Intestinal morphometrics in flying and non-flying mammals

ZHANG, Z.Q.; ARCE ME; CIUFFO GM; KARASOV, W.H.; CAVIEDES-VIDAL, E

Seattle, WA

Congreso; SOCIETY FOR INTEGRATIVE AND COMPARATIVE BIOLOGY; 2010

SOCIETY FOR INTEGRATIVE AND COMPARATIVE BIOLOGY

Studies on birds have led to the hypothesis that increased intestinal absorption between enterocytes (paracellular) evolved as a compensation for smaller intestinal size in fliers, which was perhaps selected for to minimize the mass of digesta carried. This hypothesis predicts that bats will also exhibit relatively reduced intestinal size and high paracellular absorption, compared with nonflying mammals. Published studies on two bat species do indicate relatively high paracellular absorption. One mechanism for increasing paracellular absorption per cm small intestine (SI) is increased number of tight junctions across which paracellular absorption occurs. We provide the first comparative analysis of enterocyte size and number in flying and nonflying mammals. Intestines of insectivorous bats Tadarida brasiliensis (mass 14.0 ± 0.5 [S.E.] g, n = 8) were compared with Mus musculus (37.3 ± 2.0, n = 6) using hematoxylin and eosine staining method. After correction for body size difference, the bats had 50% shorter SI length and 40% less nominal surface area than the mouse, as predicted. Villous enhancement of surface area was 89% greater in the bat than mouse, mainly because of a greater density of villi in bat SI. Bat and mouse were similar in enterocyte diameter (respectively, 4.69 ± 0.20 microns vs. 4.60 ± 0.13). Bats exceeded mice by 52% in villous area per cm length SI and by 46% in number of enterocytes per length. An increased number of tight junctions per cm length SI could be a mechanism for increasing paracellular absorption. Supported by PICT 2004 25561 and CyT.