The potto (Perodicticus potto) is an arboreal strepsirhine found in the rainforests of central Africa. In contrast to most primates, the potto shows slow-moving locomotion over the upper surface of branches, where it forages for exudates and crawling invertebrates with its head held very close to the substrate. Here, we asked whether the retina of the potto displays topographic specializations in neuronal density that correlate with its unusual lifestyle. Using stereology and retinal wholemounts, we measured the total number and topographic distribution of retinal ganglion cells (total and presumed parasol), as well as estimating the upper limits of the spatial resolution of the potto eye. We estimated ∼210,000 retinal ganglion cells, of which ∼7% (∼14,000) comprise presumed parasol ganglion cells. The topographic distribution of both total and parasol ganglion cells reveals a concentric centroperipheral organization with a nasoventral asymmetry. Combined with the upwardly shifted orbits of the potto, this nasoventral increase in parasol ganglion cell density enhances contrast sensitivity and motion detection skywards, which potentially assists with the detection of predators in the high canopy. The central area of the potto occurs ∼2.5 mm temporal to the optic disc and contains a maximum ganglion cell density of ∼4,300 cells/mm2. We found no anatomical evidence of a fovea within this region. Using maximum ganglion cell density and eye size (∼14 mm), we estimated upper limits of spatial resolving power between 4.1 and 4.4 cycles/degree. Despite their reported reliance on olfaction to detect exudates, this level of spatial resolution potentially assists pottos with foraging for small invertebrates and in the detection of predators.

Andrade-da-Costa BLS, Pessoa VF, Bousfield JD, Clarke RJ (1987): Unusual distribution of ganglion cells in the retina of the three-toed sloth (Bradypus variegatus). Braz J Med Biol Res 20:741-748.
Andrade-da-Costa BLS, Pessoa VF, Bousfield JD, Clarke RJ (1989): Ganglion cell size and distribution in the retina of the two-toed sloth (Choloepus didactylus L.). Braz J Med Biol Res 22:233-236.
Blake R, Sekuler R (2006): Perception. New York, McGraw Hill, p 652.
Bonds AB, Casagrande VA, Norton TT, DeBruyn EJ (1987): Visual resolution and sensitivity in a nocturnal primate (Galago) measured with visual evoked potentials. Vision Res 27:845-857.
Coimbra JP, Hart NS, Collin SP, Manger PR (2013): Scene from above: retinal ganglion cell topography and spatial resolving power in the giraffe (Giraffa camelopardalis). J Comp Neurol 521:2042-2057.
Coimbra JP, Kaswera-Kyamakya C, Gilissen E, Manger PR, Collin SP (2015): The retina of Ansorge's cusimanse (Crossarchus ansorgei): number, topography and convergence of photoreceptors and ganglion cells in relation to ecology and behavior. Brain Behav Evol 86:79-93.
Coimbra JP, Marceliano MLV, Andrade-da-Costa BLS, Yamada ES (2006): The retina of tyrant flycatchers: topographic organization of neuronal density and size in the ganglion cell layer of the great kiskadee Pitangus sulphuratus and the rusty margined flycatcher Myiozetetes cayanensis (Aves: Tyrannidae). Brain Behav Evol 68:15-25.
Coimbra JP, Trévia N, Marceliano MLV, Andrade-da-Costa BLS, Picanço-Diniz CW, Yamada ES (2009): Number and distribution of neurons in the retinal ganglion cell layer in relation to foraging behaviors of tyrant flycatchers. J Comp Neurol 514:66-73.
Collin SP (1999): Behavioural ecology and retinal cell topography; in Archer SN, et al (eds): Adaptive Mechanisms in the Ecology of Vision. London, Chapman and Hall, pp 509-535.
Curcio CA, Allen KA (1990): Topography of ganglion cells in human retina. J Comp Neurol 300:5-25.
DeBruyn E, Wise V, Casagrande V (1980): The size and topographic arrangement of retinal ganglion cells in the galago. Vision Res 20:315-327.
Dkhissi-Benyahya O, Szel A, Degrip WJ, Cooper HM (2001): Short and mid-wavelength cone distribution in a nocturnal Strepsirrhine primate (Microcebus murinus). J Comp Neurol 438:490-504.
Fischer Q, Kirby M (1991): Number and distribution of retinal ganglion cells in anubis baboons (Papio anubis). Brain Behav Evol 37:189-203.
Glaser EM, Wilson PD (1998): The coefficient of error of optical fractionator population size estimates: a computer simulation comparing three estimators. J Microsc 192:163-171.
Goffart M, Missotten L, Faidherbe J, Watillon M (1976): A duplex retina and the electroretinogram in the nocturnal Perodicticus potto. Arch Int Physiol Biochim 84:493-516.
