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Variation in the Bony Labyrinth (Inner Ear) of Anurans.

Amber Singh

Abstract

The inner ear provides sensory information of position and acceleration of the head during movement. It is thought that spatially specific behaviors influence the shape of the inner ear, as morphology will change to maximize sensitivity to these behaviors. In birds and mammals with agile and spatially complex movements, differences in canal shape are thought to enhance sensitivity to these behaviors. Documentation of inner ear variation in caecilians and fossorial snakes indicates that both groups may have adopted novel morphological traits thought to enhance sensitivity to movement below ground. However, it is not well understood if these relationships extend across vertebrates. By surveying the morphological variation within the inner ears of anurans, we can compare the morphological diversity against ecological niches to better understand how form relates to the life history of these animals. We present a survey of the morphological diversity of the inner ears of anurans across taxa. Inner ear endocasts were generated from high-resolution micro-computed tomography (µ-CT) data, and we document significant variation in the size and shape of the inner ears across species. We investigate the influence of size, ecology, and phylogeny on inner ear morphology using 3-D geometric morphometrics and phylogenetic comparative methods.
 

Poster Pitch

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Poster

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15 Responses
  1. Jon Bloch

    Love this poster! Nice job Amber. It been a while, but my memory with inner ears & locomotion in mammals is that some categories discriminated well based on relative size (diameters I think) of the different semicircular canals. So, for example arboreal primates had relatively larger lateral SSC size related to angular acceleration of the head?

    Presumably some of that is picked up with the shape analysis here?

    Great use of OVert data!

  4. Dan Paluh

    Great poster, Amber!

    Because the inner ear also plays a role in hearing, do you think that may be a reason why ecology alone does not tightly correspond with inner ear shape? Maybe frogs with similar ear shapes but different ecologies (and different locomotion strategies) have the same auditory capabilities.

    1. Amber Singh

      Hi Dan,

      That would be an interesting aspect to look into. I know I have a couple species which lack an outer ear, and the shape of their inner ears is not significantly different from the others.

      It is also good to note that the species with the most divergent ear shapes, are those with other weird characteristics, such as Pipa pipa, or the pebble toad. For many species, there is little to no data on life-history or behavior to make good comparisons.

  6. Paulo

    Hi Amber,
    Very interesting your poster! Your results show that the shape of the inner ear does not present great variation with the ecology. But what about the hearing, as Dan Paluh just commented? With the reconstructions you have, would you be able to study for example variation in the position and in size of the papilla amphibiorum and papilla basilaris within the inner year? Or for this you would need another technique?
    Good luck with your research!

    1. Amber

      Hi Paulo,

      I am limited by the information I can get within the inner ear. I’ve previously tried looking at the inner ears of iodine-stained specimens, but because the structures within are so small, and mostly made up of of thin membranes, it is nearly impossible to get any definitive structures from those scans. There might be other staining techniques that will work, but the best known way to get internal structure is to take histological slices, then reconstruct the shape and dimension of the structures from those, which is beyond the scope of this project.

      1. Paulo

        Oh I see! And yes, I understand that those are other questions! It was just a curiosity!
        Thank you!

  8. Samantha Ocon

    Hi Amber! I love your poster design! This is an excellent research project and I’m always fascinated by geometric morphometrics as a tool for understanding evolutionary lineages. Great work!

  9. Adania Flemming

    Hi Amber,

    How interesting! Nice presentation and good job on creating an aesthetically pleasing poster. It would be wonderful when sufficient behavioral data is available to help explain the relationship between the locomotor habits of frogs and the size of the inner ear. PhD project?