The Central Nervous System of Jawless Vertebrates: Encephalization in Lampreys and Hagfishes

2017 ◽  
Vol 89 (1) ◽  
pp. 33-47
Author(s):  
Carlos A. Salas ◽  
Kara E. Yopak ◽  
Thomas J. Lisney ◽  
Ian C. Potter ◽  
Shaun P. Collin
Keyword(s):  
Life History ◽  
Life History Traits ◽  
Brain Size ◽  
Interspecific Variation ◽  
Feeding Behaviors ◽  
Larval Phase ◽  
Parasitic Species ◽  
Anadromous Migration ◽  
The Central Nervous System ◽  
Relative Brain Size

Lampreys and hagfishes are the sole surviving representatives of the early agnathan (jawless) stage in vertebrate evolution, which has previously been regarded as the least encephalized group of all vertebrates. Very little is known, however, about the extent of interspecific variation in relative brain size in these fishes, as previous studies have focused on only a few species, even though lampreys exhibit a variety of life history traits. While some species are parasitic as adults, with varying feeding behaviors, others (nonparasitic species) do not feed after completing their macrophagous freshwater larval phase. In addition, some parasitic species remain in freshwater, while others undergo an anadromous migration. On the basis of data for postmetamorphic individuals representing approximately 40% of all lamprey species, with representatives from each of the three families, the aforementioned differences in life history traits are reflected in variations in relative brain size. Across all lampreys, brain mass increases with body mass with a scaling factor or slope (α) of 0.35, which is less than those calculated for different groups of gnathostomatous (jawed) vertebrates (α = 0.43-0.62). When parasitic and nonparasitic species are analyzed separately, with phylogeny taken into account, the scaling factors of both groups (parasitic α = 0.43, nonparasitic α = 0.45) approach those of gnathostomes. The relative brain size in fully grown adults of parasitic species is, however, less than that of the adults of nonparasitic species, paralleling differences between fully grown adults and recently metamorphosed individuals of anadromous species. The average degree of encephalization is found in anadromous parasitic lampreys and might thus represent the ancestral condition for extant lampreys. These results suggest that the degree of encephalization in lampreys varies according to both life history traits and phylogenetic relationships.

Association of social group with both life-history traits and brain size in cooperatively breeding birds

2021 ◽  
Vol 71 (3) ◽  
pp. 261-278
Author(s):  
Ying Jiang ◽  
Long Jin ◽  
Yi Qiang Fu ◽  
Wen Bo Liao
Keyword(s):  
Life History ◽  
Group Size ◽  
Social Group ◽  
Life History Traits ◽  
Brain Size ◽  
Size Variation ◽  
Breeding Birds ◽  
Alloparental Care ◽  
Cooperatively Breeding ◽  
Relative Brain Size

Abstract Social group is associated with life-history traits and can predict brain size variation in cooperative primates and some other mammal groups, but such explicit relationships remain enigmatic in cooperatively breeding birds. Indeed, some compositions of social group in cooperative species (e.g., helper number and group size) would affect the fitness of breeders by providing alloparental care. Here, we conducted comparative tests of the relationship between the social group and both life-history traits and brain size across 197 species of cooperatively breeding birds using phylogenetically controlled comparative analyses. We did not find any correlations between helper numbers and both life-history traits and brain size. However, we found that maximum group size was positively associated with clutch size. Moreover, average group size has positive associations with body mass and relative brain size. Our findings suggest that helper numbers cannot promote variation in relative brain size, while larger groups may predict bigger brains in cooperatively breeding birds.

scholarly journals The energy allocation trade-offs underlying life history traits in hypometabolic strepsirhines and other primates

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Bruno Simmen ◽  
Luca Morino ◽  
Stéphane Blanc ◽  
Cécile Garcia
Keyword(s):  
Life History ◽  
Energy Expenditure ◽  
Body Mass ◽  
Life History Traits ◽  
Brain Size ◽  
Energy Allocation ◽  
Interbirth Interval ◽  
Energy Investment ◽  
Litter Mass ◽  
Trade Offs

