Ritualized combat and intercolony communication in ants

Colonies of the honey ant Myrmecocystus mimicus engage each other in elaborate display tournaments. Hundreds of ants are often involved, but almost no physical fights occur. Instead, opponents confront one another in highly aggressive displays, during which they walk on stilt legs while raising their abdomens and heads. The tournaments serve as temporary spatial borders within which food gathering occurs. In this study we develop the hypothesis that tournaments are a mechanism of intercolony communication, which opposing colonies use to gauge each other's strength. Models are proposed for the behaviorial procedures that seem most likely to underly this capacity. For the first time it is possible to ascertain and compare the properties of such models in relation to a body of test data. It appears probable to us that intercolony communication in this species of ant may depend upon a novel capacity for integrative information harvesting by individual workers.     

THE EVOLUTION OF BIPEDAL RUNNING IN LIZARDS SUGGESTS A CONSEQUENTIAL ORIGIN MAY BE EXPLOITED IN LATER LINEAGES

The origin of bipedal locomotion in lizards is unclear. Modeling studies have suggested that bipedalism may be an exaptation, a byproduct of features originally designed to increase maneuverability, which were only later exploited. Measurement of the body center of mass (BCOM) in 124 species of lizards confirms a significant rearward shift among bipedal lineages. Further racetrack trials showed a significant acceleration threshold between bipedal and quadrupedal runs. These suggest good general support for a passive bipedal model, in which the combination of these features lead to passive lifting of the front of the body. However, variation in morphology could only account for 56% of the variation in acceleration thresholds, suggesting that dynamics have a significant influence on bipedalism. Deviation from the passive bipedal model was compared with node age, supporting an increase in the influence of dynamics over time. Together, these results show that bipedalism may have first arisen as a consequence of acceleration and a rearward shift in the BCOM, but subsequent linages have exploited this consequence to become bipedal more often, suggesting that bipedalism in lizards may convey some advantage. Exploitation of bipedalism was also associated with increased rates of phenotypic diversity, suggesting exploiting bipedalism may promote adaptive radiation.     

THE EVOLUTION OF BIPEDALISM IN JERBOAS (RODENTIA: DIPODOIDEA): ORIGIN IN HUMID AND FORESTED ENVIRONMENTS

Mammalian bipedalism has long been thought to have arisen in response to arid and open environments. Here, we tested whether bipedalism coevolved with environmental changes using molecular and paleontological data from the rodent superfamily Dipodoidea and statistical methods for reconstructing ancestral characteristics and past climates. Our results show that the post‐Late Miocene aridification exerted selective pressures on tooth shape, but not on leg length of bipedal jerboas. Cheek tooth crown height has increased since the Late Miocene, but the hind limb/head‐body length ratios remained stable and high despite the environmental change from humid and forested to arid and open conditions, rather than increasing from low to high as predicted by the arid‐bipedalism hypothesis. The decoupling of locomotor and dental character evolution indicates that bipedalism evolved under selective pressure different from that of dental hypsodonty in jerboas. We reconstructed the habitats of early jerboas using floral and faunal data, and the results show that the environments in which bipedalism evolved were forested. Our results suggest that bipedalism evolved as an adaptation to humid woodlands or forests for vertical jumping. Running at high speeds is likely a by‐product of selection for jumping, which became advantageous in open environments later on.     

Influence of male morphology on male mating status and behavior during interunit encounters in western lowland gorillas

The western lowland gorilla (Gorilla gorilla gorilla) is one of the most sexually dimorphic primate species. Mature males are twice the size of females and have grey fur on their backs and a fibrous, adipose crest on their heads. Such traits are likely to have evolved by sexual selection, either because they confer advantages during male-male fights or because females prefer males with more dimorphic traits. We developed photogrammetric methods for distance collection of morphological data from silverback males frequenting the Lokoué forest clearing in Odzala-Kokoua National Park, Republic of the Congo. Body length, head-crest size, musculature development, and extent of the grey color on the back were assessed in 87 nonbreeding and breeding mature males. Behavioral data were also collected during 312 male-male encounters involving 67 mature males in order to estimate their level of aggressiveness. The number of females belonging to a mature male positively correlated with the male crest size, body length, and musculature. Whereas morphological variables did not significantly affect the intensity of male-male encounters, the number of females attending male-male encounters strongly affected the number of agonistic displays by the two males. We discuss the mechanisms through which males with more exaggerated traits could obtain a mating advantage, namely male-male fights or female mate choice.     

