Mesonema (Mesonema) macrodactyla Brandt, 1835: 221 . ‒

Brandt, 1838: 359, pl. 4 figs 1-3.

Polycanna purpurostoma Agassiz & Mayer, 1899: 169, pl. 8

figs 26-28.

Aequorea maldivensis Browne, 1905a: 732, pl. 56, figs 4-12.

Mesonema macrodactylum . ‒ Maas, 1905: 40, pl. 8 fig. 52.

Aequorea macrodactylum . ‒ Bigelow, 1909: 174, pl. 36. ‒ Bige-

low, 1928: 313, pl. 43 fig. 7.

Aequorea pensilis .– in part Russell, 1953: 355, fig. 220C-D, 225, pl. 33 figs 1-5 [not Aequorea pensilis (Haeckel, 1879)]

Aequorea macrodactyla . – Kramp, 1959 a: 167, fig. 235. – Kramp, 1961: 207, synonymy. ‒ Kramp, 1965: 87, fig. 8. ‒ Kramp, 1968: 98, fig. 267. – Pagès et al., 1992: 26, fig. 26. – Cornelius, 1995: 208, fig. 48D-E. ‒ Bouillon & Barnett, 1999: 79, fig. 71. ‒ Mizrahi et al., 2015: 59, fig. 1A-D.

? Aequorea macrodactyla . – Nogueira et al., 2016: fig. 1.

Material examined: NIWA 119801; 8 medusae; from sediment trap in 360 m depth deployed north of Hauraki Gulf, New Zealand, - 35.0867°S 174.8833°E, sampling period 28.11. 1996 to 05.02.1997; very well-preserved in formalin, 7-30 mm diameter, gonads developed after reaching bell diameters of 20 mm.

Diagnosis: Umbrella diameter when mature 20-75 mm, central jelly thick, lens-shaped, margin thin; with conical jelly filling stomach (1/2 subumbrella height); velum spanning about 1/5 of umbrellar opening. Stomach about 2/3 as wide as umbrella, funnel-shaped, mouth region much folded, about as many folds as radial canals. 60-100 (max. 150) radial canals; gonads extending along radial canals from close to circular canal to base of the stomach (and conical jelly). Much fewer tentacles than radial canals, only 10-30 marginal tentacles of variable lengths, all with conspicuous bulbs of variable sizes, also many bulbs without tentacles, but many radial (>50%) canals end in no bulbs. Marginal bulbs characteristically broad and with rounded abaxial keel clasping the bell margin, with excretory papilla on subumbrellar side. Statocysts below circular canal, numerous, 1-3 between two radial canals, 2-5 concretions per statocyst. Colours: stomach wall pink, gonads greyish-blue or violet (after Kramp, 1965, 1968; Pagès et al., 1992; own observations).

Polyp stage unknown. Nematocysts see Russell (1939, as A. pensilis).

Distribution: Circumglobal, widely distributed in tropical and temperate regions of the Indo-Pacific, less common in the Atlantic Ocean, perhaps introduced in the Mediterranean (Kramp, 1965; Pages et al., 1992; Mizrahi et al., 2015; Nogueira et al., 2016, the latter with a map and many references of records). Type locality: Equatorial Pacific.

It is rather frequent at depths from the surface to 2000 m, but even sampling with cable lengths of 4000 m yielded specimens (Kramp, 1965).

Remarks: The relatively low tentacle number combined with the diagnostic broad marginal bulbs with an abaxial keel (Fig. 17 C-D) allows a reliable identification of this species, notably to separate it from A. pensilis (Haeckel, 1879) and A. krampi Bouillon, 1984 . Identifying Aequorea species is currently rather difficult (comp. e.g. Arai & Brinckmann-Voss, 1980; Gershwin et al., 2010) and a taxonomic revision based on a worldwide study comparing morphotypes and DNA markers is highly desirable.

Aequorea macrodactyla has been recorded from New Zealand before (Kramp, 1965; Bouillon & Barnett, 1999), but the good preservation of the specimens permitted the illustration of some structural details (Fig. 17 A-D). As in other Aequorea species, the stomach is very wide but relatively shallow and it almost covers the conical jelly that hangs down from the subumbrella like a gastric peduncle.