CLASSIFICATION OF GONIONEMUS

PHYLUM :- COELENTRATA (Tissue grade, diploblastic and acoelomate. )

CLASS :-  HYDROZOA  (The hydroids and craspedote medusa )

ORDER :-TRACHYLINA (Polypoid generation reduced or absent.)

SUB-ORDER :- TRACHYMEDUSAE (Bell margin smooth gonads in radial canals.)

GENUS :- Gonionemus

GEOGRAPHICAL DISTRIBUTION

  • Cosmopolitan, Vineyard and Long Island Sounds, Pacific coast from Washington to Alaska.

HABIT AND HABITAT

  • It is a marine solitary medusoid form
GONIONEMUS

GENERAL CHARACTERSTICS OF GONIONEMUS

  • Gonionemus is dioecious consisting of trophosome and gonosome forms. 
  • Gonosome is a medusoid hydrozoan jellyfish measuring approximately 2 cm. 
  • Superficially it resembles Obelia medusa, but differs from it in shape of ex-umbrellar surface and number and size of marginal tentacles. 
  • Body consists of ex-umbrellar and sub-umbrellar surfaces. Ex-umbrellar surface has radial canals, mouth, velum, gastro-vascular cavity, hypostome, gonads and ring canal. The marginal tentacles of sub-umbrellar surface are long. 
  • Manubrium is short and has 4 oral lobes. 
  • Marginal tentacles vary from 16 to 80 in number. They are highly contractile and bend at a sharp angle near the tip.
  • During rest, each tentacle is attached to the seaweeds by means of an adhesive disc present at its bend.
  • Polyp stage has medusa bud, mouth and tentacles. Tentacles have adhesive pads and nematocysts welts. 
  • Gonionemus is a favourite hydrozoan to study behaviour. In the presence of food, it becomes more active and displays random searching.
GONIONEMUS

IDENTIFICATION

  • The animal has characteristic shape, number of tentacles in gonosome and all above characters hence it is Gonionemus.
GONIONEMUS
GONIONEMUS
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