Ontogenetic Shifts in Brain Size and Brain Organization of the Atlantic Sharpnose Shark, Rhizoprionodon terraenovae

2020 ◽  
Vol 95 (3-4) ◽  
pp. 162-180
Author(s):  
Krista V. Laforest ◽  
Emily E. Peele ◽  
Kara E. Yopak
Keyword(s):  
Medulla Oblongata ◽  
Optic Tectum ◽  
Sexual Maturity ◽  
Brain Size ◽  
Relative Size ◽  
Later Life ◽  
Olfactory Bulbs ◽  
Ontogenetic Shifts ◽  
The Brain ◽  
Atlantic Sharpnose Shark

Throughout an animal’s life, species may occupy different environments and exhibit distinct life stages, known as ontogenetic shifts. The life histories of most sharks (class: Chondrichthyes) are characterized by these ontogenetic shifts, which can be defined by changes in habitat and diet as well as behavioral changes at the onset of sexual maturity. In addition, fishes experience indeterminate growth, whereby the brain and body grow throughout the organism’s life. Despite a presupposed lifelong neurogenesis in sharks, very little work has been done on ontogenetic changes in the brain, which may be informative about functional shifts in sensory and behavioral specializations. This study quantified changes in brain-body scaling and the scaling of six major brain regions (olfactory bulbs, telencephalon, diencephalon, optic tectum, cerebellum, and medulla oblongata) throughout ontogeny in the Atlantic sharpnose shark, <i>Rhizoprio­nodon terraenovae</i>. As documented in other fishes, brain size increased significantly with body mass throughout ontogeny in this species, with the steepest period of growth in early life. The telencephalon, diencephalon, optic tectum, and medulla oblongata scaled with negative allometry against the rest of the brain throughout ontogeny. However, notably, the olfactory bulbs and cerebellum scaled hyperallometrically to the rest of the brain, whereby these structures enlarged disproportionately as this species matured. Changes in the relative size of the olfactory bulbs throughout ontogeny may reflect an increased reliance on olfaction at later life history stages in <i>R. terraenovae</i>, while changes in the relative size of the cerebellum throughout ontogeny may be indicative of the ability to capture faster prey or an increase in migratory nature as this species moves to offshore habitats, associated with the onset of sexual maturity.

Ontogenetic Shifts in Brain Organization in the Bluespotted Stingray Neotrygon kuhlii (Chondrichthyes: Dasyatidae)

2017 ◽  
Vol 89 (2) ◽  
pp. 68-83 ◽  
Author(s):  
Thomas J. Lisney ◽  
Kara E. Yopak ◽  
Victoria Camilieri-Asch ◽  
Shaun P. Collin
Keyword(s):  
Body Size ◽  
Sexual Maturity ◽  
Initial Growth ◽  
Brain Growth ◽  
Olfactory Bulbs ◽  
Brain Areas ◽  
Brain Organization ◽  
Ontogenetic Shifts ◽  
And Behavior ◽  
The Brain

Fishes exhibit lifelong neurogenesis and continual brain growth. One consequence of this continual growth is that the nervous system has the potential to respond with enhanced plasticity to changes in ecological conditions that occur during ontogeny. The life histories of many teleost fishes are composed of a series of distinct stages that are characterized by shifts in diet, habitat, and behavior. In many cases, these shifts correlate with changes in overall brain growth and brain organization, possibly reflecting the relative importance of different senses and locomotor performance imposed by the new ecological niches they encounter throughout life. Chondrichthyan (cartilaginous) fishes also undergo ontogenetic shifts in habitat, movement patterns, diet, and behavior, but very little is known about any corresponding shifts in the size and organization of their brains. Here, we investigated postparturition ontogenetic changes in brain-body size scaling, the allometric scaling of seven major brain areas (olfactory bulbs, telencephalon, diencephalon, optic tectum, tegmentum, cerebellum, and medulla oblongata) relative to the rest of the brain, and cerebellar foliation in a chondrichthyan, i.e., the bluespotted stingray Neotrygon kuhlii. We also investigated the unusual morphological asymmetry of the cerebellum in this and other batoids. As in teleosts, the brain continues to grow throughout life, with a period of rapid initial growth relative to body size, before slowing considerably at the onset of sexual maturity. The olfactory bulbs and the cerebellum scale with positive allometry relative to the rest of the brain, whereas the other five brain areas scale with varying degrees of negative allometry. None of the major brain areas showed the stage-specific differences in rates of growth often found in teleosts. Cerebellar foliation also increases at a faster rate than overall brain growth. We speculate that changes in the olfactory bulbs and cerebellum could reflect increased olfactory and locomotor capabilities, which may be associated with ontogenetic shifts in diet, habitat use, and activity patterns, as well as shifts in behavior that occur with the onset of sexual maturity. The frequency distributions of the three cerebellar morphologies exhibited in this species best fit a 2:1:1 (right-sided:left-sided:intermediate) distribution, mirroring previous findings for another stingray species.

