nectophore

(from the article `cnidarian`) ...order Siphonophora, free-floating colonial hydrozoans, display an even greater variety of polymorphs. These include gas-filled floats called ...
Found on http://www.britannica.com/eb/a-z/n/21

nectophore

nectophore A swimming bell of a siphonophore (Hydrozoa with hollow floats).
Found on http://www.wordinfo.info/words/index/info/view_unit/1379/
No exact match found