Aglaura hemistoma Péron & Lesueur, 1810

Fig. 58 A-D

Aglaura hemistoma Péron & Lesueur, 1810: 351. – Haeckel, 1879: 275, pl. 16 figs 3-4. – Vanhöffen, 1902: 78, synonymy. – Bigelow, 1909: 119, pl. 2 fig. 6, synonymy. – Mayer, 1910: 398, fig. 254, pl. 46 figs 4-5, pl. 49 figs 3-7, pl. 50 fig. 11. – Kramp, 1959a: 192, fig. 291 – Kramp, 1961: 251. – Kramp, 1965: 127, distribution. – Kramp, 1968: 122, fig. 331. – Bouillon, 1978a: 162, cnidome. – Fagetti, 1973: 41, pl. 4 fig. 13. – Goy, 1979: 284, fig. 25. – Pagès et al., 1992: 44, fig. 53. – Bouillon et al., 2004: 241, fig. 152G. – Nagata et al., 2014: 316, figs 36-37.

Lessonia radiata Eydoux & Soulyet, 1852: 643, pl. 2 fig. 16, Pacific Ocean.

Aglaura Peronii Leuckart, 1856: 10, pl. 1 fig. 5, Mediterranean. ‒ Haeckel, 1879: 275, synonym.

Aglantha globuligera Haeckel, 1879: 272, pl. 16 fig. 8, Canary Islands. ‒ Kramp, 1959a: 192, synonym.

Aglaura nausicaa Haeckel, 1879: 274, pl. 16 fig. 1, Mediterranean.

Aglaura laterna Haeckel, 1879: 274, pl. 16 fig. 2, Canary Islands.

Stauraglaura tetragonima Haeckel, 1879: 277, pl. 16 figs 10- 11, coast of Australia. – Kramp, 1961: 264, probably A. hemistoma.

Aglaura prismatica Maas, 1897: 24, pl. 2 figs 4-5, Gulf of Panama, Pacific Ocean. – Maas, 1906 a: 97, pl. 3 fig. 12.

Aglantha octogona Bigelow, 1904: 257, pl. 7 fig. 9, Maldives.

Aglaura ciliata Perkins, 1906: 118, Tortugas.

Examined material: BFLA3808; 4 specimens observed, one collected; 19-OCT-2018; size 2 mm; preserved in alcohol for DNA extraction; 16S sequence MW528640. – BFLA4214; 1 specimen; 27-AUG-2019; 2 mm; parts preserved in formalin (UF-013830) and in alcohol for DNA extraction; 16S sequence MW528686. – 20-AUG-2019; 1 specimen photographed; size 3 mm; not collected.

MHNG-INVE-0031745; Mediterranean, Bay of Villefranche-sur-Mer, 43.6860°N 7.3170°E, depth 0-70 m; collection date 03-MAY-2001; numerous specimens collected, some preserved in formalin, one used for DNA extraction, 16S sequence KP776748.

Observations: Specimens from Florida with bell size of 2 mm, cylindrical shape, aboral side with funnellike depression (Fig. 58C), wall very thin, velum broad, with slender gastric peduncle of 2/3 of subumbrellar height (Fig. 58D). Manubrium protruding through velar opening (Fig. 58 A-D), bipartite, upper part saclike, lower half with cruciform cross-section, ending in four-lipped mouth (Fig. 58B), margins smooth, not crenulated. Gonads eight sausage-shaped apendices in a whorl attached at junction of manubrium to peduncle (Fig. 58 A-C). Eight radial canals, thin and very transparent. Seven or eight statocysts (Fig. 58B) on bell margin and about 70 thin tentacles. Mostly colourless, but interference effects often cause iridescence in rainbow colours (Fig. 58A, D).

16S Data: The two haplotypes of this study differed in 0.9% of the base pairs, while the minimal differences to other population were 2 to 5 % (Table 1). In a maximum likelihood tree (not shown) obtained by comparing it to the Trachymedusa 16S dataset of Bentlage et al. (2018) and additional trachyline sequences from GenBank, all Aglaura hemistoma clustered as a monophyletic group.

Distribution: Widely distributed and common in the warm and temperate parts of the Atlantic-, Indian-, and Pacific Oceans, usually between about 40°N and 40°S including also the Mediterranean, usually in large numbers (Kramp, 1965; Fagetti, 1973; Bouillon, 1978b; Goy, 1979; Navas-Pereira &Vannuci, 1991; Pagès et al., 1992; Nagata et al., 2014). Type locality: Mediterranean Sea, near the town of Nice.

Remarks: Although Aglaura hemistoma has numerous synonyms, it is taxonomically rather unproblematic. Providing a tabular comparison of the nominal Aglaura species, Vanhöffen (1902) concluded that they are mostly developmental stages or variants of A. hemistoma. Moreover, A. hemistoma has a very thin jelly which gets deformed quite drastically when preserved (Bigelow, 1909). Our own observations on material from the Mediterranean showed that the bell actually elongates considerably in formalin. Some authors may have misinterpreted this fixation effect as a diagnostic trait and it explains the number of synonyms. The few available 16S sequences are also relatively similar (Table 1).