Variation in movement: multiple locomotor gaits in Neotropical harvestmen

Escalante, Ignacio; Badger, Marc; Elias, Damian O.

doi:10.1093/biolinnean/blz047

Cited by 11 publications

(25 citation statements)

References 61 publications

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“…We recorded harvestmen moving during daytime across a horizontal arena (Supplementary Video S1) in the lab, using the same procedure as Ref. 35 . To simulate predation attempts, we grabbed individuals by their hind legs and then released them.…”

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“…We digitized videos using the custom scripts developed in Mathematica 10.4 (Wolfram Research, Inc., Champaign, IL, USA) described in Ref. 35 . Briefly, scripts automatically tracked the position of the animal's body across each view.…”

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confidence: 99%

“…We calculated nine performance, postural, or stride variables to describe harvestmen locomotion as in Escalante et al 35 . For performance metrics, we used the XYZ positions over time to calculate (1) the average horizontal velocity, hereafter referred to as 'velocity' , calculated as v_h = (x_final − x_initial)/(t_final − t_initial), where x_initial and x_final are the (x, y) coordinates of the body at the start and end of the trial, respectively.…”

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“…We grouped the type of gaits into "fast gaits" (running and stotting) and "slow gaits" (bobbing and walking). We grouped gaits this way because performance (velocity and acceleration) is similar within gait groups 35 . Additionally, our focus here was on understanding the consequences of autotomy regardless of gait type.…”

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Rapid recovery of locomotor performance after leg loss in harvestmen

Escalante

Badger

Elias

2020

Sci Rep

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Animals have evolved adaptations to deal with environmental challenges. for instance, voluntarily releasing appendages (autotomy) to escape potential predators. Although it may enhance immediate survival, this self-imposed bodily damage may convey long-term consequences. Hence, compensatory strategies for this type of damage might exist. We experimentally induced autotomy in Prionostemma harvestmen. these arachnids are ideal to examine this topic because they show high levels of leg loss in the field but do not regenerate their legs. We video-recorded animals moving on a horizontal track and reconstructed their 3D trajectories with custom software tools to measure locomotor performance. individuals that lost either three legs total or two legs on the same side of the body showed an immediate and substantial decrease in velocity and acceleration. Surprisingly, harvestmen recovered initial performance after 2 days. This is the quickest locomotor recovery recorded for autotomizing animals. We also found post-autotomy changes in stride and postural kinematics, suggesting a role for kinematic adjustments in recovery. Additionally, following leg loss, some animals changed the gaits used during escape maneuvers, and/or recruited the 'sensory' legs for locomotion. Together, these findings suggest that harvestmen are mechanically robust to the bodily damage imposed by leg loss. Animals face a myriad of challenges during their lives, including predation, parasitism, navigating obstacles, and physiological stress. These challenges often lead to damage and many animals have evolved adaptations to compensate for these injuries. Compensation for damage often involves gradual improvements using developmental, morphological, or behavioral changes 1,2. For instance, animals such as lizards, crickets and damselfly larvae reduce their mobility and become more cryptic after damage from potential predators 3-6. While bodily damage is often unintended, in some species injury is self-imposed and potentially adaptive. For example, many animals voluntarily lose appendages when grabbed by potential predators, a defensive strategy known as autotomy 7. Although important for immediate survival 5,7-10 , the loss of body parts may compromise other aspects of organismal function and, by extension, an individual's long term fitness 11,12. Effects of autotomy include changes for locomotion, foraging, development, sensory biology, longevity, migration, and survival 13-15. With regards to locomotion, stability and maneuverability are altered by autotomy, as found for green anole lizards 16 and leopard geckos 17. Locomotor performance (i.e. acceleration or velocity), often interpreted as evidence of the ability to escape a potentially dangerous interaction, is also affected by autotomy 7. Accordingly, wolf spiders missing legs are slower than intact individuals when running 18,19. Besides performance metrics, another set of movement parameters (stride and posture kinematics) can change after autotomy. For instance, stride length and duty factor (th...

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Rapid recovery of locomotor performance after leg loss in harvestmen

Escalante

Badger

Elias

2020

Sci Rep

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“…The presence of alarm pheromones will be beneficial for group living and will provide information on the evolutionary maintenance of this trait. By exposing groups to concentrated pheromones, the alarm function of their secretions could be correlated with (1) their fleeing behavior, (2) site tenancy, measured as the return throughout the days, (3) the transmission of the alarm signal by either olfactory or contact receptions, (4) the potential importance of bobbing behavior (Gnaspini & Hara 2007, Escalante et al 2019 as a way to disseminate the alarm pheromone (an untested strategy so far), and finally (5) the importance of the position in the group. Therefore, future research will provide important insights into the interaction between behavior, chemical communication, morphology (in the form of the extremely elongated legs in Eupnoi) in harvestmen.…”

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Chemical communication and ecology in Eupnoi harvestmen

Escalante

2019

Preprint

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Communication via chemical signals and cues is a widespread modality in animals. Producing, transmitting, receiving and processing chemical compounds impose important challenges. Nonetheless, certain arthropods rely almost exclusively on this channel for intra- and inter-specific communication. Through a preliminary literature review, I summarize here the morphological, behavioral and evolutionary implications of chemical communication in harvestmen (the arachnid order Opiliones), with particular emphasis in one group: the Eupnoi or “Daddy Long-legs”. This group has a unique secretory gland that opens in an ozopore in their dorsum. While relying mostly on short-range olfaction and contact chemoreception using different setae, some harvestmen are known to use chemicals in defense, alarm, spatial marking, recruitment, or reproduction. I then propose future research direction on the mechanisms of production and the evolutionary history of these traits. Specific questions can include (1) are chemical signals used as alarm pheromones in Eupnoi aggregations? (2) Do harvestmen rely on chemicals to mark their traditional roosting sites? If so, what are the chemicals involved and how do those differ from the ones used as alarm signals? Also, (3) what are the specific functions of the chemical communication during in female-male communication and multi-specific roosting aggregations? And (4) to what extent the use of chemical defenses imposes a trade-off with other defense mechanisms such as ‘playing dead’ or voluntarily releasing legs. Overall, these harvestmen provide a unique opportunity to test comprehensive and interdisciplinary hypotheses to understand the evolution of chemical communication, as well as the importance of chemical ecology on species diversification in arthropods.

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