Glossary | R

Radial symmetry
symmetrical arrangement of an animal's body around a central axis
Radula
tongue-like band of teeth used by many mollusks to scrape, tear or bore
Raft
large number of animals together in the water; usually applied to birds and pinnepeds
Rasp
to scrape or rub as with a file
Red tide
concentrations of certain microscopic organisms, particularly dinoflagellates, that discolor surface waters, usually in coastal regions and reduce oxygen supplies to animals deeper in the water column; some may be toxic
Regeneration
ability of some organisms to renew or replace an injured or lost organ or body part
Regurgitation
casting up of incompletely digested food, usually for the feeding of young
Reptile
vertebrate animal characterized as cold-blooded and having scales
Respiration
breathing; the act of assimilating oxygen and releasing carbon dioxide and other products
Rhizomes
horizontal plants capable of producing the upward shoot and downward root of a new plant
Rhopalia
concentration of neurons and sensory organs around a jelly's bell and between lobes; contains statocysts and ocelli
Rostrum
in fish - forward projection of snout; in cetaceans - upper jaw forming part of snout or beak; in crustaceans - forward pointing spine on the carapace
Rufous
reddish; tinged with red; brownish-red