Solmundella bitentaculata

Solmundella bitentaculata (Quoy & Gaimard, 1833)

Fig. 57 A-C

Carybdea bitentaculata Quoy & Gaimard, 1833: 295, pl. 25 figs 4-5.

Campanella capitulum Quoy & Gaimard in de Blainville, 1834: 286. – Agassiz, 1865: 169.

Aeginopsis mediterranea Müller, 1851: 277, pl. 11, Mediterranean.

Aeginella dissonema Haeckel, 1879: 340, pl. 20 fig. 16, Canary Islands. – Kramp, 1955b: 308, synonym.

Solmundella muelleri Haeckel, 1879: 352, Canary Islands. – Kramp, 1955b: 308, synonym.

Solmundella henseni Maas, 1893: 55, pl. 5 fig. 11, Florida Current.

Aeginella bitentaculata. – Haeckel, 1879: 341.

Solmundella bitentaculata. – Bigelow, 1909: 77, pl. 2 fig. 3. – Mayer, 1910: 455, fig. 301, record Florida. – Vanhöffen, 1912: 392. – Vanhöffen, 1913a: 428, record Florida. – Kramp, 1959a: 195, fig. 297. – Kramp, 1961: 270. – Rajan, 1963: 314, figs 1-5, larval stages. – Kramp, 1968: 124, fig. 338. – Goy, 1979: 285, fig. 26. – Segura- Puertas, 1984: 44, pl. 13 fig. 3. – Bouillon, 1987: 239, fig. 5, pl. 1 figs 1-5, development. – Pagès et al., 1992: 38, fig. 43. – Buecher et al., 2005: 30. – Galea, 2007: 96, pl. 2O. – Wang et al., 2014: 98, fig. 3

Solmundella bitentaculata var. mediterranea. – Mayer, 1910: 456, fig. 302, pl. 54 figs 1-3, pl. 55 fig. 4. – Neppi & Stiasny, 1913: 60.

Solmundella mediterranea. – Vanhöffen, 1912: 393, status. – Browne, 1916: 201. – Thiel, 1936: 68, synonym.

Examined material: BFLA4119; 1 specimen; 04-JUN- 2019; size 4 mm; preserved in alcohol for DNA extraction; 16S sequence MW528677. – BFLA4422; 1 specimen; 28-MAY-2020; size 2 mm; preserved in alcohol for DNA extraction but specimen was lost. – 24-SEP-2018; 1 specimen; photographed, not collected. MHNG-INVE-31746; Mediterranean, Bay of Villefranche-sur-Mer; 43.6860°N 7.3170°E; 0-70 m depth; collection date 03-MAY-2001; 2 mature males, 4 mm diameter; part preserved in formalin, part in ethanol in alcohol for DNA extraction; 16S sequence KX355407. – 28-APR-2014; locality as previous sample; 1 specimen, 3 mm diameter, with gonads; preserved in alcohol for DNA extraction; 16S sequence MG811640.

Description: Florida specimens with bell size up to 4 mm, as wide as high, umbrella circumference round (not oval, Fig. 57C), apical jelly thick resembling an apical process (Fig. 57B), evenly rounded and not keeled or oval in transverse section. Stomach wide, up to 7/10 of bell diameter, lenticular, without distinct gastric jelly cone; eight rectangular stomach pouches, no peripheral canal visible. Two opposite tentacles, these thick and long (~ 18 mm), tapering, originating in middle of bell, held variably upward or downward, held upwards in furrow of exumbrella that reaches almost to top of umbrella, below tentacles also a furrow with peronium, intertentacular peronium indistinct. Bases (roots) of tentacles in mesoglea, tapering, curved towards oral. 14 or more statocysts. Mouth region green, tentacles sometimes with broad yellow regions.

16S Data: See Table 1 and Fig. 48. The available 16S sequences appear polyphyletic, notably the one from an Antarctic medusa is clearly not related to the other ones which all form a well supported clade, but with deep subdivisions.

Distribution: Widely distributed in all oceans, including the Mediterranean, but rare in the northern parts of the Atlantic and Pacific Oceans; circumpolar in Antarctic seas; from surface to fairly deep water (Kramp, 1959a). This species is one of the most widespread of planktonic animals and is found at nearly all latitudes (Larson & Harbison, 1990). Type locality: Pacific Ocean, Banda Sea, Bay of Ambon (Moluccas, Indonesia).

Remarks: The taxonomic history of Solmundella bitentaculata is marked by the question whether S. mediterranea is distinct from it or conspecific. Summarizing Mayer (1910) and Browne (1916), the two differ by the following traits [in square brackets traits observed in the present study]:

- size when fully mature (12-15 mm versus 4-6 mm) [4 mm]

- shape (bell outline, diameter in tentacular axis larger than in intertentacular axis, bell apex keel-shaped versus circular bell and apex rounded)[round]

- tentacle length (up to 100 mm versus 10-18 mm) [18] - peronial furrows (perradial ones deep versus all shallow)[shallow]

- statocysts in fully grown animals (16 versus 8) [14] Mayer (1910) and Browne (1916) thought that the two names refer to simple variants or growth stages. Thiel (1936) and Kramp (1955b; 1961) listed them as synonyms, this being accepted by subsequent authors. Our Florida specimens matched mostly the S. mediterranea morphotype, except for the statocyst number.

Another geographic variation was reported by Vanhöffen (1912) and Browne (1916) for Antarctic populations: they have clusters of nematocysts on the ex-umbrella, especially near the margin.

The maximum likelihood tree (Fig. 48) shows that one sequence (EU293998, from Antarctica according to voucher specimen data) is far apart from the other Solmundella which cluster in a monophyletic clade. However, there are possibly some problems with the identification of this specimen as it has almost the same sequence as an Aegina citrea of unknown origin (KY007598). The 16S of the Pacific, Mediterranean, and Gulf stream samples formed a well supported clade. The divergences within this clade are high (Table 1) and the three subclades could represent three species. A reconsideration of the morphological differences and the different nominal species in the synonymy listed above is thus warranted. Unfortunately, no morphological data are available for the Pacific specimens used to get the 16S sequences.