Halecium banzare Watson 2008

Halecium banzare Watson, 2008

(Fig. 3 A–D)

Halecium banzare Watson, 2008: 167 –168, fig. 3A–F.

Halecium pallens—Broch, 1948: 4, 7–8, fig. 1; Peña Cantero, 2004: 769; 2006: 935, fig. 3B; 2008: 455, fig. 1h, i; 2010: 766, fig.4; 2013: 128, fig. 3f; Peña Cantero & Vervoort, 2009: 85, fig. 1g, h.

Halecium pallens — Stepanjants, 1979: 105, pl. 20 fig. 2 (in part).

? Halecium pallens — Galea & Schories, 2012a: 36, pl. 3A, B, fig. 3G–M.

Material examined. Holotype, BANZARE Stn 41, 65°48'S 53°16'E (Enderby Land), 209 m, three microslides: NMV F147450.1, one distal stem fragment, c. 18 mm long; NMV F147450.2, one distal stem fragment, c. 24 mm long; NMV F147450.3, one distal stem fragment, c. 15 mm long. Spanish Antarctic Expedition Bentart 95.- Stn 3BC, one stem, c. 70 mm high; Stn 6A-2, one stem, c. 190 mm high, with female gonothecae; Stn 10A, two stems, up to 90 mm high, with female gonothecae; Stn 22R, one stem, c. 30 mm high, on pebble; Stn 29A, one stem, c. 70 mm high. Spanish Antarctic Expedition Bentart 2006.- Stn Low 46, a large, strongly polysiphonic stem, c. 135 mm high, basibiont of Filellum sp.

Diagnosis. Polysiphonic stems, up to 190 mm high. Branching regular, stem giving rise alternately every third hydrotheca to paired branches forming two distinct, longitudinal series. Branches originating from hydrophore of primary hydrotheca. Hydrothecae alternately arranged in one plane. Hydrotheca at the end of long, free hydrophore close to internode and with thick perisarc development; sometimes with distinct pseudodiaphragm. Hydrothecal diameter barely increasing distally; rim very slightly everted. A single, if any, secondary hydrotheca. Male gonoteca laterally flattened, maximum width by distal third. Female gonotheca Pinna bivalve-shaped, abcauline and adcauline walls of similar length. Aperture extending the entire diameter from the widest part upwards. Cnidome consisting of microbasic mastigophores? and microbasic euryteles?

Description (type material). “Colonies originally 80–140 mm high, the tallest stem arising from a tufted hydrorhiza of thin, tangled, shining stolons. Stem thick, brittle, branched, heavily fascicled; polysiphonic tubes parallel, running almost to top of stem, along primary branches and along some secondary branches. Primary branches long, held out stiffly more or less in plane almost perpendicular to stem, succeeding branches in three or four orders” (Watson, 2008: 167).

Stem and branches divided into internodes by alternately arranged oblique nodes (Fig. 3 A–C). Stem internodes arranged in a straight pattern. Diameter of internodes much larger in stems than in branches (e.g. 240 vs 120 µm). Stems giving rise to paired branches, alternately every third hydrotheca.

Hydrothecae alternately arranged in more or less one plane, placed at the end of long hydrophores; ratio between adcauline length of hydrophore and diameter at diaphragm 1.6–1.7. Hydrothecae surpassing distal node of internode for a considerable distance (Fig. 3 A–C). Hydrophores (Fig. 3 A–C) straight or with a slight basal abcauline convexity (more marked in cauline internodes). Hydrophores with thick perisarc development on both adcauline and abcauline sides, but much more marked on adcauline side (Fig. 3 A–C). Sometimes with a distinct pseudodiaphragm (Fig. 3 A–B), particularly in stem internodes.

Hydrotheca low (Fig. 3 A–C), height sometimes slightly larger at abcauline side. Diameter barely increasing from diaphragm to rim (Fig. 3 A–C), particularly at adcauline side. Rim very slightly everted. Usually a single, if any, secondary hydrotheca (Fig. 3 B–C).

Gonothecae absent in the material examined. “Gonothecae of both sexes inverted conical, compressed, borne prolifically on younger branches, inserted without distinct pedicel in wall of hydrophore or lower down on internode; male gonotheca with a minute apical peak (visible only in side view), female similar in shape to male, gonophore containing large scattered ova; gonophores of both sexes with an apical pad of tissue. No visible aperture in either sex” (Watson 2008: 167).

No nematocysts could be observed.

Measurements (in µm). Hydrothecae: diameter at aperture 135–160, diameter at diaphragm 115–135, height 40–50. Hydrophore: adcauline length 185–220.

Description (Bentart material). Stems up to 190 mm high, strongly polysiphonic over their whole extension. Hydrorhiza filiform, strongly developed. Stems giving rise alternately to paired branches. Branching pattern giving colonies a regular structure: with two distinct series of paired branches, approximately arranged in one plane, in the polysiphonic part. Stem divided into internodes by slight perisarc constrictions.

Hydrothecae alternately arranged in one plane, resting on long hydrophores close to internodes. Hydrotheca extending over next internode for considerable distance.

Primary paired branches originating from hydrophore of stem hydrothecae, each on one side. Main paired branches approximately of same length. However, some much more developed (up to 20 mm long in some cases), becoming polysiphonic to a variable extension and giving rise in turn up to five secondary branches. These unpaired, only one branch arising from hydrothecal hydrophores. Up to third-order branches observed.

Female gonothecae bivalve-shaped (cf. Peña Cantero, 2008: fig. 1i), c. 620 µm high and 450 µm wide in frontal view. Aperture extending the entire diameter in frontal view, from the widest part upwards.

Male gonotheca laterally flattened, c. 1180 µm high and 870 µm wide in frontal view (Fig. 3 D). Maximum width by distal third, decreasing both distally, to form a rounded part, and basally, forming a sort of basal, triangular pedicel.

Measurements (Stn Low 46 - in µm). Cnidome: microbasic euryteles?, with rounded ends [range 7 x 2.5–3.5, mean 7.0±0.0 x 3.0±0.2 (n=10); ratio, range 2.0–2.8, mean 2.4±0.2 (n=10)], and microbasic mastigophores?, with sharp ends [range 6.5–7 x 2 –2.5, mean 6.8±0.2 x 2.3±0.2 (n=3); ratio, range 2.8–3.3, mean 3.0±0.2 (n= 3)].

Remarks. Although the type material examined is in microslides, it is possible to observe clearly a few paired branches, alternate every third hydrotheca (especially visible in 147450.3), feature not noted by Watson (2008).

Halecium banzare is similar to H. pallens (see below for a description of that species and a discussion about their differences and similarities). I believe that all Antarctic material previously assigned to Jäderholm’s species actually belongs to H. banzare.

As indicated above, Stepanjants’ (1979) material of H. pallens cannot be taken into account because she considered H. antarcticum and H. pallens conspecific. Consequently, it is necessary to re-examine her material to determine to which species it belongs.

Ecology and distribution. Halecium banzare has been collected at depths from 200 (Broch 1948) to 603 m (Watson 2008). Epibiotic on ascidians (Peña Cantero 2010) and basibiont for colonies of other hydroids (Peña Cantero 2010).

Halecium banzare has a circum-Antarctic distribution, being known from off Enderby Land and Mawson Coast (Watson 2008), and the Davis and Cosmonauts seas (Stepanjants 1979), in East Antarctica, and off Peter I Island (Broch 1948; Peña Cantero 2010), the South Shetland Islands area (Peña Cantero 2006, 2008) and Low Island (Peña Cantero 2013), in West Antarctica.