Athorybia rosacea   Forskal,  1775 (Hydrozoan)
Organism information awaits expert curation
Class: Hydrozoa

Image copyrights: Woods Hole Oceanographic Institution

Size: Upto 14 mm in diameter.

Nectosome: Nectosome and nectophores absent.

Pneumatophore: Large, 4 mm in diameter. Apically pigmented with reddish brown granules, or flecks arranged in radiating clusters. Apical half thin walled, transparent basal half thick, opaque due to presence of opaque gas-secreting giant cells in septa connecting saccus to pneumatophore form irregular or finger like processes clearly seen on surface. Contracted specimen with pneumatophore half covered on one side by enlarged nectostyle or growing point or zone of proliferation for bracts and gastrozooids.
No apical pore; basal pore large. When living speci¬men sinks down, bracts close down and minute air bubbles appear amongst them probably released through this basal opening. Morphologically longitudinal axis tilted to ventral side: two zones of proliferation for bracts and gastrozooids on ventral side. In contracted specimen this zone lies above level of apex of pneumatophore as a hood-like structure; with minute buds (papilla-like) on its surface.

Cormidia: Arranged in linear manner in young colony with 8 gastrozooids; in alternate manner towards left and right side in colony with 10-12 gastrozooids and in radial manner around vesicular siphosome in colony with 16-18 gastrozooids, with bilateral and radial symmetry.

Bracts: In 4 or 5 to 8 or 9 groups (according to growth stages) with 3-4 bracts in each group, in a corona around pneumatophore forming several circlets. Three times as long as broad, with a keel at thick proximal end for attachment to muscular lamella. Distal half thin, dorso-ventrally flattened. Convex dorsal surface with seven inconspicuous longitudinal rows of nematocysts.

Gastrozooids: Borne on stalks, with well developed basigaster, and eight radiating hepatic ridges in stomach region. Tentacle at base bearing two types of tentilla.

Tentacle: 6 cm long, bearing 25-30 tentilla, 1-2 mm apart, and 2-3 mm long. Terminal part of tentacle thick, devoid of tentilla. Cnidoband involucrate, either straight (young) or with 2-2 ½ loosely coiled spiral turns (older). Tricornuate-two long, slender lateral horns and small median ampulla. Dendritic – fewer in number at distal end of tentacle; with many branches. With ‘rosette’ like structure at base and dorsal spur.
Palpon: Many vermiform, transparent, forming a circlet above gastrozooids; bearing nematocysts at pink tips. Palpacles small, inconspicuous. At bases of special 8 or 9 secondary gonopalpons occur gonodendra.
Gonodendra: With thick stalks, 8-9 in number, between two gastrozooids, dividing into two branches, each bearing male and female gonostyles in alternate manner (i.e. 2 male or 2 female gonostyles do not occur side by side).

Male Gonophores: With long pedicles, medusoid; manubrium bearing sperms.

Female Gonophores: With short pedicles, medusoid; single ovum. Two radial canals lying close.

Synonym (s)
Anthophysa rosea Bigelow, 1911
Athorybia rosacea Daniel, 1974
Physophora rosacea Forskal, 1775
Athorybia longifolia Kawamura, 1954
Physophora rosacea Forskal, 1775

Common Name (s)
Economic Importance and Threats

Habitat:  Pelagic


• Bay of Bengal (Lat: 15) (Long: 90) INDIA
• Bay of Bengal (Record: 1962-1965)
• Arabian Sea (Record: 1962-1965)

Literature Source(s)
  • Daniel, R (1985) Fauna of India and the adjacent countries (Coelenterata: Hydrozoa: Siphonophora) ZSI 440 pp Available at - NIO, Goa
  • Society for the Management of European Biodiversity Data (2009) World Register of Marine Species (WoRMS) Available at -
  • Sealifebase Available at -
  • Oceanus Available at -

Page last updated on:2010-06-09

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