Biochemical and microbiological evidence for fermentative digestion in free-living land iguanas (Conolophus pallidus) and marine iguanas (Amblyrhynchus cristatus) on the Galapagos archipelago

Roderick I. Mackie, Mathew Rycyk, Rebecca L. Ruemmler, Rustam Aminov, Martin Wikelski

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Abstract

Herbivorous lizards are potentially capable of high digestive efficiency, but the presence of an indigenous microbial population has been implied from measurements of activity rather than directly studied. This study is the first to provide direct biochemical and microbiological evidence for fermentative digestion in free-living land iguanas (Conolophus pallidus) and marine iguanas (Amblyrhynchus cristatus) from the Galapagos archipelago. In marine iguanas, the stomach and large capacious colon contained ca. 32% and 60%, respectively, of the weight of total gut content. Total volatile fatty acid concentration was ca. 150 and 180 mM, respectively, for marine and land iguanas. Molar proportions of acetate, propionate, and butyrate (80.3%, 9.5%, and 3.5%) in land iguana fecal samples were similar to those for marine iguanas. Examination of fecal samples using confocal and transmission electron microscopy, as well as cultivable counts, revealed a dense and diverse population of bacteria, with spores prominent. Total culturable counts of anaerobes (2.22 x 10(8) g(-1) wet weight of fecal material) outnumbered aerobes on average by a factor of ca. 700. Combined, these results strongly support the contention that these unique herbivorous lizards are largely dependent on the presence and metabolic activities of a resident bacterial population in order to hydrolyze and ferment plant polymers that are indigestible to the host.
Original languageEnglish
JournalPhysiological and Biochemical Zoology
Volume77
Issue number1
Pages (from-to)127-138
Number of pages12
ISSN1522-2152
DOIs
Publication statusPublished - 2004
Externally publishedYes

Keywords

  • Animals
  • Bacteria
  • Body Weights and Measures
  • Digestive System Physiological Phenomena
  • Ecuador
  • Fatty Acids
  • Feces
  • Fermentation
  • Gastrointestinal Tract
  • Hydrogen-Ion Concentration
  • Iguanas
  • Microscopy, Confocal
  • Microscopy, Electron
  • fatty acid
  • digestion
  • fermentation
  • herbivory
  • lizard
  • microbial activity
  • animal
  • article
  • bacterium
  • chemistry
  • comparative study
  • confocal microscopy
  • digestive function
  • electron microscopy
  • feces
  • gastrointestinal tract
  • histology
  • metabolism
  • microbiology
  • morphometrics
  • pH
  • physiology
  • ultrastructure
  • Digestive Physiology
  • Galapagos Islands
  • Pacific islands
  • Pacific Ocean
  • South America
  • Amblyrhynchus cristatus
  • Amphibia
  • Animalia
  • Bacteria (microorganisms)
  • Conolophus pallidus
  • Iguana
  • Iguania
  • Reptilia
  • Squamata
  • Vertebrata
  • LIZARDS
  • PHYSIOLOGY
  • ZOOLOGY
  • HERBIVOROUS LIZARD
  • POPULATION BIOLOGY
  • BODY-TEMPERATURE
  • SURVIVAL
  • SIZE
  • FIBERS
  • FECUNDITY
  • EVOLUTION
  • MICROBES
  • CRASH
  • Galapagos Archipelago Ecuador, South America Neotropical region
  • fermentative digestion
  • Reptilia Vertebrata Chordata Animalia (Animals, Chordates, Nonhuman Vertebrates, Reptiles, Vertebrates) - Sauria [85408] Amblyrhychus cristatus species iguana common Conolophus pallidus species iguana common
  • 14004, Digestive system - Physiology and biochemistry
  • Ingestion and Assimilation
  • colon digestive system
  • stomach digestive system
  • Digestive System

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