ENERGY AND CARBON SOURCES FOR ENDOSYMBIOSES 

 BETWEEN BACTERIA AND MARINE INVERTEBRATES 



James J. Childress and Charles R. Fisher 



Marine Science Institute and 



Department of Biological Sciences 



University of California 



Santa Barbara, CA 93106 



ABSTRACT 



The major sessile invertebrate species living around the 

 hydrocarbon seeps on the Louisiana Slope were collected alive 

 using the Johnson Sea-Link submersible in June of 1987. 

 Specimens collected were either frozen for later studies, studied 

 on board the RV Seward Johnson or brought alive to UC Santa 

 Barbara for live maintenance and further study. Extensive 

 studies have been carried out on these materials to determine 

 the carbon and energy sources utilized by the endosymbionts. 

 These tests have indicated that the symbionts of the mytilid 

 mussel are methanotrophs which use methane as both an energy and 

 carbon source. In contrast all of the other symbioses from this 

 environment which we have studied appear to have endosymbionts 

 which derive energy from the oxidation of reduced sulfur 

 compounds and carbon from the fixation of inorganic carbon. 

 Several lines of evidence indicate that the endosymbionts provide 

 much, if not all, of the carbon utilized by the hosts in some of 

 these symbioses. 



INTRODUCTION 



Shortly after the discovery of the deep-sea hydrothermal 

 vents in 1977 (Corliss et al . 1978), biologists realized that 

 the major sessile animal species contained chemoautotrophic 

 bacterial symbionts within their bodies ( Cavanaugh et al. 1981; 

 Felbeck 1981; Felbeck, Childress, and Somero 1981). This 

 initial realization was quickly followed by the discovery of 

 similar symbioses in other reducing habitats as well as in other 

 invertebrate taxa (Cavanaugh 1985; Felbeck, Childress, and 

 Somero 1981; Southward et al. 1981). In the flurry of searching 

 for new symbioses, the nutritional bases of the various 

 symbioses were only superficially described. However, the energy 

 source for all of the symbioses appeared to be reduced sulfur 

 compounds. The remarkable discovery of vent-type taxa around 

 hydrocarbon seeps on the Louisiana Slope (Brooks et al. 1985) 

 raised the question of the energy and carbon sources of the 

 animals in this hydrocarbon rich environment. 



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