AbstractLife history, brain size and energy expenditure scale with body mass in mammals but there is little conclusive evidence for a correlated evolution between life history and energy expenditure (either basal/resting or daily) independent of body mass. We addressed this question by examining the relationship between primate free-living daily energy expenditure (DEE) measured by doubly labeled water method (n = 18 species), life history variables (maximum lifespan, gestation and lactation duration, interbirth interval, litter mass, age at first reproduction), resting metabolic rate (RMR) and brain size. We also analyzed whether the hypometabolic primates of Madagascar (lemurs) make distinct energy allocation tradeoffs compared to other primates (monkeys and apes) with different life history traits and ecological constraints. None of the life-history traits correlated with DEE after controlling for body mass and phylogeny. In contrast, a regression model showed that DEE increased with increasing RMR and decreasing reproductive output (i.e., litter mass/interbirth interval) independent of body mass. Despite their low RMR and smaller brains, lemurs had an average DEE remarkably similar to that of haplorhines. The data suggest that lemurs have evolved energy strategies that maximize energy investment to survive in the unusually harsh and unpredictable environments of Madagascar at the expense of reproduction.

scholarly journals Species' Life-History Traits Explain Interspecific Variation in Reservoir Competence: A Possible Mechanism Underlying the Dilution Effect

PLoS ONE ◽  
2013 ◽  
Vol 8 (1) ◽  
pp. e54341 ◽  
Author(s):  
Zheng Y. X. Huang ◽  
Willem F. de Boer ◽  
Frank van Langevelde ◽  
Valerie Olson ◽  
Tim M. Blackburn ◽  
...  
Keyword(s):  
Life History ◽  
Life History Traits ◽  
Dilution Effect ◽  
Interspecific Variation

Brain size evolution in anurans: a review

2019 ◽  
Vol 69 (3) ◽  
pp. 265-279 ◽  
Author(s):  
Chun Lan Mai ◽  
Wen Bo Liao
Keyword(s):  
Sexual Selection ◽  
Life History ◽  
Life History Traits ◽  
Developmental Stages ◽  
Brain Size ◽  
Ecological Factors ◽  
Brain Regions ◽  
Sperm Length ◽  
Testis Size ◽  
Size Evolution

Abstract Selection pressure is an important force in shaping the evolution of vertebrate brain size among populations within species as well as between species. The evolution of brain size is tightly linked to natural and sexual selection, and life-history traits. In particular, increased environmental stress, intensity of sexual selection, and slower life history usually result in enlarged brains. However, although previous studies have addressed the causes of brain size evolution, no systematic reviews have been conducted to explain brain size in anurans. Here, we review whether brain size evolution supports the cognitive buffer hypothesis (CBH), the expensive tissue hypothesis (ETH), or the developmental cost hypothesis (DCH) by analyzing the intraspecific and/or interspecific patterns in brain size and brain regions (i.e., olfactory nerves, olfactory bulbs, telencephalon, optic tectum, and cerebellum) associated with ecological factors (habitat, diet and predator risk), sexual selection intensity, life-history traits (age at sexual maturity, mean age, longevity, clutch size and egg size, testis size and sperm length), and other energetic organs. Our findings suggest that brain size evolution in anurans supports the CBH, ETH or DCH. We also suggest future directions for studying the relationships between brain size evolution and crypsis (i.e., ordinary mucous glands in the skin), and food alteration in different developmental stages.

scholarly journals Mismatches between demographic niches and geographic distributions are strongest in poorly dispersed and highly persistent plant species

2020 ◽  
Vol 117 (7) ◽  
pp. 3663-3669 ◽  
Author(s):  
Jörn Pagel ◽  
Martina Treurnicht ◽  
William J. Bond ◽  
Tineke Kraaij ◽  
Henning Nottebrock ◽  
...  
Keyword(s):  
Life History ◽  
Plant Species ◽  
Ecological Niche ◽  
Life History Traits ◽  
Environmental Gradients ◽  
Demographic Data ◽  
Interspecific Variation ◽  
Ecological Niches ◽  
Geographic Ranges ◽  
Geographic Distributions

