Renewal of the ciliary axoneme in cone outer segments of the retina of Xenopus laevis.

The ciliary axoneme in photoreceptors from the retina of Xenopus laevis was examined by immunofluorescent staining of tubulin throughout the light/dark cycle. The immunofluorescent axoneme extended along only part of the length of rod outer segments but the entire length of cone outer segments. Both the cone axoneme and outer segment elongated during the day and shortened (presumably by shedding) during the night. Fragments of immunofluorescent axonemes were found within packets of outer segment material breaking off from cone tips. These findings show that the ciliary axoneme in the Xenopus retina is replaced during the renewal of outer segments in cones. No evidence has been found for renewal of the axoneme in rods, and thus the stability of the ciliary axoneme may differ in rod and cone photoreceptors.