The problem of the number of tarsomeres in the regenerated cockroach leg

Moving in an Uncertain World: Robust and Adaptive Control of Locomotion from Organisms to Machine Intelligence

Whether walking, running, slithering, or flying, organisms display a remarkable ability to move through complex and uncertain environments. In particular, animals have evolved to cope with a host of uncertainties-both of internal and external origin-to maintain adequate performance in an ever-changing world. In this review, we present mathematical methods in engineering to highlight emerging principles of robust and adaptive control of organismal locomotion. Specifically, by drawing on the mathematical framework of control theory, we decompose the robust and adaptive hierarchical structure of locomotor control. We show how this decomposition along the robust-adaptive axis provides testable hypotheses to classify behavioral outcomes to perturbations. With a focus on studies in non-human animals, we contextualize recent findings along the robust-adaptive axis by emphasizing two broad classes of behaviors: (1) compensation to appendage loss and (2) image stabilization and fixation. Next, we attempt to map robust and adaptive control of locomotion across some animal groups and existing bio-inspired robots. Finally, we highlight exciting future directions and interdisciplinary collaborations that are needed to unravel principles of robust and adaptive locomotion.

Effect of larval thermal conditions on limb regeneration in a ladybird beetle, Cheilomenes sexmaculata

In view of global environmental change, ecological factors especially temperature, affect development of the poikilotherms like insects. Since ladybirds are at risk of injury under mass-rearing conditions, their ability to regenerate injured limbs is highly crucial for their survival. Therefore, the effect of limb regeneration in relation to temperature forms the basis of the present study. The immature stages of insects, being more vulnerable to the surrounding temperature, were considered to study the effect of the prior thermal experience of larvae on regeneration. We exposed the early larval stages of the ladybird beetle, Cheilomenes sexmaculata, to different temperature conditions pre- and postamputation. Exposure of immature stages to extreme temperatures did not affect the ability to regenerate and regeneration occurred at given temperature conditions. However, the regenerated legs were smaller in size across given temperatures as compared to unamputated legs. Body weights in amputated treatments showed no difference and remained unchanged across temperatures when compared to unamputated treatments. Postamputation developmental duration, equivalent to recovery time postlimb amputation, was found to be affected by larval thermal conditions. Recovery was faster in larval treatments exposed to higher temperatures. Thus, larval thermal conditions though did not affect the ability to regenerate lost limbs directly, it does modulate the time taken to regenerate.

Physiological and molecular mechanisms of insect appendage regeneration

Regeneration, as a fascinating scientific field, refers to the ability of animals replacing lost tissue or body parts. Many metazoan organisms have been reported with the regeneration phenomena, but showing evolutionarily variable abilities. As the most diverse metazoan taxon, hundreds of insects show strong appendage regeneration ability. The regeneration process and ability are dependent on many factors, including macroscopic physiological conditions and microscopic molecular mechanisms. This article reviews research progress on the physiological conditions and internal underlying mechanisms controlling appendage regeneration in insects.

Predators or Herbivores: Cockroaches of Manipulatoridae Revisited with a New Genus from Cretaceous Myanmar Amber (Dictyoptera: Blattaria: Corydioidea)

Manipulator modificaputis Vršanský and Bechly, 2015 (Manipulatoridae, Corydioidea) is a purported predatory cockroach from Cretaceous Myanmar amber, based on a single male. It is distinctive by the nimble head, elongate pronotum and legs, and particularly by the extraordinarily long maxillary palpi. In the present study, we redescribe Manipulator modificaputis based on six new fossils including males and females, and comment on the original description. The closely related Manipulatoides obscura gen. & sp. nov. is proposed on the basis of five fossils, including males and females. It differs from Manipulator in weaker spination of the legs, including the type-C forefemoral spination instead of the type-A of Manipulator. Some undetermined adults and nymphs are also described. We discuss the ethology of Manipulatoridae and speculate that they might feed on flowers. They are unlikely to be specialized predators since they lack necessary weaponry for capturing prey; in contrast, their unique morphotype appears to be suitable for efficient foraging and locomotion amid flowering twigs. The possibility of being kleptoparasites of the spider-web is also discussed. In addition, regenerated four-segmented tarsi are found from the new species.

Leg regeneration in Drosophila abridges the normal developmental program

Regeneration of lost body parts has traditionally been seen as a redeployment of embryonic development. However, whether regeneration and embryonic development are controlled by identical, similar or different genetic programmes has not been fully tested. Here, we analyse proximal-distal regeneration in Drosophila leg imaginal discs using the expression of positional markers, and by cell-lineage experiments, and we compare it with the pattern already known in normal development. During regeneration, the first proximal-distal positional markers reappear in overlapping patterns. As the regenerate expands, they segregate and further markers appear until the normal pattern is produced, following a proximal to distal sequence that is in fact the reverse of normal leg imaginal disc development. The results of lineage tracing support this interpretation and show that regenerated structures derive from cells near the wound edge. Although leg development and leg regeneration are served by a set of identical genes, the ways their proximal-distal patterns are achieved are distinct from each other. Such differences can result from similar developmental gene interactions acting under different starting conditions.

Unified description of regeneration by coupled dynamical systems theory: intercalary/segmented regeneration in insect legs

Regeneration phenomena are ubiquitous in nature and are studied in a variety of experiments. Positional information and feedback-loop hierarchy are theories that have been proposed to explain ordering rules in regeneration; however, some regeneration phenomena violate the rules derived from them. In particular, grafted junction stumps with the same value/hierarchy sometimes lead to one extra segmented portion, termed segmented regeneration. To present a unified description of all insect leg regeneration phenomena, we propose a theoretical mechanism for regeneration without postulating positional information, by using a model that consists of intracellular reaction dynamics of chemical concentrations, cell-to-cell interactions, and an increase in cell number. As a normal developmental process, successive differentiation from pluripotent cells appears, as described by transition from cells with intracellular chaotic dynamics to those with oscillatory or fixed-point dynamics. By assigning chaotic and nonchaotic cell types to corresponding positions instead of positional information, intercalary, segmented, and tarsus regeneration are explained coherently. With this assignment of pluripotency to chaotic dynamics, a unified description of regeneration is obtained with some predictive value for new experiments.