Octophialucium indicum Kramp, 1958

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 : 367-368

Octocanna polynema . – Menon, 1932: 23, pl. 3 fig. 25. [not Octocanna polynema Haeckel, 1879 = species inquirenda] Octophialucium indicum Kramp, 1958: 347 , figs 2a-b. – Kramp, 1961: 184. ‒ Kramp, 1965: 72. – Kramp, 1968: 87, fig. 235. – Bouillon & Barnett, 1999: 90, fig. 89. ‒ Xu et al., 2014: 623, fig. 510A-B.

Octophialucium funerarium . – Wear, 1965: 7, fig. 3E. [not Oc-

tophialucium funerarium ( Quoy & Gaimard, 1827) ]

Material examined: Numerous mature medusae; Greta Point, Evans Bay, Wellington, New Zealand; 41.3055° S 174.8023° E; surface plankton; 15.11.1993 and 02.02.1994; material used in part for the study of Bouillon & Barnett (1999). ‒ MHNG-INVE-29970, 10 medusae ; same locality as previous lot; 26.10.1994; one medusa used to extract DNA sample N 126 ; 16 S AY 787897 , 18 S FJ 550522 , 28 S FJ 550375 ; DNA extract of second medusa (sample DNA 1167) resulted in identical 16 S as AY787897 .

Description of NZ material: Octophialucium medusa with bell diameter up to 15 mm, bell flatter than a hemisphere, bell rim somewhat incurved, lateral walls thin and relatively straight, apical jelly thick (1/2 or more of total height). Velum narrow, about 1/10 of radius. Manubrium short, cross-section an eightpointed star, 8 more or less crenulated lips. Eight radial canals. Gonads short, sausage-shaped, along distal fourth of radial canals but not reaching circular canal. Eight perradial tentacles and 0-8 additional tentacles between perradial tentacles, thus when fully grown usually 16 tentacles in total. Tentacles thin, relatively short. Between each pair of tentacles 3 rudimentary bulbs, small, without tentacle rudiments. All bulbs with very short, conical excretory papilla projecting into subumbrella, difficult to observe. Bulbs without abaxial spurs. Statocysts closed, oval vesicles along circular canal, 32 or more, small, with 2 (occasionally 1 or 3) concretions. Tissues colourless.

Variation: younger stages have only 4 radial canals, the interradial canals develop by outgrowth from the manubrium. Younger stages may have four developing gonads only.

Hydroid unknown.

Distribution: Tropical Indo-West-Pacific from Madagascar to Tahiti and New Zealand ( Kramp, 1965). Type locality: Sittwe (formerly Akyab) Harbour, Burma, surface plankton.

Similar species: The Atlantic Octophialucium medium Kramp, 1955 is very similar, differing only in the more elongated gonads. Another similar species is Octophialucium sinensis Huang, Xu, Guo & Qiu, 2010 , but this species has only 8 tentacles and smaller bulbs with tentacle rudiments. Octophialucium funerarium ( Quoy & Gaimard, 1827) from the NE Atlantic has considerably more tentacles, 64-128.

Remarks: The identification of the present material was largely based on Bouillon & Barnett (1999), who also had part of this material at their disposal. However, there is one marked difference of the New Zealand material to the original description given in Kramp (1958): the excretory papillae are not long and conspicuous, they are rather small and very inconspicuous ( Fig. 16 B-C). Additionally, there are fewer tentacles (max. 16 versus 19-28). While the tentacle number difference is likely not significant for a species level distinction, the different excretory papillae could indicate that we have a distinguishable morphotype and perhaps also a different species or a subspecies.

It is possible that not all known nominal Octophialucium species are really distinct. Little is known about the interpopulation variation in Octophialucium species and only molecular genetic studies can reliably assess the status of the different Octophialucium species (for species see Schuchert, 2017b; Kramp, 1955b; 1961).

Family Aequoreidae Eschscholtz, 1829 Genus Aequorea Péron & Lesueur, 1810

Figures

Fig. 16. Octophialucium indicum, combined from several preserved specimens. (A) Oblique view, diameter 13 - l 5 mm when alive. (B) Schematic side view of perradial tentacle bulb. (C) Adaxial view of tentaculate bulb in optical section. (D) Statocyst with two concretions. Abbreviations: ep ‒ excretory papilla, ex ‒ exumbrella, tb ‒ tentacle bulb, ve ‒ velum.