Gomes FL, Silveira LCL, Saito CA, Yamada ES (2005): Density, proportion, and dendritic coverage of retinal ganglion cells of the common marmoset (Callithrix jacchus jacchus). Braz J Med Biol Res 38:915-924.
Grünert U, Greferath U, Boycott BB, Wässle H (1993): Parasol (Pα) ganglion-cells of the primate fovea: immunocytochemical staining with antibodies against GABAA-receptors. Vision Res 33:1-14.
Gundersen HJG (1977): Notes on the estimation of the numerical density of arbitrary profiles: the edge effect. J Microsc 111:219-223.
Gundersen HJG, Bagger P, Bendtsen TF, Evans SM, Korbo L, Marcussen N, Møller A, Nielsen K, Nyengaard JR, Pakkenberg B, Sørensen FB, Vesterby A, West MJ (1988): The new stereological tools: disector, fractionator, nucleator and point sampled intercepts and their use in pathological research and diagnosis. APMIS 96:857-881.
Hanke FD, Peichl L, Dehnhardt G (2009): Retinal ganglion cell topography in juvenile harbor seals (Phoca vitulina). Brain Behav Evol 74:102-109.
Hendrickson AE (2009): Fovea: primate; in Squire L (ed): Encyclopedia of Neuroscience. Oxford, Academic Press, pp 327-334.
Herbin M, Boire D, Ptito M (1997): Size and distribution of retinal ganglion cells in the St. Kitts green monkey (Cercopithecus aethiops sabeus). J Comp Neurol 383:459-472.
Hill WCO (1953): Primates: Comparative Anatomy and Taxonomy. I. Strepsirhini. Edinburgh, Edinburgh University Press.
Hladik CM (1979): Diet and ecology of prosimians; in Doyle GA, Martin RD (eds): The Study of Prosimian Behavior. New York, Academic Press, pp 307-357.
Hughes A (1977): The topography of vision in mammals of contrasting lifestyle: comparative optics and retinal organization; in Cresitelli F (ed): Handbook of Sensory Physiology. Canberra, Australian National University.
Hughes A (1981a): Population magnitudes and distribution of the major modal classes of cat retinal ganglion cell as estimated from HRP filling and a systematic survey of the soma diameter spectra for classical neurones. J Comp Neurol 197:303-339.
Hughes A (1981b): Cat retina and the sampling theorem; the relation of transient and sustained brisk-unit cut-off frequency to α and β-mode cell density. Exp Brain Res 42:196-202.
Jarvis JR, Wathes CM (2008): A mechanistic inter-species comparison of spatial contrast sensitivity. Vision Res 48:2284-2292.
Katz ML, Robison JWG (1986): Evidence of cell loss from the rat retina during senescence. Exp Eye Res 42:293-304.
Kingdon J (2005): The Kingdon pocket guide to African mammals. Princeton Pocket Guide. Princeton, Princeton University Press.
Langston A, Casagrande VA, Fox R (1986): Spatial resolution of the galago. Vision Res 26:791-796.
Lennie P, Fairchild MD (1994): Ganglion cell pathways for rod vision. Vision Res 34:477-482.
Lima S, Silveira LCL, Perry VH (1996): Distribution of M retinal ganglion cells in diurnal and nocturnal new world monkeys. J Comp Neurol 368:538-552.
Marshall NJ (2000): Communication and camouflage with the same ‘bright' colours in reef fishes. Philos Trans R Soc Lond B Biol Sci 355:1243-1248.
Mass AM, Supin AY (1992): Peak density, size and regional distribution of ganglion cells in the retina of the fur seal Callorhinus ursinus. Brain Behav Evol 39:69-76.
Mass AM, Supin AY (2003): Retinal topography of the harp seal Pagophilus groenlandicus. Brain Behav Evol 62:212-222.
Mass AM, Supin AY (2010): Retinal ganglion cell layer of the caspian seal Pusa caspica: topography and localization of the high-resolution area. Brain Behav Evol 76:144-153.
Matsui A, Rakotondraparany F, Munechika I, Hasegawa M, Horai S (2009): Molecular phylogeny and evolution of prosimians based on complete sequences of mitochondrial DNAs. Gene 441:53-66.
Merigan WH, Byrne C, Maunsell JHR (1991a): Does primate motion perception depend on the magnocellular pathway? J Neurosci 11:3422-3429.
Merigan WH, Katz LM, Maunsell JHR (1991b): The effects of parvocellular lateral geniculate lesions on the acuity and contrast sensitivity of macaque monkeys. J Neurosci 11:994-1001.
Miller RA (1935): Functional adaptations in the forelimb of the sloths. J Mammal 16:38-51.