Ontogenetic shifts and sexual dimorphism in the brain organization of the small-spotted catshark Scyliorhinus canicula

2021 ◽  
pp. 1-10
Author(s):  
Ioannis Roussos ◽  
Persefoni Megalofonou
Keyword(s):  
Sexual Dimorphism ◽  
Medulla Oblongata ◽  
Relative Size ◽  
Brain Growth ◽  
Olfactory Bulbs ◽  
Brain Areas ◽  
Brain Organization ◽  
Positive Allometry ◽  
Scyliorhinus Canicula ◽  
The Brain

Abstract In this study, we investigated ontogenetic and sexual changes of the brain scaling as well as the scaling and the relative size of six major brain areas in the small-spotted catshark Scyliorhinus canicula from the Mediterranean Sea. The brain somatic index (0.31–1.25%) did not differ significantly between sexes but was significantly affected by size with smaller specimens exhibiting higher values. Brain growth exhibited negative allometry (allometric coefficient 0.634), not affected by sex or maturity status. The brain growth rate was found to be higher compared with a previous study from the Atlantic Ocean. Regarding the scaling of the brain areas, the olfactory bulbs scaled with positive allometry, the telencephalon and the diencephalon scaled with the same rate of negative allometry, the mesencephalon exhibited even higher negative allometry, while the cerebellum and the medulla oblongata both followed a close-to-isometric growth pattern. Immature S. canicula possessed a larger mesencephalon and diencephalon, highlighting the importance of vision in this life period, while mature specimens had enlarged olfactory bulbs, indicating that olfaction may be more important after the animal attains sexual maturity. In respect of sexual dimorphism, males had a larger cerebellum and medulla oblongata, while females had enlarged telencephalon and olfactory bulbs.

scholarly journals Environmentally induced changes to brain morphology predict cognitive performance

2018 ◽  
Vol 373 (1756) ◽  
pp. 20170287 ◽  
Author(s):  
Thomas W. Pike ◽  
Michael Ramsey ◽  
Anna Wilkinson
Keyword(s):  
Cognitive Performance ◽  
Optic Tectum ◽  
Relative Size ◽  
Brain Regions ◽  
Cognitive Capacity ◽  
Brain Morphology ◽  
Chemical Information ◽  
Brain Anatomy ◽  
Short Term ◽  
Olfactory Bulbs

The relationship between the size and structure of a species' brain and its cognitive capacity has long interested scientists. Generally, this work relates interspecific variation in brain anatomy with performance on a variety of cognitive tasks. However, brains are known to show considerable short-term plasticity in response to a range of social, ecological and environmental factors. Despite this, we have a remarkably poor understanding of how this impacts on an animal's cognitive performance. Here, we non-invasively manipulated the relative size of brain regions associated with processing visual and chemical information in fish (the optic tectum and olfactory bulbs, respectively). We then tested performance in a cognitive task in which information from the two sensory modalities was in conflict. Although the fish could effectively use both visual and chemical information if presented in isolation, when they received cues from both modalities simultaneously, those with a relatively better developed optic tectum showed a greater reliance on visual information, while individuals with relatively better developed olfactory bulbs showed a greater reliance on chemical information. These results suggest that short-term changes in brain structure, possibly resulting from an attempt to minimize the costs of developing unnecessary but energetically expensive brain regions, may have marked effects on cognitive performance. This article is part of the theme issue ‘Causes and consequences of individual differences in cognitive abilities’.

scholarly journals The impact of locomotion on the brain evolution of squirrels and close relatives

