Journal Title
Title of Journal: J Comp Physiol B
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Abbravation: Journal of Comparative Physiology B
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Publisher
Springer-Verlag
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Authors: Martin Zimmer Andreas Brune
Publish Date: 2005/04/12
Volume: 175, Issue: 4, Pages: 275-283
Abstract
Since any given trait of an organism is considered to represent either an adaptation to the environment or a phylogenetic constraint most physiological gut characteristics should be adaptive in terms of optimizing digestion and utilization of the respective food source Among the Crustacea the taxon Oniscidea Isopoda is the only suborder that includes and essentially consists of species inhabiting terrestrial environments feeding on food sources different from those of most other Crustacea ie terrestrial leaf litter Microelectrodes were used to assay physiological characteristics of the gut lumen from representatives of four families of terrestrial isopods Trichoniscus pusillus Trichoniscidae Oniscus asellus Oniscidae Porcellio scaber Porcellionidae and Trachelipus rathkii Trachelipodidae Microsensor measurements of oxygen pressure Clarktype oxygen microelectrodes revealed that O2consuming processes inside the gut lumen created steep radial oxygen gradients Although all guts were oxic in the periphery the radial center of the posterior hindgut was microoxic or even anoxic in the adults of the larger species The entire gut lumen of all examined species was strongly oxidizing Pt microelectrodes apparent redox potential Eh +600–700 mV Such conditions would allow for the coexistence of aerobic and anaerobic microorganisms with both oxidative and fermentative activities contributing to digestion Although bacterial O2 consumption was also observed in the midgut glands hepatopancreas they remained entirely oxic probably owing to their large surfacetovolume ratio and high oxygen fluxes across the hepatopancreatic epithelium into the gland lumen Measurements with pH microelectrodes LIXtype showed a slight pH gradient from acidic conditions in the anterior hindgut to neutral conditions in the posterior hindgut of O asellus P scaber and T rathkii By contrast the pH in the hindgut lumen of T pusillus was almost constant We discuss to what extent these physiological characteristics may be adaptive to the digestion of terrestrial food sources that are rich in lignocellulose
Keywords:
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