Eumedusa sp.
Creators: name: Zhenzu Xu
name: Jiaqi Huang
name: Mao Lin
name: Donghui Guo
name: Chunguang Wang
Publisher: name: Zenodo
Year: 2016
Subjects: Biodiversity
Taxonomy
Animalia
Cnidaria
Hydrozoa
Anthoathecata
Bythotiaridae
Eumedusa
Eumedusa sp.

description: 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.
description: Published as part of Zhenzu Xu, Jiaqi Huang, Mao Lin, Donghui Guo & Chunguang Wang, 2016, Taxonomic notes on Hydroidomedusae (Cnidaria) from South China Sea II: Family Bythotiaridae (Anthomedusae), pp. 149-157 in Zoological Systematics 41 (2) on pages 152-153, DOI: 10.11865/zs.2016013, http://zenodo.org/record/270289