Chapter 57 



Host and Habitat Relationships of Marine 

 Commensal Bacteria'*' t 



J. LisTON and R. R. Colwell 



I 



t is now generally accepted that free swimming fish normally 

 carry a population of commensal bacteria, and the nature of this 

 flora has been defined for a number of species of fish in particu- 

 lar habitats (mainly northern) (11, 5). Much less is known con- 

 cerning the natural bacterial populations of marine invertebrate 

 animals. A few observations concerning individual types of bac- 

 teria, such as Achromohacter and Cristispim, isolated from shell- 

 fish, have been recorded (1, 2, 8) and rather limited accounts of 

 the bacterial flora of soft shelled clams (My a arenaria) (9, 10) 

 have been published. Scattered observations and descriptions of 

 individual bacteria isolated from marine invertebrates have been 

 published by other workers. Evidence has been presented (4) 

 that a distinct commensal bacteria flora is associated with the 

 Pacific oyster (Crassostrea gigcis) and that habitat conditions may 

 affect the balance of types in this population to a limited extent. 



The dual importance of host and habitat in determining the 

 bacterial flora of fish has been emphasized by Wood ( 12, 13, 14 ) 

 who reported marked differences between the generic composi- 

 tion and physiological capabilities of teleost and elasmobranch 

 fish caught off Australia. Liston (6) was unable to distinguish 

 significant differences between teleost and elasmobranch fishes 

 in the North Sea and concluded that habitat max- he more im- 

 portant than host species in this respect. 



A continued interest by the autliors in the effects of the host- 



* This research was supported by a Grant (E2417) from the National Institutes 

 of Health. 



t Contriboition No. 123, College of Fisheries, University of Washington, Seattle, 

 Washington. 



611 



