Obelia

Nagata, Renato Mitsuo, Júnior, Miodeli Nogueira & Haddad, Maria Angélica, 2014, Faunistic survey of Hydromedusae (Cnidaria, Medusozoa) from the coast of Paraná State, Southern Brazil, Zootaxa 3768 (3), pp. 291-326 : 309

Obelia spp.

( Fig. 23 )

References consulted. Russell 1953: 297–303, figs 182–184. Vannucci 1955: 55–60, figs 1–2. Kramp 1961: 162– 164. Cornelius 1990: 543–546. Bouillon 1999: 430–431, fig. 3.129. Tronolone 2001: 96–98, fig. 23. Bouillon et al. 2004: 199, fig. 114 A. Tronolone 2007: 59–60, fig. 2.24.

Material. Municipality of Pontal do Paraná, Balneário de Praia de Leste (25º42’65”S – 48º27’85”W): 01/12/ 1997 — 5 specimens; 20/02/1998 — 1 specimen; (25º48’10”S – 48º04’90”W): 16/07/1998 — 32 specimens; (25º42’65”S – 48º27’85”W): 20/08/1998 — 3 specimens; (25º44’15”S – 48º21’60”W): 20/08/1998 — 6 specimens; (25º48’10”S – 48º04’90”W): 20/08/1998 — 1 specimen; (25º46’32”S – 48º12’15”W): 02/10/1998 — 1 specimen.

Reference specimens deposited. Dzoo-Cn 254, 4 specimens.

World distribution. Occurs in coastal regions worldwide (Bouillon et al. 2004).

Distribution in Brazil. From the state of Rio de Janeiro (Navas-Pereira 1980) to Rio Grande do Sul (Navas- Pereira 1981).

Description. Umbrella flat, 0.5–1.6 mm in diameter. Mesoglea thin, without velum. 4 narrow radial canals, circular canal. About 8 statocysts. 26–88 marginal tentacles solid, non-extensible, short (somewhat longer than half the subumbrellar radius), and with a short endoderm extension to the mesoglea. Tiny individuals, about 0.5 mm in diameter, with 24–32 tentacles. Manubrium short, with square base and 4 simple lips. Gonads spherical to ovoid, hanging on the distal part of the radial canal.

Systematic remarks. Obelia medusae are much modified from the basic morphology of a hydromedusa of other genera of Campanulariidae . Easily recognized by the umbrellar shape, typically flatter and without subumbrellar cavity; absence of the velum; and solid marginal tentacles. Obelia m edusae do not have morphological characters for specific identification ( Russell 1953; Bouillon et al. 2004). Between 1830 and 1948, 70 nominal species of Obelia were described ( Cornelius 1975), which were classified into five valid species ( Cornelius 1990). Three of these forms are known in Brazil: Obelia bidentata Clarke , Obelia dichotoma (Linnaeus) , and Obelia geniculata (Linnaeus) (Migotto et al. 2002) .

Biological data. Boero et al. (2007) demonstrated its ability to feed on bacterioplankton, rather than the mesozooplankton, which is the more common food of the planktonic cnidarians.

Figures

FIGURE 19 – 26. Eucheilota paradoxica Mayer: lateral view, radial canal with medusa bud (19); Clytia sp. Lamouroux: adult medusae with the base of the manubrium stretched, possible a sampling damage (20); adult medusae in oral view, linear gonads along radial canals (21), and a detail of the stretching of the base of manubrium (22); Obelia sp. Péron & Lesueur: oral view, specimen with 5 radial canals (23); Gossea brachymera Bigelow: adult medusae (24) detail of gonads (25), and marginal tentacles (26).