About Gregory Knox

About the Project

Title Interesting Intestines: How Pregnancy Changes the Guts of Bats

Presentation Watch the research video

Mentor Dr. Caleb Phillips
Biological Sciences, Texas Tech University

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  • Your passion and interest is very evident as your video progresses! Due to the shorter than expected intestines, what other benefits/disadvantages do you believe are given due to this?

    • Thank you! I was very nervous while recording this, but I'm glad it turned out okay. Based on what I read during my time working on this project, I think the primary benefit is the decreased weight of the intestines. The disadvantage could be that the bats don't have as much time to absorb nutrients. I've tried searching for anything quantifying intestinal peristalsis in bats and nothing turned up, so I'm not sure if the food moves more slowly to compensate. The shorter intestines could also make it more difficult to absorb water, but it's also possible that the increased paracellular absorption in bats compensates for this. If I didn't mention this in the video, bats actually have increased levels of paracellular absorption compared to non-flying vertebrates. More information about bats and paracellular absorption of fluids and nutrients can be found here: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2141920/.


      The digestive adaptation of flying vertebrates: High intestinal paracellular absorption compensates…
      Anecdotal evidence suggests that birds have smaller intestines than mammals. In the present analysis, we show that small birds and bats have signific…
  • Interesting video and topic! Regarding the length of bat intestines, can a length change be found in the species' phylogeny tree? Was the legth always short? Or did it shorten due to evolution, and if so when? 

    • To be completely honest, I'm actually not sure you could find this characteristic on a phylogeny tree. It always made sense to me that the intestines would have shortened through the course of evolution, but I suppose I can't really tell you much for certain about when it would have happened. I wouldn't even be comfortable venturing to give you a "best guess" lol. Good question!

      If you're interested in phylogenies then you may want to check out Zach Nguyen's video. I believe he used to work on phylogenies for crocodilians.


  • Your video was very descriptive and easy to follow along! Do you believe that the high efficiency of the small intestine could be because of their behavior of immediate migration after mating? 

    • Thank you! I'm not sure that alone would account for overall higher efficiency, but it might play a part. Now, if the intestines gain cells or surface area during pregnancy but the intestines of other mammals don't (or just change more slowly) then perhaps their immediate migration would be a driving force for such a change? My understanding is that the evidence is leaning toward intestines gaining surface area or cells in other mammals as well.


  • Hi Greg,

    Your presentation was very engaging and informative. In the intestines of these bats, how do you decide where to cut and stain? Could cell density vary depending on the area you are staining at? Thanks. 

    • Thanks! I decided where to cut and stain based on a study by Caviedes-Vidal et al (2008). They divided the intestines into proximal, medial, and distal regions. I did the same but tried to take segments from both sides of each division. Based on previous studies, it seemed like the length of villi were longest in the medial region, so this would be the region of highest cell density. I tried to take 12 slides to stain from each segment to get a good representation of the cell count in each area.


  • What are the cells are responsible for absorbing nutrients called? Do they differ from mammal to mammal?

    • Nutrients that are absorbed through cells (transcellular absorption) would utilize what are called enterocytes. These cells are intestinal epithelial cells. Epithelial cells are a general group of cells that line the body. These absorptive cells in question are referred to as "columnar" which just means that they are in the shape of columns rather than spheres or scales. To my knowledge, all mammals use enterocytes like these although the proteins that sit on the cells would vary from animal to animal. The junctions that connect the enterocytes, however, can vary between different classes of animals or even between mammals; with bats being an excellent example. These junctions can allow fluids and other specific molecules to move through without having to traverse a cell. 

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