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We quantified both proliferative (Ki-67 immunohistochemistry) and immature (doublecortin immunohistochemistry) cells within the dentate gyrus of adult Egyptian fruit bats from three distinct environments: (a) primary rainforest, (b) subtropical woodland, and (c) fifth-generation captive-bred. We used four different previously reported methods to assess the effect of the environment on proliferative and immature cells: (a) the comparison of raw totals of proliferative and immature cells; (b) these totals standardized to brain mass; (c) these totals expressed as a density using the volume of the granular cell layer (GCLv) for standardization; and (d) these totals expressed as a percentage of the total number of granule cells. For all methods, the numbers of proliferative cells did not differ statistically among the three groups, indicating that the rate of proliferation, while malleable to experimental manipulation or transiently in response to events of importance in the natural habitat, appears to occur, for the most part, at a predetermined rate within a species. For the immature cells, raw numbers and standardizations to brain mass and GCLv revealed no difference between the three groups studied; however, standardization to total granule cell numbers indicated that the two groups of wild-caught bats had significantly higher numbers of immature neurons than the captive-bred bats. These contrasting results indicate that the interpretation of the effect of the environment on the numbers of immature neurons appears method dependent. It is possible that current methods are not sensitive enough to reveal the effect of different environments on proliferative and immature cells.

This study investigated the pattern of adult neurogenesis throughout the brains of three prosimian primate species using immunohistochemical techniques for endogenous markers of this neural process. Two species, Galago demidoff and Perodicticus potto, were obtained from wild populations in the primary rainforest of central Africa, while one species, Lemur catta, was captive-bred. Two brains from each species, perfusion-fixed with 4% paraformaldehyde, were sectioned (50 µm section thickness) in sagittal and coronal planes. Using Ki-67 and doublecortin (DCX) antibodies, proliferating cells and immature neurons were identified in the two canonical neurogenic sites of mammals, the subventricular zone of the lateral ventricle (SVZ) giving rise to the rostral migratory stream (RMS), and the subgranular zone of the dentate gyrus of the hippocampus. In addition a temporal migratory stream (TMS), emerging from the temporal horn of the lateral ventricle to supply the piriform cortex and adjacent brain regions with new neurons, was also evident in the three prosimian species. While no Ki-67-immunoreactive cells were observed in the cerebellum, DCX-immunopositive cells were observed in the cerebellar cortex of all three species. These findings are discussed in a phylogenetic context., SCOPUS: ar.j, info:eu-repo/semantics/published

Megachiropteran bats (megabats) show remarkable diversity in microhabitat occupation and trophic specializations, but information on how vision relates to their behavioral ecology is scarce. Using stereology and retinal wholemounts, we measured the topographic distribution of retinal ganglion cells and determined the spatial resolution of eight African megachiropterans with distinct roosting and feeding ecologies. We found that species roosting in open microhabitats have a pronounced streak of high retinal ganglion cell density, whereas those favoring more enclosed microhabitats have a less pronounced streak (or its absence in Hypsignathus monstrosus). An exception is the cave-dwelling Rousettus aegyptiacus, which has a pronounced horizontal streak that potentially correlates with its occurrence in more open environments during foraging. In all species, we found a temporal area with maximum retinal ganglion cell density (∼5,000–7,000 cells/mm2) that affords enhanced resolution in the frontal visual field. Our estimates of spatial resolution based on peak retinal ganglion cell density and eye size (∼6–12 mm in axial length) range between ∼2 and 4 cycles/degree. Species that occur in more enclosed microhabitats and feed on plant material have lower spatial resolution (∼2 cycles/degree) compared with those that roost in open and semiopen areas (∼3–3.8 cycles/degree). We suggest that the larger eye and concomitant higher spatial resolution (∼4 cycles/degree) in H. monstrosus may have facilitated the carnivorous aspect of its diet. In conclusion, variations in the topographic organization and magnitude of retinal ganglion density reflect the specific ecological needs to detect food/predators and the structural complexity of the environments. J. Comp. Neurol. 525:186–203, 2017. © 2016 Wiley Periodicals, Inc., SCOPUS: ar.j, FLWIN, info:eu-repo/semantics/published

