Clytia gigantea ( Hincks, 1866 )

Peña Cantero, Álvaro L. & Horton, Tammy, 2017, Benthic hydroids (Cnidaria, Hydrozoa) from bathyal and abyssal depths of the Northeast Atlantic held in the modern Discovery Collections, Zootaxa 4347 (1), pp. 1-30 : 13

Clytia gigantea ( Hincks, 1866)

( Fig. 5A–B )

Campanularia gigantea Hincks, 1866: 297 ; 1868: 174, pl. 35 fig. 1; Jäderholm, 1909: 69, pl. 7, figs 1–3; Christiansen, 1972: 293.

Clytia gigantea — Hirohito, 1995: 61 –63, fig. 18a, b; Vervoort & Watson, 2003: 418, 419, fig. 102J; Calder, 2012: 46 –47, figs 46–47.

Material examined. 51103#5, one stem 13 mm high and two extra hydrothecae, no gonothecae.

Description. The 13-mm-high stem is provided with three hydrothecae (two of them broken). The isolated hydrothecae are provided with a very long pedicel. Hydrotheca elongate, roughly cylindrical in distal half, tapering in basal half ( Fig. 5A ). Rim of hydrothecal aperture with eight to 13 cusps, with smoothly curved distal part, curved inwards, and separated by deep, rounded embayments ( Fig. 5B ).

Measurements (in µm). Hydrotheca: height 1100–2000, diameter at aperture 400–840, diameter at diaphragm 100–140, height of basal chamber 40–100.

Remarks. The two isolated hydrothecae are distinctly smaller (1100–1240 high and 400–460 in maximum diameter) than the undamaged one of the branched stem (2000 high and 840 in maximum diameter). Calder (2012) also found hydrothecae exceeding 2000 µm in length in his material and Christiansen (1972) even reaching 3000 µm.

The gonotheca of this species was recently described by Calder (2012).

As indicated by other authors (e.g. Calder 2012) this species is easily recognizable by the large size of the hydrotheca, as well as by the shape of the hydrothecal cusp (linguiform sensu Calder 2012).

According to Calder (2012), reports of this species from the Mediterranean and the Atlantic and Pacific coasts of North America need confirmation. The species has also been reported from Chile ( Leloup 1974; Galea et al. 2009), but Galea & Schories (2012) indicated that Leloup’s record was based on a misidentification and that the attributable record by Galea et al. (2009) was also erroneous.

Ecology and distribution. This species was found at depths between 20 ( Calder 2012) and 512 m ( Vervoort & Watson 2003); the present material comes from 930 to 950 m, extending its lower bathymetric limit.

According to Calder (2012), Clytia gigantea is distributed for the boreal waters of the North Atlantic. However, the species has also been reported from Japanese waters ( Hirohito 1995) and from the Chatham Islands region, in the South Pacific ( Vervoort & Watson 2003). Our material comes from the Porcupine Seabight.

Figures

FIGURE 5. Clytia gigantea (Hincks, 1866): A, hydrotheca; B, detail of distal part of hydrotheca showing aperture with cusps. Zygophylax levinseni (Saemundsson, 1911): C, fragment of branch showing hydrothecal arrangement; D, hydrotheca, pedicel and apophysis; E, origin of branch showing apophysis and perisarc hole left by missing nematotheca; F, nematotheca; G, gonotheca; H, nematocyst (arrow). Scale bars: 200 µm (A, C, G), 100 µm (B, D – F), 10 µm (H).