Toward Energetically Autonomous Foraging Soft Robots

© 2016, Mary Ann Liebert, Inc. A significant goal of robotics is to develop autonomous machines, capable of independent and collective operation free from human assistance. To operate with complete autonomy robots must be capable of independent movement and total energy self-sufficiency. We present the design of a soft robotic mouth and artificial stomach for aquatic robots that will allow them to feed on biomatter in their surrounding environment. The robot is powered by electrical energy generated through bacterial respiration within a microbial fuel cell (MFC) stomach, and harvested using state-of-the-art voltage step-up electronics. Through innovative exploitation of compliant, biomimetic actuation, the soft robotic feeding mechanism enables the connection of multiple MFC stomachs in series configuration in an aquatic environment, previously a significant challenge. We investigate how a similar soft robotic feeding mechanism could be driven by electroactive polymer artificial muscles from the same bioenergy supply. This work demonstrates the potential for energetically autonomous soft robotic artificial organisms and sets the stage for radically different future robots

Evolution of High Trophic Diversity Based on Limited Functional Disparity in the Feeding Apparatus of Marine Angelfishes (f. Pomacanthidae)

The use of biting to obtain food items attached to the substratum is an ecologically widespread and important mode of feeding among aquatic vertebrates, which rarely has been studied. We did the first evolutionary analyses of morphology and motion kinematics of the feeding apparatus in Indo-Pacific members of an iconic family of biters, the marine angelfishes (f. Pomacanthidae). We found clear interspecific differences in gut morphology that clearly reflected a wide range of trophic niches. In contrast, feeding apparatus morphology appeared to be conserved. A few unusual structural innovations enabled angelfishes to protrude their jaws, close them in the protruded state, and tear food items from the substratum at a high velocity. Only one clade, the speciose pygmy angelfishes, showed functional departure from the generalized and clade-defining grab-and-tearing feeding pattern. By comparing the feeding kinematics of angelfishes with wrasses and parrotfishes (f. Labridae) we showed that grab-and-tearing is based on low kinematics disparity. Regardless of its restricted disparity, the grab-and-tearing feeding apparatus has enabled angelfishes to negotiate ecological thresholds: Given their widely different body sizes, angelfishes can access many structurally complex benthic surfaces that other biters likely are unable to exploit. From these surfaces, angelfishes can dislodge sturdy food items from their tough attachments. Angelfishes thus provide an intriguing example of a successful group that appears to have evolved considerable trophic diversity based on an unusual yet conserved feeding apparatus configuration that is characterized by limited functional disparity

Evolution of a unique predatory feeding apparatus: functional anatomy, development and a genetic locus for jaw laterality in Lake Tanganyika scale-eating cichlids

Background While bilaterality is a defining characteristic of triploblastic animals, several assemblages have managed to break this symmetry in order to exploit the adaptive peaks garnered through the lateralization of behaviour or morphology. One striking example of an evolved asymmetry in vertebrates comes from a group of scale-eating cichlid fishes from Lake Tanganyika. Members of the Perissodini tribe of cichlid fishes have evolved dental and craniofacial asymmetries in order to more effectively remove scales from the left or right flanks of prey. Here we examine the evolution and development of craniofacial morphology and laterality among Lake Tanganyika scale-eating cichlids. Results Using both geometric and traditional morphometric methods we found that the craniofacial evolution in the Perissodini involved discrete shifts in skeletal anatomy that reflect differences in habitat preference and predation strategies. Further, we show that the evolutionary history of the Perissodini is characterized by an accentuation of craniofacial laterality such that certain taxa show elaborate sided differences in craniofacial shape consistent with the sub-partitioning of function between sides of the head during attacks. Craniofacial laterality in the scale-eating specialist Perissodus microlepis was found to be evident early in development and exhibited a unimodal distribution, which is contrary to the adult condition where jaw laterality has been described as a discrete, bimodal antisymmetry. Finally, using linkage and association analyses we identified a conserved locus for jaw handedness that segregates among East African cichlids. Conclusions We suggest that, during the evolution of the Perissodini, selection has accentuated a latent, genetically determined handedness of the craniofacial skeleton, enabling the evolution of jaw asymmetries in order to increase predation success. Continued work on the developmental genetic basis of laterality in the Perissodini will facilitate a better understanding of the evolution of this unique group of fishes, as well as of left-right axis determination among vertebrates in general

Dealing with Food and Eggs in Mouthbrooding Cichlids: Structural and Functional Trade-Offs in Fitness Related Traits

