Unusual topographic specializations of retinal ganglion cell density and spatial resolution in a cliff-dwelling artiodactyl, the Nubian ibex (Capra nubiana)

Morphological Characteristics of Retinal Ganglion Cells in the Retinas of Giant Pandas (Ailuropoda melanoleuca)

Vision plays a crucial role in the survival of animals, and the visual system has particularly selectively evolved in response to the visual environment, ecological niche, and species habitats in vertebrate species. To date, a horizontal streak of retinal ganglion cell (RGC) distribution pattern is observed across mammal species. Here, we report that the giant panda's vertically oriented visual streak, combined with current evidence of the animal's forward-placed eyes, ocular structure, and retinal neural topographic distribution patterns, presents the emergence of a well-adapted binocular visual system. Our results suggest that the giant panda may use a unique way to processing binocular visual information. Results of mathematical simulation are in favor of this hypothesis. The topographic distribution properties of RGCs reported here could be essential for understanding the visual adaptation and evolution of this living fossil.

Tree-Climbing Behavior of a Forest-Dwelling Ungulate: The Formosan Serow

Ungulates are terrestrial herbivores, basically adapted to running fast on the ground; tree-climbing behavior has been reported only in seven species, and five of them live in open habitats (Capra hircus, C. aegagrus, C. falconeri, C. cylindricornis, Oreotragus oreotragus). Tree-climbing behavior may also be evolved in ungulates inhabiting dense forests with abundant trees; however, this has rarely been reported in such species (Moschus leucogaster, M. moschiferus), probably due to the difficulty of observing in the wild. The numerous publicly available records in social networks hold potentially valuable information on the atypical behaviors of wild ungulates. Here, we explored the tree-climbing behavior of a forest-dwelling ungulate, the Formosan serow in Taiwan, a subtropical island, by extracting information from online social media platforms. We researched images and videos of Formosan serows through Facebook and YouTube and collected a total of 15 tree-climbing events. In these materials, Formosan serows climbed 10 tree species, including evergreen coniferous and broad-leaved trees, and a variety of parts, ranging in height from 0.6 to 4 m, and from branches of shrubs to trunks of tall trees. Tree-climbing behavior was recorded throughout Taiwan and from lowlands to subalpine zones, suggesting that tree climbing may be a common behavior in this species. Foraging while climbing trees was frequently observed (53.3%), suggesting that the purpose or benefit for climbing is to obtain additional food other than plants growing near the ground surface. In contrast to other tree-climbing ungulates, Formosan serows climbed trees not only in winter, but also in other seasons, when food is relatively abundant. This is the first scientific report of tree-climbing behavior in the Formosan serow that is typically a forest dweller.

A Review of Cervidae Visual Ecology

This review examines the visual systems of cervids in relation to their ability to meet their ecological needs and how their visual systems are specialized for particular tasks. Cervidae encompasses a diverse group of mammals that serve as important ecological drivers within their ecosystems. Despite evidence of highly specialized visual systems, a large portion of cervid research ignores or fails to consider the realities of cervid vision as it relates to their ecology. Failure to account for an animal's visual ecology during research can lead to unintentional biases and uninformed conclusions regarding the decision making and behaviors for a species or population. Our review addresses core behaviors and their interrelationship with cervid visual characteristics. Historically, the study of cervid visual characteristics has been restricted to specific areas of inquiry such as color vision and contains limited integration into broader ecological and behavioral research. The purpose of our review is to bridge these gaps by offering a comprehensive review of cervid visual ecology that emphasizes the interplay between the visual adaptations of cervids and their interactions with habitats and other species. Ultimately, a better understanding of cervid visual ecology allows researchers to gain deeper insights into their behavior and ecology, providing critical information for conservation and management efforts.

Ganglion cells and displaced amacrine cells density in the retina of the collared peccary (Pecari tajacu)

In the present study, we investigated the topographical distribution of ganglion cells and displaced amacrine cells in the retina of the collared peccary (Pecari tajacu), a diurnal neotropical mammal of the suborder Suina (Order Artiodactyla) widely distributed across central and mainly South America. Retinas were prepared and processed following the Nissl staining method. The number and distribution of retinal ganglion cells and displaced amacrine cells were determined in six flat-mounted retinas from three animals. The average density of ganglion cells was 351.822 ± 31.434 GC/mm². The peccary shows a well-developed visual streak. The average peak density was 6,767 GC/mm² and located within the visual range and displaced temporally as an area temporalis. Displaced amacrine cells have an average density of 300 DAC/mm², but the density was not homogeneous along the retina, closer to the center of the retina the number of cells decreases and when approaching the periphery the density increases, in addition, amacrine cells do not form retinal specialization like ganglion cells. Outside the area temporalis, amacrine cells reach up to 80% in the ganglion cell layer. However, in the region of the area temporalis, the proportion of amacrine cells drops to 32%. Thus, three retinal specializations were found in peccary’s retina by ganglion cells: visual streak, area temporalis and dorsotemporal extension. The topography of the ganglion cells layer in the retina of the peccary resembles other species of Order Artiodactyla already described and is directly related to its evolutionary history and ecology of the species.