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)
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.
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.
- The animal contains fused oral arms and all above characters and hence it is Rhizostoma.