*Formerly at the Leibniz Institute for Zoo and Wildlife Research (IZW), Berlin, Germany (retired).
Convergence in the macroscopic anatomy of the reticulum in wild ruminant species of different feeding types and a new resulting hypothesis on reticular function
Article first published online: 22 DEC 2009
© 2009 The Authors. Journal compilation © 2009 The Zoological Society of London
Journal of Zoology
Volume 281, Issue 1, pages 26–38, May 2010
How to Cite
Clauss, M., Hofmann, R. R., Streich, W. J., Fickel, J. and Hummel, J. (2010), Convergence in the macroscopic anatomy of the reticulum in wild ruminant species of different feeding types and a new resulting hypothesis on reticular function. Journal of Zoology, 281: 26–38. doi: 10.1111/j.1469-7998.2009.00675.x
Editor: Virginia Hayssen
- Issue published online: 22 APR 2010
- Article first published online: 22 DEC 2009
- Received 2 September 2009; revised 4 November 2009; accepted 11 November 2009
The reticulum is the second part of the ruminant forestomach, located between the rumen and the omasum and characterized by honeycomb-like internal mucosa. With its fluid contents, it plays a decisive role in particle separation. Differences among species have been linked to their feeding style. We investigated whether reticulum size (absolute and in relation to rumen size) and size of the crests that form the mucosal honeycomb pattern differ among over 60 ruminant species of various body sizes and feeding type, controlling for phylogeny. Linear dimensions generally scaled allometrically, that is to body mass0.33. With or without controlling for phylogeny, species that ingest a higher proportion of grass in their natural diet had both significantly larger (higher) rumens and higher reticular mucosa crests, but neither reticulum height nor reticulum width varied with feeding type. The height of the reticular mucosa crests represents a dietary adaptation in ruminants. We suggest that the reticular honeycomb structures do not separate particles by acting as traps (neither for small nor for large particles), but that the structures reduce the lumen of the reticulum during contractions – at varying degrees of completeness in the different feeding types. In browsing species with rumen contents that may be less fluid and more viscous than those of the reticulum, incomplete closure of the lumen may allow the reticulum to retain the fluid necessary for particle separation. In grazing species, whose rumen contents are more stratified with a larger distinct fluid pool, a more complete closure of the reticular lumen due to higher crests may be beneficial as the reticulum can quickly re-fill with fluid rumen contents that contain pre-sorted particles.