The present study describes the nuclear organization of the cholinergic, catecholaminergic, serotonergic and orexinergic systems in the brains of the springhare and Beecroft's scaly-tailed squirrel following immunohistochemical labelling. We aimed to investigate any differences in the nuclear organization of these neural systems when compared to previous data on other species of rodents, as these two rodent species have relatively large brains − 1.2 to 1.4 times larger than would be expected for mammals of their body mass and 1.7–1.9 times larger than would be expected for rodents of their body mass. A series of coronal sections were taken through two brains of each species and immunohistochemically labelled with antibodies against choline acetyltransferase, tyrosine hydroxylase, serotonin and orexin-A. Generally, the nuclear complement of these systems revealed extensive similarities between both species and to previously studied rodents. While no differences were observed in the nuclear complement of the serotonergic and orexinergic systems, some differences were observed in the nuclear complement of the cholinergic and catecholaminergic systems. These include the presence of cholinergic neurons in the cerebral cortex and nucleus of the trapezoid body in the springhare; while the Beecroft's scaly-tailed squirrel exhibited cholinergic neurons in the pretectal area of the midbrain. For the catecholaminergic system it was observed that Beecroft's scaly-tailed squirrel possessed immunoreactive neurons in the accessory olfactory bulb. Despite these four differences, most not previously observed in rodents, the remaining complement of cholinergic and catecholaminergic nuclei were identical to that observed in other rodents, including the presence of the rodent specific catecholaminergic rostral dorsal midline medullary (C3) nucleus in the medulla oblongata. Thus, even with a significant increase in relative brain size, the overall complement of nuclei forming these syst, SCOPUS: ar.j, info:eu-repo/semantics/published

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., SCOPUS: ar.j, info:eu-repo/semantics/published

This study uses Ki-67 and doublecortin (DCX) immunohistochemistry to delineate potential neurogenic zones, migratory pathways, and terminal fields associated with adult neurogenesis in the brains of three microchiropterans. As with most mammals studied to date, the canonical subgranular and subventricular neurogenic zones were observed. Distinct labeling of newly born cells and immature neurons within the dentate gyrus of the hippocampus was observed in all species. A distinct rostral migratory stream (RMS) that appears to split around the medial aspect of the caudate nucleus was observed. These two rostral stream divisions appear to merge at the rostroventral corner of the caudate nucleus to turn and enter the olfactory bulb, where a large terminal field of immature neurons was observed. DCX immunolabeled neurons were observed mostly in the rostral neocortex, but a potential migratory stream to the neocortex was not identified. A broad swathe of newly born cells and immature neurons was found between the caudoventral division of the RMS and the piriform cortex. In addition, occasional immature neurons were observed in the amygdala and DCX-immunopositive axons were observed in the anterior commissure. While the majority of these features have been found in several mammal species, the large number of DCX immunolabeled cells found between the RMS and the piriform cortex and the presence of DCX immunostained axons in the anterior commissure are features only observed in microchiropterans and insectivores to date. In the diphyletic scenario of chiropteran evolution, these observations align the microchiropterans with the insectivores. Anat Rec, 299:1548–1560, 2016. © 2016 Wiley Periodicals, Inc., SCOPUS: ar.j, FLWIN, info:eu-repo/semantics/published

The organization of the cholinergic, catecholaminergic, and serotonergic neurons in the brains of five species of insectivores and the orexinergic (hypocretinergic) system in four insectivore species is presented. We aimed to investigate the nuclear complement of these neural systems in comparison to those of other mammalian species. Brains of insectivores were coronally sectioned and immunohistochemically stained with antibodies against choline acetyltransferase, tyrosine hydroxylase, serotonin and orexin-A. The majority of nuclei were similar among the species investigated and to mammals in general, but certain differences in the nuclear complement highlighted potential phylogenetic interrelationships. In the cholinergic system, the three shrew species lacked parabigeminal and Edinger-Westphal nuclei. In addition, the appearance of the laterodorsal tegmental nucleus in all insectivores revealed a mediodorsal arch. All three of these features are the same as those present in microchiropterans. The catecholaminergic system of the three shrew species lacked the A4 and A15d nuclei, as well as having an incipient A9v nucleus, again features found in microchiropteran brains. The serotonergic and orexinergic systems of the insectivores are similar to those seen across most eutherian mammals. The analysis of similarities and differences across mammalian species indicates a potential phylogenetic relationship between the Soricidae (shrews) and the microchiropterans., SCOPUS: ar.j, info:eu-repo/semantics/published

