scholarly journals Mandibular morphology, task specialization and bite mechanics in Pheidole ants (Hymenoptera: Formicidae)

2021 ◽  
Vol 18 (179) ◽  
pp. 20210318
Author(s):  
Cristian L. Klunk ◽  
Marco A. Argenta ◽  
Alexandre Casadei-Ferreira ◽  
Evan P. Economo ◽  
Marcio R. Pie
Keyword(s):  
Social Life ◽  
Division Of Labour ◽  
Ecological Significance ◽  
Task Specialization ◽  
Element Analysis ◽  
Differential Performance ◽  
Biomechanical Responses ◽  
Evolutionary Success ◽  
Morphological Differences ◽  
Apical Tooth

Ants show remarkable ecological and evolutionary success due to their social life history and division of labour among colony members. In some lineages, the worker force became subdivided into morphologically distinct individuals (i.e. minor versus major workers), allowing for the differential performance of particular roles in the colony. However, the functional and ecological significance of these morphological differences are not well understood. Here, we applied finite element analysis (FEA) to explore the biomechanical differences between major and minor ant worker mandibles. Analyses were carried out on mandibles of two Pheidole species, a dimorphic ant genus. We tested whether major mandibles evolved to minimize stress when compared to minors using combinations of the apical tooth and masticatory margin bites under strike and pressure conditions. Majors performed better in pressure conditions yet, contrary to our expectations, minors performed better in strike bite scenarios. Moreover, we demonstrated that even small morphological differences in ant mandibles might lead to substantial differences in biomechanical responses to bite loading. These results also underscore the potential of FEA to uncover biomechanical consequences of morphological differences within and between ant workers.

scholarly journals Mandibular morphology, task specialization, and bite mechanics in Pheidole ants (Hymenoptera: Formicidae)

2020 ◽  
Author(s):  
C.L. Klunk ◽  
M.A. Argenta ◽  
A. Casadei-Ferreira ◽  
E.P. Economo ◽  
M.R. Pie
Keyword(s):  
Task Specialization ◽  
Element Analysis ◽  
Functional Differences ◽  
Differential Performance ◽  
Biomechanical Responses ◽  
Evolutionary Success ◽  
Morphological Differences ◽  
Worker Castes ◽  
Reproductive Division Of Labor ◽  
Reproductive Division

AbstractThe remarkable ecological and evolutionary success of ants was associated with the evolution of reproductive division of labor, in which sterile workers perform most colony tasks whereas reproductives become specialized in reproduction. In some lineages, the worker force became further subdivided into morphologically distinct subcastes (e.g. minor vs. major workers), allowing for the differential performance of particular roles in the colony. However, the functional and ecological significance of morphological differences between subcastes is not well understood. Here, we applied Finite Element Analysis (FEA) to explore the functional differences between major and minor ant worker mandibles. Analyses were carried out on mandibles of two Pheidole species, a dimorphic ant genus. In particular, we test whether major mandibles evolved to minimize stress when compared to minors using combinations of tooth and masticatory margin bites under strike and pressure conditions. Majors performed better in pressure conditions yet, contrary to our expectations, minors performed better in strike bite scenarios. Moreover, we demonstrate that even small morphological differences in ant mandibles might lead to substantial differences in biomechanical responses to bite loading. These results also underscore the potential of FEA to uncover biomechanical consequences of morphological differences within and between ant worker castes.

scholarly journals Polymorphism and division of labour in a socially complex ant: neuromodulation of aggression in the Australian weaver ant, Oecophylla smaragdina

2015 ◽  
Vol 282 (1811) ◽  
pp. 20150704 ◽  
Author(s):  
J. Frances Kamhi ◽  
Kelley Nunn ◽  
Simon K. A. Robson ◽  
James F. A. Traniello
Keyword(s):  
Social Systems ◽  
Division Of Labour ◽  
Oecophylla Smaragdina ◽  
Minor Worker ◽  
Task Specialization ◽  
Territorial Defence ◽  
Weaver Ant ◽  
Eusocial Insects ◽  
Worker Size ◽  
Pharmacological Manipulations

Complex social structure in eusocial insects can involve worker morphological and behavioural differentiation. Neuroanatomical variation may underscore worker division of labour, but the regulatory mechanisms of size-based task specialization in polymorphic species are unknown. The Australian weaver ant, Oecophylla smaragdina , exhibits worker polyphenism: larger major workers aggressively defend arboreal territories, whereas smaller minors nurse brood. Here, we demonstrate that octopamine (OA) modulates worker size-related aggression in O. smaragdina . We found that the brains of majors had significantly higher titres of OA than those of minors and that OA was positively and specifically correlated with the frequency of aggressive responses to non-nestmates, a key component of territorial defence. Pharmacological manipulations that effectively switched OA action in major and minor worker brains reversed levels of aggression characteristic of each worker size class. Results suggest that altering OA action is sufficient to produce differences in aggression characteristic of size-related social roles. Neuromodulators therefore may generate variation in responsiveness to task-related stimuli associated with worker size differentiation and collateral behavioural specializations, a significant component of division of labour in complex social systems.

