Ptychogena lactea A. Agassiz 1865

Ptychogena lactea A. Agassiz, 1865

Fig. 5

Ptychogena lactea A. Agassiz, 1865: 137, figs 220-224. ‒ Mayer, 1910: 215, fig. 109. ‒ Kramp, 1919: 31, pl. 3. ‒ Kramp, 1959a: 137, fig. 157. ‒ Kramp, 1961: 146. – Kramp, 1968: 67, fig. 175. – in part Naumov, 1969: 321, figs 90, not hydroid. – Arai & Brinckmann-Voss, 1980: 83, fig. 46. ‒ Miyake et al., 2004: 40, fig. 5.

Ptychogena pinnulata Haeckel, 1879: 148. ‒ Haeckel, 1882: 7, pl. 2. ‒ Mayer, 1910: 215, synonym. ‒ Kramp, 1955a: 157.

Ptychogena pinnulata var. intermedia Linko, 1905: 217. not Ptychogena lactea. – Calder, 1970: 1512, pl. 3 fig. 1, hy-

droid.

Material examined: MHNG-INVE-82311; 1 subadult specimen, 20 mm diameter, formalin preserved; Canada, British Columbia, Vancouver Island, 49.36667°N 124.08517°W, depth 0-238 m; date collected 15.06.2012; leg. Moria Galbraith.

Diagnosis: Umbrella in mature animals 15-70 mm in diameter, but exceptionally up to 90 mm wide and 30 mm high, bell hemispherical to flatter than a hemisphere (depending on size, state of contraction and health). Jelly thick, apical jelly about one third of bell height. Stomach relatively large, prismatic, attached to sububrella via cross-shaped base, mouth wide, irregular, rim in folds. Four radial canals, relatively thick, in proximal half connected to stomach via a funnel-shaped, laterally compressed, mesentery-like basal outgrowth of the manubrium. On both sides of each radial canal up to 30 relatively thin, transverse lamellar folds, their upper end connected to subumbrella. The lamellar folds also present distal to the perradial basal outgrowths of the manubrium. Gonads covering lamellar folds. Large animals with papillae along edges of lamellar folds and some folds branched. Bell margin with 70-300 (max. 500) tentacles, no marginal warts or rudimentary tentacles. Between pairs of tentacles 1-3 club-shaped cordyli attached to bell margin.

Colour: gonads, radial canals, and tentacles characteristic milk-white (but also with a peachy or greenish tint, Schuchert et al., 2017).

Hydroid unknown (Schuchert et al., 2017).

Distribution: A predominantly Arctic species that penetrates into Boreal zones of the Atlantic and Pacific Oceans. Its southern limits in the Atlantic Ocean are Cape Cod and the Faroe-Shetland Channel, in the Pacific Ocean northern Japan and British Columbia. Often collected at depths of over 250 m but may be found near the surface where the water is very cold (Arai & Brinckmann-Voss, 1980; Fraser, 1974). Type locality: Nahant, Massachusetts Bay, USA, Atlantic Ocean.