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Ornella C. Bertrand ◽  
Hans P. Püschel ◽  
Julia A. Schwab ◽  
Mary T. Silcox ◽  
Stephen L. Brusatte
Keyword(s):  
Body Mass ◽  
Brain Size ◽  
Brain Evolution ◽  
Olfactory Bulbs ◽  
Component Size ◽  
Highly Correlated ◽  
Close Relatives ◽  
The Impact ◽  
The Brain ◽  
Opposing Effect

AbstractHow do brain size and proportions relate to ecology and evolutionary history? Here, we use virtual endocasts from 38 extinct and extant rodent species spanning 50+ million years of evolution to assess the impact of locomotion, body mass, and phylogeny on the size of the brain, olfactory bulbs, petrosal lobules, and neocortex. We find that body mass and phylogeny are highly correlated with relative brain and brain component size, and that locomotion strongly influences brain, petrosal lobule, and neocortical sizes. Notably, species living in trees have greater relative overall brain, petrosal lobule, and neocortical sizes compared to other locomotor categories, especially fossorial taxa. Across millions of years of Eocene-Recent environmental change, arboreality played a major role in the early evolution of squirrels and closely related aplodontiids, promoting the expansion of the neocortex and petrosal lobules. Fossoriality in aplodontiids had an opposing effect by reducing the need for large brains.

scholarly journals Beyond Endocasts: Using Predicted Brain-Structure Volumes of Extinct Birds to Assess Neuroanatomical and Behavioral Inferences

Diversity ◽  
2020 ◽  
Vol 12 (1) ◽  
pp. 34 ◽  
Author(s):  
Catherine M. Early ◽  
Ryan C. Ridgely ◽  
Lawrence M. Witmer
Keyword(s):  
Optic Tectum ◽  
Brain Structure ◽  
Brain Size ◽  
Prediction Method ◽  
Brain Structures ◽  
Analytical Framework ◽  
Skull Morphology ◽  
Surface Areas ◽  
Structure Surface ◽  
The Brain

The shape of the brain influences skull morphology in birds, and both traits are driven by phylogenetic and functional constraints. Studies on avian cranial and neuroanatomical evolution are strengthened by data on extinct birds, but complete, 3D-preserved vertebrate brains are not known from the fossil record, so brain endocasts often serve as proxies. Recent work on extant birds shows that the Wulst and optic lobe faithfully represent the size of their underlying brain structures, both of which are involved in avian visual pathways. The endocasts of seven extinct birds were generated from microCT scans of their skulls to add to an existing sample of endocasts of extant birds, and the surface areas of their Wulsts and optic lobes were measured. A phylogenetic prediction method based on Bayesian inference was used to calculate the volumes of the brain structures of these extinct birds based on the surface areas of their overlying endocast structures. This analysis resulted in hyperpallium volumes of five of these extinct birds and optic tectum volumes of all seven extinct birds. Phylogenetic ANCOVA (phyANCOVA) were performed on regressions of the brain-structure volumes and endocast structure surface areas on various brain size metrics to determine if the relative sizes of these structures in any extinct birds were significantly different from those of the extant birds in the sample. Phylogenetic ANCOVA indicated that no extinct birds studied had relative hyperpallial volumes that were significantly different from the extant sample, nor were any of their optic tecta relatively hypertrophied. The optic tectum of Dinornis robustus was significantly smaller relative to brain size than any of the extant birds in our sample. This study provides an analytical framework for testing the hypotheses of potential functional behavioral capabilities of other extinct birds based on their endocasts.

scholarly journals Molecular evolutionary analysis of human primary microcephaly genes

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Nashaiman Pervaiz ◽  
Hongen Kang ◽  
Yiming Bao ◽  
Amir Ali Abbasi
Keyword(s):  
Evolutionary History ◽  
Genetic Basis ◽  
Brain Size ◽  
Primate Species ◽  
Evolutionary Analysis ◽  
Australopithecus Afarensis ◽  
Primary Microcephaly ◽  
Modern Humans ◽  
History Of ◽  
The Brain

