Characterizing the resident, fermentative microbial consortium in the hindgut of the temperate-zone herbivorous fish, Hermosilla azurea (Teleostei: Kyphosidae)
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The zebraperch, Hermosilla azurea Jenkins and Evermann, a warm-temperate marine fish species with a strictly macroalgal diet, has a relatively long digestive tract with an enlarged hindgut and an associated blind caecum (HC). In zebraperch sampled off Santa Catalina Island, California (33°19′42′′N; 118°18′37′′W) in years 1995 through 2001, direct cell counts, gut epithelium assessment of bacterial attachment, and short-chain fatty acid (SCFA) analyses verified that the zebraperch HC possesses a dense and morphologically diverse, fermentative microbiota. Bacterial cell counts and morphological diversity were significantly higher in HC contents compared to anterior gut regions, suggesting that microbial populations were growing along the digestive tract. Similarly, electron micrographs of the HC epithelium revealed attached microbes, further supporting the possibility that these organisms constitute resident microbiota. Five different SCFAs were detected in all three regions of the digestive tract, but levels were up to three times greater in HC contents. Acetate was consistently the prevailing SCFA in all gut regions. Sequence analysis of bacterial 16S rDNA was used to identify predominant bacterial groups in HC contents. Of the seven main bacterial types identified, Enterovibrio spp. were the dominant bacteria in HC contents followed by species of Bacteroides,Faecalibacterium, and Desulfovibrio. Taken together, our findings show that the zebraperch HC harbors a consortium of microbes that appears to assist in the breakdown of algal polysaccharides in the herbivorous diet of the fish.
KeywordsDigestive Tract Desulfovibrio Herbivorous Fish Algal Polysaccharide SCFA Level
We thank Captain J. Cvitanovich and the crew of the R.V. Yellowfin for their help in capturing fish. We also thank W. Van Antwerp for performing SCFA analyses, E. Sturm for leading several expeditions to collect fish, and E. DeLong for his generous donation of PCR primers. T. Parker, J. Ferreira, W. Katzenstein, C. Hamilton, D. Tessier, S. Ecker, J. Haygood, and D. Asher provided valuable assistance with fish collection and lab work. The Departmental Associations Council and the Department of Biological Science at California State University, Fullerton, provided financial support. All experiments herein comply with the laws of the United States of America.
- Horn MH (1989) Biology of marine herbivorous fishes. Oceanogr Mar Biol Annu Rev 27:167–272Google Scholar
- Horn MH (1992) Herbivorous fishes: feeding and digestive mechanisms. In: John DM, Hawkins SJ, Price JH (eds) Plant–animal interactions in the marine benthos. Systematics association special, vol 46. Clarendon Press, Oxford, pp 339–362Google Scholar
- MacCormack WP, Fraile ER (1990) Bacterial flora of newly caught Antarctic fish Notothenia neglecta. Polar Bio 10:413–417Google Scholar
- Sturm EA, Horn MH (2001) Increase in occurrence and abundance of zebraperch (Hermosilla azurea) in the Southern California Bight in recent decades. Bull So Cal Acad Sci 100:170–174Google Scholar
- Sutton D, Clements KD (1988) Aerobic heterotrophic gastrointestinal microflora of tropical marine fishes. Proc Sixth Int Coral Reef Symp (Aust) 3:185–190Google Scholar
- Titus E, Ahearn GA (1991) Transintestinal acetate transport in a herbivorous teleost: anion exchange at the basolateral membrane. J Exp Biol 156:41–61Google Scholar
- Van der Maarel MJ, Artz R, Haanstra R, Forney LJ (1998) Association of marine archaea with the digestive tracts of two marine fish species. Appl Environ Microbiol 64:2894–2898Google Scholar