, but no gonothecae, on algae; 26.01.2008 – a few hydrothecae, but no gonothecae, on rock.