The evolution of sweat glands

Mammals have two kinds of sweat glands, apocrine and eccrine, which provide for thermal cooling. In this paper we describe the distribution and characteristics of these glands in selected mammals, especially primates, and reject the suggested development of the eccrine gland from the apocrine gland during the Tertiary geological period. The evidence strongly suggests that the two glands, depending on the presence or absence of fur, have equal and similar functions among mammals; apocrine glands are not primitive. However, there is a unique and remarkable thermal eccrine system in humans; we suggest that this system evolved in concert with bipedalism and a smooth hairless skin.Iowa Quaternary Studies Contribution No. 47     

滩羊裘皮毛色调控基因的研究进展

滩羊是中国裘皮来源的珍稀地方绵羊品种,以所产二毛裘皮而著称,二毛裘皮在国内外毛皮市场上均享有较高的声誉。毛色是宁夏滩羊重要的经济性状,滩羊多为体躯白色,头部有黑褐斑,个别个体黑头或体躯黑杂色,少数纯白。毛色与体内黑色素的数量、种类和分布等情况有关。掌握调控滩羊毛色基因的作用机制,可以有效控制其毛色性状。本文从滩羊的裘皮特性、毛色形成机理、毛色相关基因(MC1R基因、Agouti基因、TYR基因、MITF基因和KIT基因)的功能及选择信号检测等方面进行了综述。     

On the origin of avian flight: Compromise and system approaches

Based on evolutionary morphological analysis of the fore and hind limbs of extinct and extant birds, a new compromise hypothesis of the origin of flight in birds and theropod dinosaurs is proposed. The bipedalism and anisodactylous foot suitable for various functions were key adaptations for the development of flight. The bipedalism freed forelimbs from the supporting function and promoted transformation into wings, as animals moved from one tree branch to another and descended from trees. At the initial stage, the strong hind limbs provided the opportunity to climb and leap onto trees, bushes, or eminence, while the anisodactylous foot provided a firm support on both dry land and trees. The support provided by this foot allowed the reduction of the tail, which was initially composed of a long row of vertebrae. Thus, a stage of gliding flight was not necessarily passed by early birds. In the other lineages of feathered creatures, functional changes in forelimbs that resulted in the formation of wings developed in parallel and followed almost the same scenario.     

Park or Ride? Evolution of Infant Carrying in Primates

Few mammalian orders carry their infants clinging to the mother's fur. I investigated the evolution of carrying behavior in primates and the life-history and ecological correlates of infant care patterns. Primates are ideal for the study as there is variation in infant care patterns. Primate infants are left hidden in nests or parked in trees, both of which strategies I term parking, and are carried orally or ride clinging to the mother's fur: riding. Infant carrying has evolved several times in the Primates and, once evolved, it has been conserved. Significant energetic costs of riding are indicated as riding species maintain smaller home ranges than those of non-riders of the same body size. With body size and phylogenetic influences taken into account, riders appear to incur a reproductive cost by weaning and breeding later than parkers. Although riders do not have lower birth rates than those of parkers, their later age at first reproduction leads to their having a lower reproductive rate, measured by the intrinsic rate of population increase. Precociality of infants is not correlated with either riding or nesting behavior. Although non-nesting species have larger litter sizes, their infants are not significantly smaller, nor are their neonatal brains relatively smaller. Although riding may have some energetic and reproductive costs, its repeated evolution in the Primates suggests that it also has some benefits, the most likely being a reduced mortality risk for carried infants.     

Morphological changes leading to hominid bipedalism

The adoption of habitual bipedal locomotion required a backward shift of the centre of gravity of the body, to a level relative to the supporting surface area of the body and pivotal axis of the hips at which walking with extended knees became practicable. In the morphology of the immediate ancestors to hominids, there were relatively few features whose change could have effectively affected the position of the gravity vertical of the body. Weight could be distributed posteriorly mainly by increasing the mass of the hindlimbs and the kyphotic curve of the vertebral column, by developing buttocks. and by flattening the thorax and abdomen. Estimates indicate that the adoption of a suitable curvature of the vertebral column alone was not sufficient for shifting the centre of gravity behind the 'threshold of bipedalism'. A considerable increase in the mass of the hindlimbs was also required, and the addition of the mass of the buttocks may have represented the decisive factor for crossing the threshold. A possible physical enviroment in which the change to bipedalism could have taken place was a mountainous terrain with long, steep slopes, transected by gorges and precipices. In such a terrain the increase in the power and mass of both the hindlimbs and the gluteus maximus proprius muscle could have been favoured by selection, leading ultimately to a condition in which the combined effect of heavy hindlimbs. a suitable curvature of the spine and the weight of the buttocks shifted the centre of gravity of the body backwards to a level at which habitual walking with extended knees became practicable. □ Hominid evolution. bipedalism, evolutionary thresholds.     

