Feeding rate in adult Manduca sexta is unaffected by proboscis submersion depth.

Adult moths from framily Spingidae (i.e. hawkmoths or sphinx moths) commonly feed on flower nectar through an extended proboscis, often several centimeters in length and longer than the body of the moth. Feeding on a viscous liquid (nectar) through a long and narrow tube is a challenging fluid dynamic problem and the subject of long-running scientific investigation. Here we characterized the relationship between proboscis submergence depth and nectar drinking rate in Manduca sexta hawkmoths. Video recordings of moth feeding bouts were collected and neural networks were used to extract data by object localization, tracking the location of the nectar meniscus and moths' proboscis tips. We found that although feeding rates vary among bouts, the variation was not associated with proboscis submergence depth. These results show that despite the theoretical possibility of fluid uptake through the walls of the proboscis, such effects do not have a substantial effect on nectar uptake rate, and suggest that nectar must traverse the full length of the proboscis.

Toward an Understanding of Octopus Arm Motor Control.

Octopuses have the extraordinary ability to control eight prehensile arms with hundreds of suckers. With these highly flexible limbs, they engage in a wide variety of tasks, including hunting, grooming, and exploring their environment. The neural circuitry generating these movements engages every division of the octopus nervous system, from the nerve cords of the arms to the supraesophegeal brain. In this review, the current knowledge on the neural control of octopus arm movements is discussed, highlighting open questions and areas for further study.

Elephant trunks use an adaptable prehensile grip.

Elephants have long been observed to grip objects with their trunk, but little is known about how they adjust their strategy for different weights. In this study, we challenge a female African elephant at Zoo Atlanta to lift 20-60 kg barbell weights with only its trunk. We measure the trunk's shape and wrinkle geometry from a frozen elephant trunk at the Smithsonian. We observe several strategies employed to accommodate heavier weights, including accelerating less, orienting the trunk vertically, and wrapping the barbell with a greater trunk length. Mathematical models show that increasing barbell weights are associated with constant trunk tensile force and an increasing barbell-wrapping surface area due to the trunk's wrinkles. Our findings may inspire the design of more adaptable soft robotic grippers that can improve grip using surface morphology such as wrinkles.

Pygidial glands of three ground beetle taxa (Insecta, Coleoptera, Carabidae): a study on their morphology and chemical composition of their secretions.

Morphology of the pygidial glands and chemical compositions of their secretion were analysed in the adults of three selected ground beetle taxa. Secretions of pygidial glands of Cychrus (Cychrus) semigranosus, Patrobus atrorufus and Pterostichus (Platysma) niger were chemically tested. Additionally, pygidial glands of the latter two species were investigated using bright-field microscopy and nonlinear microscopy and morphological features of the glands were described in detail. Both C. (C.) semigranosus and P. atrorufus were studied for the first time in terms of chemical ecology, while the latter species was analysed for the first time in terms of pygidial gland morphology. Altogether, eight compounds were detected in the dichloromethane extracts of the pygidial gland secretions of the three ground beetle taxa analysed. The simplest secretion mixtures were present in C. (C.) semigranosus and P. atrorufus (with two compounds each), while the extract of P. (P.) niger contained five compounds. The presence of 1-tetradecanol in the secretion of P. (P.) niger represents the first finding of this compound from the pygidial gland secretion extracts of ground beetles.

Biochemical and morphological features of the uropygial gland of the Chilean Flamingo and their functional implications.

Flamingos inhabit specialized habitats and breed in large colonies, building their nests on islands that limit the access of terrestrial predators. Many aspects of their uropygial gland are still unknown. The uropygial gland, a sebaceous organ exclusive to birds, shares some histological features among species such as the presence of a capsule, adenomers with stratified epithelium and secondary and primary chambers. We found that the uropygial gland of the Chilean Flamingo (Phoenicopterus chilensis) displays most of these characteristics but lacks a primary storage chamber. This absence may be an adaptation to their aquatic environment. The uropygial secretion of this species has a variety of glycoconjugates while its lipid moiety is largely dominated by waxes and minor amounts of triacylglycerols and fatty acids. Mass spectrometry analysis of the preen wax showed branched fatty acids of varied chain length and unbranched fatty alcohols, resulting in a complex mixture of wax esters and no differences between sexes were observed. The glycoconjugates present in the preen secretion could play a role as antimicrobial molecules, as suggested for other bird species, while the absence of diester waxes in flamingos might be related with their nesting habits and limited exposure to predation. Our results were evaluated according to physiological and ecological aspects of the flamingo's biology.

