Eucodonium bitentaculatum

Mao Lin, Zhenzu Xu, Jiaqi Huang, Donghui Guo & Chunguang Wang, 2016, Taxonomic notes on Hydroidomedusae (Cnidaria) from South China Sea I: Family Eucodoniidae (Anthomedusae), Zoological Systematics 41 (1), pp. 48-53 : 49-50

Eucodonium bitentaculatum Xu, Huang & Guo, sp. nov.

( Figs 1 , 4–6 )

Material examined. Holotype ( TIO 006 ), coastal waters of southern Taiwan, Station 18 (21°56'N, 120°46'E), horizontal towing at depth 5 m to 10 m, 1 May 2008, coll. Meng-Hsien Chen . Paratype ( TIO 007–008 ), same data as holotype.

Diagnosis. Umbrella bell-shaped, without apical projection; manubrium with conical peduncle; oral tube long about the same length of stomach; mouth with 4 inconspicuous perradial lips, each containing a row of nematocysts; medusa buds on interradial region of stomach; two equally developed tentacles with a terminal swelling, which terminates in a thin fibrous appendage, other two opposite perradial rudimentary bulbs no tentacles; without ocelli.

Description. Medusa with bell-shaped, up to 0.5–0.8 mm in height, slight higher or as high as broad; apical jelly slightly thickened; gastric peduncle broad conical, half as long as manubrium, oral tube long, about the same length as that of stomach; manubrium length 2/3 of bell cavity, cylindrical; mouth quadrangular with 4 inconspicuous perradial lips, each containing a row of numerous nematocysts; medusa buds arise from interradial region of stomach; 4 narrow radial canals and circular canal present; 2 equally developed tentacles with a conspicuous terminal swelling terminated in a thin fibrous appendage, with large marginal bulbs containing brown pigment granules, and other 2 opposite rudimentary marginal bulbs without tentacles; no ocelli present; nematocyst not only present in terminal swelling but also along the whole tentacle covered with ring nematocysts; velum middle broad.

Distribution. Northern South China Sea (Southern Taiwan).

Etymology. The specific name is from the Latin bitentaculatum , meaning bi-tentacles, referring to the two opposite large marginal bulbs with solid equally developed tentacles.

Remarks. This new species has following characters which are in common with Eucodonium Hartlaub, 1907 : quadrangular manubrium on conical gastric peduncle; mouth with 4 inconspicuous cnidocyst armed lips; medusa buds on stomach; no ocelli present.

The new species can be distinguished from the Eucodonium browni Hartlaub, 1907 by following: 1) the former has 2 opposite large marginal bulbs with solid equally developed tentacles with a conspicuous terminal swelling, which terminates in a thin fibrous appendage, and other 2 opposite marginal bulbs very rudimentary without tentacles, while the latter has 4 small marginal bulbs with 4 equally developed tentacles with a conspicuous terminal swelling, which terminal without fibrous appendage; 2) the former has 4 inconspicuous perradial lips, each containing a row of numerous nematocysts, while the latter has 4 inconspicuous perradial lips, each containing a group of about 100 nematocysts (see the key of Eucodonium ).

Figures

Figures 1 – 3. Eucodonium spp., lateral view. 1. E. bitentaculatum Xu, Huang & Guo, sp. nov. 2. E. brevistyle Xu, Huang & Lin, sp. nov. 3. E. longitentaculatum Xu, Huang & Wang, sp. nov. Scale bars = 0.5 mm.

Figures 4 – 9. Eucodonium spp. 4 – 6. E. bitentaculatum Xu, Huang & Guo, sp. nov. 7 – 8. E. brevistyle Xu, Huang & Lin, sp. nov. 9. E. longitentaculatum Xu, Huang & Wang, sp. nov. 4, 7, 9. Lateral view. 5, 8. Gonads, dorsal view. 6. Gonads, lateral view. Scale bars = 0.5 mm.