| 1. |
- Adden, Andrea, et al.
(författare)
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The brain of a nocturnal migratory insect, the Australian Bogong moth
- 2020
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Ingår i: Journal of Comparative Neurology. - : Wiley. - 0021-9967 .- 1096-9861. ; 528:11, s. 1942-1963
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Tidskriftsartikel (refereegranskat)abstract
- Every year, millions of Australian Bogong moths (Agrotis infusa) complete an astonishing journey: In Spring, they migrate over 1,000 km from their breeding grounds to the alpine regions of the Snowy Mountains, where they endure the hot summer in the cool climate of alpine caves. In autumn, the moths return to their breeding grounds, where they mate, lay eggs and die. These moths can use visual cues in combination with the geomagnetic field to guide their flight, but how these cues are processed and integrated into the brain to drive migratory behavior is unknown. To generate an access point for functional studies, we provide a detailed description of the Bogong moth's brain. Based on immunohistochemical stainings against synapsin and serotonin (5HT), we describe the overall layout as well as the fine structure of all major neuropils, including the regions that have previously been implicated in compass-based navigation. The resulting average brain atlas consists of 3D reconstructions of 25 separate neuropils, comprising the most detailed account of a moth brain to date. Our results show that the Bogong moth brain follows the typical lepidopteran ground pattern, with no major specializations that can be attributed to their spectacular migratory lifestyle. These findings suggest that migratory behavior does not require widespread modifications of brain structure, but might be achievable via small adjustments of neural circuitry in key brain areas. Locating these subtle changes will be a challenging task for the future, for which our study provides an essential anatomical framework.
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| 2. |
- Homberg, Uwe, et al.
(författare)
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Orcokinin in the central complex of the locust Schistocerca gregaria : Identification of immunostained neurons and colocalization with other neuroactive substances
- 2021
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Ingår i: Journal of Comparative Neurology. - : Wiley. - 0021-9967 .- 1096-9861. ; 529:8, s. 1876-1894
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Tidskriftsartikel (refereegranskat)abstract
- The central complex is a group of highly interconnected neuropils in the insect brain. It is involved in the control of spatial orientation, based on external compass cues and various internal needs. The functional and neurochemical organization of the central complex has been studied in detail in the desert locust Schistocerca gregaria. In addition to classical neurotransmitters, immunocytochemistry has provided evidence for a major contribution of neuropeptides to neural signalling within the central complex. To complement these data, we have identified all orcokinin‐immunoreactive neurons in the locust central complex and associated brain areas. About 50 bilateral pairs of neurons innervating all substructures of the central complex exhibit orcokinin immunoreactivity. Among these were about 20 columnar neurons, 33 bilateral pairs of tangential neurons of the central body, and seven pairs of tangential neurons of the protocerebral bridge. In silico transcript analysis suggests the presence of eight different orcokinin‐A type peptides in the desert locust. Double label experiments showed that all orcokinin‐immunostained tangential neurons of the lateral accessory lobe cluster were also immunoreactive for GABA and the GABA‐synthesizing enzyme glutamic acid decarboxylase. Two types of tangential neurons of the upper division of the central body were, furthermore, also labeled with an antiserum against Dip‐allatostatin I. No colocalization was found with serotonin immunostaining. The data provide additional insights into the neurochemical organization of the locust central complex and suggest that orcokinin‐peptides of the orcokinin‐A gene act as neuroactive substances at all stages of signal processing in this brain area.
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| 3. |
- Lisney, Thomas J., et al.
(författare)
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Retinal topography in two species of flamingo (Phoenicopteriformes : Phoenicopteridae)
- 2020
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Ingår i: Journal of Comparative Neurology. - : Wiley. - 0021-9967 .- 1096-9861. ; 528:17, s. 2848-2863
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we assessed eye morphology and retinal topography in two flamingo species, the Caribbean flamingo (Phoenicopterus ruber) and the Chilean flamingo (P. chilensis). Eye morphology is similar in both species and cornea size relative to eye size (C:A ratio) is intermediate between those previously reported for diurnal and nocturnal birds. Using stereology and retinal whole mounts, we estimate that the total number of Nissl-stained neurons in the retinal ganglion cell (RGC) layer in the Caribbean and Chilean flamingo is ~1.70 and 1.38 million, respectively. Both species have a well-defined visual streak with a peak neuron density of between 13,000 and 16,000 cells mm−2 located in a small central area. Neurons in the high-density regions are smaller and more homogeneous compared to those in medium- and low-density regions. Peak anatomical spatial resolving power in both species is approximately 10–11 cycles/deg. En-face images of the fundus in live Caribbean flamingos acquired using spectral domain optical coherence tomography (SD-OCT) revealed a thin, dark band running nasotemporally just dorsal to the pecten, which aligned with the visual streak in the retinal topography maps. Cross-sectional images (B-scans) obtained with SD-OCT showed that this dark band corresponds with an area of retinal thickening compared to adjacent areas. Neither the retinal whole mounts, nor the SD-OCT imaging revealed any evidence of a central fovea in either species. Overall, we suggest that eye morphology and retinal topography in flamingos reflects their cathemeral activity pattern and the physical nature of the habitats in which they live.
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| 4. |
- Thoen, Hanne Halkinrud, et al.
