Retinal ganglion cell topography and spatial resolution estimation in the Japanese tree frog Hyla japonica (Günther, 1859)

Abstract

Tree frogs are an interesting and diverse group of frogs. They display a number of unique adaptations to life in the arboreal environment. Vision plays a crucial role in their ecology. The topography of retinal ganglion cells (GCs) is closely related to a species' visual behavior. Despite a large amount of research addressing GC topography in vertebrates, there is scarce data on this subject in tree frogs. I studied the topography of GCs in the retina of the Japanese tree frog Hyla japonica. The GC density distribution was locally fairly homogeneous, with spatial density increasing gradually from the dorsal and ventral periphery towards the equator. A moderately pronounced visual streak was found close to the equator in the dorsal hemiretina, with a distinct area retinae temporalis in the dorsotemporal quadrant potentially subserving binocular vision. The minimum GC density (mean AE SEM, n = 5) was 3060 AE 60 and the maximum 12 800 AE 170 cells/mm 2 . The total number of GCs was 292 AE 7 9 10 3 . The theoretical anatomical spatial resolution estimated from GC densities and eye optics was lowest in the ventral periphery (ca. 0.9 and 1.3 cycles/degree in air and water, respectively) and highest in the area retinae temporalis (ca. 2.1 and 2.8 cycles/degree). The relatively high GC density and presence of specialized retinal regions in Hyla japonica are consistent with its highly visual behavior. The present findings contribute to our understanding of the relative role of common ancestry and environmental pressure in GC topography variation within Anura.

Ecology drives patterns of spectral transmission in the ocular lenses of frogs and salamanders

“…Spatial acuity is most reliably determined by behavioural means, which has been investigated in few amphibians (Aho, 1996; Birukow, 1937; Manteuffel & Himstedt, 1978). However, because the ability of vertebrate eyes to resolve spatial detail depends largely on the focal length of the eye and the density of retinal neurons (Land & Nilsson, 2012), these can be used to calculate a theoretical spatial resolving power for a species, which often closely matches that determined by behavioural means (Pushchin, 2019). Large eyes and an increased density of cones and retinal ganglion cells potentially result in higher spatial resolution.…”

“…Large eyes and an increased density of cones and retinal ganglion cells potentially result in higher spatial resolution. Unfortunately, such anatomically based estimates of spatial resolution have only been calculated for four anuran species (see Pushchin, 2021 for review), and ganglion cell density alone has been determined in an additional eight (see Pushchin, 2019 for review). From these limited behavioural and morphological data, maximum resolving power was highest in a scansorial hylid, Boana ( Hyla ) raniceps (Bousfield & Pessoa, 1980).…”

A closer look at pupil diversity and evolution in frogs and toads

“…Pupil shape and its contractility are of major importance to deal with different light intensities and to establish a suitable compromise between high acuity and sensitivity [73,74]. However, pupil shape diversity is only one aspect of the eye that is relevant from the perspective of the evolution of visual perception, others being for example eye size [30,75], cornea and lens transmittance [27,28], lens optics [32,76], photoreceptor composition and size [25,26], oil droplets and visual pigments [77][78][79][80], and neural pathways [22,81].…”

“…[14,15]), there has been a renewal in the attention to the amphibian visual system. Over the last decade, the main focus has been set on visual pigments and especially in the unique green rods only present in the amphibian retina (see reviews by [16,17]), but some studies also focused on different aspects of eye morphology [18][19][20][21][22][23]. Anurans display a vast diversity of ecological traits including habits, diel activity, and reproductive mode [8,24].…”

“…Pupil shape diversity in adult frogs and toads. Seven general pupil shapes were defined, with a remarkable internal diversity in most of them: vertical (1-6), horizontal(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17), rhomboidal/subrhomboidal(18)(19)(20)(21)(22)(23), triangular(24)(25)(26), circular(27), fan(28)(29), inverted fan(30).1, Agalychnis callidryas (Hylidae); 2, Afrixalus fornasini (Hyperoliidae); 3, Limnomedusa macroglossa (Alsodidae); 4, Pelobates fuscus (Pelobatidae); 5, Calyptocephalella gayi (Calyptocephalellidae); 6, Pipa pipa (Pipidae); 7, Sphaenorhynchus lacteus (Hylidae); 8, Pristimantis metabates (Craugastoridae); 9, Boophis pauliani (Mantellidae); 10, Aplastodiscus cavicola (Hylidae); 11, Itapotihyla langsdorffii (Hylidae); 12, Chiromantis rufescens (Rhacophoridae); 13, Eupsophus roseus (Alsodidae); 14, Hyloscirtus ptychodactylus (Hylidae); 15, Espadarana durrellorum (Centrolenidae); 16, Boophis lilianae (Mantellidae); 17, Hyperolius marmoratus (Hyperoliidae); 18, Nyctibatrachus karnatakaensis (Nyctibatrachidae); 19, Odontophrynus americanus (Odontophrynidae); 20, Dyscophus antongilii (Microhylidae); 21, Boana geographica (Hylidae); 22, Morerella cyanophthalma (Hyperoliidae); 23, Spinomantis aglavei (Mantellidae); 24, Crinia sloanei (Myobatrachidae); 25, Bombina variegata (Bombinatoridae); 26, Barbourula busuangensis (Bombinatoridae); 27, Xenopus laevis (Pipidae); 28, Occidozyga lima (Dicroglossidae); 29, Ranoidea cryptotis (Hylidae); 30, Phrynella pulchra (Microhylidae).…”