scholarly journals The loss of flight in ant workers enabled an evolutionary redesign of the thorax for ground labour

2020 ◽  
Author(s):  
Christian Peeters ◽  
Roberto A. Keller ◽  
Adam Khalife ◽  
Georg Fischer ◽  
Julian Katzke ◽  
...  
Keyword(s):  
Central Place ◽  
Division Of Labour ◽  
The Body ◽  
Selective Pressures ◽  
Muscle Adaptations ◽  
Flight Muscles ◽  
Heavy Loads ◽  
Ecological Dominance ◽  
Worker Caste ◽  
Cuticular Structures

Abstract Background Explanations for the ecological dominance of ants generally focus on the benefits of division of labour and cooperation during foraging. However, the principal innovation of ants relative to their wasp ancestors was the evolution of a new phenotype: a wingless worker caste optimized for ground labour. Ant workers are famous for their ability to lift and carry heavy loads, but we know surprisingly little about the morphological basis of their strength. Here we examine the consequences of the universal loss of flight in ant workers on skeletomuscular adaptations in the thorax for enhanced foraging on six legs. Results Using X-ray microcomputed tomography and 3D segmentation, we compared winged queens and wingless workers in Euponera sikorae (subfamily Ponerinae) and Cataglyphis savignyi (subfamily Formicinae). Workers are characterized by five major changes to their thorax: i) fusion of the articulated flight thorax (queens) into a rigid box optimized to support the muscles that operate the head, legs and abdomen, ii) redesign of internal cuticular structures for better bracing and muscle attachment, iii) substantial enlargement of the neck muscles for suspending and moving the head, iv) lengthening of the external trochanter muscles, predominant for the leg actions that lift the body off the ground, v) modified angle of the petiole muscles that are key for flexion of the abdomen. We measured volumes and pennation angles for a few key muscles to assess their increased efficacy. Our comparisons of additional workers across five genera in subfamilies Dorylinae and Myrmicinae show these modifications in the wingless thorax to be consistent. In contrast, a mutillid wasp showed a different pattern of muscle adaptations as a result of the lack of wing muscles. Conclusions Rather than simply a subtraction of costly flight muscles, we propose the ant worker thorax evolved into a power core underlying stronger mandibles, legs, and sting. This contrasts with solitary flightless insects where the lack of central place foraging generated distinct selective pressures for rearranging the thorax. Stronger emphasis is needed on innovations of social insects as individuals at the phenotypic level to further our understanding of the evolution of social behaviours.

scholarly journals The loss of flight in ant workers enabled an evolutionary redesign of the thorax for ground labour

2020 ◽  
Author(s):  
Christian Peeters ◽  
Roberto A. Keller ◽  
Adam Khalife ◽  
Georg Fischer ◽  
Julian Katzke ◽  
...  
Keyword(s):  
Central Place ◽  
Division Of Labour ◽  
The Body ◽  
Selective Pressures ◽  
Muscle Adaptations ◽  
Flight Muscles ◽  
Heavy Loads ◽  
Ecological Dominance ◽  
Worker Caste ◽  
Cuticular Structures

Abstract Background Explanations for the ecological dominance of ants generally focus on the benefits of division of labour and cooperation during foraging. However, the principal innovation of ants relative to their wasp ancestors was the evolution of a new phenotype: a wingless worker caste optimized for ground labour. Ant workers are famous for their ability to lift and carry heavy loads, but we know surprisingly little about the morphological basis of their strength. Here we examine the consequences of the universal loss of flight in ant workers on skeletomuscular adaptations in the thorax for enhanced foraging on six legs. Results Using X-ray microcomputed tomography and 3D segmentation, we compared winged queens and wingless workers in Euponera sikorae (subfamily Ponerinae) and Cataglyphis savignyi (subfamily Formicinae). Workers are characterized by five major changes to their thorax: i) fusion of the articulated flight thorax (queens) into a rigid box optimized to support the muscles that operate the head, legs and abdomen, ii) redesign of internal cuticular structures for better bracing and muscle attachment, iii) substantial enlargement of the neck muscles for suspending and moving the head, iv) lengthening of the external trochanter muscles, predominant for the leg actions that lift the body off the ground, v) modified angle of the petiole muscles that are key for flexion of the abdomen. We measured volumes and pennation angles for a few key muscles to assess their increased efficacy. Our comparisons of additional workers across five genera in subfamilies Dorylinae and Myrmicinae show these modifications in the wingless thorax to be consistent. In contrast, a mutillid wasp showed a different pattern of muscle adaptations as a result of the lack of wing muscles. Conclusions Rather than simply a subtraction of costly flight muscles, we propose the ant worker thorax evolved into a power core underlying stronger mandibles, legs, and sting. This contrasts with solitary flightless insects where the lack of central place foraging generated distinct selective pressures for rearranging the thorax. Stronger emphasis is needed on innovations of social insects as individuals at the phenotypic level to further our understanding of the evolution of social behaviours.

