114 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I28 



Among the polychaetes there must be commensal relationships that 

 could not be determined with certainty. For instance, the polynoid 

 worm Antinoe sarsi is undoubtedly commensal with the echiuroid 

 worm Echinrus echiurus alaskanus. The polynoid Enipo gracilis is 

 known to be commensal (Alaska) with the maldanid Nicomache 

 lumhricalis, and although both of these worms were collected at Point 

 Barrow they were not found within the same tube. The polynoid 

 Arcteohia antic ostiensis is also known to be commensal with the tere- 

 bellid Pista flexiiosa in Labrador. This polynoid occurs at Point 

 Barrow, and even though P. flexuosa was not found there, other suit- 

 able terebellid hosts were abundant. One or two of the other poly- 

 noids showed characteristics of commensalism, but appearances could 

 not be substantiated by evidence. 



The bryozoan Alcyonidium polyoum was often found growing on 

 snail shells, and several species of hydroids were found on clam shells 

 and snail shells, especially Boreotrophon sp., Neptunea ventricosa, 

 and N. sp. 



The following table summarizes most of the parasitic relationships 

 that were found : 



Table 8. — The parasites of Point Barrow, Alaska, and their hosts 

 HOST PARASITE 



Decapod Rhizocephalans 



Pagiiriis trigoiiocheirus (Stimpson), on Clistosacciis pagiiri 



abdomen 



Peltogaster depressus 



Polychaetes Copepods 



Antinoe sarsi Herpyllobius arcticus 

 Gattyana cirrosa " " 



Harmothoe extenuata " " 



H. imbricata, on head " " 



Terebellides stroemi Saccopsis terebellidis 



Amphipods 



Onisimus affinis, in marsupium Unidentified 

 Haploops laevis, in marsupium " 



Macro dahae, in marsupium " 



Decapod 

 Eualus gaimardi, under branchiostegite Choniostoma mirabile 



Tunicates 

 Boltenia echinata, in branchial basket Doropygus sp. 



B. ovifera, in branchial basket Schizoproctus inflatus 