Male attractiveness covaries with fighting ability but not with prior fight outcome in house crickets

In many species males that tend to win fights against othermales are more attractive to females. There are three ways inwhich male fighting ability and attractiveness may be associated:(1) attractiveness and fighting ability are influenced by thesame underlying traits (e.g., body size), (2) females prefermales that have directly observed winning fights, or (3) winningprevious fights indirectly improves a male's chance of beingpreferred by females. The last possibility may arise as a consequenceof the "loser effect"; in many species when a male loses a fighthis probability of losing subsequent fights increases. Thereare, however, no studies testing whether such a "loser effect"also influences male attractiveness. Here we show that maleattractiveness and fighting ability are positively correlatedin the house cricket, Acheta domesticus. Our experiment wasdesigned so that females could not directly observe the outcomeof fights, thus eliminating possibility (2) above. We then testedbetween possibilities (1) and (3) by making use of the factthat in some cricket species the "loser effect" can be eliminatedexperimentally by ‘shaking’ a male and stimulatingthe motor program for flying. We showed that in A. domesticus‘shaking’ does affect the outcome of subsequentfights. Males that had won two previous fights were less likelyto win a fight after being ‘shaken’ than when subjectto a control treatment. In contrast, males that had lost twoprevious fights were more likely to win a fight after being‘shaken’ than when they were not shaken. There was,however, no effect of ‘shaking’ on male attractiveness.We conclude that the "loser effect" does not alter the tendencyfor large, dominant males to be attractive to females. Instead,it appears that there are traits correlated with both fightingability and attractiveness. One such trait is body size. Fightwinners were significantly larger than losers and attractivenesswas positively correlated with male body size.     

Three-dimensional kinematics of capuchin monkey bipedalism

Capuchin monkeys are known to use bipedalism when transporting food items and tools. The bipedal gait of two capuchin monkeys in the laboratory was studied with three-dimensional kinematics. Capuchins progress bipedally with a bent-hip, bent-knee gait. The knee collapses into flexion during stance and the hip drops in height. The knee is also highly flexed during swing to allow the foot which is plantarflexed to clear the ground. The forefoot makes first contact at touchdown. Stride frequency is high, and stride length and limb excursion low. Hind limb retraction is limited, presumably to reduce the pitch moment of the forward-leaning trunk. Unlike human bipedalism, the bipedal gait of capuchins is not a vaulting gait, and energy recovery from pendulum-like exchanges is unlikely. It extends into speeds at which humans and other animals run, but without a human-like gait transition. In this respect it resembles avian bipedal gaits. It remains to be tested whether energy is recovered through cyclic elastic storage and release as in bipedal birds at higher speeds. Capuchin bipedalism has many features in common with the facultative bipedalism of other primates which is further evidence for restrictions on a fully upright striding gait in primates that transition to bipedalism. It differs from the facultative bipedalism of other primates in the lack of an extended double-support phase and short aerial phases at higher speeds that make it a run by kinematic definition. This demonstrates that facultative bipedalism of quadrupedal primates need not necessarily be a walking gait.     

1H NMR-based lipidomics of rodent fur: species-specific lipid profiles and SCD1 inhibitor-related dermal toxicity

A method is described that allows noninvasive identification and quantitative assessment of lipid classes present in sebaceous excretions in rodents. The method relies on direct high-field proton NMR analysis of common group lipid protons in deuterated organic solvent extracts of fur. Extracts from as little as 15 mg of fur from rat, mouse, and hamster provided acceptable results on a 600 MHz NMR equipped with a cryogenically cooled proton-observe probe. In rats, sex- and age-related differences in lipid composition are larger than differences in fur collected from various body regions within an individual and much larger than interanimal differences in age- and sex-matched specimens. The utility of this method to noninvasively monitor drug-induced sebaceous gland atrophy in rodents is demonstrated in rats dosed with a stearoyl-CoA desaturase 1 (SCD1) inhibitor. In this model, a 35% reduction in sebum lipids, extracted from fur, was observed. Finally, structural elucidation of cholesta-7,24-dien-3β-ol ester as the most prominent, previously unidentified sebum sterol ester in male Syrian hamsters is described. The utility of this method for drug and cosmetic safety and efficacy assessment is discussed.     

