Journal of Comparative Physiology A

, Volume 190, Issue 2, pp 139–146 | Cite as

Accommodation behaviour during prey capture in the vietnamese leaf turtle (Geoemyda spengleri)

  • M. J. Henze
  • F. Schaeffel
  • H.-J. Wagner
  • M. OttEmail author
Original Paper


Vietnamese leaf turtles (Geoemyda spengleri) were tested for their ability to focus on prey objects at various distances. Accommodation was continuously measured by infrared photoretinoscopy. All animals investigated during this study showed a surprisingly high precision of accommodation over a range of over 30 D. Measured accommodation matched the target distance accurately for distances between 3 and 17 cm. The turtles switched between independent and coupled accommodation in the two eyes. Independent accommodation was observed when the turtles inspected their environment visually without a defined object of interest. Coupled accommodation was only observed during binocular prey fixation. When a turtle aimed at a target, the symmetrical focus of both eyes persisted even if vision was totally blocked in one eye or altered by ophthalmic lenses. This suggests that the eyes were linked by internal neuronal mechanisms. The pupil of the eye responded clearly to changes in ambient light intensity. A strong decrease in pupil size was also observed when the eye was focused on a close target. In this case, the constriction of the pupil probably aids in the deformation of the eye lens during near-accommodation.


Binocular coupling Eye Pupillary reflex Retinoscope Stereopsis 



We thank M. and W. Matzanke for putting their Vietnamese Leaf Turtles at our disposal to take some preliminary measures. The experiments reported in this paper comply with the Principles of Animal care, publication No. 86-23, revised 1985, of the National Institutes of Health and were carried out in accordance with the German “Tierschutzgesetz”.


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Copyright information

© Springer-Verlag 2004

Authors and Affiliations

  • M. J. Henze
    • 1
  • F. Schaeffel
    • 2
  • H.-J. Wagner
    • 1
  • M. Ott
    • 1
    Email author
  1. 1.Institute for AnatomyUniversity of TübingenTübingenGermany
  2. 2.Section of Neurobiology of the Eye, Department IIUniversity Eye HospitalTübingenGermany

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