CLASSIFICATION OF RHIZOSTOMA

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

CLASS :- SCYPHOZOA (Medusa well developed, hydroid reduced.)

ORDER :- RHIZOSTOMAE (Tentacles absent, mouth obliterated.)

GENUS :- Rhizostoma (= Pilema)

GEOGRAPHICAL DISTRIBUTION

  • It is found in shallow waters in tropical and sub-tropical regions, especially Indo-pacific regions, North Carolina and South Wales, U.S.A.

HABIT AND HABITAT

  • Rhizostoma is a marine solitary medusoid Scyphozoa. It is a vigorous swimmer.

RHIZOSTOMA

GENERAL CHARACTERSTICS OF RHIZOSTOMA

  • Body is hemispherical without marginal tentacles and divisible into ex-umbrellar and sub-umbrellar surfaces. 
  • Under sub-umbrellar surface 8 fused oral arms hang down in central position. 
  • Oral arms are folded looking like root in appearance called as scapulets. 
  • Mouth is obliterated by growth of oral arms which are modified as funnel like securing pores called as suctorial mouths.
  • Each oral arm ends in a terminal tentacle. 
  • Stomach is continued into canals, which open by funnel-shaped apertures on the edges of the arms.
  • Young medusa has a single mouth which closes in the adult. 
  • Entire animal has 96% water, but does not contain gelatin or mucilage. Feeds on small fishes.
RHIZOSTOMA

IDENTIFICATION

  • The animal contains fused oral arms and all above characters and hence it is Rhizostoma.
RHIZOSTOMA
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