The ecological niche of a species describes the variation in population growth rates along environmental gradients that drives geographic range dynamics. Niches are thus central for understanding and forecasting species’ geographic distributions. However, theory predicts that migration limitation, source–sink dynamics, and time-lagged local extinction can cause mismatches between niches and geographic distributions. It is still unclear how relevant these niche–distribution mismatches are for biodiversity dynamics and how they depend on species life-history traits. This is mainly due to a lack of the comprehensive, range-wide demographic data needed to directly infer ecological niches for multiple species. Here we quantify niches from extensive demographic measurements along environmental gradients across the geographic ranges of 26 plant species (Proteaceae; South Africa). We then test whether life history explains variation in species’ niches and niche–distribution mismatches. Niches are generally wider for species with high seed dispersal or persistence abilities. Life-history traits also explain the considerable interspecific variation in niche–distribution mismatches: poorer dispersers are absent from larger parts of their potential geographic ranges, whereas species with higher persistence ability more frequently occupy environments outside their ecological niche. Our study thus identifies major demographic and functional determinants of species’ niches and geographic distributions. It highlights that the inference of ecological niches from geographical distributions is most problematic for poorly dispersed and highly persistent species. We conclude that the direct quantification of ecological niches from demographic responses to environmental variation is a crucial step toward a better predictive understanding of biodiversity dynamics under environmental change.

Interspecific variation in life history traits of Elasmostethus (Hemiptera: Acanthosomatidae)

2018 ◽  
Vol 151 (1) ◽  
pp. 69-72 ◽  
Author(s):  
S. Kudo ◽  
Aki Yamamoto ◽  
Tadao Ichita ◽  
Haruki Tatsuta
Keyword(s):  
Life History ◽  
Clutch Size ◽  
Maternal Care ◽  
Female Body ◽  
Egg Size ◽  
Life History Traits ◽  
Interspecific Variation ◽  
Japanese Species ◽  
Comparative Analyses ◽  
The Family

AbstractLife history traits, such as clutch size, egg size (weight), developmental periods of eggs, and female body (abdomen) size, were investigated in Japanese species of the genus Elasmostethus Fieber (Hemiptera: Acanthosomatidae): E. amabilis Yamamoto, E. brevis Lindberg, E. humeralis Jakovlev, E. interstinctus (Linnaeus), E. kerzhneri Yamamoto, and E. nubilus (Dallas). With the exception of clutch size, significant differences were observed in the traits among species. No species exhibited maternal care of eggs. These data form a solid basis for future comparative analyses in the family Acanthosomatidae, which contains both subsocial and asocial species.

Interspecific variation in relative brain size is not correlated with intensity of sexual selection in waterfowl (Anseriformes)

2008 ◽  
Vol 56 (5) ◽  
pp. 311 ◽  
Author(s):  
P.-J. Guay ◽  
A. N. Iwaniuk
Keyword(s):  
Sexual Selection ◽  
Sexual Dimorphism ◽  
Sperm Competition ◽  
Brain Size ◽  
Interspecific Variation ◽  
Morphological Characters ◽  
Comparative Approach ◽  
Pair Bonds ◽  
Relative Brain Size

The role of sexual selection in shaping the brain is poorly understood. Although numerous studies have investigated the role of natural selection, relatively few have focussed on the role of sexual selection. Two important factors influencing the intensity of sexual selection are sperm competition and pair bonding and three different hypotheses have been proposed to explain how they could influence relative brain size. (1) The ‘extra-pair mating’ hypothesis predicts that sexual dimorphism in brain size will increase with sperm competition intensity. (2) The ‘Machiavellian intelligence’ hypothesis predicts that brain size will be larger in species with intense sperm competition. (3) The ‘relationship intelligence’ hypothesis predicts that species forming long-term pair bonds will have larger brains. We investigated sexual dimorphism in brain size and tested these three hypotheses in waterfowl by studying correlations between relative brain volume and three measures of sperm competition (testicular mass, phallus length and mating strategy) and pair-bond duration using the modern phylogenetic comparative approach. We found no evidence of sexual dimorphism in brain size in waterfowl after controlling for body mass and found no support for any of the three hypotheses. This suggests that brain size may not be sexually selected in waterfowl, despite evidence of sexual selection pressures on other morphological characters.

scholarly journals Absolute, not relative brain size correlates with sociality in ground squirrels

2016 ◽  
Vol 283 (1827) ◽  
pp. 20152725 ◽  
Author(s):  
Jan Matějů ◽  
Lukáš Kratochvíl ◽  
Zuzana Pavelková ◽  
Věra Pavelková Řičánková ◽  
Vladimír Vohralík ◽  
...  
Keyword(s):  
Body Mass ◽  
Life History Traits ◽  
Brain Size ◽  
Empirical Support ◽  
Ground Squirrels ◽  
Single Family ◽  
Social Brain ◽  
The Social ◽  
Tightly Coupled ◽  
Relative Brain Size

