Eileen Garvey

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Eileen Garvey

• Article Comparative Morphology of the Eye
• in Primates
• E. CHRISTOPHER KIRK
• The Anatomical Record Part A Discoveries in
  Molecular, Cellular, and Evolutionary Biology
• Volume 281A, Issue 1, Pages 1095-1103
• Published Online November 2004

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Background

• Components of the eye
• Rods neurosensory cells which are insensitive to
  color, absorb light over the entire range of the
  visual spectrum, and are most effective in
  relatively low intesities of light, such as
  shade, dusk or night time.
• Cones neurosensory cells that are senstive to
  color, absorb light in only one part of the
  visible spectrum (red, green, blue), and function
  only in prescene of light that falls into this
  wavelength.
• Diurnal species are usually more active during
  the day when the light levels are in the range of
  cone mediated vision.
• Nocturnal species are usually active at night
  when light levels are in the range of rod
  mediated vision.
• However there are many mammalian species that are
  considered, cathemeral, which means they are
  active in both light and dark periods.

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Background continued

• In the article, the morphological adaptations for
  different activity patterns are compared with the
  gross anatomy of the eye of primates.
• The size of the cornea places an upper limit on
  the maximum amount of light that the eye can
  absorb.
• Nocturnal species increase the size of the cornea
  compared to the transverse diameter of the eye so
  that it is possible to absorb more light.
• Diurnal species have smaller corneas compared to
  the transverse diameter of the eye.

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Hypothesis

• The goal of the analysis
• Provide a quantitative description of the
  relationship between eye morphology and activity
  pattern in broad sample of primate species.
• The researchers asked many questions for
  example
• Do nocturnal, cathemeral, and diurnal primates
  exhibit systematic differences in eye morphology
  as has been predicted by other studies conducted
  on mammalian eyes?

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Methods and Materials

• Data were collected on eye and cornea size for
  147 specimens of 55 primate species
• Samples were taken from preserved specimens that
  were frozen directly after the animal died or
  were preserved in formalin
• Eyes were removed from the orbit and cleaned
• Each eye was refilled to prevent it from
  collapsing
• A needle was inserted into the optic nerve and
  then the measurements were determined
• Activity patterns and mean eye measurements were
  determined for all included taxa

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Methods and Materials

• Data/calculations included
• Activty Patterns DDiurnal, NNocturnal,
  CCathemeral
• Mean transvers diameter in mm
• Standard deviation
• Mean transverse corneal diameter in mm
• Ratio of corneal diameter and mean transverse eye
  diameter (CE ratio)
• Example of calculations Table 2

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Calculations
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Results and Discussion

• CE ratios varied between primates that were of
  different suborders and had different activity
  patterns however within the same subgroup the
  functional morphology was consistent with
  previous testing results.
• For example diurnal species had smaller relative
  cornea size than nocturnal or cathemeral species
• As expected nocturnal species showed higher CE
  ratios compared to diurnal species
• Haplorhines had diurnal species with
  significantly lower CE ratios than the nocturnal
  species.
• Strepsirrhines had diurnal species with
  significantly lower CE ratios than the nocturnal
  species
• Cathemeral strepsirrhines had CE ratios that
  were larger than the diurnal strepsirrhines and
  smaller than the nocturnal strepsirrhines

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Summary

• Eye morphology changed consistently with activity
  pattern in primate suborders
• For most suborders tested, such as
  strepsirrhines, and haplorhines, relative cornea
  size was largest in nocturnal species and
  smallest in diurnal species

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Discussion

• Data supports the hypothesis that cornea size is
  largest for species that are most active in dark
  periods compared to those that are active in the
  light
• Primates have evolved their eye morphologies to
  maximize their visual sensitivity, in order to
  adapt to the activity patterns