Ganglion layer topography and retinal resolution of the caribbean manatee (Trichechus manatus latirostris)

TitleGanglion layer topography and retinal resolution of the caribbean manatee (Trichechus manatus latirostris)
Publication TypeJournal Article
Year of Publication1997
AuthorsMass, A. M., D. K. Odell, D. R. Ketten, and A. Y. Supin
JournalDoklady Akademii Nauk [In Russian], Doklady Biological Sciences [English translation]
Start Page427
Pagination427-430 [In Russian], 392-394 [English translation]
Date Published1997
Call NumberDRK6826
Keywordscarribean manatee, eye, ganglion cell, manatees, marine mammals, morphology, retina, sirenia, trichechus manatus, trichechus manatus latirostris, vision

The Caribbean manatee (Trichechus manatus latirostris) belongs to the order Sirenia, a relict group of unique, completely aquatic mannnals adapted to a herbivorous life style. The study of these animals is of significant interest for evolutionary and ecological neuromorphology. Little is known about the sensory systems of manatees, and estimates of their visual capacity are contradictory (see review [1]). Researchers' estimates range from poor vision [2] to the existence of binocular vision [3]. Only'a few reports on the manatee retina have been published. Piggins et al. [1] showed that the retina of the Amazon manatee T. inunguis is adapted to night vision. It contains almost no retina cones and very few ganglion cells [1]. According to the only comprehensive study [4], the retina of the Caribbean manatee has a completely laminar structure and contains both rod like and cone like photoreceptors. However, the visual acuity of manatees has not yet been assessed quantitatively. To solve this problem, we used a method based on the examination of the ganglion cell distribution in retinal whole mounts. This method allows the areas of the maximum cell density to be detected, and the retinal resolution to be calculated. The retinal resolution of some terrestrial [5] and aquatic [6-9] mannnals has been determined with this method. The goal of this work was to determine the distribution of ganglion cells in whole mounts of the retina of the Caribbean manatee (T. manatus latirostris) and to calculate the retinal resolution.