The social brain hypothesis (SBH) contends that cognitive demands associated with living in cohesive social groups favour the evolution of large brains. Although the correlation between relative brain size and sociality reported in various groups of birds and mammals provides broad empirical support for this hypothesis, it has never been tested in rodents, the largest mammalian order. Here, we test the predictions of the SBH in the ground squirrels from the tribe Marmotini. These rodents exhibit levels of sociality ranging from solitary and single-family female kin groups to egalitarian polygynous harems but feature similar ecologies and life-history traits. We found little support for the association between increase in sociality and increase in relative brain size. Thus, sociality does not drive the evolution of encephalization in this group of rodents, a finding inconsistent with the SBH. However, body mass and absolute brain size increase with sociality. These findings suggest that increased social complexity in the ground squirrels goes hand in hand with larger body mass and brain size, which are tightly coupled to each other.

scholarly journals The life-history basis of behavioural innovations

2016 ◽  
Vol 371 (1690) ◽  
pp. 20150187 ◽  
Author(s):  
Daniel Sol ◽  
Ferran Sayol ◽  
Simon Ducatez ◽  
Louis Lefebvre
Keyword(s):  
Life History ◽  
Life Histories ◽  
Life History Traits ◽  
Environmental Changes ◽  
Adaptive System ◽  
Brain Size ◽  
Life History Strategy ◽  
Evolutionary Origin ◽  
Generalist Species ◽  
Previous Evidence

The evolutionary origin of innovativeness remains puzzling because innovating means responding to novel or unusual problems and hence is unlikely to be selected by itself. A plausible alternative is considering innovativeness as a co-opted product of traits that have evolved for other functions yet together predispose individuals to solve problems by adopting novel behaviours. However, this raises the question of why these adaptations should evolve together in an animal. Here, we develop the argument that the adaptations enabling animals to innovate evolve together because they are jointly part of a life-history strategy for coping with environmental changes. In support of this claim, we present comparative evidence showing that in birds, (i) innovative propensity is linked to life histories that prioritize future over current reproduction, (ii) the link is in part explained by differences in brain size, and (iii) innovative propensity and life-history traits may evolve together in generalist species that frequently expose themselves to novel or unusual conditions. Combined with previous evidence, these findings suggest that innovativeness is not a specialized adaptation but more likely part of a broader general adaptive system to cope with changes in the environment.

scholarly journals Parental provisioning drives brain size in birds

2021 ◽  
Author(s):  
Michael Griesser ◽  
Szymon M Drobniak ◽  
Sereina M Graber ◽  
Carel van Schaik
Keyword(s):  
Cognitive Abilities ◽  
Brain Size ◽  
Bird Species ◽  
Behavioral Flexibility ◽  
Interspecific Variation ◽  
Adult Brain ◽  
Egg Mass ◽  
Adult Body Mass ◽  
Parental Provisioning ◽  
Relative Brain Size

Larger brains should be adaptive because they support numerous eco- and socio-cognitive benefits, but these benefits explain only a modest part of the interspecific variation in brain size. Notably underexplored are the high energetic costs of developing brains, and thus the possible role of parental provisioning in the evolution of adult brain size. We explore this idea in birds, which show considerable variation in both socio-ecological traits and the energy transfer from parents to offspring. Comparative analyses of 1,176 bird species show that the combination of adult body mass, mode of development at hatching, relative egg mass, and the time spent provisioning the young in combination strongly predict relative brain size across species. Adding adult eco- and socio-cognitive predictors only marginally adds explanatory value. We therefore conclude that parental provisioning enabled bird species to evolve into skill-intensive niches, reducing interspecific competition and consequently promoting survival prospects and population stability. Critically, parental provisioning also explains why precocial bird species have smaller brains than altricial ones. Finally, these results suggest that the cognitive adaptations that provide the behavioral flexibility to improve reproductive success and survival are intrinsically linked to successful parental provisioning. Our findings also suggest that the traditionally assessed cognitive abilities may not predict relative brain size.

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