Agalma okeni   Eschscholtz,  1825 (Hydrozoan)
Organism information awaits expert curation
Class: Hydrozoa

Image copyrights: Casey Dunn

Size: 13 cm long and 2 cm wide at nectosome and Siphosome sub-equal in size.

Pneumatophore: Slender, elongated, with red-brown pigment at tip 8 lamellae stretch from pneumatosaccus to pneumatocodon, with circular constriction at mid-level.

Nectosome: With 14 pairs of mature nectophores biserially and alternately arranged in a large specimen.

Nectophores: 10-12 mm broad, characteristically dorso-ventrally flattened, prismatic, transparent. Lateral facet with one or two vertical ridges. Upper lateral corners prolonged into wings or wedges. Dorso-lateral and ventro-lateral ridges occur at extreme lateral edges of nectophore. Nectosac characteristically 'Y'-shaped, not extending into lateral wings of mature nectophore but do so in immature nectophores. Muscular lamella broad, with short pedicular canal. Dorsal and ventral radial canals short and simple, lateral radial canals long, forming loops at baso-lateral sides of nectophore. Ostium tetragonal in shape, with well developed velum.

Siphosome: Stiff, non-contractile. Number of cormidia 5-15 according to growth stages. Each cormidium with one gastrozooid, 8-12 palpons, their tentacles and bunches of male and female gonodendra. Succession of zooids regular and characteristic. Internode with only bracts.

Gastrozooid with prominent basigaster; its tentacle, thick, long with 12-15 tentilla; each tentillum ending in involucrate, much coiled (6-17 turns) maroon colored cnidoband, tricornuate- median ampulla, spindle - shaped, thick, with vibratile sensory hairs and two long, thin, highly contractile lateral filaments.
Palpons long, about 10-12 mm, spindle shaped, transparent with brown nematocyst patches on surface. Palpacles simple, unbranched, thin, with beaded appearance.

Bracts: Occur in groups of 4 or 5 all budded from ventral side of stem; triangular in shape, transparent, prismatic, with thick, facetted distal ends. All bracts closely applied together to form a carapace around cormidia. Distal end divided into three to five concave facets by 2-3 vertical ridges. Younger bracts with sloping distal edges and thick bracteal canal.

Gonodendra: Male and female gonodendra with short stalk, occurring at bases of palpons, male and female gonodendra arranged in an alternating manner, separated by a group of bracts.

Androphore: 10-12 in number, with thin long pedicels, distinctly medusoid in structure with umbrella, radial canals, and ostium. Manubrium mouthless bearing germ cells.

Gynophore: Many, in various stages of development, smaller than male gonophores with short stalk, medusoids, with single large ovum in each.

Synonym (s)
Agalma okeni Eschscholtz, 1825
Agalma okeni Bigelow, 1911
Agalma okeni Daniel, 1974

Common Name (s)
Economic Importance and Threats

Habitat:  Pelagic, Coastal


• Bay of Bengal (Lat: 15) (Long: 90) INDIA
• Andaman and Nicobar Islands (Lat: 10) (Long: 93) INDIA
• West Coast INDIA (Record: 1962-1965)
• Bay of Bengal (Record: 1962-1965)
• Arabian Sea (Record: 1962-1965)
• Tamil Nadu, Chennai Coast INDIA
• East Coast INDIA (Record: 1962-1965)
• West Coast (Lat: 8.63) (Long: 76.21) INDIA (Record: 01/1962-12/1963)
• West Coast (Lat: 8.25) (Long: 73.06) INDIA (Record: 01/1962-12/1963)
• West Coast (Lat: 11.46) (Long: 74.81) INDIA (Record: 01/1962-12/1963)
• West Coast (Lat: 11.15) (Long: 75.05) INDIA (Record: 01/1962-12/1963)
• West Coast (Lat: 11) (Long: 75.2) INDIA (Record: 01/1962-12/1963)
• West Coast (Lat: 11.16) (Long: 75.45) INDIA (Record: 01/1962-12/1963)
• West Coast (Lat: 10.58) (Long: 75.41) INDIA (Record: 01/1962-12/1963)
• West Coast (Lat: 14.68) (Long: 73.53) INDIA (Record: 01/1962-12/1963)
• West Coast (Lat: 17.38) (Long: 71.81) INDIA (Record: 01/1962-12/1963)
• West Coast (Lat: 17.36) (Long: 72.33) INDIA (Record: 01/1962-12/1963)
• West Coast (Lat: 18.05) (Long: 72.1) INDIA (Record: 01/1962-12/1963)
• West Coast (Lat: 18.05) (Long: 70.81) INDIA (Record: 01/1962-12/1963)
• West Coast (Lat: 18.5) (Long: 70) INDIA (Record: 01/1962-12/1963)
• West Coast (Lat: 16.16) (Long: 72.75) INDIA (Record: 01/1962-12/1963)
• West Coast INDIA
• Lakshadweep Sea INDIA

Literature Source(s)
  • Daniel, R (1985) Fauna of India and the adjacent countries (Coelenterata: Hydrozoa: Siphonophora) ZSI 440 pp Available at - NIO, Goa
  • Zoological Survey of India (Eds) (1991) Animal resources of India (Protozoa to Mammalia) ZSI 1-694 Available at - NCL, Pune
  • (2001) Invertebrate zoology collections Available at -
  • Hussain, SM Brief report on biodiversity in the coastal areas of Pakistan p 113
  • Daniel, R and Daniel, A (1969) Siphonophora collected during the 35th cruise of the R. V. VITYAZ in the eastern part of the Indian Ocean Symposium on Indian Ocean, Part II 571-574 Available at - Library, CAS, Parangipettai
  • Society for the Management of European Biodiversity Data (2009) World Register of Marine Species (WoRMS) Available at -
  • Sealifebase Available at -
  • Casey Dunn Siphonophores Available at -
  • Dr. Ramesh, R; Dr. Nammalwar, P and Dr. Gowri, VS (2008) Database on coastal information of Tamil Nadu Report Submitted to Environmental Information System (ENVIS) Centre, Department of Environment, Government of Tamil Nadu Institute for Ocean Management, Anna University, Chennai, Tamil Nadu. Available at -
  • Rengarajan, K (1973) Siphonophores obtained during the cruises of R. V. Varuna from the west coast of India and the Laccadive Sea Journal of the Marine Biological Association of India The Marine Biological Association of India, Cochin, India 15(1) 125-129 Available at -
  • Daniel, R and Daniel, A (1963) On the siphonophores of the Bay of Bengal I.Madras coast2( Journal of the Marine Biological Association of India The marine biological association of India 5(2) 185-220 Available at - NIO, Goa
  • Rengarajan, K (1975) Distribution of siphonophores along the west coast of India and the Laccadive sea Journal of the marine biological association of India The marine biological association of India 17(1) 56-72 Available at - NIO, Goa

Page last updated on:2011-06-06

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