As in any vertebrate, heads of fishes are densely packed with functions. These functions often impose conflicting mechanical demands resulting in trade-offs in the species-specific phenotype. When phenotypical traits are linked to gender-specific parental behavior, we expect sexual differences in these trade-offs. This study aims to use mouthbrooding cichlids as an example to test hypotheses on evolutionary trade-offs between intricately linked traits that affect different aspects of fitness. We focused on the oral apparatus, which is not only equipped with features used to feed and breathe, but is also used for the incubation of eggs. We used this approach to study mouthbrooding as part of an integrated functional system with diverging performance requirements and to explore gender-specific selective environments within a species.Because cichlids are morphologically very diverse, we hypothesize that the implications of the added constraint of mouthbrooding will primarily depend on the dominant mode of feeding of the studied species. To test this, we compared the trade-off for two maternal mouthbrooding cichlid species: a "suction feeder" (Haplochromis piceatus) and a "biter" (H. fischeri). The comparison of morphology and performance of both species revealed clear interspecific and intersex differences. Our observation that females have larger heads was interpreted as a possible consequence of the fact that in both the studied species mouthbrooding is done by females only. As hypothesized, the observed sexual dimorphism in head shape is inferred as being suboptimal for some aspects of the feeding performance in each of the studied species. Our comparison also demonstrated that the suction feeding species had smaller egg clutches and more elongated eggs.Our findings support the hypothesis that there is a trade-off between mouthbrooding and feeding performance in the two studied haplochromine cichlids, stressing the importance of including species-specific information at the gender level when addressing interspecific functional/morphological differences

Atomic Force Microscopy Study of Nano-Physiological Response of Ladybird Beetles to Photostimuli

Background: Insects are of interest not only as the most numerous and diverse group of animals but also as highly efficient bio-machines varying greatly in size. They are the main human competitors for crop, can transmit various diseases, etc. However, little study of insects with modern nanotechnology tools has been done. Methodology/Principal Findings: Here we applied an atomic force microscopy (AFM) method to study stimulation of ladybird beetles with light. This method allows for measuring of the internal physiological responses of insects by recording surface oscillations in different parts of the insect at sub-nanometer amplitude level and sub-millisecond time. Specifically, we studied the sensitivity of ladybird beetles to light of different wavelengths. We demonstrated previously unknown blindness of ladybird beetles to emerald color (,500nm) light, while being able to see UV-blue and green light. Furthermore, we showed how one could study the speed of the beetle adaptation to repetitive flashing light and its relaxation back to the initial stage. Conclusions: The results show the potential of the method in studying insects. We see this research as a part of what might be a new emerging area of ‘‘nanophysiology’ ’ of insects

The Early Evolution of Biting–Chewing Performance in Hexapoda

Insects show a plethora of different mandible shapes. It was advocated that these mandible shapes are mainly a function of different feeding habits. This hypothesis was tested on a larger sampling of non-holometabolan biting–chewing insects with additional tests to understand the interplay of mandible function, feeding guild, and phylogeny. The results show that at the studied systematic level, variation in mandible biting–chewing effectivity is regulated to a large extent by phylogenetic history and the configuration of the mandible joints rather than the food preference of a given taxon. Additionally, lineages with multiple mandibular joints such as primary wingless hexapods show a wider functional space occupation of mandibular effectivity than dicondylic insects (= silverfish + winged insects) at significantly different evolutionary rates. The evolution and occupation of a comparably narrow functional performance space of dicondylic insects is surprising given the low effectivity values of this food uptake solution. Possible reasons for this relative evolutionary “stasis” are discussed

Jaw Laterality and Related Handedness in the Hunting Behavior of a Scale-Eating Characin, Exodon paradoxus