scholarly journals The loss of flight in ant workers enabled an evolutionary redesign of the thorax for ground labour

2020 ◽  
Vol 17 (1) ◽  
Author(s):  
Christian Peeters ◽  
Roberto A. Keller ◽  
Adam Khalife ◽  
Georg Fischer ◽  
Julian Katzke ◽  
...  
Keyword(s):  
Central Place ◽  
Division Of Labour ◽  
The Body ◽  
Selective Pressures ◽  
Muscle Adaptations ◽  
Flight Muscles ◽  
Heavy Loads ◽  
Ecological Dominance ◽  
Worker Caste ◽  
Cuticular Structures

Abstract Background Explanations for the ecological dominance of ants generally focus on the benefits of division of labour and cooperation during foraging. However, the principal innovation of ants relative to their wasp ancestors was the evolution of a new phenotype: a wingless worker caste optimized for ground labour. Ant workers are famous for their ability to lift and carry heavy loads, but we know surprisingly little about the morphological basis of their strength. Here we examine the consequences of the universal loss of flight in ant workers on skeletomuscular adaptations in the thorax for enhanced foraging on six legs. Results Using X-ray microcomputed tomography and 3D segmentation, we compared winged queens and wingless workers in Euponera sikorae (subfamily Ponerinae) and Cataglyphis savignyi (subfamily Formicinae). Workers are characterized by five major changes to their thorax: i) fusion of the articulated flight thorax (queens) into a rigid box optimized to support the muscles that operate the head, legs and abdomen, ii) redesign of internal cuticular structures for better bracing and muscle attachment, iii) substantial enlargement of the neck muscles for suspending and moving the head, iv) lengthening of the external trochanter muscles, predominant for the leg actions that lift the body off the ground, v) modified angle of the petiole muscles that are key for flexion of the abdomen. We measured volumes and pennation angles for a few key muscles to assess their increased efficacy. Our comparisons of additional workers across five genera in subfamilies Dorylinae and Myrmicinae show these modifications in the wingless thorax to be consistent. In contrast, a mutillid wasp showed a different pattern of muscle adaptations resulting from the lack of wing muscles. Conclusions Rather than simply a subtraction of costly flight muscles, we propose the ant worker thorax evolved into a power core underlying stronger mandibles, legs, and sting. This contrasts with solitary flightless insects where the lack of central place foraging generated distinct selective pressures for rearranging the thorax. Stronger emphasis is needed on morphological innovations of social insects to further our understanding of the evolution of social behaviours.

Telomere Length and Arsenic: Improving Animal Models of Toxicity by Choosing Mice With Shorter Telomeres

2021 ◽  
Vol 40 (3) ◽  
pp. 211-217
Author(s):  
Brayden Whitlock
Keyword(s):  
Animal Models ◽  
Telomere Length ◽  
Mouse Models ◽  
Arsenic Exposure ◽  
Tumor Formation ◽  
The Body ◽  
Cancer Resistance ◽  
Selective Pressures ◽  
Toxicity Monitoring ◽  
In Captivity