A narrow ear canal reduces sound velocity to create additional acoustic inputs in a microscale insect ear.

Located in the forelegs, katydid ears are unique among arthropods in having outer, middle, and inner components, analogous to the mammalian ear. Unlike mammals, sound is received externally via two tympanic membranes in each ear and internally via a narrow ear canal (EC) derived from the respiratory tracheal system. Inside the EC, sound travels slower than in free air, causing temporal and pressure differences between external and internal inputs. The delay was suspected to arise as a consequence of the narrowing EC geometry. If true, a reduction in sound velocity should persist independently of the gas composition in the EC (e.g., air, [Formula: see text]). Integrating laser Doppler vibrometry, microcomputed tomography, and numerical analysis on precise three-dimensional geometries of each experimental animal EC, we demonstrate that the narrowing radius of the EC is the main factor reducing sound velocity. Both experimental and numerical data also show that sound velocity is reduced further when excess [Formula: see text] fills the EC. Likewise, the EC bifurcates at the tympanal level (one branch for each tympanic membrane), creating two additional narrow internal sound paths and imposing different sound velocities for each tympanic membrane. Therefore, external and internal inputs total to four sound paths for each ear (only one for the human ear). Research paths and implication of findings in avian directional hearing are discussed.

Study on the heterogeneous material coupling connection characteristics and mechanical strength of Oratosquilla oratoria mantis shrimp saddle.

The microstructure, chemical composition and mechanical strength of heterogeneous materials of mantis shrimp (Oratosquilla oratoria) saddle were studied. As the key component of the striking system, the saddle comprised two distinct layers including outer layer and inner layer. The outer layer contained blocky microtubules and exhibited compact appearance. The inner layer presented a typical periodic lamellar structure. Due to the change of the thickness of the mineralized outer layer, the organic multilamellar structure became the foundation and enhanced the connection strength (4.55 MPa) at the connect regions between the saddle and merus exoskeleton and membrane, respectively. In the process of fracture, the lamellar structure dispersed the stress effectively by the change of the crack deflection direction and the microfibrils ordered arrangement. The exploration of mantis shrimp saddle region is beneficial to understand the striking system and provided the possibility for the stable connection of heterogeneous materials in engineering fields. The microstructure, heterogeneous material connection characteristics and high mechanical strength of saddle provide bionic models for the preparation of fiber-reinforced resin composites and soft composites.

A portable pen-sized instrumentation to measure stiffness of soft tissues in vivo.

Quantitative assessment of soft tissue elasticity is crucial to a broad range of applications, such as biomechanical modeling, physiological monitoring, and tissue diseases diagnosing. However, the modulus measurement of soft tissues, particularly in vivo, has proved challenging since the instrument has to reach the site of soft tissue and be able to measure in a very short time. Here, we present a simple method to measure the elastic modulus of soft tissues on site by exploiting buckling of a long slender bar to quantify the applied force and a spherical indentation to extract the elastic modulus. The method is realized by developing a portable pen-sized instrument (EPen: Elastic modulus pen). The measurement accuracies are verified by independent modulus measures using commercial nanoindenter. Quantitative measurements of the elastic modulus of mouse pancreas, healthy and cancerous, surgically exposed but attached to the body further confirm the potential clinical utility of the EPen.

Making the cut: mechanics of cutting and steering of insect probes.

Many insects forage, oviposit or inject venom in their prey by penetrating or cutting through substrates. From a physical perspective, cutting involves creation of new free surfaces. The cutting parts of insects, such as their mandibles or ovipositor tips, are often zinc-enriched and hardened as compared to the other cuticular regions. Whereas tip hardening is key to their ability to penetrate surfaces, it is often also important for probes to be maneuverable through substrates. How do insect probes negotiate the trade-off between cutting and steering through substrates of diverse stiffness? To address this question, we review the morphology, mechanics, and adaptations in the cutting parts of various insects. Understanding these mechanisms will allow us to develop biomimetic tools, including agricultural and surgical tools, that can both cut and steer through diverse substrates.

Ocrepeira klamt sp. n. (Araneae: Araneidae), a novel spider species from an Andean páramo in Colombia.

Herein we describe Ocrepeira klamt sp. n. (Araneae: Araneidae), a new orb-weaving spider species from a Colombian páramo, which was formerly inaccessible for scientific studies due to decades long armed conflicts. Both, phenotypic and molecular data are used to confirm genus affiliation, and the new species is placed into phylogenetic context with other araneid spiders. Morphological characteristics and ecological notes of Ocrepeira klamt sp. n. are reported together with the sequence of the barcoding region of cytochrome c oxidase subunit I (COI) to provide a comprehensive description of the spider, facilitating future identification beyond taxonomic experts. With this study we contribute to the taxonomic knowledge that is required to inventory the hyper diverse yet threatened ecosystem of the Colombian páramos.