BACKGROUND: Asymmetry in animal bodies and behavior has evolved several times, but our knowledge of their linkage is limited. Tanganyikan scale-eating cichlids have well-known antisymmetry in their bodies and behavior; individuals open their mouths leftward (righty) or rightward (lefty), and righties always attack the right flank of the prey, whereas lefties attack the left. This study analyzed the morphological asymmetry in a scale-eating characiform, Exodon paradoxus, and its behavioral handedness. METHODOLOGY/PRINCIPAL FINDINGS: Each eight E. paradoxus was observed for 1-h with a prey goldfish in an aquarium to detect the behavioral handedness. Following the experiment, the lateral differences in the mandibles and head-inclination of these eight and ten additional specimens were analyzed. Both measurements on the morphology showed a bimodal distribution, and the laterality identified by these two methods was always consistent within a given individual, indicating that the characin has morphological antisymmetry. Furthermore, this laterality significantly corresponded to behavioral handedness; that is, lefties more often rasped scales from the right flank of the prey and vice versa. However, the correlation between laterality and handedness is the opposite of that in the cichlids. This is due to differences in the feeding apparatus and technique. The characin has cuspids pointing forward on the external side of the premaxilla, and it thrusts its dominant body side outward from its body axis on the flank of the prey to tear off scales. By contrast, the cichlids draw their dominant body side inward toward the axis or rotate it to scrape or wrench off scales with the teeth lined in the opened mouth. CONCLUSIONS/SIGNIFICANCE: This study demonstrated that the antisymmetry in external morphology and the corresponding behavioral handedness have evolved in two lineages of scale-eating fishes independently, and these fishes adopt different utilization of their body asymmetry to tear off scales

Fin-Tail Coordination during Escape and Predatory Behavior in Larval Zebrafish

Larval zebrafish innately perform a suite of behaviors that are tightly linked to their evolutionary past, notably escape from threatening stimuli and pursuit and capture of prey. These behaviors have been carefully examined in the past, but mostly with regard to the movements of the trunk and tail of the larvae. Here, we employ kinematics analyses to describe the movements of the pectoral fins during escape and predatory behavior. In accord with previous studies, we find roles for the pectoral fins in slow swimming and immediately after striking prey. We find novel roles for the pectoral fins in long-latency, but not in short-latency C-bends. We also observe fin movements that occur during orienting J-turns and S-starts that drive high-velocity predatory strikes. Finally, we find that the use of pectoral fins following a predatory strike is scaled to the velocity of the strike, supporting a role for the fins in braking. The implications of these results for central control of coordinated movements are discussed, and we hope that these results will provide baselines for future analyses of cross-body coordination using mutants, morphants, and transgenic approaches

Real-time phase-contrast x-ray imaging: a new technique for the study of animal form and function

BACKGROUND: Despite advances in imaging techniques, real-time visualization of the structure and dynamics of tissues and organs inside small living animals has remained elusive. Recently, we have been using synchrotron x-rays to visualize the internal anatomy of millimeter-sized opaque, living animals. This technique takes advantage of partially-coherent x-rays and diffraction to enable clear visualization of internal soft tissue not viewable via conventional absorption radiography. However, because higher quality images require greater x-ray fluxes, there exists an inherent tradeoff between image quality and tissue damage. RESULTS: We evaluated the tradeoff between image quality and harm to the animal by determining the impact of targeted synchrotron x-rays on insect physiology, behavior and survival. Using 25 keV x-rays at a flux density of 80 μW/mm(-2), high quality video-rate images can be obtained without major detrimental effects on the insects for multiple minutes, a duration sufficient for many physiological studies. At this setting, insects do not heat up. Additionally, we demonstrate the range of uses of synchrotron phase-contrast imaging by showing high-resolution images of internal anatomy and observations of labeled food movement during ingestion and digestion. CONCLUSION: Synchrotron x-ray phase contrast imaging has the potential to revolutionize the study of physiology and internal biomechanics in small animals. This is the only generally applicable technique that has the necessary spatial and temporal resolutions, penetrating power, and sensitivity to soft tissue that is required to visualize the internal physiology of living animals on the scale from millimeters to microns

Revealing the respiratory system of the coffee berry borer (Hypothenemus hampei; Coleoptera: Curculionidae: Scolytinae) using micro-computed tomography

The coffee berry borer (Hypothenemus hampei) is the most economically important insect pest of coffee globally. Micro-computed tomography (micro-CT) was used to reconstruct the respiratory system of this species for the first time; this is the smallest insect (ca. 2 mm long) for which this has been done to date. Anatomical details of the spiracles and tracheal tubes are described, images presented, and new terms introduced. The total volume and the relationship between tracheal lumen diameter, length and volume are also presented. The total length of the tracheal tubes are seventy times the length of the entire animal. Videos and a 3D model for use with mobile devices are included as supplementary information; these could be useful for future research and for teaching insect anatomy to students and the public in general.This paper benefitted from the sub-award agreement S15192.01 between Kansas State University (KSU) and the University of Granada, as part of a USDANIFA Award 2014-70016-23028 to S.J. Brown (KSU), “Developing an Infrastructure and Product Test Pipeline to Deliver Novel Therapies for Citrus Greening Disease” (2015–2020)