Abstract Background There has been a rapid increase in the brain size relative to body size during mammalian evolutionary history. In particular, the enlarged and globular brain is the most distinctive anatomical feature of modern humans that set us apart from other extinct and extant primate species. Genetic basis of large brain size in modern humans has largely remained enigmatic. Genes associated with the pathological reduction of brain size (primary microcephaly-MCPH) have the characteristics and functions to be considered ideal candidates to unravel the genetic basis of evolutionary enlargement of human brain size. For instance, the brain size of microcephaly patients is similar to the brain size of Pan troglodyte and the very early hominids like the Sahelanthropus tchadensis and Australopithecus afarensis. Results The present study investigates the molecular evolutionary history of subset of autosomal recessive primary microcephaly (MCPH) genes; CEP135, ZNF335, PHC1, SASS6, CDK6, MFSD2A, CIT, and KIF14 across 48 mammalian species. Codon based substitutions site analysis indicated that ZNF335, SASS6, CIT, and KIF14 have experienced positive selection in eutherian evolutionary history. Estimation of divergent selection pressure revealed that almost all of the MCPH genes analyzed in the present study have maintained their functions throughout the history of placental mammals. Contrary to our expectations, human-specific adoptive evolution was not detected for any of the MCPH genes analyzed in the present study. Conclusion Based on these data it can be inferred that protein-coding sequence of MCPH genes might not be the sole determinant of increase in relative brain size during primate evolutionary history.

scholarly journals Effects of Brain Size on Adult Neurogenesis in Shrews

2021 ◽  
Vol 22 (14) ◽  
pp. 7664
Author(s):  
Katarzyna Bartkowska ◽  
Krzysztof Turlejski ◽  
Beata Tepper ◽  
Leszek Rychlik ◽  
Peter Vogel ◽  
...  
Keyword(s):  
Adult Neurogenesis ◽  
Subventricular Zone ◽  
Molecular Mechanisms ◽  
Brain Size ◽  
Hippocampal Formation ◽  
Small Animals ◽  
Suncus Murinus ◽  
The Brain ◽  
Neomys Fodiens ◽  
Migratory Stream

Shrews are small animals found in many different habitats. Like other mammals, adult neurogenesis occurs in the subventricular zone of the lateral ventricle (SVZ) and the dentate gyrus (DG) of the hippocampal formation. We asked whether the number of new generated cells in shrews depends on their brain size. We examined Crocidura russula and Neomys fodiens, weighing 10–22 g, and Crocidura olivieri and Suncus murinus that weigh three times more. We found that the density of proliferated cells in the SVZ was approximately at the same level in all species. These cells migrated from the SVZ through the rostral migratory stream to the olfactory bulb (OB). In this pathway, a low level of neurogenesis occurred in C. olivieri compared to three other species of shrews. In the DG, the rate of adult neurogenesis was regulated differently. Specifically, the lowest density of newly generated neurons was observed in C. russula, which had a substantial number of new neurons in the OB compared with C. olivieri. We suggest that the number of newly generated neurons in an adult shrew’s brain is independent of the brain size, and molecular mechanisms of neurogenesis appeared to be different in two neurogenic structures.

Abstract P717: Central Midbrain Strokes Are More Liable for Respiratory Failure Then Other Brain Stem Strokes

Stroke ◽  
2021 ◽  
Vol 52 (Suppl_1) ◽  
Author(s):  
Omar M Hussein ◽  
Eder Caceres ◽  
kasser saba ◽  
Hera Kamdar ◽  
khalid Sawalha ◽  
...  
Keyword(s):  
Respiratory Failure ◽  
Brain Stem ◽  
Medulla Oblongata ◽  
Multivariate Regression ◽  
Clear Understanding ◽  
Regression Analyses ◽  
Periaqueductal Grey ◽  
Stroke Registry ◽  
Adaptive Nature ◽  
The Brain

