Corymorpha microrhiza ( Hickson & Gravely, 1907 )

Soto, Joan J. & Peña, Álvaro L., 2019, Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica), Zootaxa 4570 (1), pp. 1-78 : 18-19

Corymorpha microrhiza ( Hickson & Gravely, 1907)

( Fig. 5 i–l)

Material examined. ANT XVII/3: 111-9, few polyps, up to 80 mm high, on gravel, with mature gonophores; ANT XXI/2: PS65/253, few polyps, up to 80 mm high, with developing gonophores; PS65/280, few polyps, up to 140 mm high, with mature gonophores.

Remarks. Similarly to Z. parvula , Corymorpha microrhiza was first described as Lampra microrhiza ( Hickson & Gravely, 1907) , and then allocated within Corymorpha by Stepanjants (1972), re-allocated within Lampra by Stepanjants & Svoboda (1999), and in Monocaulus by Svoboda & Stepanjants (2001). However, the species is now considered to belong to Corymorpha ( Vervoort 2009) .

Svoboda & Stepanjants (2001) provided a detailed description of the syntypes and additional material from the Weddell Sea. Specimens examined here concur in every aspect, but for the presence of branched blastostyles, although exclusively observed in large and mature specimens ( Fig. 5j ). The original description by Hickson & Gravely (1907) refers branched blastostyles, but Svoboda & Stepanjants (2001) were not able to determine this character in the type material. This discrepancy could be attributed either to putative sexual dimorphism or to the fact that the material examined by these authors was not completely developed. Cnidome information was not given in previous descriptions. Therefore, until the analysis of the cnidome in the type series, none of the records can be ascribed with confidence to C. microrhiza .

Cnidome consisting of stenoteles [range 11.0–13.0 x 8.0–11.0 µm, mean 11.9±0.8 x 9.9±0.9 µm (n=15)], rounded haplonemes [range 16.0–17.5 x 13.5–14.5 µm, mean 17.0±0.5 x 14.1±0.3 µm (n=15)] and desmonemes [range 7.0–7.5 x 6.5–7.5 µm, mean 7.3±0.3 x 7.1±0.3 µm (n=15)].

Ecology and distribution. Species previously known from 237 to 629 m ( Svoboda & Stepanjants 2001, as Monocaulus microrhiza ); present material collected from 62 to 309 m. Little-recorded species, only known from the Ross Sea ( Hickson & Gravely 1907, as Lampra microrhiza ) and the Weddell Sea ( Svoboda & Stepanjants 2001). Probably circum-Antarctic distribution ( Svoboda & Stepanjants 2001). Present contribution represents the third record of the species.

Figures

FIGURE 5. a–h Zyzzyzus parvula: a–f polyps in different developmental stages; g detail of juvenile polyps in the basal portion of a mature specimen; h blastostyle with developing gonophores. i-l Corymorpha microrhiza: i mature polyp; j blastostyle with gonophores; k–l juvenile polyps.