Sertularia tongensis Stechow 1919

Sertularia tongensis (Stechow, 1919)

(fig. 5H–M, table 2)

Sertularella tongensis Stechow, 1919: 89, fig. F1, G1.― Vervoort & Vasseur, 1977: 52, fig. 23. not Sertularia tongensis Stechow, 1919: 101, fig. N1 (= Sertularia ephemera nom. nov.). Sertularia thecocarpa Jarvis, 1922: 341, pl. 24 fig. 10, syn. nov. ― Millard & Bouillon, 1973: 71, fig. 9C–D.― Morri et

al., 2009: 54, figs 2E–F, 4 A–D.

Sertularella minuscula Billard, 1924: 648, fig. 2F, syn. nov. ― Billard, 1925: 139, fig. 9.― Leloup, 1932: 161, figs 26, 27.― Leloup, 1935: 45.― Fraser, 1944: 266, pl. 57 fig. 254.― Pennycuik, 1959: 195, pl. 6 fig. 2.―Van Gemerden- Hoogeveen, 1965: 34, figs 8–12.―Hirohito, 1974: 18, fig. 7.― Cooke, 1975: 98.― Gibbons & Ryland, 1989: 417, fig. 33.― Watson, 2002: 343, fig. 3.

Sertularella parvula Mammen, 1965: 37, fig. 69, syn. nov. (not Calamphora parvula Allman, 1888).

Sertularia stechowi Hirohito, 1995: 215, figs 72D–F, 73A–C, pl. 12 fig. C, syn. nov.

Sertularella cumberlandica ― Stechow, 1913: 140, fig. 115 [not Sertularella (= Symplectoscyphus) cumberlandica Jäderholm, 1905].

Symplectoscyphus cumberlandicus ― Yamada, 1959: 60 [not Symplectoscyphus cumberlandicus (Jäderholm, 1905)].

Material examined. Stn.9: 21.11.2009, 21 m—several sterile stems to 7 mm high, on concretions and stem of Eudendrium sp. (MNHN-IK.2009-818). Stn.10: 19.11.2009, 17 m—several stems to 7 mm high, of which one bears a gonotheca and another two side branches, on sponge; 0 2.12.2009, 15–20 m—several sterile stems, to 9 mm high, on sponge and Dictyota sp. (MHNG-INVE-68724) Stn.12: 30.11.2009, 12–15 m—several sterile stems, to 6 mm high, on sponge and worm tube.

contiuned.

Remarks. This remarkable hydroid is characterized by: 1) its alternate hydrothecae (fig. 5H), instead of (sub)opposite as in the majority of species assigned to Sertularia Linnaeus, 1758; 2) a hydrothecal aperture closed by two peculiar opercular flaps, both pleated along a median line, giving the impression of a fourflapped operculum when the hydrotheca is seen apically (fig. 5K); 3) its gonothecae (fig. 5L) and, when present, side branches (fig. 5I) arising from within the stem hydrothecae.

In spite of its peculiar morphology, four additional nominal species from the Indo-Pacific have been erected for the present hydroid, viz. Sertularia thecocarpa Jarvis, 1922, Sertularella minuscula Billard, 1924, Sertularella parvula Mammen, 1965, and Sertularia stechowi Hirohito, 1995. All the available descriptions and illustrations referring to them leave no doubt about their conspecificity with Stechow’s (1919) species. Comparison of measurements from various sources (table 2) show that all fall into a common range of variation. The length of both abcauline and free adcauline sides of the hydrotheca appears highly variable and is in relation to whether the renovations (sometimes numerous, though often inconspicuous) have been included when measuring the size of the thecae. The differences in the size of the gonotheca may be due to different stages of maturation and/or to possible sexual dimorphism, though their shape is substantially the same in all the available accounts.

Two types of nematocysts occur in the present material (undischarged capsules): microbasic mastigophores (6.1–6.4 × 1.8–2.0 µm), and larger, unidentified capsules (10.8–11.4 × 3.1–3.3 µm).

Since Sertularella tongenis Stechow, 1919 clearly belongs to Sertularia Linnaeus, 1758 (see SEM images in Morri et al. 2009), it appears that this species and Sertularia tongensis Stechow, 1919 become secondary homonyms. As Sertularella tongensis was described on p. 89, and Sertularia tongensis on p. 101 of the same publication (Stechow 1919), I consider the former specific name as the senior homonym (ICZN Art. 24.2, Principle of the First Reviser), and I propose the new name Sertularia ephemera nom. nov. for the latter (ICZN Art. 60). Better knowledge of the taxonomical status of Sertularia ephemera is actually needed, especially with respect to its relationship with S. maldivensis (Borradaile, 1905).

Caribbean records. Bonaire (Leloup 1935, Van Gemerden-Hogeveen 1965), Farallón Centinela (Venezuela) (Van Gemerden-Hoogeveen 1965).

World distribution. Kingdom of Tonga (Stechow 1919), Chagos Archipelago (Jarvis 1922), Indonesia (Billard 1924, 1925), Gulf of Manaar (Leloup 1932), Queensland (Australia) (Pennycuik 1959, Watson 2002), southern India (Mammen 1965), Seychelles (Millard & Bouillon 1973), Bonin Islands (Hirohito 1974), Marshall Islands (Cooke 1975), Moorea (Vervoort & Vasseur 1977), Fiji (Gibbons & Ryland 1989), Japan (Stechow 1913, Yamada 1959, Hirohito 1995), Levant Sea (Morri et al. 2009).