Retinal topography in two species of flamingo (Phoenicopteriformes: Phoenicopteridae)

Research output: Contribution to journalArticle

Abstract

In this study, we assessed eye morphology and retinal topography in two flamingo species, the Caribbean flamingo (Phoenicopterus ruber) and the Chilean flamingo (P. chilensis). Eye morphology is similar in both species and cornea size relative to eye size (C:A ratio) is intermediate between those previously reported for diurnal and nocturnal birds. Using stereology and retinal whole mounts, we estimate that the total number of Nissl-stained neurons in the retinal ganglion cell (RGC) layer in the Caribbean and Chilean flamingo is ~1.70 and 1.38 million, respectively. Both species have a well-defined visual streak with a peak neuron density of between 13,000 and 16,000 cells mm−2 located in a small central area. Neurons in the high-density regions are smaller and more homogeneous compared to those in medium- and low-density regions. Peak anatomical spatial resolving power in both species is approximately 10–11 cycles/deg. En-face images of the fundus in live Caribbean flamingos acquired using spectral domain optical coherence tomography (SD-OCT) revealed a thin, dark band running nasotemporally just dorsal to the pecten, which aligned with the visual streak in the retinal topography maps. Cross-sectional images (B-scans) obtained with SD-OCT showed that this dark band corresponds with an area of retinal thickening compared to adjacent areas. Neither the retinal whole mounts, nor the SD-OCT imaging revealed any evidence of a central fovea in either species. Overall, we suggest that eye morphology and retinal topography in flamingos reflects their cathemeral activity pattern and the physical nature of the habitats in which they live.

Details

Authors
  • Thomas J. Lisney
  • Simon Potier
  • Pierre François Isard
  • Marielle Mentek
  • Mindaugas Mitkus
  • Shaun P. Collin
Organisations
External organisations
  • University of Western Australia, Crawley
  • Vilnius University
  • La Trobe University
  • Paul Valéry University of Montpellier
  • Centre Hospitalier Vétérinaire Saint-Martin
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Zoology

Keywords

  • bird, eye morphology, optical coherence tomography, retinal ganglion cell, retinal topography, RRID:SCR_002798, RRID:SCR_003070, RRID:SCR_014199, RRID:SCR_018084, spatial resolving power, visual streak
Original languageEnglish
JournalJournal of Comparative Neurology
Publication statusE-pub ahead of print - 2020 Mar 10
Publication categoryResearch
Peer-reviewedYes