(författare)
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The reniform body : An integrative lateral protocerebral neuropil complex of Eumalacostraca identified in Stomatopoda and Brachyura
- 2020
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Ingår i: Journal of Comparative Neurology. - : Wiley. - 1096-9861 .- 0021-9967. ; 528:7, s. 1079-1094
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Tidskriftsartikel (refereegranskat)abstract
- Mantis shrimps (Stomatopoda) possess in common with other crustaceans, and with Hexapoda, specific neuroanatomical attributes of the protocerebrum, the most anterior part of the arthropod brain. These attributes include assemblages of interconnected centers called the central body complex and in the lateral protocerebra, situated in the eyestalks, paired mushroom bodies. The phenotypic homologues of these centers across Panarthropoda support the view that ancestral integrative circuits crucial to action selection and memory have persisted since the early Cambrian or late Ediacaran. However, the discovery of another prominent integrative neuropil in the stomatopod lateral protocerebrum raises the question whether it is unique to Stomatopoda or at least most developed in this lineage, which may have originated in the upper Ordovician or early Devonian. Here, we describe the neuroanatomical structure of this center, called the reniform body. Using confocal microscopy and classical silver staining, we demonstrate that the reniform body receives inputs from multiple sources, including the optic lobe's lobula. Although the mushroom body also receives projections from the lobula, it is entirely distinct from the reniform body, albeit connected to it by discrete tracts. We discuss the implications of their coexistence in Stomatopoda, the occurrence of the reniform body in another eumalacostracan lineage and what this may mean for our understanding of brain functionality in Pancrustacea.
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| 5. |
- Warrington, Rachael E., et al.
(författare)
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Visual opsin expression and morphological characterization of retinal photoreceptors in the pouched lamprey (Geotria australis, Gray)
- 2021
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Ingår i: Journal of Comparative Neurology. - : John Wiley & Sons. - 0021-9967 .- 1096-9861. ; 529:9, s. 2265-2282
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Tidskriftsartikel (refereegranskat)abstract
- Lampreys are extant members of the agnathan (jawless) vertebrates that diverged ~500 million years ago, during a critical stage of vertebrate evolution when image‐forming eyes first emerged. Among lamprey species assessed thus far, the retina of the southern hemisphere pouched lamprey, Geotria australis, is unique, in that it possesses morphologically distinct photoreceptors and expresses five visual photopigments. This study focused on determining the number of different photoreceptors present in the retina of G. australis and whether each cell type expresses a single opsin class. Five photoreceptor subtypes were identified based on ultrastructure and differential expression of one of each of the five different visual opsin classes (lws, sws1, sws2, rh1, and rh2) known to be expressed in the retina. This suggests, therefore, that the retina of G. australis possesses five spectrally and morphologically distinct photoreceptors, with the potential for complex color vision. Each photoreceptor subtype was shown to have a specific spatial distribution in the retina, which is potentially associated with changes in spectral radiance across different lines of sight. These results suggest that there have been strong selection pressures for G. australis to maintain broad spectral sensitivity for the brightly lit surface waters that this species inhabits during its marine phase. These findings provide important insights into the functional anatomy of the early vertebrate retina and the selection pressures that may have led to the evolution of complex color vision.
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| 6. |
- Wheaton, Benjamin J., et al.
(författare)
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Identification of regenerative processes in neonatal spinal cord injury in the opossum (Monodelphis domestica) : A transcriptomic study
- 2021
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Ingår i: Journal of Comparative Neurology. - : John Wiley & Sons. - 0021-9967 .- 1096-9861. ; 529:5, s. 969-986
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Tidskriftsartikel (refereegranskat)abstract
- This study investigates the response to spinal cord injury in the gray short‐tailed opossum (Monodelphis domestica). In opossums spinal injury early in development results in spontaneous axon growth through the injury, but this regenerative potential diminishes with maturity until it is lost entirely. The mechanisms underlying this regeneration remain unknown. RNA sequencing was used to identify differential gene expression in regenerating (SCI at postnatal Day 7, P7SCI) and nonregenerating (SCI at Day 28, P28SCI) cords +1d, +3d, and +7d after complete spinal transection, compared to age‐matched controls. Genes showing significant differential expression (log2FC ≥ 1, Padj ≤ 0.05) were used for downstream analysis. Across all time‐points 233 genes altered expression after P7SCI, and 472 genes altered expression after P28SCI. One hundred and forty‐seven genes altered expression in both injury ages (63% of P7SCI data set). The majority of changes were gene upregulations. Gene ontology overrepresentation analysis in P7SCI gene‐sets showed significant overrepresentations only in immune‐associated categories, while P28SCI gene‐sets showed overrepresentations in these same immune categories, along with other categories such as “cell proliferation,” “cell adhesion,” and “apoptosis.” Cell‐type–association analysis suggested that, regardless of injury age, injury‐associated gene transcripts were most strongly associated with microglia and endothelial cells, with strikingly fewer astrocyte, oligodendrocyte and neuron‐related genes, the notable exception being a cluster of mostly downregulated oligodendrocyte‐associated genes in the P7SCI + 7d gene‐set. Our findings demonstrate a more complex transcriptomic response in nonregenerating cords, suggesting a strong influence of non‐neuronal cells in the outcome after injury and providing the largest survey yet of the transcriptomic changes occurring after SCI in this model.
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