Biology subjects

Clemente, C. J.

Publications and source records attributed to Clemente, C. J..

3 recordsLinked to original sources

bioRxiv2021

Using a biologically mimicking climbing robot to explore the performance landscape of climbing in lizards

The life and death of an organism often depends on its ability to perform well at some ecologically relevant task. Yet despite this significance we have little idea how well species are optimised for competing locomotor tasks. Most scientists generally accept that the ability for natural systems to become optimised for a specific task is limited by structural, historic or functional constraints. Climbing lizards provide a good example of constraint where climbing ability requires the optimization of conflicting tasks such as speed, stability, or efficiency. Here we reconstruct multiple performance landscapes of climbing locomotion using a 10-DOF robot based upon the lizard bauplan, including an actuated spine, shoulders, and feet, the latter which interlock with the surface via claws. This design allows us to independently vary speed, foot angles, and range of motion, while simultaneously collecting data on climbed distance, stability and efficiency. We first demonstrate a trade-off between speed and stability with high speeds resulting in decreased stability and low speeds an increased cost of transport. By varying foot orientation of fore and hindfeet independently, we found geckos converge on a narrow optimum for both speed and stability, but avoid a secondary wider optimum highlighting a possible constraint. Modifying the spine and limb range of movement revealed a gradient in performance. Evolutionary modifications in movement among extant species appear to follow this gradient towards areas which promote speed and efficiency. This approach can give us a better understanding about locomotor optimization, and provide inspiration for industrial and search-and-rescue robots. Significance StatementClimbing requires the optimization of conflicting tasks such as speed, stability, or efficiency, but understanding the relative importance of these competing performance traits is difficult. We used a highly modular bio-inspired climbing robot to reconstruct performance landscapes for climbing lizards. We then compared the performance of extant species onto these and show strong congruence with lizard phenotypes and robotic optima. Using this method we can show why certain phenotypes are not present among extant species, illustrating why these would be potentially mal-adaptive. These principles may be useful to compare with relative rates of evolution along differing evolutionary histories. It also highlights the importance of biological inspiration towards the optimization of industrial climbing robots, which like lizards, must negotiate complex environments.

evolutionary biology↗

bioRxiv2020

The Mystery of a Marine Monster: Morphological and Performance Modifications in the World's only Marine Lizard, the Galapagos Marine Iguana

Reptiles have repeatedly invaded and thrived in aquatic environments throughout history, however fewer than 8% of the 6000 extant species are primarily aquatic. The Galapagos Marine Iguana (Amblyrhynchus cristatus), the worlds only marine lizard, may have had one of the most unique and challenging transitions to aquatic life. Curiously, previous studies have identified relatively few physiological adaptations in Marine Iguanas, however, little is known about the extent of morphological specialisation and performance trade-offs associated with the marine environment. By examining the morphology and locomotory performance of the Marine Iguana in comparison to their closely related mainland ancestors, the Black Spiny-tailed iguana (Ctenosaura similis) and Green Iguana (Iguana iguana), we found variation reflected specialisation to ecological niches. However, variation was more pronounced among subspecies of Marine Iguana, suggesting that little morphological or performance modification is required for iguanids to successfully invade aquatic environments, thus raising the question why there are so few extant aquatic reptilian lineages. We found that specialisation for the marine environment resulted in a trade-off in sprint speed in a terrestrial environment, similar to that seen in extant crocodilians. Reduced performance in a terrestrial environment likely poses little risk to large-bodied apex predators, whereas in iguanids, a performance trade-off would likely incur increased predation. As such, we suggest that this may explain why iguanids and other ancestral lineages have not undergone transitions to aquatic life. Additionally, we found that the magnitude of morphological and performance variation was more pronounced between subspecies of Marine Iguana than between iguanid species. Summary StatementThe Marine Iguana has undergone a unique evolutionary transition to aquatic behaviour, we explore the extent of morphological and performance specialisation required and why there are so few extant marine reptiles. O_FIG_DISPLAY_L [Figure 1] M_FIG_DISPLAY C_FIG_DISPLAY

evolutionary biology↗

bioRxiv2018

Moving in complex environments: a biomechanical analysis of locomotion on inclined and narrow substrates

Characterisation of an organisms performance in different habitats provides insight into the conditions that allow it to survive and reproduce. In recent years, Northern quolls (Dasyurus hallucatus)--a medium-sized semi-arboreal marsupial native to northern Australia--have undergone significant population declines within open forest, woodland and riparian habitats, but less so in rocky areas. To explore this decline, we quantified the biomechanical performance of wild Northern quolls over inclined narrow (13 mm pole) and inclined wide (90 mm platform) substrates. We predicted that quolls may possess biomechanical adaptations to increase stability on narrow surfaces, which are more common in rocky habitats. Our results display that quolls have some biomechanical characteristics consistent with a stability advantage on narrow surfaces. This includes the coupled use of limb pairs and high grip torques (Max = 68.9 N.m, Min = -69.9 N.m), highlighting their ability to generate corrective forces to counteract the toppling moments commonly encountered during gait on narrow surfaces. However, unlike other arboreal specialists such as primates, speed was constrained on narrow surfaces, and quolls did not adopt diagonal sequence gaits. Quolls appear to adopt similar performance characteristics to cats and dogs which may limit their ability to outperform these key predators (invasive or otherwise) in particular habitats. This overlap may contribute to the declining population of Northern quolls on mainland Australia.

zoology↗