Kinematics of maleEupalaestrus weijenberghi(Araneae, Theraphosidae) locomotion on different substrates and inclines

Abstract

Background The mechanics and energetics of spider locomotion have not been deeply investigated, despite their importance in the life of a spider. For example, the reproductive success of males of several species is dependent upon their ability to move from one area to another. The aim of this work was to describe gait patterns and analyze the gait parameters of Eupalaestrus weijenberghi (Araneae, Theraphosidae) in order to investigate the mechanics of their locomotion and the mechanisms by which they conserve energy while traversing different inclinations and surfaces. Methods Tarantulas were collected and marked for kinematic analysis. Free displacements, both level and on an incline, were recorded using glass and Teflon as experimental surfaces. Body segments of the experimental animals were measured, weighed, and their center of mass was experimentally determined. Through reconstruction of the trajectories of the body segments, we were able to estimate their internal and external mechanical work and analyze their gait patterns. Results Spiders mainly employed a walk-trot gait. Significant differences between the first two pairs and the second two pairs were detected. No significant differences were detected regarding the different planes or surfaces with respect to duty factor, time lags, stride frequency, and stride length. However, postural changes were observed on slippery surfaces. The mechanical work required for traversing a level plane was lower than expected. In all conditions, the external work, and within it the vertical work, accounted for almost all of the total mechanical work. The internal work was extremely low and did not rise as the gradient increased. Discussion Our results support the idea of considering the eight limbs functionally divided into two quadrupeds in series. The anterior was composed of the first two pairs of limbs, which have an explorative and steering purpose and the posterior was more involved in supporting the weight of the body. The mechanical work to move one unit of mass a unit distance is almost constant among the different species tested. However, spiders showed lower values than expected. Minimizing the mechanical work could help to limit metabolic energy expenditure that, in small animals, is relatively very high. However, energy recovery due to inverted pendulum mechanics only accounts for only a small fraction of the energy saved. Adhesive setae present in the tarsal, scopulae, and claw tufts could contribute in different ways during different moments of the step cycle, compensating for part of the energetic cost on gradients which could also help to maintain constant gait parameters.

Warming is here: using locomotor performance to infer thermal parameters and vulnerability for an endemic Argentinean tarantula Grammostola vachoni

“…Locomotor ability is frequently used as a performance measurement that is strongly related to thermal physiology (Shillington, 2005;Kruse et al, 2008;Carlson & Rowe, 2009;Wu et al, 2010;Schwerdt et al, 2020). This could have potential consequences in behaviour and ecological aspects, as avoiding predators, prey capture, find refuge, or a potential mate (Huey & Stevenson, 1979;Bonino et al, 2015;Booster et al, 2015;Silva-Pereyra et al, 2019). Also, in small-sized ectotherms, fitness may be maximized by reducing the probability of becoming trapped in thermally unfavourable environments rather than maximizing performance (Crickenberger et al, 2019).…”

“…Also, it is an easy-obtainable measure in tarantulas (Stork, 2012;Booster et al, 2015;Schwerdt et al, 2020). Sprint speed is strongly related to spider ecology, as it is related to the ability to escape from a predator, or acquiring food, and it also affects social interactions such as mating during the reproductive period (Huey & Stevenson, 1979;Booster et al, 2015;Silva-Pereyra et al, 2019). Relationship between the temperature and sprint speed were described with a thermal performance curve (TPC).We estimated from this curve the performance limits through critical thermal minimum (CT min ), and critical thermal maximum (CT max ).…”

Bio-inspired design of hard-bodied mobile robots based on arthropod morphologies: a 10 year systematic review and bibliometric analysis

“…Arachnids move by using gaits in which they alternate the number and type of legs in predictable patterns. For example, wolf spiders, tarantulas and scorpions move using an alternate tetrapod gait [33][34][35]. At a given time, four legs contact the ground (stance phase), whereas the remaining four are lifted (aerial phase).…”