Arsenic is both a chemotherapeutic drug and an environmental toxicant that affects hundreds of millions of people each year. Arsenic exposure in drinking water has been called the worst poisoning in human history. How arsenic is handled in the body is frequently studied using rodent models to investigate how arsenic both causes and treats disease. These models, used in a variety of arsenic-related testing, from tumor formation to drug toxicity monitoring, have virtually always been developed from animals with telomeres that are unnaturally long, likely because of accidental artificial selective pressures. Mice that have been bred in captivity in laboratory conditions, often for over 100 years, are the standard in creating animal models for this research. Using these mice introduces challenges to any work that can be affected by the length of telomeres and the related capacities for tissue repair and cancer resistance. However, arsenic research is particularly susceptible to the misuse of such animal models due to the multiple and various interactions between arsenic and telomeres. Researchers in the field commonly find mouse models and humans behaving very differently upon exposure to acute and chronic arsenic, including drug therapies which seem safe in mice but are toxic in humans. Here, some complexities and apparent contradictions of the arsenic carcinogenicity and toxicity research are reconciled by an explanatory model that involves telomere length explained by the evolutionary pressures in laboratory mice. A low-risk hypothesis is proposed which has the power to determine whether researchers can easily develop more powerful and accurate mouse models by simply avoiding mouse lineages that are very old and have strangely long telomeres. Swapping in newer mouse lineages for the older, long-telomere mice may vastly improve our ability to research arsenic toxicity with virtually no increase in cost or difficulty of research.

scholarly journals Load carriage, human performance, and employment standards

2016 ◽  
Vol 41 (6 (Suppl. 2)) ◽  
pp. S131-S147 ◽  
Author(s):  
Nigel A.S. Taylor ◽  
Gregory E. Peoples ◽  
Stewart R. Petersen
Keyword(s):  
Work Performance ◽  
Human Performance ◽  
Performance Testing ◽  
The Body ◽  
Load Carriage ◽  
Physical Endurance ◽  
Physiological Strain ◽  
Employment Standards ◽  
Heavy Loads ◽  
External Loads

The focus of this review is on the physiological considerations necessary for developing employment standards within occupations that have a heavy reliance on load carriage. Employees within military, fire fighting, law enforcement, and search and rescue occupations regularly work with heavy loads. For example, soldiers often carry loads >50 kg, whilst structural firefighters wear 20–25 kg of protective clothing and equipment, in addition to carrying external loads. It has long been known that heavy loads modify gait, mobility, metabolic rate, and efficiency, while concurrently elevating the risk of muscle fatigue and injury. In addition, load carriage often occurs within environmentally stressful conditions, with protective ensembles adding to the thermal burden of the workplace. Indeed, physiological strain relates not just to the mass and dimensions of carried objects, but to how those loads are positioned on and around the body. Yet heavy loads must be borne by men and women of varying body size, and with the expectation that operational capability will not be impinged. This presents a recruitment conundrum. How do employers identify capable and injury-resistant individuals while simultaneously avoiding discriminatory selection practices? In this communication, the relevant metabolic, cardiopulmonary, and thermoregulatory consequences of loaded work are reviewed, along with concomitant impediments to physical endurance and mobility. Also emphasised is the importance of including occupation-specific clothing, protective equipment, and loads during work-performance testing. Finally, recommendations are presented for how to address these issues when evaluating readiness for duty.

Climbing Performance of Harris' Hawks (Parabuteo Unicinctus) with Added Load: Implications for Muscle Mechanics and for Radiotracking

1989 ◽  
Vol 142 (1) ◽  
pp. 17-29 ◽  
Author(s):  
C. J. PENNYCUICK ◽  
M. R. FULLER ◽  
LYNNE McALLISTER
Keyword(s):  
Body Mass ◽  
Power Output ◽  
Muscle Power ◽  
Muscle Mechanics ◽  
The Body ◽  
Power Product ◽  
Horizontal Flight ◽  
Flight Muscles ◽  
Food Load ◽  
Parabuteo Unicinctus

Two Harris' hawks were trained to fly along horizontal and climbing flight paths, while carrying loads of various masses, to provide data for estimating available muscle power during short flights. The body mass of both hawks was about 920 g, and they were able to carry loads up to 630 g in horizontal flight. The rate of climb decreased with increasing all-up mass, as also did the climbing power (product of weight and rate of climb). Various assumptions about the aerodynamic power in low-speed climbs led to estimates of the maximum power output of the flight muscles ranging from 41 to 46 W. This, in turn, would imply a stress during shortening of around 210 kPa. The effects of a radio package on a bird that is raising young should be considered in relation to the food load that the forager can normally carry, rather than in relation to its body mass.

