Gangliostoma abaxialispura Xu, Huang & Guo, 2019

Guo, Donghui, Xu, Zhenzu, Huang, Jiaqi, Wang, Chunguang & Lin, Mao, 2019, Two new hydrozoan species from the Taiwan Strait, China (Cnidaria: Hydrozoa: Leptothecata), Zoological Systematics 44 (3), pp. 185-190 : 187

Gangliostoma abaxialispura Xu, Huang & Guo , sp. nov. ( Figs 1–3 )

Type materials. Holotype ( TIO 032 ), China, south of Taiwan Strait , Station ZD-MJK535 (26°09’N, 120°45’E), depth 67 m, sampling depth 67–0 m, 20 July 2006, coll. Peng Xiang.

Diagnosis. The species is diagnosed by following: umbrella nearly disk shaped, apex jelly very thick; manubrium very broad, with a basal circular row of as many papillae as radial canals; with 8 marginal tentacles, tentacular bulbs with a distinct abaxial spurs upwards over margin of bell; with 6 rudimentary bulbs and 6 statocysts between the tentacles.

Description. Umbrella 5.0 mm in height, 8.0 mm in width, nearly disk shaped, apex jelly very thick, thinning towards margin; with very broad manubrium which devoid of a peduncle, about half as wide as diameter of umbrella, with a basal circular row of as many as papillae as radial canals; without subumbrella gelatinous papillae; with 32 simple radial canals, oral lips short, less numerous than radial canals; gonads extending along whole length of radial canals, but not connected to ring canal; with 8 well-developed hollow marginal tentacles, about 1/4 as many as number of radial canals, tentacular bulbs large, nearly spherical-like with a distinct abaxial spurs upwards over margin of bell; no ocelli; with 6 rudimentary bulbs between tentacles, medium one larger than other two or three; with many statocysts of same number as rudimentary bulbs; velum broad.

Distribution. Taiwan Strait, China.

Etymology. The specific name derived from the Latin abaxialispura , meaning abaxial-spur, in reference to the morphology of tentacular bulbs with an abaxial spur.

Remarks. This new species has following characters which are in common with Gangliostoma Xu, 1983 : medusa with a very broad manubrium, with a basal circular row of papillae of the same number as the radial canals.

Before the work, only two species of Gangliostoma , G. dayaensis and G. guangdongensis , are known ( Xu, 1983; Bouillon et al., 2006; Du et al., 2010; Xu et al., 2014). The new species can be distinguished from other two by following: 1) umbrella with 8 marginal tentacles, about 1/4 as many as the number of radial canals; 2) each tentacular bulbs with a distinct abaxial spurs, without excretory papillae; 3) with 6 rudimentary bulbs and 7 statocysts between the tentacles.

Figures

Figures 1–5. Gangliostoma spp. 1–3. G. abaxialispura Xu, Huang & Guo, sp. nov. 1. Oral view. 2. Lateral view. 3. Part enlargement of marginal tentacles. 4. Part enlargement of the subumbrella of G. dayaensis Xu, Huang & Du, 2010 (after Du et al., 2010). 5. Part enlargement of the subumbrella of G. guangdongensis Xu, 1983 (after Xu, 1983). Abbreviation: p—papilla; g—gonad; t—tentacle. Scale bars=2.0mm.