Halecium interpolatum Ritchie 1907

Halecium interpolatum Ritchie, 1907

Figure 7A, B

Halecium interpolatum Ritchie, 1907: 526, pl. 1, fig 3, pl. 2, fig. 3.– Rees and Thursfield, 1965: 107, 197.- Smaldon et al, 1976: 17.- Stepanjants, 1979: 103, pl. 16, fig. 7.- Blanco, 1994a:156.- Blanco, 1994b: 186.

Material examined. NMV F147466, Station 88, two microslides displaying small branch fragments; a preserved male colony.

Description. Colonies branched, reaching a height of 30 mm. Hydrorhiza a mass of corrugated tubular stolons. Stems fascicled, lower stem region a loose aggregation of, stolons becoming polysiphonic tubes, passing along lower branches to mid-region of colony; stems thereafter profusely and irregularly branched.

Younger branches monosiphonic, typically a single branch given offfroma geniculationofhydrophore belowa hydrotheca, sometimes a second branch given off on opposite side of hydrophore; branches rugose to deeply corrugated and jointed but lacking true nodes; joints transverse to weakly oblique. Hydrophores variable in length, often corrugated, typically a short more or less smooth segment below hydrotheca.

Hydrotheca deep bowl-shaped, expanding strongly from diaphragm to margin; margin circular, rim strongly outrolled. Diaphragm distinct, some secondary and succeeding hydrophores arising in a linear series from diaphragm of preceding hydrotheca; hydrophores fairly short, typically deeply corrugated.

Hydranths with c. 20 – 24 rather stubby tentacles, not well preserved.

Male gonotheca ovoid to balloon-shaped, flattened, inserted on a very short narrow pedicel in an axil or in a hydrotheca, a minute apical protuberance visible in some gonothecae. Gonophores near maturity, almost filling cavity of gonotheca.

Perisarc of stems and branches very thick, thinner on hydrotheca and gonotheca.

Colour (preserved material), pale honey brown, youngest branches yellowish, gonophores darker brown.

Measurements (μm)

Branch

distance between hydrothecae on 745 – 1470 branch

width of smooth section of branch 134 – 158 Hydrotheca

diameter at diaphragm 134 – 150 diameter at margin 269 – 300 depth, margin to diaphragm 95 – 134 Gonotheca

length, including pedicel 869 – 909 maximum width 474 – 553

Remarks. Ritchie’s material of H. interpolatum was infertile, his description was general and lacked important dimensions. In many respects the present material falls within the range of dimensions of H. ovatum Totton, 1930 and measurements deduced from Ritchie’s description. Although the hydrocauli of the two species are superficially alike, the ovoid to quadrangular gonotheca of H. ovatum is considerably smaller than the lenticular gonotheca of H. interpolatum. Itherefore assign the present material to H. interpolatum.

Distribution. South Orkneys. This is the first record of the species from Antarctica.