Tessiera medusifera : Bouillon 1978

Tessiera medusifera Bouillon, 1978

Tessiera medusifera: Bouillon 1978 a: 272–279, figs 14–16.

Description: Single specimen. Bell-shaped umbrella, slightly taller than broad, with solid apical projection, transparent; 1.3 mm in height. Exumbrella surface smooth, with cnidocysts in short club-like tracks above marginal bulbs. Mesoglea thick at apex, thinning laterally. Velum narrow. Peripheral canal and four narrow radial canals present, latter with smooth margin; with neither centripetal nor apical canals. With two (opposite) perradial marginal tentacles; each arising from very enlarged and pendulous bulb on umbrella margin. Tentaculate bulbs orange, with dense cnidophores on abaxial surface; atentaculate marginal bulbs minute and rudimentary. Tentacles of similar size, long, solid, unbranched but with numerous, regularly spaced abaxial cnidophores. Manubrium flask-shaped with quadrangular base, shorter than bell cavity, not connected to radial canals by mesenteries, pale orange in colour. Mouth simple, circular, may be cylindrical, without lips; without gastric peduncle. Without ocelli at apex of cnidocyst tracks. Gonads interradial, of moderate size; may have an incubation chamber apically (not seen on present specimen); developing medusoids may be present on manubrium.

Material examined: H5046.

Comments: Three species are considered to be valid (Bouillon & Boero 2000 b), all of which appear to be restricted to the Indian Ocean. Although the only other species that has been recovered from the west Indian Ocean is T. milleporoides Bouillon, 1974 from Seychelles (Bouillon 1974), it is not unlikely—given the known distribution of the presently described specimen—that T. australe Bouillon, 1978 might also be found in the region. The species can be separated by the presence/absence of an apical projection to the bell; the colour of the bell, manubrium and the tentaculate bulbs.

Distribution: New Guinea. This is the first record from the west Indian Ocean. Neritic.

Subclass Leptomedusae Haeckel, 1879

Family Aequoreidae Eschscholtz, 1829

Aequorea forskalea Péron & Lesueur, 1810

Medusae aequorea: Forskål 1775: 110.

Aequorea forskalea: Péron & Lesueur 1810: 336; Kramp 1959 a: 167, fig. 270; 1961: 203.

Description: 12 specimens from seven stations. Umbrella as slightly flattened hemisphere, broader than wide, without apical projection; up to 6.4 mm in diameter. Exumbrella surface smooth, without rows of gelatinous papillae. Mesoglea thick, with a lens-like central disk. Velum broad. Peripheral canal and up to 160 radial canals present, latter narrow, with smooth margin and unbranched; without centripetal canals.Up to twice as many perradial tentacles as radial canals; connected to peripheral canal,arising from conspicuous, elongated conical bulbs on umbrella margin. Tentacles of similar size, long, hollow, unbranched, filiform. Few irregularly distributed rudimentary bulbs present at umbrella margin. Marginal bulbs without keel but with an excretory papilla. Lateral and marginal cirri absent. Manubrium up to 1/2 umbrella width, broad and flat, not extending to velum, not connected to radial canals by mesenteries. Mouth simple, circular, with credulated lips; gastric peduncle absent. Statocysts closed; approx. twice as numerous as marginal bulbs. Without ocelli. Gonads extending almost entire length of radial canals; essentially linear, not reaching to peripheral canal.

Material examined: H5048.

Comments: Bouillon and Boero (2000 b) recognise 16 named species of Aequorea.Aside from those described here, four others have been recorded from the Indian Ocean (Kramp 1961): A. australis Uchida, 1947 (from the Indo-West Pacific – Kramp 1965; Bouillon 1978 a), A. macrodactyla (Brandt, 1835) (‘from all parts of the Indian Ocean’ – Kramp 1965; Bouillon 1978 b), A. coerulescens (Brandt, 1938) (off the cost of India – Kramp 1965) and A. parva Browne, 1905 (from the coast of India – Ganapati & Nagabhushanam 1958). Species of Aequorea can be differentiated by examination of the number of radial canals, marginal tentacles, bulbs and statocysts. The overall shape of the umbrella and the thickness of the mesoglea, as well as the structure and distribution of the gonads, and the morphology of the tentacle bulbs can also be used to separate species.

Distribution: Worldwide in tropical and temperate coastal waters (but see Pagès et al. 1992). This species has previously been recorded off Durban and in the Mozambique Channel (Kramp 1965), as well as off the Seychelles (Bouillon 1978 b). Neritic.