Brain Behavior and Evolution最新文献

Introduction: Shared selection pressures often explain convergent trait loss, yet anurans (frogs and toads) have lost their middle ears at least 38 times with no obvious shared selection pressures unifying "earless" taxa. Anuran tympanic middle ear loss is especially perplexing because acoustic communication is dominant within Anura and tympanic middle ears enhance airborne hearing in most tetrapods.

Methods: Here, we use phylogenetic comparative methods to examine whether particular geographic ranges, microhabitats, activity patterns, or aspects of acoustic communication are associated with anuran tympanic middle ear loss.

Results: Although we find some differences between the geographic ranges of eared and earless species on average, there is plenty of overlap between the geographic distributions of eared and earless species. Additionally, we find a higher prevalence of diurnality in earless species, but not all earless species are diurnal. We find no universal adaptive explanation for the many instances of anuran tympanic middle ear loss.

Conclusion: The puzzling lack of universally shared selection pressures among earless species motivates discussion of alternative hypotheses, including genetic or developmental constraints, and the possibility that tympanic middle ear loss is maladaptive.

Introduction: The present study demonstrates that in the same brain area the astroglia can express GFAP (the main cytoskeletal protein of astroglia) in some species but not in the others of the same vertebrate class. It contrasts the former opinions that the distribution of GFAP found in a species is characteristic of the entire class. The present study investigated birds in different phylogenetic positions: duck (Cairina moschata domestica), chicken (Gallus gallus domesticus), and quails (Coturnix japonica and Excalfactoria chinensis) of Galloanserae; pigeon (Columba livia domestica) of a group of Neoaves, in comparison with representatives of other Neoaves lineages, which emerged more recently in evolution: finches (Taeniopygia guttata and Erythrura gouldiae), magpie (Pica pica), and parrots (Melopsittacus undulatus and Nymphicus hollandicus).

Methods: Following a perfusion with 4% buffered paraformaldehyde, immunoperoxidase reactions were performed with two types of anti-GFAP: monoclonal and polyclonal, on floating sections.

Results: The entopallium (formerly "ectostriatum," a telencephalic area in birds) was GFAP-immunopositive in pigeon and in the representatives of Galloanserae but not in songbirds and parrots, which emerged more recently in evolution. The lack of GFAP expression of a brain area, however, does not mean the lack of astroglia. Lesions induced GFAP expression in the territory of GFAP-immunonegative entopallia. It proved that the GFAP immunonegativity is not due to the lack of capability, but rather the suppression of GFAP production of the astrocytes in this territory. In the other areas investigated besides the entopallium (optic tectum and cerebellum), no considerable interspecific differences of GFAP immunopositivity were found. It proved that the immunonegativity of entopallium is due to neither the general lack of GFAP expression nor the incapability of our reagents to detect GFAP in these species.

Conclusion: The data are congruent with our proposal that a lack of GFAP expression has evolved in different brain areas in vertebrate evolution, typically in lineages that emerged more recently. Comparative studies on GFAP-immunopositive and GFAP-immunonegative entopallia may promote understanding the role of GFAP in neural networks.

Local circuit neurons are present in the thalamus of all vertebrates where they are considered inhibitory. They play an important role in computation and influence the transmission of information from the thalamus to the telencephalon. In mammals, the percentage of local circuit neurons in the dorsal lateral geniculate nucleus remains relatively constant across a variety of species. In contrast, the numbers of local circuit neurons in the ventral division of the medial geniculate body in mammals vary significantly depending on the species examined. To explain these observations, the numbers of local circuit neurons were investigated by reviewing the literature on this subject in these two nuclei in mammals and their respective homologs in sauropsids and by providing additional data on a crocodilian. Local circuit neurons are present in the dorsal geniculate nucleus of sauropsids just as is the case for this nucleus in mammals. However, sauropsids lack local circuits neurons in the auditory thalamic nuclei homologous to the ventral division of the medial geniculate body. A cladistic analysis of these results suggests that differences in the numbers of local circuit neurons in the dorsal lateral geniculate nucleus of amniotes reflect an elaboration of these local circuit neurons as a result of evolution from a common ancestor. In contrast, the numbers of local circuit neurons in the ventral division of the medial geniculate body changed independently in several mammalian lineages.

The hippocampus plays an important role in spatial navigation and spatial learning across a variety of vertebrate species. Sex and seasonal differences in space use and behavior are known to affect hippocampal volume. Similarly, territoriality and differences in home range size are known to affect the volume of the reptile hippocampal homologues, the medial and dorsal cortices (MC, DC). However, studies have almost exclusively investigated males and little is known about sex or seasonal differences in MC and/or DC volumes in lizards. Here, we are the first to simultaneously examine sex and seasonal differences in MC and DC volumes in a wild lizard population. In Sceloporus occidentalis, males display territorial behaviors that are more pronounced during the breeding season. Given this sex difference in behavioral ecology, we expected males to have larger MC and/or DC volumes than females and for this difference to be most pronounced during the breeding season when territorial behavior is increased. Male and female S. occidentalis were captured from the wild during the breeding season and the post-breeding season and were sacrificed within 2 days of capture. Brains were collected and processed for histology. Cresyl-violet-stained sections were used to quantify brain region volumes. In these lizards, breeding females had larger DC volumes than breeding males and nonbreeding females. There was no sex or seasonal difference in MC volumes. Differences in spatial navigation in these lizards may involve aspects of spatial memory related to breeding other than territoriality that affect plasticity of the DC. This study highlights the importance of investigating sex differences and including females in studies of spatial ecology and neuroplasticity.

Mudskippers are intertidal burrowing fish with unique living habits. So far, studies on the cytoarchitecture of the brain in fish with such behaviors remain limited. Therefore, documenting the neuroanatomy of this animal is of interest because of its unique characteristics. In this study, we examined the cytoarchitecture of mudskipper (Boleophthalmus pectinirostris) brain and investigated whether it has any peculiarities in its brain structures. In general, the basic composition, morphology, and organization of mudskipper brain do not vary markedly from those of other teleosts. The main differences appear in the telencephalon and diencephalon. In addition to Nissl staining, immunostainings for catecholaminergic and cholinergic systems were performed to help identify certain nuclei. The results showed that the number of subdivisions of the central division of pallium, lateral division of pallium, and medial division of pallium were different with other teleost species. In addition, some diencephalic nuclei, including the nucleus subglomerulosus, lateral thalamic nucleus, and intermediate superficial pretectal nucleus, were absent, which suggests the corresponding functions, such as visual or gustatory function, are less developed or specialized in B. pectinirostris. These results will provide a fundamental neuroanatomical basis for future studies on neuroendocrine regulation of behavior in intertidal burrowing fish.