A Finite Element Analysis of the C2-C7 Sheep Spine

2010 ◽  
Author(s):  
Nicole A. DeVries ◽  
Nicole A. Kallemeyn ◽  
Kiran H. Shivanna ◽  
Nicole M. Grosland
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Surgical Techniques ◽  
In Vitro Studies ◽  
Element Analysis ◽  
Spinal Disorders ◽  
Biomechanical Responses ◽  
Experimental Biomechanics ◽  
Similarities And Differences

Due to the limited availability of human cadaveric specimens, sheep are often utilized for in vitro studies of various spinal disorders and surgical techniques. Understanding the similarities and differences between the human and sheep spine is crucial for constructing a valuable study and interpreting the results. Several studies have identified the anatomical similarities between the sheep and human spine; however these studies have been limited to quantifying the anatomic dimensions as opposed to the biomechanical responses [1–2]. Although anatomical similarities are important, biomechanical correspondence is imperative for studying the effects of disorders, surgical techniques, and implant designs. Studies by Wilke and colleagues [3] and Clarke et al. [4] have focused on experimental biomechanics of the sheep cervical functional spinal units (FSUs).

scholarly journals Polymorphic organization in a planktonic graptoloid (Hemichordata: Pterobranchia) colony of Late Ordovician age

2012 ◽  
Vol 150 (1) ◽  
pp. 143-152 ◽  
Author(s):  
JAN A. ZALASIEWICZ ◽  
ALEX PAGE ◽  
R. BARRIE RICKARDS ◽  
MARK WILLIAMS ◽  
PHILIP R. WILBY ◽  
...  
Keyword(s):  
Soft Part ◽  
Division Of Labour ◽  
Alternative Interpretation ◽  
Late Ordovician ◽  
Evolutionary Success ◽  
Early Palaeozoic

AbstractGraptolites are common fossils in Early Palaeozoic strata, but little is known of their soft-part anatomy. However, we report a long-overlooked specimen ofDicranograptusaff.ramosusfrom Late Ordovician strata of southern Scotland that preserves a strongly polymorphic, recalcitrant, organic-walled network hitherto unseen in graptoloid graptolites. This network displays three morphologies: proximally, a strap-like pattern, likely of flattened tubes; these transform distally into isolated, hourglass-shaped structures; then, yet more distally, revert to a (simpler) strap-like pattern. The network most likely represents a stolon-like system, hitherto unknown in graptoloids, that connected individual zooids. Its alternative interpretation, as colonial xenobionts that infested a graptoloid colony and mimicked its architecture, is considered less likely on taphonomic and palaeobiological grounds. Such polymorphism is not known in non-graptolite pterobranchs, which are less diverse and morphologically more conservative: a division of labour between graptoloid zooids for such functions as feeding, breeding and rhabdosome construction may have been the key to their remarkable evolutionary success.

scholarly journals How within-group behavioural variation and task efficiency enhance fitness in a social group

2010 ◽  
Vol 278 (1709) ◽  
pp. 1209-1215 ◽  
Author(s):  
Jonathan N. Pruitt ◽  
Susan E. Riechert
Keyword(s):  
Prey Capture ◽  
Common Garden ◽  
Division Of Labour ◽  
Large Prey ◽  
Task Specialization ◽  
Capture Success ◽  
Social Phenotype ◽  
Individual Task ◽  
Task Efficiency

How task specialization, individual task performance and within-group behavioural variation affects fitness is a longstanding and unresolved problem in our understanding of animal societies. In the temperate social spider, Anelosimus studiosus , colony members exhibit a behavioural polymorphism; females either exhibit an aggressive ‘asocial’ or docile ‘social’ phenotype. We assessed individual prey-capture success for both phenotypes, and the role of phenotypic composition on group-level prey-capture success for three prey size classes. We then estimated the effect of group phenotypic composition on fitness in a common garden, as inferred from individual egg-case masses. On average, asocial females were more successful than social females at capturing large prey, and colony-level prey-capture success was positively associated with the frequency of the asocial phenotype. Asocial colony members were also more likely to engage in prey-capture behaviour in group-foraging situations. Interestingly, our fitness estimates indicate females of both phenotypes experience increased fitness when occupying colonies containing unlike individuals. These results imply a reciprocal fitness benefit of within-colony behavioural variation, and perhaps division of labour in a spider society.

