Eye Morphology in Cathemeral Lemurids and Other Mammals

University of Texas at Austin, Austin, TX 78712, USA.
Folia Primatologica (Impact Factor: 0.89). 02/2006; 77(1-2):27-49. DOI: 10.1159/000089694
Source: PubMed


The visual systems of cathemeral mammals are subject to selection pressures that are not encountered by strictly diurnal or nocturnal species. In particular, the cathemeral eye and retina must be able to function effectively across a broad range of ambient light intensities. This paper provides a review of the current state of knowledge regarding the visual anatomy of cathemeral primates, and presents an analysis of the influence of cathemerality on eye morphology in the genus Eulemur. Due to the mutual antagonism between most adaptations for increased visual acuity and sensitivity, cathemeral lemurs are expected to resemble other cathemeral mammals in having eye morphologies that are intermediate between those of diurnal and nocturnal close relatives. However, if lemurs only recently adopted cathemeral activity patterns, then cathemeral lemurids would be expected to demonstrate eye morphologies more comparable to those of nocturnal strepsirrhines. Both predictions were tested through a comparative study of relative cornea size in mammals. Intact eyes were collected from 147 specimens of 55 primate species, and relative corneal dimensions were compared to measurements taken from a large sample of non-primate mammals. These data reveal that the five extant species of the cathemeral genus Eulemur have relative cornea sizes intermediate between those of diurnal and nocturnal strepsirrhines. Moreover, all Eulemur species have relative cornea sizes that are comparable to those of cathemeral non-primate mammals and significantly smaller than those of nocturnal mammals. These results suggest that Eulemur species resemble other cathemeral mammals in having eyes that are adapted to function under variable environmental light levels. These results also suggest that cathemerality is a relatively ancient adaptation in Eulemur that was present in the last common ancestor of the genus (ca. 8-12 MYA).

16 Reads
  • Source
    • "comm.). Other species of Eulemur appear to be devoid of this sensitivity-enhancing structure, although the histological evidence is contradictory and uncertain (Castenholz 1965; Kirk 2006). Field reports variously describe the presence or absence of eyeshine in closely related species (e.g., E. (macaco) macaco -absent, Colquhoun 1997; E (macaco) flavifrons -present, Schwitzer et al. 2007, but see Fig S7). "
    [Show abstract] [Hide abstract]
    ABSTRACT: In contrast to the majority of primates, which exhibit dedicated diurnality or nocturnality, all species of Eulemur are cathemeral. Color vision, in particular, is strongly affected by the spectral composition and intensity of ambient light, and the impact of activity period on the evolution of primate color vision is actively debated. We studied three groups of wild brown lemurs (Eulemur fulvus) in Ankarafantsika National Park, Madagascar over a one-year span. We also used non-invasive fecal DNA collection and analysis to study the opsin genes underlying the color vision of 24 individuals. We quantify the color and brightness of dietary fruits and modeled the chromaticity and discriminability of food objects to different visual phenotypes under daylight, twilight, and moonlight conditions. We found that E. fulvus possesses routine dichromacy, unlike its congener E. flavifrons, for which polymorphic trichromacy has been reported. Our models suggest that dichromacy is well-suited to the foraging ecology of E. fulvus. The performance of modeled dichromats and trichromats is comparable under nocturnal illuminants and the luminance values of most diet items are detectable across light conditions. The trichromatic phenotype demonstrates a modest advantage under daylight conditions only. Our results, taken together with reports of polymorphic trichromacy in E. flavifrons, suggest functional ecological variation in the visual system of the genus Eulemur. Interspecific phenotypic variation in the color vision of a genus is both unexpected and instructive. Ecological differences between species of Eulemur could reveal thresholds for the origins of polymorphic trichromacy, which preceded the evolution of routine trichromatic vision in humans and other primates. This article is protected by copyright. All rights reserved.
    Functional Ecology 09/2015; DOI:10.1111/1365-2435.12575 · 4.83 Impact Factor
  • Source
    • "Diurnal mammals often exhibit smaller relative cornea and lens sizes , lower rod : cone ratios , and lower retinal summation than nocturnal species ( all of which tend to increase acuity ) [ Walls , 1942 ; Hughes , 1977 ; Arrese et al . , 1999 ; Kay and Kirk , 2000 ; Ross , 2000 ; Kirk , 2004 ; Kirk and Kay , 2004 ; Silveira , 2004 ; Peichl , 2005 ; Kirk , 2006b ; Ross and Kirk , 2007 ; Hall et al . , 2012 ] . "
    [Show abstract] [Hide abstract]
    ABSTRACT: Previous comparative research has attributed interspecific variation in eye size among mammals to selection related to visual acuity. Mammalian species have also been hypothesized to differ in visual acuity partly as a result of differences in ecology. While a number of prior studies have explored ecological and phylogenetic effects on eye shape, a broad comparative analysis of the relationships between visual acuity, eye size and ecology in mammals is currently lacking. Here we use phylogenetic comparative methods to explore these relationships in a taxonomically and ecologically diverse sample of 91 mammal species. These data confirm that axial eye length and visual acuity are significantly positively correlated in mammals. This relationship conforms to expectations based on theoretical optics and prior analyses of smaller comparative samples. Our data also demonstrate that higher visual acuity in mammals is associated with: (1) diurnality and (2) predatory habits once the effects of eye size and phylogeny have been statistically controlled. These results suggest that interspecific variation in mammalian visual acuity is the result of a complex interplay between phylogenetic history, visual anatomy and ecology. © 2014 S. Karger AG, Basel.
    Brain Behavior and Evolution 02/2014; 83(1):43-53. DOI:10.1159/000357830 · 2.01 Impact Factor
  • Source
    • "For activity pattern, animals were scored as an ordinal variable with " 0, " " 1 " or " 2 " if they were nocturnal, cathemeral, or diurnal, respectively based on Mittermeier et al. (2010) (Table 2). This coding assumes that cathemerality will require adaptations that are intermediate between the other two states (e.g., Kirk 2006b). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Adaptive radiations provide important insights into many aspects of evolution, including the relationship between ecology and morphological diversification as well as between ecology and speciation. Many such radiations include divergence along a dietary axis, although other ecological variables may also drive diversification, including differences in diel activity patterns. This study examines the role of two key ecological variables, diet and activity patterns, in shaping the radiation of a diverse clade of primates, the Malagasy lemurs. When phylogeny is ignored, activity pattern and several dietary variables predicted a significant proportion of cranial shape variation. However, when phylogeny was taken into account, only typical diet accounted for a significant proportion of shape variation. One possible explanation for this discrepancy is that this radiation was characterized by a relatively small number of dietary shifts (and possibly changes in body size) that occurred in conjunction with the divergence of major clades. This pattern may be difficult to detect with the phylogenetic comparative methods used here, but may characterize not just lemurs but other mammals. This article is protected by copyright. All rights reserved.
    Evolution 01/2014; 68(5). DOI:10.1111/evo.12361 · 4.61 Impact Factor
Show more


16 Reads
Available from