Mills SL, Massey SC (1999): AII amacrine cells limit scotopic acuity in central macaque retina: a confocal analysis of calretinin labeling. J Comp Neurol 411:19-34.
Mitchell DE (1988): The extent of visual recovery from early monocular or bionocular visual deprivations in kittens. J Physiol 395:639-660.
Mittermeier RA (2013): Introduction; in Mittermeier RA, et al (eds): Handbook of the Mammals of the World: Primates. Barcelona, Lynx Edicions, vol 3, pp 13-26.
Muniz JAPC, Athaide LM, Gomes BD, Finlay BL, Silveira LC (2014): Ganglion cell and displaced amacrine cell density distribution in the retina of the howler monkey (Alouatta caraya). PloS One 9:e115291.
Nekaris KAI (2013): Family Lorisidae (angwantibos, pottos and loirises); in Mittermeier RA, et al (eds): Handbook of Mammals of the World. Barcelona, Lynx Edicions, vol 3, pp 210-235.
Nekaris KAI, Pimley E, Ablard K (2007): Predator defense by slender lorises and pottos; in Gursky S, Nekaris KAI (eds): Primate Anti-Predator Strategies. New York, Springer, pp 222-240.
Nyakatura JA (2012): The convergent evolution of suspensory posture and locomotion in tree sloths. J Mammal Evol 19:225-234.
Oates JF (1984): The niche of the potto, Perodicticus potto. Int J Primatol 5:51-61.
Pariente G (1979): The Role of Vision in Prosimian Behavior. New York, Academic Press.
Peichl L, Ott H, Boycott BB (1987): Alpha ganglion cells in mammalian retinae. Proc R Soc Lond B Biol Sci 231:169-197.
Peichl L (1991): Alpha ganglion cells in mammalian retinae: common properties, species differences, and some comments on other ganglion cells. Vis Neurosci 7:155-169.
Peichl L, Rakotondraparany F, Kaiser A, Goodman SM, Kappeler PM (2004): Cone types and distributions in nocturnal and diurnal lemurs of Madagascar. Sydney, XVI International Congress of Eye Research.
Peichl L, Rakotondraparany F, Kappeler PM (2001): Photoreceptor types and distributions in nocturnal and diurnal Malagasy primates. Invest Ophthalmol Vis Sci 42:S48.
Peichl L (1992): Topography of ganglion cells in the dog and wolf retina. J Comp Neurol 324:603-620.
Perry VH, Cowey A (1985): The ganglion cell and cone distributions in the monkey's retina: implications for central magnification factors. Vision Res 25:1795-1810.
Perry VH, Öhler R, Cowey A (1984): Retinal ganglion cells that project to the dorsal lateral geniculate nucleus in the macaque money. Neuroscience 12:1101-1123.
Pettigrew JD, Dreher B, Hopkins CS, McCall MJ, Brown M (1988): Peak density and distribution of ganglion cells in the retinae of microchiropteran bats: implications for visual acuity. Brain Behav Evol 32:39-56.
Pimley ER, Bearder SK (2013): Perodicticus potto Potto; in Butynski TM, Kingdon J, Kalina J (eds): Mammals of Africa: Primates. London, Bloomsbury, vol 2, pp 393-398.
Reuter T, Peichl L (2008): Structure and function of the retina in aquatic tetrapods; in Thewissen JGM, Nummela S (eds): Sensory Evolution on the Threshold: Adaptations in Secondarily Aquatic Vertebrates. San Diego, University of California Press, pp 149-172.
Reymond L (1985): Spatial visual acuity of the eagle Aquila audax: a behavioural, optical and anatomical investigation. Vision Res 25:1477-1491.
Reymond L (1987): Spatial visual acuity of the falcon, Falco berigora: a behavioural, optical and anatomical investigation. Vision Res 27:1859-1874.
Rodieck RW (1988): The primate retina; in Steklis HD, Brown J (eds): Comparative Primate Biology. New York, Liss, pp 203-278.
Ross CF (2004): The tarsier fovea: functionless vestige or nocturnal adaptation?; in Ross CF, Kay RF (eds): Anthropoid Origins: New Visions. New York, Kluwer Academic/Plenum, pp 477-537.
Ross CF, Kirk EC (2007): Evolution of eye size and shape in primates. J Hum Evol 52:294-313.
Schiller PH, Logothetis NK, Charles ER (1990): Function of the color-opponent and broad-band channels of the visual system. Nature 343:68-70.
Schiller PH, Logothetis NK, Charles ER (1991): Parallel pathways in the visual system: their role in perception at isoluminance. Neuropsychologia 29:433-441.
Shapley R, Perry VH (1986): Cat and monkey retinal ganglion cells and their visual functional roles. Trends Neurosci 9:229-235.