Eco-evolutionary adaptations of ochotonids (Mammalia: Lagomorpha) to islands: new insights into Late Miocene pikas from the Gargano palaeo-archipelago (Italy)

2020 ◽  
Author(s):  
Blanca Moncunill-Solé
Keyword(s):  
Climate Change ◽  
Growth Rate ◽  
Late Miocene ◽  
Ecological Niche ◽  
Rate Increase ◽  
The Body ◽  
Evolutionary Patterns ◽  
Selective Pressures ◽  
Extant Species ◽  
Management And Conservation

Abstract Climate change strongly affects the range of ochotonids (Order Lagomorpha), fragmenting their habitats and restricting them to ecological islands. The present paper discusses the adaptations of extinct ochotonids to insular stressors, providing baseline data for the management and conservation of extant species. For this purpose, the body mass (BM) and locomotion of the endemic Prolagus apricenicus and Prolagus imperialis from the Gargano palaeo archipelago (Late Miocene) were assessed. P. apricenicus was a small-sized ochotonid (BM 150–250 g) and P. imperialis was probably the largest Prolagus that ever lived (BM 500–750 g). The eco-evolutionary BM dynamics suggest a targeted ecological niche for P. apricenicus, whereas the BM of P. imperialis rose abruptly as a result of growth-rate increase. In both species, the locomotion was stable and less cursorial, with leaping skills, resembling extant rocky ochotonids. Convergent eco-evolutionary patterns are observed in extinct insular ochotonids, concerning an increase of BM (giants), more efficient chewing, less cursorial and more stable locomotion, leaping skills, as well as a slower life history (longer lifespan). Such adaptations are triggered by the specific selective pressures of insular regimes. The present results point to the long-lasting insular Prolagus species as reference taxa for addressing the management of extant rocky ochotonids.

Design of Compliant Bamboo Poles for Carrying Loads

2015 ◽  
Vol 137 (1) ◽  
Author(s):  
Karna Potwar ◽  
Jeffrey Ackerman ◽  
Justin Seipel
Keyword(s):  
Low Cost ◽  
Material Design ◽  
The Body ◽  
Load Carriage ◽  
Design Parameters ◽  
Beam Model ◽  
Load Carrying ◽  
Predictive Design ◽  
Force Reduction ◽  
Heavy Loads

Carriage of heavy loads is common in developing countries and can impart large repetitive forces on the body that could lead to musculoskeletal fatigue and injury. Compliant bamboo poles have been used to carry heavy loads in Asia for generations and could be a low-cost, sustainable, and culturally acceptable way to minimize the forces acting on the body during load carriage. Experimental evidence of running with a 15 kg load suspended from a pair of compliant poly(vinyl chloride), or PVC, poles shows that the poles act as a vibration-isolating suspension, which can reduce the peak forces on the body during locomotion. However, it is currently not well-understood how to design and optimize poles for load carrying such that the peak forces on the body are minimized during carrying. Further, current users of bamboo poles do not have a reliable way to measure forces on the body and so cannot empirically optimize their poles for force reduction. Our objective is to determine the geometric and material design parameters that optimize bamboo poles for load carriage and to develop recommendations that could make it easier for load carriers to fabricate well-suited poles. Our approach is to synthesize a predictive model of walking and running from the field of biomechanics, which can predict the peak forces on the body as a function of pole stiffness, with a bending beam model of the bamboo pole that relates pole geometry and material to the effective pole stiffness. We first check our model's ability to predict the experimental results from a well-established study with PVC poles. We then extend the predictive design study to include a wider range of stiffness values and pole geometries that may be more effective and realistic for practical load carrying situations. Based on stiffness, deflection, strength, and pole mass design constraints, we specify an appropriate range of dimensions for selecting bamboo poles to carry a 15 kg load. The design methodology presented could simplify the selection and design of bamboo carrying poles in order to reduce the likelihood of musculoskeletal injury.

