ON THE HABITS OF THE CRUSTACEANS FOUND IN 



CH^TOPTERUS TUBES AT WOODS HOLE, 



MASSACHUSETTS. 



A. S. PEARSE, 

 ZOOLOGY DEPARTMENT, UNIVERSITY OF WISCONSIN. 



Among the numerous species of crustaceans which live as 

 commensals, three interesting representatives occur in the 

 leathery tubes of the worm Chtztopterus variopedatus Renier et 

 Claparede, at Woods Hole. The tubes of this annelid are 

 U-shaped and taper toward the round opening at either end 

 (Fig. 7). The tips of the tube may be seen protruding above the 

 mud in open shallow water where eel-grass grows. Enders 

 ('05, '09) has published two papers describing the habits of 

 Chatopterus and its commensals as he observed them at Beaufort, 

 North Carolina. Van Beneden ('76, p. 20) also mentions a 

 worm, which is doubtless the same, as associated with .crabs on 

 the coast of Brazil. While occupying a room in the Marine 

 Biological Laboratory during the past summer I was able to 

 verify Ender's work and to add some new observations. My 

 thanks are due to the staff of the laboratory for their courtesy, 

 particularly to Mr. George Gray. 



Enders ('05) took four species of crustaceans (Polyonyx 

 macrocheles (Gibbes), Pinnixa chcetopterana Stimpson, Pin- 

 notheres maculatus Say, Menippe sp.?) from tubes at Beaufort. 

 All of these crustaceans except Menippe were taken at Woods 

 Hole. Usually a male and a female of the same species were 

 found together in each tube, but several solitary individuals were 

 captured, and once two Pinnixce of each sex were found in a 

 single tube. The results of the collections at the two localities 

 are compared in Table I. The table shows that Polyonyx is the 

 most abundant commensal at Beaufort, whereas Pinnixa is the 

 most frequent at Woods Hole. Mr. George Gray, who has 

 collected Chatopterus for several years at the latter place, affirms 

 that he had never observed Polyonyx until about 1909, and that 



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