Stresses on the limbs of quadrupedal primates

Data is presented from eight primates on the ground reaction forces on the limbs during locomotion. These subjects supported from 30 to 45% of their body weight on their forelimbs. Other quadrupedal mammals support 55-60% of their body weight on their forelimbs. The increase of peak vertical force with speed varies greatly between the subjects. The variation in weight supported by the forelimbs and the peak forces on the forelimbs is proposed to correlate with variation in locomotor adaptations. It is suggested that the occurrence of bipedalism in primates represents the extreme expression of the tendency in primates to reduce the compressive forces on their forelimbs.     

Ground reaction forces and center of mass mechanics of bipedal capuchin monkeys: Implications for the evolution of human bipedalism

Tufted capuchin monkeys are known to use both quadrupedalism and bipedalism in their natural environments. Although previous studies have investigated limb kinematics and metabolic costs, their ground reaction forces (GRFs) and center of mass (CoM) mechanics during two and four‐legged locomotion are unknown. Here, we determine the hind limb GRFs and CoM energy, work, and power during bipedalism and quadrupedalism over a range of speeds and gaits to investigate the effect of differential limb number on locomotor performance. Our results indicate that capuchin monkeys use a “grounded run” during bipedalism (0.83–1.43 ms^?1) and primarily ambling and galloping gaits during quadrupedalism (0.91–6.0 ms^?1). CoM energy recoveries are quite low during bipedalism (2–17%), and in general higher during quadrupedalism (4–72%). Consistent with this, hind limb vertical GRFs as well as CoM work, power, and collisional losses are higher in bipedalism than quadrupedalism. The positive CoM work is 2.04 ± 0.40 Jkg^?1 m^?1 (bipedalism) and 0.70 ± 0.29 Jkg^?1 m^?1 (quadrupedalism), which is within the range of published values for two and four‐legged terrestrial animals. The results of this study confirm that facultative bipedalism in capuchins and other nonhuman primates need not be restricted to a pendulum‐like walking gait, but rather can include running, albeit without an aerial phase. Based on these results and similar studies of other facultative bipeds, we suggest that important transitions in the evolution of hominin locomotor performance were the emergences of an obligate, pendulum‐like walking gait and a bouncy running gait that included a whole‐body aerial phase. Am J Phys Anthropol, 2013. © 2012 Wiley Periodicals, Inc.     

Simulation of sensible and latent heat losses from wet-skin surface and fur layer

A simulation model that simultaneously calculates heat and mass transfer from a wetted skin surface and fur layer of a cow is presented. The model predicts evaporative, convective and radiant heat losses for different levels of skin and fur wetness, air velocity, air temperature and relative humidity. In the model, fur layer (hair coat) properties such as fur thickness and hair density assumed are that of summer conditions. Evaporative cooling from wet-skin surface and hair coat is the dominant mode of heat mitigation mechanism in stressful hot environments and is further enhanced by increased air velocity. Evaporative cooling is, however, depressed by increased relative humidity because of deficit of water-vapor concentration between the skin surface and ambient air.     

Use of energy reserves in fighting hermit crabs

When animals engage in fights they face a series of decisions, which are based on the value of the contested resource and either their relative or their absolute fighting ability. Certain correlates of fighting ability or 'resource holding potential' such as body size are fixed but physiological correlates are expected to vary during the encounter. We examine the role of energy reserves in determining fight outcomes and parameters during 'shell fighting' in hermit crabs. During these fights, the two contestants perform very different roles of attacker and defender. We show that the balance of the total energy pool, in the form of glucose and glycogen, determines the ability of defenders to resist eviction from their shells. Low glucose in evicted defenders is not caused by depletion of energy reserves, rather mobilization of glycogen appears to be the result of a strategic decision about whether to resist effectively, based on the perceived fighting ability of the attacker. Attackers, however, always initiate the fight so such a decision for this role appears unlikely. In addition to influencing decisions and ability during fights, physiological correlates of fighting ability can in turn be influenced by strategic decisions.     

