Comnu'nsalis))i without Continuous Contact 



379 



host no significant amount of harm. The commensal is still within 

 the cavity of the shell when the oyster is opened in the kitchen, and 

 the crab sometimes startles an uninformed diner by appearing in his 

 oyster stew. (Oyster crabs are perfectly edible and are regarded 

 as a delicacy by some, including many who are not ecologists. ) 



Perhaps the most extraordinary instance of a commensal living 

 within its host is that of the small tropical fish Fierasfer which finds 



Fig. 10.9. Diagrammatic vertical section of a Chaetopterus tube in the mud 

 bottom of the httoral zone, showing the position of the worm and two commensal 

 crabs (Polyonyx). (By permission from Animal Ecology by A. S. Pearse, Copy- 

 right 1939, McGraw-Hill Book Co. ) 



