Eumedusa sp.

Zhenzu Xu, Jiaqi Huang, Mao Lin, Donghui Guo & Chunguang Wang, 2016, Taxonomic notes on Hydroidomedusae (Cnidaria) from South China Sea II: Family Bythotiaridae (Anthomedusae), Zoological Systematics 41 (2), pp. 149-157 : 152-153

Eumedusa sp.

( Figs 7 , 10 )

Material examined. One specimen (TIO 014), southern South China Sea, Station NNXW 12014 S01-14 (11°57’N, 110°16’E), 21 September 2012, sampling depth 2 284– 200 m, coll. Xiang Peng.

Description. Umbrella 5.5 mm in height, 7.5 mm in width, wider than the height, bell almost hemispherical, jelly thick, slightly thicker at apex; upper portion of manubrium broad, extended on 4 unbranched radial canals forming a cross as seen from above, manubrium short, about 1/4 of the height of bell cavity; mouth simple, quadrate shaped, with 4 small perradial lips; with 4 interradial and 8 adradial centripetal canals arising from circular canal, and all interradial and most of the adradial centripetal canals, joining base of manubrium, but some short and diverticular; with 4 perradial, 4 interradial, and 8 adradial tentacles, with perradial and interradial tentacles are all fully developed, but all adradial tentacles very short and developing; all tentacles without base swelling, but their basal part adnate to exumbrella, each tentacular base with red pigment spot; all full-length tentacles end in a terminal swelling and thus forming long club-shaped, with a distal concentration of nematocysts; tentacles shorter than full-length ones without distal swelling; without ocelli; gonads slightly folded and developing, on perradial region of the manubrium, and extended base of perradial radial canals.

Remarks. The medusa is placed under the genus Eumedusa because of following: 4 unbranched radial canals and 4 interradial and 8 adradial centripetal canals, tentacles of two kinds, large hollow ones with terminal knob, small ones without terminal knob, tentacle without base swelling; no ocelli.

Only one species, E. birulai (Linko, 1913) , is reported under the genus Eumedusa ( Bouillon et al., 2006) . The unnamed medusa is similar to E. birulai (Linko, 1913) , but it can be separated from the latter by: 1) medusa with 8 adradial centripetal canals, and most of adradial centripetal canals joining the base of manubrium; 2) with 8 fully developed tentacles with terminal knob of nematocysts and 8 short adradial tentacles without terminal konb; 3) all tentacular base with red pigment spot.

Although non-mature gonad was found in the preserved samples, the medusa from south of China Sea is a probably new species. As only one immature animal was found and the adult morphology of gonad in Eumedusa is irregularly folded, it seems advisable to defer creation of a new species name until the life cycle is known.

This genus is recorded from Chinese waters for the first time.

Figures

Figures 7 – 9. Bythotiaridae spp., side view. 7. Eumedusa sp. 8. Protiaropsis pedunculata Xu, Huang & Guo, sp. nov. 9. P. tetranema Xu, Huang & Wang, sp. nov. Scale bars: 7 = 1.0 mm; 8 – 9 = 0.5 mm.

Figures 10 – 13. Bythotiaridae spp. 10. Eumedusa sp., side view. 11 – 12. Protiaropsis pedunculata Xu, Huang & Guo, sp. nov. 11. Side view. 12. Gonads, apical view. 13. P. tetranema Xu, Huang & Wang, sp. nov., side view. Scale bars: 10 = 1.0 mm; 11 – 13 = 0.5 mm.