Mitrocomella polydiademata ( Romanes, 1876 )

Peter Schuchert, 2017, Systematic notes on some leptomedusa species with a description of Neotima galeai n. spec. (Hydrozoa, Cnidaria), Revue suisse de Zoologie 124 (2), pp. 351-375 : 364-365

Tiaropsis polydiademata Romanes, 1876a: 274 , nomen nudum.

Tiaropsis polydiademata Romanes, 1876b: 526 . ‒ Romanes,

1877: 194, pl. 15 fig. 3.

Mitrocomella polydiademata . ‒ Kramp, 1932: 346, text-figs 3, 5, 11, 18, 29, 30, 40, pl. 10 figs 3-4. – Russell, 1953: 257, figs 147-149. – Naumov, 1969: 326, fig. 193. – Edwards, 1973b: 601, figs 1-2, life cycle. – Arai & Brinckmann-Voss, 1980: 93, figs 51-52. – Pagès et al., 1992: 32. – Ramil & Vervoort, 1992: 38, fig. 6a-i. – Cornelius, 1995: 143, fig. 32.

? Cuspidella grandis Hincks, 1868: 210 , pl. 40, fig. 4.

Cuspidella polydiademata . ‒ Naumov, 1969: 327, fig. 194.

Mitrocomella fulva Browne, 1904: 17 , pl. 1 fig. 3, pl. 3 figs 1-2. ‒ Kramp, 1932: 344. – Kramp, 1961: 156. ‒ Edwards, 1973b: 601, synonym. – Pagès et al., 1992: 32.

Material examined: 1 specimen; Scotland, Firth of Lorn, Dunstaffnage Bay, 56.455°N 05.434°E, 0 m depth, temperature 8-10°C; collection date 11.05.2004; DNA 1133 ; 16S sequence KY363939 , COI MF000501 ; archived document see Table 1. ‒> 2 specimens; Norway, Fanafjord , 60.24079°N 05.22941°W, 0 m depth; collection date 23.04.2015 ; DNA isolate 1115; 16S sequence KY363949 , COI MF000508 , 18S KY363979 ; archived document see Table 1.

Diagnosis: Umbrella diameter 9-30 mm, mostly around 10-12 mm, umbrella usually hemispherical or slightly higher, apical jelly thickened, no gastric peduncle. Top of subumbrella sometimes rather flat. Velum width about 1/4 of bell radius. Manubrium short, small, cruciform cross-section, base not much larger than oral end, mouth simple, four perradial, slightly recurved lips. Radial canals 4, relatively thick close to manubrium. Gonads elongate in females, covering 2/3 of radial canals, separated from circular canal and manubrium, when fully developed pendant and usually in zig-zag (Fig. 13D). Marginal tentacles typically 28-36 (reportedly up to 64) when mature, with basal bulbs, some bulbs without tentacles, 5-9 cirri between adjacent tentacles, coiling spirally. 16 large statocysts, each with numerous concretions aligned in two curved rows. When irritated, the medusa emits a greenish light.

Polyp stage tiny, of “ Cuspidella ” type, see Cornelius (1995).

Distribution: Northern boreal species, known from North Atlantic and NE Pacific. Type locality: Cromarty Frith, Scotland.

References: Russell (1953), Arai-Brinckmann-Voss, 1980, Cornelius (1995a).

Figures

Fig. 13. Mitrocomella polydiademata, gonads not fully developed, after life combined from several specimens. (A) Lateral view, diameter about 10 mm. (B) Oral view. (C) Enlarged bell rim showing tentacle bulbs, cirri, and one statocyst. (D) Fully developed gonad, oral view.