Background: Respiratory centers are known to be present in the central medulla oblongata and pons. There are multiple complex respiratory networks involving these centers. The midbrain periaqueductal grey is believed to act as a regulator of the respiratory function. The effect of brain-stem strokes on respiration remains understudied. There is a lack of clear understanding of the anatomical influence of such strokes on respiration. We attempted to identify brain-stem locations with the highest liability for respiratory failure in case of stroke. Methods: We included all ischemic and hemorrhagic brain-stem strokes from our stroke-registry between 2016 and 2018 then performed univariate/multivariate regression-analyses on variables that might predict respiratory failure and the need for intubation. The brain stem was divided into nine locations (right lateral, central, left lateral in each of the midbrain, pons, and medulla oblongata). Results: Out of 128 brain-stem strokes of different sizes and etiologies, central midbrain strokes were the only significant and independent affected location associated with respiratory failure and endotracheal intubation (coefficient= 0.1256, 95%-CI= 0.0175, 0.2338, p= 0.023). R-squared was equal to 15% when only central midbrain strokes stayed in the model. Conclusions: While one might assume that central medullary and pontine strokes have the most impact on respiration; our results show that central midbrain is the most impactful, accounting for about 15% of respiratory instability associated with brain-stem strokes. This can be explained by the adaptive nature of respiratory circuits within the medulla and pons. Central periaqueductal grey within the midbrain controls the rate and depth of respiration and might not have the same flexibility present elsewhere.

Lateral Medullary Infarction with Contralateral Segmental Dysesthesia and Ipsilateral Headache: A Case Report

2021 ◽  
Vol 17 ◽  
Author(s):  
Renjie Wang ◽  
Yankun Shao ◽  
Lei Xu
Keyword(s):  
Medulla Oblongata ◽  
Clinical Manifestations ◽  
Lateral Medullary Infarction ◽  
Case Presentation ◽  
Specific Sign ◽  
Temperature Sense ◽  
Magnetic Resonance Imaging Mri ◽  
The Right ◽  
The Brain ◽  
Medullary Infarction

Introduction: The medulla oblongata is the lowest segment of the brain stem, located adjacent to the spinal cord, with a complex anatomical structure. Thus, a small injury to the medulla oblongata can show complex clinical manifestations. Case Presentation: A patient experienced dysesthesia, which manifested as numbness in her right lower limb and decreased temperature sense, and dizziness 20 days before admission. The numbness worsened 1 week before admission, reaching the right thoracic (T) 12 dermatomes. Her thermoception below the T12 dermatomes decreased, and the degree of dizziness increased, accompanied by nausea and vomiting. Magnetic resonance imaging (MRI) of the neck, chest, and abdomen performed at a local hospital showed no abnormalities. MRI of the brain was performed after admission. One week after admission, she experienced a severe headache in the upper left periorbital area. The numbness extended to T4, and thermoception decreased below T4. Diagnosis: Lateral medullary infarction. Interventions: Anti-platelet aggregation and mitochondrial nutritional therapies were performed along with treatments for improving circulation and establishing collateral circulation. Outcomes: The intensity of limb numbness decreased, and the symptoms of headache and dizziness resolved. Conclusion: Lesions leading to segmental sensory disorders can occur in the medulla oblongata. Ipsilateral headaches with contralateral segmental paresthesia can be a specific sign of lateral medullary infarction.

On the anatomic relation of choroid plexus to brain: a comparative study

1980 ◽  
Vol 238 (1) ◽  
pp. R76-R81 ◽  
Author(s):  
H. F. Cserr ◽  
M. Bundgaard ◽  
J. K. Ashby ◽  
M. Murray
Keyword(s):  
Choroid Plexus ◽  
Brain Volume ◽  
Brain Size ◽  
Ventricular Volume ◽  
Brain Weight ◽  
Air Breathing ◽  
Original Proposal ◽  
Adaptive Value ◽  
Choroid Plexuses ◽  
The Brain

The size of choroid plexuses and cerebral ventricles relative to brain varies widely among vertebrates. The functional significance of this variability has attracted little attention since Herrick's original proposal that large choroid plexuses might enhance oxygen delivery to the brain and therefore be of adaptive value in the transition of vertebrates from water to air breathing. We compared choroid plexus and brain weight or ventricular and brain volume in 40 species from nine vertebrate groups. Both choroid plexus weight and ventricular volume were unrelated to brain size. Plexus weight ranged from 0 to 5.2% of brain weight and ventricular volume from 0.9 to 132% of brain volume. Amid this diversity the dipnoans, chondrosteans, holosteans, amphibians, and crossopterygian examined in this study are exceptional in uniformly having large plexuses. The adaptive significance of large choroid plexuses may lie in the presence of specific homeostatic mechanisms and their role in the response to the increases in PCO2 that accompany the transition to air breathing.

Sign in / Sign up

Export Citation Format

Share Document