Figure 3.

Structural Specializations of the Holcocephala Eye

(A) Two-photon image of the Holcocephala head showing the enlarged frontal facets. The line and box mark the locations of the oblique section shown in (B) and the cross-section shown in (C), respectively.

(B) Oblique eye section showing the acute zone with enlarged sizes and focal lengths of the facet lenses, as well as a flat cornea and basement membrane.

(C) Cross-section of an ommatidium in the acute zone showing the rhabdomeres with tip diameter ∼0.9 μm.

(D) Image of a grating pattern created by an isolated cornea with the hanging drop method, which allowed calculation of the focal length (f).