Ontogeny and potential function of poacher armor (Actinopterygii: Agonidae).

Many vertebrates are armored over all or part of their body. The armor may serve several functional roles including defense, offense, visual display, and signal of experience/capability. Different roles imply different tradeoffs; for example, defensive armor usually trades resistance to attack for maneuverability. The poachers (Agonidae), 47 species of scorpaeniform fishes, are a useful system for understanding the evolution and function of armor due to their variety and extent of armoring. Using publically available CT-scan data from 27 species in 16 of 21 genera of poachers we compared the armor to axial skeletal in the mid body region. The ratio of average armor density to average skeleton density ranged from 0.77 to 1.17. From a defensive point of view, the total investment in mineralization (volume * average density) is more interesting. There was 10 times the material invested in the armor as in the endoskeleton in some small, smooth plated species, like Aspidophoroides olrikii. At the low end, some visually arresting species like Percis japonica, had ratios as low as 2:1. We categorized the extent and type (impact vs. abrasion) in 34 Agonopsis vulsa across all 35+ plates in the eight rows along the body. The ventral rows show abrasive damage along the entire length of the fish that gets worse with age. Impact damage to head and tail plates gets more severe and occurs at higher rates with age. The observed damage rates and the large investment in mineralization of the armor suggest that it is not just for show, but is a functional defensive structure. We cannot say what the armor is defense against, but the abrasive damage on the ventrum implies their benthic lifestyle involves rubbing on the substrate. The impact damage could result from predatory attacks or from intraspecific combat.

Spiracular fluttering increases oxygen uptake.

Many insects show discontinuous respiration with three phases, open, closed, and fluttering, in which the spiracles open and close rapidly. The relative durations of the three phases and the rate of fluttering during the flutter phase vary for individual insects depending on developmental stage and activity, vary between insects of the same species, and vary even more between different species. We studied how the rate of oxygen uptake during the flutter phase depends on the rate of fluttering. Using a mathematical model of oxygen diffusion in the insect tracheal system, we derive a formula for oxygen uptake during the flutter phase and how it depends on the length of the tracheal system, percentage of time open during the flutter phase, and the flutter rate. Surprisingly, our results show that an insect can have its spiracles closed a high percentage of time during the flutter phase and yet receive almost as much oxygen as if the spiracles were always open, provided the spiracles open and close rapidly. We investigate the respiratory gain due to fluttering for four specific insects. Our formula shows that respiratory gain increases with body size and with increased rate of fluttering. Therefore, insects can regulate their rate of oxygen uptake by varying the rate of fluttering while keeping the spiracles closed during a large fraction of the time during the flutter phase. We also use a mathematical model to show that water loss is approximately proportional to the percentage of time the spiracles are open. Thus, insects can achieve both high oxygen intake and low water loss by keeping the spiracles closed most of the time and fluttering while open, thereby decoupling the challenge of preventing water loss from the challenge of obtaining adequate oxygen uptake.

Active Notch signaling is required for arm regeneration in a brittle star.

Cell signaling pathways play key roles in coordinating cellular events in development. The Notch signaling pathway is highly conserved across all multicellular animals and is known to coordinate a multitude of diverse cellular events, including proliferation, differentiation, fate specification, and cell death. Specific functions of the pathway are, however, highly context-dependent and are not well characterized in post-traumatic regeneration. Here, we use a small-molecule inhibitor of the pathway (DAPT) to demonstrate that Notch signaling is required for proper arm regeneration in the brittle star Ophioderma brevispina, a highly regenerative member of the phylum Echinodermata. We also employ a transcriptome-wide gene expression analysis (RNA-seq) to characterize the downstream genes controlled by the Notch pathway in the brittle star regeneration. We demonstrate that arm regeneration involves an extensive cross-talk between the Notch pathway and other cell signaling pathways. In the regrowing arm, Notch regulates the composition of the extracellular matrix, cell migration, proliferation, and apoptosis, as well as components of the innate immune response. We also show for the first time that Notch signaling regulates the activity of several transposable elements. Our data also suggests that one of the possible mechanisms through which Notch sustains its activity in the regenerating tissues is via suppression of Neuralized1.

Structure and Function of the Armored Keel in Piranhas, Pacus, and their Allies.

