Eirene hexanemalis ( Goette, 1886 )

Peter Schuchert, 2017, Systematic notes on some leptomedusa species with a description of Neotima galeai n. spec. (Hydrozoa, Cnidaria), Revue suisse de Zoologie 124 (2), pp. 351-375 : 359-360

Eirene hexanemalis ( Goette, 1886)

Irenopsis hexanemalis Goette, 1886: 832 . ‒ Browne, 1905b: 142, pl. 1 fig. 4, pl. 3 figs 5-8. ‒ Maas, 1905: 37, pl. 6 figs 38-40. ‒ Mayer, 1910: 310, figs 171, 171a. ‒ Vanhöffen, 1911: 229, fig. 19.

Phortis pellucida forma hexanemalis . ‒ Vanhöffen, 1913: 17.

Phortis pellucida forma pentanemalis Vanhöffen, 1913: 18 .

Eirene hexanemalis . ‒ Kramp, 1936: 248, bibliography, synonymy. ‒ Kramp, 1953: 281, fig. 5, variation, seasonality. – Kramp, 1961: 188. ‒ Kramp, 1965: 77, fig. 5, variation. – Kramp, 1968: 91, fig. 245. – Bouillon, 1983: 421, figs 1-3, life cycle, ecology. – Bouillon, 1984: 39, fig. 6, hydroid, nematocysts.

Eirene octonemalis Guo, Xu, & Huang, 2008 : 61, fig. 1. new

synonym

? Eirene pentanemalis Lin, Xu & Huang, 2013 in: Lin et al.,

2013: 756, figs 1-3.

Material examined: MHNG-INVE-53565; 22 formalin-preserved medusae, fertile males and females; Abu Dhabi, 24.4666°N 54.3272°E, depth 0 m; collection date 20- 26.08.2006; one individual with 12 radial canals; leg. H. Galea.

Diagnosis: Mature medusa 10-18 mm in diameter, bell hemispherical, thick apical jelly, gastric peduncle broad, length variable but usually not reaching beyond velum level. Velum narrow. Manubrium six-rayed in cross-section, perradial corners of the mouth drawn out as lips, mouth margin with many folds. Majority of individuals with six radial canals, in a minority with other numbers varying from 4 to 12. Gonads thin, more or less straight, along radial canal from base of peduncle to circular canal. 40-60 short tentacles on small bulbs, bulbs with adaxial, conical excretory papilla. In-between 2 tentacle bulbs 1-2 rudimentary bulbs (marginal warts) and 2-4 round statocysts with one concretion (occasionally 2-4, Browne, 1905b).

Polyp planktonic, solitary, see Bouillon (1983).

Distribution: Coastal waters from South- and East Africa to Australia, Indonesia, China, and Japan ( Kramp, 1965). Type locality: Zanzibar, East Africa.

Remarks: This is a well-known species, the only new information is the existence of a specimen with 12 radial canals which was mixed with the 22 specimens with 6 radial canals. Until now, the maximal number of canals was 11. The variation in the number of radial canals has been summarized by Kramp (1965) and Bouillon (1983). A minority of individuals of a particular population can have from 4 to 12 tentacles.

It is thus evident that Eirene octonemalis Guo, Xu, & Huang, 2008 must be regarded as not separable from E. hexanemalis . The former species differs from the latter in having 8 radial canals. The only peculiarity of E. octonemalis is that all four known specimens had 8 radial canals. This could, however, be a population specific trait.

Likewise, Eirene pentanemalis Lin, Xu & Huang, 2013 , which is characterised by five radial canals and the purported absence of excretory papillae, could also be a young E. hexanemalis . The species is based on badly mutilated material for which a reliable observation of the excretory papillae appears doubtful.

References: Browne (1905b), Kramp (1936, 1953), Bouillon (1983).