Colour and polarised light vision in stomatopods : a neuroanatomical study.
The mantis shrimp Gonodactylus oerstedii is known to possess eyes capable of
colour and polarised light vision. The apposition compound eyes of these creatures are
highly mobile and their ommatidia are specialised to analyse the spectral and e-vector
qualities of light in a central strip of the eye called the midband.
The retina of the midband of Rows 1-4 is tiered with each row being sensitive
to a narrow region of the colour spectrum. Row 5 and 6 ommatidia possess many
structural features designed to allow the e-vector direction of light to be detected.
This thesis investigates the neuroanatomy in the neuropile regions below the
retina in an attempt to elucidate the mechanisms which allow colour and polarised light
vision to take place.
In Chapter 2 the retina-lamina projection of the retinal axons is studied in an
ommatidium in Row 3 of the midband, and the findings suggest that the stomatopod is
similar to all other crustacea so far studied, despite its unusual retina.
Chapter 3 investigates the neuroanatomy of the medulla neuropile regions. A
novel region of the medulla externa which deals with colour information is discovered.
In Chapter 4 the lamina of Rows 1-4 is looked at in more detail, with the
number of monopolar cells and the detailed arrangements of the retinular cell terminals
being ascertained. The terminals sensitive to different regions of the spectrum are
located in different areas of the lamina cartridge.
Chapter 5 looks at many of the issues above but this time in relation to rows 5
and 6 of the midband, which are specialised for polarisation vision. The lamina
neuropile is very different to that of Rows 1-4 and again a specialised region of the
medulla externa is found which processes information from these rows.
This thesis provides evidence that the optic lobes of Gonodactylus oerstedii are
comparable to other crustacea but nevertheless may possess some intriguing
specialisations related to their extraordinary colour and polarised light vision.