The serrasalmids: piranhas, pacus, and their relatives, are ubiquitous Neotropical fishes with diverse diets, ecologies, and behaviors. Serrasalmids have a bony, serrated keel which lines the underbellies of these fishes, the structure for which the family is named. We examined the diversity and structure of the keel in piranhas and allies using micro-computed tomography scanning in over 30 species of serrasalmids, a third of the species richness for the family, and for 95 total characiform specimens. The keel is highly diverse across serrasalmids, with serrae shape dictating the overall form of the keel. Serrae shape varies considerably among different species and even within keels themselves. The keel morphology can be divided into distinct anterior and posterior regions, as separated by the pelvic fins. Compared to other characiform fishes, serrasalmid skeletons are frequently damaged. Gouging perforations and signs of healing (serrae fusion) are common on the keel. We propose the keel is a defensive structure based on the high incidence of injury (>50%) in our dataset. This is the highest incidence of damage ever recorded in the skeletons of bony fishes. The loss of the anterior keel region in rheophilic taxa suggests competing performance demands and selective pressures on this structure. Competition and aggression among conspecifics or confamilials is a frequently invoked phenomenon for explaining animal weaponry and armor in terrestrial vertebrates. The keel in serrasalmids and other instances of armor in fishes could be complementary study systems for examining competitive rivalry in vertebrates. Anat Rec, 2018. © 2018 American Association for Anatomy.

Continual Learning in a Multi-Layer Network of an Electric Fish.

Distributing learning across multiple layers has proven extremely powerful in artificial neural networks. However, little is known about how multi-layer learning is implemented in the brain. Here, we provide an account of learning across multiple processing layers in the electrosensory lobe (ELL) of mormyrid fish and report how it solves problems well known from machine learning. Because the ELL operates and learns continuously, it must reconcile learning and signaling functions without switching its mode of operation. We show that this is accomplished through a functional compartmentalization within intermediate layer neurons in which inputs driving learning differentially affect dendritic and axonal spikes. We also find that connectivity based on learning rather than sensory response selectivity assures that plasticity at synapses onto intermediate-layer neurons is matched to the requirements of output neurons. The mechanisms we uncover have relevance to learning in the cerebellum, hippocampus, and cerebral cortex, as well as in artificial systems.

Investigating reproductive success of the ladybird beetle Harmonia axyridis from the perspective of micropyle variation.

Micropyles in insects are small openings that allow sperm entry into, and the number was usually decreased on unfertilized and (or) undeveloped eggs. However, reports showed that Harmonia axyridis, a reproductive success model, deposited similar number of micropyles on undeveloped and developing eggs. Thus, it was confusing whether micropyles in H. axyridis were unaffected. To solve this confusion, two experiments were conducted here. Firstly, virgin female and four different days delayed mating (DDM) experiments were conducted to reveal the effects of fertilization stimulus and delayed-fertilization. Secondly, intercrosses between a light-colored mutant (HAM, an adaptive deficiency) and wild type (HAW) were conducted to further reveal whether there were female and male interactions. We found that (1) eggs produced by virgin and DDM females had significantly less micropyles than control. Even so, more than 18 micropyles were observed on eggs following fertilization and, consequently, egg production as well as hatch rate was not negatively affected by mating delay; (2) number of micropyles was significantly varied among the four reciprocal crosses and virgin HAW female. Specifically, the heterozygous eggs (Cross-D) and wild-type homozygous eggs (Cross-B) respectively had the least and maximum micropyles, and eggs from virgin HAW female had significantly less micropyles compared to those from HAW female (Cross-B or Cross-C), but the number was significantly higher than those from HAM female (Cross-A or Cross-D). These results informed us that the number of micropyles in H. axyridis is plastic but maintaining a high-quantity that offers many benefits, which should contribute to its reproduction success.

Ticks home in on body heat: A new understanding of Haller's organ and repellent action.

