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