How to Carry Loads Economically: Analysis Based on a Predictive Biped Model

2019 ◽  
Vol 142 (4) ◽  
Author(s):  
Tong Li ◽  
Qingguo Li ◽  
Tao Liu ◽  
Jingang Yi
Keyword(s):  
Relative Motion ◽  
Energy Cost ◽  
Interaction Force ◽  
The Body ◽  
Additional Energy ◽  
Load Carrying ◽  
Walking Motion ◽  
Carrier Interaction ◽  
Heavy Loads ◽  
And Control

Abstract Carrying heavy loads costs additional energy during walking and leads to fatigue of the user. Conventionally, the load is fixed on the body. Some recent studies showed energy cost reduction when the relative motion of the load with respect to the body was allowed. However, the influences of the load's relative motion on the user are still not fully understood. We employed an optimization-based biped model, which can generate human-like walking motion to study the load–carrier interaction. The relative motion can be achieved by a passive mechanism (such as springs) or a powered mechanism (such as actuators), and the relative motion can occur in the vertical or fore-aft directions. The connection between the load and body is added to the biped model in four scenarios (two types × two directions). The optimization results indicate that the stiffness values affect energy cost differently and the same stiffness value in different directions may have opposite effects. Powered relative motion in either direction can potentially reduce energy cost but the vertical relative motion can achieve a higher reduction than fore-aft relative motion. Surprisingly, powered relative motion only performs marginally better than the passive conditions at similar peak interaction force levels. This work provides insights into developing more economical load-carrying methods and the model presented may be applied to the design and control of wearable load-carrying devices.

DYNAMIC LOADS ON THE DRIVE SHAFT BEARINGS OF A SWASH PLATE AXIAL PISTON PUMP WITH CONICAL CYLINDER BLOCK

2004 ◽  
Vol 27 (4) ◽  
pp. 309-318
Author(s):  
M.K. Bahr Khalil ◽  
J.V. Svoboda ◽  
R.B. Bhat
Keyword(s):  
The Body ◽  
Drive Shaft ◽  
Dynamic Loads ◽  
Cylinder Block ◽  
Axial Piston Pump ◽  
Static And Dynamic Characteristics ◽  
Swash Plate ◽  
Variable Displacement ◽  
Heavy Loads ◽  
Axial Piston

Variable displacement swash plate pumps are invariably used under conditions that involve heavy loads with variable flow demands. Swash plate pumps with conical cylinder blocks are now widely used in view of their good static and dynamic characteristics. However, drive shafts of these pumps experience dynamic loads due to the pressure forces transmitted through the body of the conical cylinder block to the supporting bearings. Dynamics of such rotating mechanism are quite interesting and should be considered in the design process of the drive shaft and the supporting bearings. A mathematical model is formulated for a 9-piston swash plate pump with conical cylinder block in order to evaluate the dynamic loads on the drive shaft. Results are presented and discussed.

scholarly journals Body Size Differences between Foraging and Intranidal Workers of the Monomorphic Ant Lasius niger

Insects ◽  
2020 ◽  
Vol 11 (7) ◽  
pp. 433
Author(s):  
Mateusz Okrutniak ◽  
Bartosz Rom ◽  
Filip Turza ◽  
Irena M. Grześ
Keyword(s):  
Body Size ◽  
Field Experiment ◽  
Important Determinant ◽  
Size Variation ◽  
Division Of Labour ◽  
The Body ◽  
Food Type ◽  
Lasius Niger ◽  
Worker Size ◽  
Body Sizes

The association between the division of labour and worker body size of ants is typical for species that maintain physical castes. Some studies showed that this phenomenon can be also observed in the absence of distinct morphological subcastes among workers. However, the general and consistent patterns in the size-based division of labour in monomorphic ants are largely unidentified. In this study, we performed a field experiment to investigate the link between worker body size and the division of labour of the ant Lasius niger (Linnaeus, 1758), which displays limited worker size variation. We demonstrated that the body size of workers exploring tuna baits is slightly but significantly smaller than the size of workers located in the upper parts of the nest. Comparing the present results with existing studies, large workers do not seem to be dedicated to work outside the nest. We suggest that monomorphic workers of certain body sizes are flexible in the choice of task they perform, and food type may be the important determinant of this choice.

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