The nuclear organization of the cholinergic, catecholaminergic, serotonergic and orexinergic systems in the brains of three species of strepsirrhine primates is presented. We aimed to investigate the nuclear complement of these neural systems in comparison to those of simian primates, megachiropterans and other mammalian species. The brains were coronally sectioned and immunohistochemically stained with antibodies against choline acetyltransferase, tyrosine hydroxylase, serotonin and orexin-A. The nuclei identified were identical among the strepsirrhine species investigated and identical to previous reports in simian primates. Moreover, a general similarity to other mammals was found, but specific differences in the nuclear complement highlighted potential phylogenetic interrelationships. The central feature of interest was the structure of the locus coeruleus complex in the primates, where a central compactly packed core (A6c) of tyrosine hydroxylase immunopositive neurons was surrounded by a shell of less densely packed (A6d) tyrosine hydroxylase immunopositive neurons. This combination of compact and diffuse divisions of the locus coeruleus complex is only found in primates and megachiropterans of all the mammalian species studied to date. This neural character, along with variances in a range of other neural characters, supports the phylogenetic grouping of primates with megachiropterans as a sister group., SCOPUS: ar.j, info:eu-repo/semantics/published

The family Herpestidae (cusimanses and mongooses) is a monophyletic radiation of carnivores with remarkable variation in microhabitat occupation and diel activity, but virtually nothing is known about how they use vision in the context of their behavioral ecology. In this paper, we measured the number and topographic distribution of neurons (rods, cones and retinal ganglion cells) and estimated the spatial resolving power of the eye of the diurnal, forest-dwelling Ansorge's cusimanse (Crossarchus ansorgei) .Using retinal wholemounts and stereology, we found that rods are more numerous (42,500,000; 92%) than cones (3,900,000; 8%). Rod densities form a concentric and dorsotemporally asymmetric plateau that matches the location and shape of a bright yellow tapetum lucidum located within the dorsal aspect of the eye. Maximum rod density (340,300 cells/mm2 ) occurs within an elongated plateau below the optic disc that cor-responds to a transitional region between the tapetum lucidum and the pigmented choroid. Cone densities form a temporal area with a peak density of 44,500 cells/mm2 embedded in a weak horizontal streak that matches the topographic distribution of retinal ganglion cells. Convergence ratios of cones to retinal ganglion cells vary from 50: 1 in the far periphery to 3: 1 in the temporal area. With a ganglion cell peak density of 13,400 cells/mm2 and an eye size of 11 mm in axial length, we estimated upper limits of spatial resolution of 7.5-8 cycles/degree, which is comparable to other carnivores such as hyenas. In conclusion, we suggest that the topographic retinal traits described for Ansorge's cusimanse conform to a presumed carnivore retinal blueprint but also show variations that reflect its specific ecological needs., SCOPUS: ar.j, info:eu-repo/semantics/published

Adult neurogenesis in the mammalian brain is now a widely accepted phenomenon, typically occurring in two forebrain structures: the subgranular zone (SGZ) of the hippocampal dentate gyrus and the subventricular zone (SVZ). Until recently, the majority of studies have focused on laboratory rodents, and it is under debate whether the process of adult neurogenesis occurs outside of the SGZ and the SVZ in other mammalian species. In the present study, we investigated potential adult neurogenetic sites in the brains of two elephant shrews/sengis, a golden mole and a rock hyrax, all members of the superorder Afrotheria. Doublecortin (DCX) immunoreactivity was used as a proxy to visualise adult neu- rogenesis, which is expressed in neuronal precursor cells and immature neurons. In all four species, densely packed DCXpositive cells were present in the SVZ, from where cells appear to migrate along the rostral migratory stream towards the olfactory bulb (OB). DCX-immunopositive cells were present in the granular cell layer and the glomerular layer of the OB. In the hippocampus, DCX-immunopositive cells were observed in the SGZ and in the granular layer of the dentate gyrus, with DCX-immunopositive processes extending into the molecular layer. In addition to these well-established adult neurogenic regions, DCX-immunopositive cells were also observed in layer II of the neocortex and the piriform cortex. While the present study reveals a similar pattern of adult neurogenesis to that reported previously in other mammals, further studies are needed to clarify if the cortical DCX-immunopositive cells are newly generated neurons or cells undergoing cortical remodelling., SCOPUS: ar.j, info:eu-repo/semantics/published