Silveira LCL, Perry VH (1991): The topography of magnocellular projecting ganglion cells (M-ganglion cells) in the primate retina. Neuroscience 40:217-237.
Silveira LCL, Perry VH, Yamada ES (1993): The retinal ganglion cell distribution and the representation of the visual field in area 17 of the owl monkey, Aotus trivirgatus. Vis Neurosci 10:887-897.
Silveira LCL, Picanço-Diniz CW, Oswaldo-Cruz E (1989a): Distribution and size of ganglion cells in the retinae of large Amazon rodents. Vis Neurosci 2:221-235.
Silveira LCL, Picanço-Diniz CW, Sampaio L, Oswaldo-Cruz E (1989b): Retinal ganglion cell distribution in the cebus monkey: a comparison with the cortical magnification factors. Vision Res 29:1471-1483.
Skinner J, Chimimba CT (2005): The Mammals of the Southern African Sub-Region. Cambridge, Cambridge University Press.
Slomianka L, West MJ (2005): Estimators of the precision of stereological estimates: an example based on the CA1 pyramidal cell layer of rats. Neuroscience 136:757-767.
Snyder AW, Miller WH (1977): Photoreceptor diameter and spacing for highest resolving power. J Opt Soc Am 67:696-698.
Snyder AW, Miller WH (1978): Telephoto lens system of falconiform eyes. Nature 275:127-129.
Stone J (1981): The Wholemount Handbook: A Guide to the Preparation and Analysis of Retinal Wholemounts. Sydney, Maitland Publications.
Tetreault N, Hakeem A, Allman JM (2004): The distribution and size of retinal ganglion cells in Microcebus murinus, Cheirogaleus medius, and Tarsius syrichta: implications for the evolution of sensory systems in primates; in Ross C, Kay RF (eds): Anthropoid Origins: New Visions. New York, Springer, pp 463-475.
Troilo D, Rowland HC, Judge SJ (1993): Visual optics and retinal cone topography in the common marmoset (Callithrix jacchus). Vision Res 33:1301-1310.
van Rompaey H, Ray JC (2013): Nandinia binotata two spotted African palm civet; in Kingdon J, Hoffman M (eds): Mammals of Africa: Carnivores, Pangolins, Equids and Rhinoceroses. London, Bloomsbury, vol 5, pp 140-143.
Veilleux CC, Kirk EC (2009): Visual acuity in the cathemeral strepsirrhine Eulemur macaco flavifrons. Am J Primatol 71:343-352.
Veilleux CC, Kirk EC (2014): Visual acuity in mammals: effects of eye size and ecology. Brain Behav Evol 83:43-53.
Walker A (1969): The locomotion of the lorises, with special reference to the potto. Afr J Ecol 7:1-5.
Wässle H (2004): Parallel processing in the mammalian retina. Nat Rev Neurosci 5:747-757.
Wässle H, Boycott BB (1991): Functional architecture of the mammalian retina. Physiol Rev 71:447-480.
Wässle H, Grünert U, Röhrenbeck J, Boycott BB (1990): Retinal ganglion cell density and cortical magnification factor in the primate. Vision Res 30:1897-1911.
Wässle H, Peichl L, Boycott BB (1981): Morphology and topography of on- and off-alpha cells in the cat retina. Proc R Soc Lond B Biol Sci 212:157-175.
Webb S, Kaas J (1976): The sizes and distribution of ganglion cells in the retina of the owl monkey, Aotus trivirgatus. Vision Res 16:1247-1254.
West MJ, Slomianka L, Gundersen HJG (1991): Unbiased stereological estimation of the total number of neurons in the subdivisions of the rat hippocampus using the optical fractionator. Anat Rec 231:482-497.
Wikler KC, Rakic P (1990): Distribution of photoreceptor subtypes in the retina of diurnal and nocturnal primates. J Neurosci 10:3390-3401.
Williams DR, Coletta NJ (1987): Cone spacing and the visual resolution limit. J Opt Soc Am A 4:1514-1523.
Wong ROL, Wye-Dvorak J, Henry GH (1986): Morphology and distribution of neurons in the retinal ganglion cell layer of the adult tammar wallaby - Macropus eugenii. J Comp Neurol 253:1-12.
Yamada ES, Marshak DW, Silveira LC, Casagrande VA (1998): Morphology of P and M retinal ganglion cells of the bush baby. Vision Res 38:3345-3352.
Yamada ES, Silveira LCL, Perry VH, Franco ECS (2001): M and P retinal ganglion cells of the owl monkey: morphology, size and photoreceptor convergence. Vision Res 41:119-131.
Copyright / Drug Dosage / Disclaimer
Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher.
Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug.
Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.
You do not currently have access to this content.