Birth intervention and non-maternal infant-handling during parturition in a nonhuman primate

Direct intervention in infant delivery by non-parturient individuals is a rare phenomenon in nonhuman primates. In contrast, birth assistance by other individuals, or the practice of midwifery, is universal among human societies and generally believed to be a behavior unique to our species. It has been proposed that the enlarged head of the human fetus and the relatively narrow birth canal constrained by bipedalism has made human parturition more difficult than in nonhuman primates, and these anatomic challenges have led to the rotation of the fetus in the birth canal and an occiput anterior (i.e., backward-facing) orientation of emergence. These characteristics have hindered the mother’s ability to self-assist the delivery of the infant, therefore necessitating assistance by other individuals or midwives for successful birth. Here we report the first high-definition video recordings of birth intervention behavior in a wild nonhuman primate, the white-headed langur (Trachypithecus leucocephalus). We observed that while a primiparous female gave birth to an infant in an occiput posterior (i.e., forward-facing) orientation, a multiparous female intervened in the delivery by manually pulling the infant out of the birth canal and cared for it in the following hours. Our finding shows extensive social interactions throughout parturition, and presents an unequivocal case of non-maternal intervention with infant birth in a nonhuman primate.     

Biomechanical interpretation of the early hominid hip

A new pelvic fragment from Swartkrans provides the opportunity to analyze the hip joint mechanics of the robust form of early hominid. The function of the lateral support system provided by the abductor muscles of the hip appears to be similar to that of the gracile early hominid from Sterkfontein. The system is well adapted for providing the lateral support necessary for efficient bipedalism. The hip extensor mechanism and hip internal rotatory system also appear to be well adapted for efficient bipedalism in a way very similar to the other early hominids. The conclusion reached is that the robust and gracile forms of South African early hominids were basically similar in their locomotor adaptation and were most likely habitual bipeds.     

Thermoregulation and the determinants of heat transfer in Colias butterflies

Summary As a means of exploring behavioral and morphological adaptations for thermoregulation in Colias butterflies, convective heat transfer coefficients of real and model butterflies were measured in a wind tunnel as a function of wind speed and body orientation (yaw angle). Results are reported in terms of a dimensionless heat transfer coefficient (Nusselt number, Nu) and a dimensionless wind speed (Reynolds number, Re), for a wind speed range typical of that experienced by basking Colias in the field. The resultant Nusselt-Reynolds (Nu-Re) plots thus indicate the rates of heat transfer by forced convection as a function of wind speed for particular model geometries.For Reynolds numbers throughout the measured range, Nusselt numbers for C. eurytheme butterflies are consistently lower than those for long cylinders, and are independent of yaw angle. There is significant variation among individual butterflies in heat transfer coefficients throughout the Re range. Model butterflies without artificial fur have Nu-Re relations similar to those for cylinders. Heat transfer in these models depends upon yaw angle, with higher heat transfer at intermediate yaw angles (30–60°); these yaw effects increase with increasing Reynolds number. Models with artificial fur, like real Colias, have Nusselt numbers which are consistently lower than those for models without fur at given Reynolds numbers throughout the Re range. Unlike real Colias, however, the models with fur do show yaw angle effects similar to those for models without fur.The independence of heat loss from yaw angle for real Colias is consistent with field observations indicating no behavioral orientation to wind direction. The presence of fur on the models reduces heat loss but does not affect yaw dependence. The large individual variation in heat transfer coefficients among butterflies is probably due to differences in fur characteristics rather than to differences in wing morphology.Finally, a physical model of a butterfly was constructed which accurately simulates the body temperatures of basking Colias in the field for a variety of radiation and wind velocity conditions. The success of the butterfly simulator in mimicking Colias thermal characteristics confirms our preliminary understanding of the physical bases for and heat transfer mechanisms underlying thermoregulatory adaptations in these butterflies.     

Origin of bipedalism

Human and chimpanzee locomotor behaviors are described and compared using field patterns derived from measurements of the motions at the joints. Field patterns of human and ape bipedalism are so different that it is doubted whether the nonhuman type could ever have been a precursor of the human type. Chimpanzee quadrupedal vertical climbing and human bipedalism are, on the other hand, similar and a particular variety of this kind of climbing probably was the precursor of human bipedalism. Animals adapted to this variation would have had some brachiation-like morphological traits in their pectoral limbs and some hominid-like morphological traits in their pelvic limbs, traits anticipating the human condition. The australopithecines possessed these traits and must have been adapted to arboreal quadrupedal vertical climbing, having the capacity, at the same time, to perform facultative terrestrial bipedalism, moving on the ground in a manner visually identical to that of humans.