Finite Element Analysis of a Close Head Axonal Injury Model: Relating Brain Tissue Biomechanics to Skull Deformation

2008 ◽  
Author(s):  
Haojie Mao ◽  
Liying Zhang ◽  
King H. Yang ◽  
Albert I. King ◽  
J’ozsef Pál ◽  
...  
Keyword(s):  
Finite Element ◽  
Compressive Strain ◽  
Axonal Injury ◽  
Element Model ◽  
Element Analysis ◽  
Injury Model ◽  
Weight Drop ◽  
Biomechanical Responses ◽  
Histological Results ◽  
The Impact

Biomechanical responses of a rat brain in a new weight-drop model were investigated by comparing histological results against finite element model predictions. This graded axonal injury rat model differed from others because of its utilization of intact skull without global angular motion to confound data analyses. Results demonstrated that the maximum principal strain and the compressive strain along the impact direction best correlated the experimentally observed injury locations while the shear strain did not have positive correlation.

Work and Care in the Life Course: Understanding the Context for Family Arrangements

1996 ◽  
Vol 25 (4) ◽  
pp. 507-527 ◽  
Author(s):  
Sue Yeandle
Keyword(s):  
Social Life ◽  
Division Of Labour ◽  
Unintended Effects ◽  
Family Responsibilities ◽  
Individual Agency ◽  
Care And Support ◽  
The Social ◽  
Human Decision ◽  
History Of ◽  
The Life Course

ABSTRACTThe article develops a case study of the family and work history of an interviewee which is used to illustrate the context in which family arrangements for work, care and support develop. The study uses Finch and Mason's (1993) focus on human agency to develop a ‘family responsibilities account’, and then goes on to explore three aspects of the social structural context in which the life has been lived. These are developed from Connell's analysis (1987) of gender relations: constraints associated with the division of labour, with issues of power and with emotional and personal life (cathexis).A detailed account of the life in question is given, and this is reanalysed using the four approaches indicated. The result is an overall account which emphasises the complexity of social life and of human decision-making, even at the apparently mundane level of choices about family life, paid employment, domestic work and the care and support of kin. The extent to which constraining factors interweave with individual agency is demonstrated, and the significance of the analysis for policymakers is noted: each change in arrangements for work and care in a life affects others, and policy must be made in an awareness of the complexity of its unintended effects as well as of its objectives.

scholarly journals Introduction: elusive equalities – sex, gender and women

2014 ◽  
Vol 10 (4) ◽  
pp. 421-426 ◽  
Author(s):  
Catherine Albertyn ◽  
Sandra Fredman ◽  
Judy Fudge
Keyword(s):  
Maternal Health ◽  
Gender Equality ◽  
Social Life ◽  
Millennium Development Goals ◽  
Division Of Labour ◽  
Care Work ◽  
Employment Opportunities ◽  
Life Chances ◽  
The World ◽  
Development Goals

Despite the fact that the Millennium Development Goals promised to achieve gender equality and maternal health by 2015, equality remains elusive for too many women. Indeed, austerity, the rise of fundamentalism and the continuing gendered division of labour, especially when it comes to socially necessary but unremunerated care work, have contributed to the increase in gendered inequalities in many areas of social life and in most regions of the world. There is a plenitude of international, transnational and national equality instruments and strategies at the same time as gendered inequality is increasing both within and between nations. These equality instruments and strategies have also had an uneven impact: some women benefit more than others. Moreover, if interpreted in a formal manner, equality can be achieved as much through levelling down men's employment opportunities as by elevating women's life chances.

THE GENUS PROROCENTRUM EHRENBERG. MORPHODYNAMICS, PROTOPLASMATIC STRUCTURES, AND TAXONOMY

1959 ◽  
Vol 37 (1) ◽  
pp. 1-31 ◽  
Author(s):  
Adam Bursa
Keyword(s):  
New Species ◽  
Life Cycle ◽  
Cell Membrane ◽  
Morphological Variation ◽  
Membrane Structure ◽  
Prorocentrum Micans ◽  
Morphological Differences ◽  
Apical Tooth ◽  
Made In

The morphodynamics of Prorocentrum species have been studied comparatively in cultures and in plankton. Plankton populations show little morphological variation. In cultures a variety of forms, often similar to other species of Prorocentrum which have been described from distant seas, are found. Morphological variation in Prorocentrum species depends upon various life phases, individual features of the clones, and various types of the cysts. Formation of morphological aberrants is also affected by aging of cultures. All protoplasmatic structures, including the cell membrane, possess their own particular features, changing in the course of the life cycle. Since both physiological and morphodynamic metabolisms are inseparable in their activities, it is useful to complete taxonomic diagnoses with physiological observations. Five new species are described: Prorocentrum cordiformis, Prorocentrum pomoideum, Prorocentrum pyrenoideum, Prorocentrum redfieldi, and Prorocentrum levanlinoides. Morphodynamics in Prorocentrum micans and Prorocentrum scutellum was also studied. Most of the observations were made in vivo. Specific morphological differences in form and structure of protoplasmatic organelles were demonstrated in each species concerned. An attempt was made also to base taxonomic diagnoses upon the apical tooth, trichocysts, and membrane structure.

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