Steiner, N, Clauss, M, Martin, LF, Imper, C, Meloro, C and Duque-Correa, MJ (2022) No news from old drawings? Stomach anatomy in muroid rodents in relation to body size and ecology. Journal of Morphology, 283 (9). pp. 1200-1209. ISSN 0362-2525

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Abstract

Muroid rodents mostly have a complex stomach: one part is lined with a cornified (nonglandular) epithelium, referred to as a “forestomach”, whereas the rest is lined with glandular epithelium. Numerous functions for the forestomach have been proposed. We collated a catalog of anatomical depictions of the stomach of 174 muroid species from which the respective nonglandular and glandular areas could be digitally measured, yielding a “stomach ratio” (nonglandular:glandular area) as a scale-independent variable. Stomach ratios ranged from 0.13 to 20.15, and the coefficient of intraspecific variation if more than one picture was available for a species averaged at 29.7% (±21.5). We tested relationships of the ratio with body mass and various anatomical and ecological variables, including diet. There was a consistent phylogenetic signal, suggesting that closely related species share a similar anatomy. Apart from classifying stomachs into hemiglandular and discoglandular, no anatomical or ecological measure showed a consistent relationship to the stomach ratio. In particular, irrespective of statistical method or the source of dietary information, dietary proxies did not significantly correlate with the stomach ratio, except for a trend towards significance for invertivory (insectivory). Yet, even this relationship was not convincing: whereas highly insectivorous species had high but no low stomach ratios, herbivorous species had both low and high stomach ratios. Thus, the statistical effect is not due to a systematic increase in the relative forestomach size with invertivory. The most plausible hypotheses so far associate the muroid forestomach and its microbiome with a generic protective role against microbial or fungal toxins and diseases, without evident correlates of a peculiar need for this function under specific ecological conditions. Yet, this function remains to be confirmed. While providing a catalog of published depictions and hypotheses, this study highlights that the function of the muroid rodent forestomach remains enigmatic to date.

Item Type:	Article
Uncontrolled Keywords:	0606 Physiology; 0608 Zoology; Anatomy & Morphology
Subjects:	Q Science > QH Natural history > QH301 Biology Q Science > QL Zoology Q Science > QP Physiology
Divisions:	Biological & Environmental Sciences (from Sep 19)
Publisher:	Wiley
SWORD Depositor:	A Symplectic
Date Deposited:	31 Aug 2022 08:58
Last Modified:	31 Aug 2022 09:00
DOI or ID number:	10.1002/jmor.21496
URI:	https://researchonline.ljmu.ac.uk/id/eprint/17464

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