Linearly polarized light is common in most environments and is utilised by many animals. It is used for a number of tasks including navigation, object recognition and communication. Unlike linearly polarized light, circularly polarized light is not very common and the only animals known to have visual systems capable of detecting it are stomatopods¹.

A subsection of the complex retina of stomatopods is responsible for circular polarization vision². In this area the eighth retinular cell (R8) has the unique ability to act as a ¼ wave retarder³. When circularly polarized light enters the eye and passes through these cells it is converted to linearly polarized light. The main photoreceptor, which sits below the R8 cell, can now detect the light, as it is linear polarization sensitive².

Cell size is important factor in an R8 cells ability to act optimally as a ¼ wave retarder. The length of the R8 cell and the width of the microvilli they are made up of are critical to its function⁴. Variation in R8 size can change the polarization sensitivity of the eye, resulting in a visual system that is sensitive to elliptically polarized light.

Electrophysiological evidence has revealed that Haptosquilla trispinosa are sensitive to elliptically polarized light⁵. And unlike Odontodactylus scyllarus, the first species demonstrated to have circular polarization vision¹, H trispinosa are unable to discriminate between the two forms of circularly polarized light, left and right handed (p= 38).

This research will examine the presence of an elliptical polarization vision system in H trispinosa through a series of two-way choice paradigms, utilising operant conditioning techniques. Innate behaviour will also be used to help determine the biological relevance of an elliptical polarization vison system.