Modeeria rotunda ( Quoy & Gaimard, 1827 )

Calder, Dale R., 2012, On a collection of hydroids (Cnidaria, Hydrozoa, Hydroidolina) from the west coast of Sweden, with a checklist of species from the region 3171, Zootaxa 3171 (1), pp. 1-77 : 20

Modeeria rotunda ( Quoy & Gaimard, 1827)

Fig. 19

Dianaea rotunda Quoy & Gaimard, 1827: 181 , pl. 6A, figs. 1, 2 [medusa stage].

Calycella fastigiata .— Segerstedt, 1889: 14, 25.

Stegopoma fastigiatum .— Jäderholm, 1909: 78, pl. 8, fig. 1.— Rees & Rowe, 1969: 13.— Jägerskiöld, 1971: 64.

Modeeria rotunda .— Edwards, 1973a: 577, figs. 3a–c.

Type locality. Strait of Gibraltar ( Quoy & Gaimard 1827: 182) .

Museum material. Kosterhavet, 58°53.093’N, 11°05.668’E, 20–30 m, 09.ix.2010, biological dredge, R / V Nereus , two stolonal colonies, one on stem of Tubularia indivisa and another on stem of a campanulariid, without gonophores, ROMIZ B3915.

Remarks. Edwards (1973a) formally linked the hydroid of Stegopoma fastigiatum ( Alder, 1860) and the medusa of Modeeria rotunda ( Quoy & Gaimard, 1827) , based in part on material studied by W.J. Rees from the Kosterfjord, Sweden. An extensive synonymy of the species, now widely known by the senior synonym M. rotunda , was included. Edwards also included observations on distribution and ecology. Additional information has been provided by Cornelius (1995a), among others, and an updated synonymy was given by Vervoort (2006).

The hydroids Modeeria rotunda and Stegopoma plicatile (M. Sars, 1863) were observed together at the same station during this study, raising the possibility that colonies thought to be the former might simply be stolonal colonies of the latter. That likelihood was ruled out because all parts of colonies of M. rotunda were stolonal with long pedicels, while the basal-most segments of hydrocauli of S. plicatile , even in early stages of development, were short and polysiphonic. Rees & Rowe (1969) also found both species at the same station (Säcken Reef) on the same day (23.ix.1964) and on the same substrate ( Tubularia indivisa Linnaeus, 1758 ) in the Kosterfjord, so the two species are known to occur together. Kramp (1935b) distinguished M. rotunda from S. plicatile in being stolonal with long pedicels (at least 1/5 as long as the hydrothecae) instead of erect with short pedicels.

This species is known from the Oslofjord ( Christiansen 1972) and from scattered locations along the west coast of Sweden (see Checklist), but it has yet to be reported from Denmark ( Kramp 1935b).

Reported distribution. West coast of Sweden.—From the border with Norway to middle Kattegat ( Jägerskiöld 1971: 64, as Stegopoma fastigiatum ).

Elsewhere.—North Atlantic from the northern seas of the Russian Federation ( Stepanjants 1989) to the tropics ( Cornelius 1995a) in the east, and from Greenland ( Schuchert 2001a) to south of the Dry Tortugas ( Fraser 1944) in the west. This species has also been reported in the South Atlantic, in the Pacific and Indian oceans, and in Arctic and Antarctic regions ( Ramil & Vervoort 1992).

Figures

FIGURE 19. Modeeria rotunda: part of stolonal colony, with one hydrotheca, ROMIZ B3915. Scale equals 0.5 mm. FIGURE 20. Stegopoma plicatile: part of branch with three hydrothecae, ROMIZ B3913. Scale equals 0.5 mm.