Ticks are second only to mosquitoes as vectors of disease to humans and animals. Tick host detection is mainly ascribed to Haller's organ, a complex sensory structure on the tick foreleg that detects odors, carbon dioxide and heat, but these host detection mechanisms are not well understood. There is anecdotal evidence that ticks and other ectoparasites are attracted to heat, but it has never been demonstrated that they use radiant heat to detect hosts at a distance. In fact, previous attempts to do this have concluded that radiant heat was not used by ticks. Here we use a novel thermotaxis assay to investigate the detection range, temperature dependence and repellent sensitivity of heat perception in ticks and to identify the sensory organ responsible for this sense. We show that Amblyomma americanum and Dermacentor variabilis ticks can locate a human from several meters away by radiant heat sensed by the part of Haller's organ known as the capsule, a covered spherical pit organ. An aperture in the capsule cover confers directionality and highly reflective interior surfaces of the capsule concentrate radiation on the sensilla to sharpen directionality and increase sensitivity. Commercial insect repellents provide an effective means of personal protection against potentially infectious tick bites by hindering host-seeking behavior. Low concentrations of the insect repellents DEET, picaridin, 2-undecanone, citronellal and nootkatone eliminate thermotaxis without affecting olfaction-stimulated host-seeking behavior. Our results demonstrate that the tick Haller's organ capsule is a radiant heat sensor used in host-finding and that repellents disrupt this sense at concentrations that do not disrupt olfaction. We anticipate that this discovery will significantly aid insect repellent research and provide novel targets for the development of innovative integrated pest management programs and personal protection strategies for ectoparasites and vector-borne disease.

Comparative morphology refines the conventional model of spider reproduction.

Our understanding of spider reproductive biology is hampered by the vast anatomical diversity and difficulties associated with its study. Although authors agree on the two general types of female spider genitalia, haplogyne (plesiomorphic) and entelegyne (apomorphic), our understanding of variation within each group mostly concerns the external genital part, while the internal connections with the reproductive duct are largely unknown. Conventionally and simplistically, the spermathecae of haplogynes have simple two-way ducts, and those of entelegynes have separate copulatory and fertilization ducts for sperm to be transferred in and out of spermathecae, respectively. Sperm is discharged from the spermathecae directly into the uterus externus (a distal extension of the oviduct), which, commonly thought as homologous in both groups, is the purported location of internal fertilization in spiders. However, the structural evolution from haplo- to entelegyny remains unresolved, and thus the precise fertilization site in entelegynes is ambiguous. We aim to clarify this anatomical problem through a widely comparative morphological study of internal female genital system in entelegynes. Our survey of 147 epigyna (121 examined species in 97 genera, 34 families) surprisingly finds no direct connection between the fertilization ducts and the uterus externus, which, based on the homology with basal-most spider lineages, is a dead-end caecum in entelegynes. Instead, fertilization ducts usually connect with a secondary uterus externus, a novel feature taking over the functional role of the plesiomorphic uterus externus. We hypothesize that the transition from haplo- to entelegyny entailed not only the emergence of the two separate duct systems (copulatory, fertilization), but also involved substantial morphological changes in the distal part of the oviduct. Thus, the common oviduct may have shifted its distal connection from the uterus externus to the secondary uterus externus, perhaps facilitating discharge of larger eggs. Our findings suggest that the conventional model of entelegyne reproduction needs redefinition.

Mechanisms of physiological tissue remodeling in animals: Manipulating tissue, organ, and organism morphology.

Tissue remodeling is broadly defined as the reorganization or restoration of existing tissues. Tissue remodeling processes are responsible for directing the development and maintenance of tissues, organs, and overall morphology of an organism. Therefore, studying the regulatory and mechanistic aspects of tissue remodeling allows one to decipher how tissue structure and function is manipulated in animals. As such, research focused on investigating natural tissue reorganization in animal model organisms has great potential for advancing medical therapies, in conjunction with tissue engineering and regenerative medicine. Here we discuss the molecular and cellular mechanisms responsible for tissue remodeling events that occur across several animal phyla. Notably, this review emphasizes the molecular and cellular mechanisms involved in embryonic and postnatal physiological tissue remodeling events, ranging from metamorphosis to bone remodeling during functional adaptation.

Evolutionary history of burrowing asps (Lamprophiidae: Atractaspidinae) with emphasis on fang evolution and prey selection.

Atractaspidines are poorly studied, fossorial snakes that are found throughout Africa and western Asia, including the Middle East. We employed concatenated gene-tree analyses and divergence dating approaches to investigate evolutionary relationships and biogeographic patterns of atractaspidines with a multi-locus data set consisting of three mitochondrial (16S, cyt b, and ND4) and two nuclear genes (c-mos and RAG1). We sampled 91 individuals from both atractaspidine genera (Atractaspis and Homoroselaps). Additionally, we used ancestral-state reconstructions to investigate fang and diet evolution within Atractaspidinae and its sister lineage (Aparallactinae). Our results indicated that current classification of atractaspidines underestimates diversity within the group. Diversification occurred predominantly between the Miocene and Pliocene. Ancestral-state reconstructions suggest that snake dentition in these taxa might be highly plastic within relatively short periods of time to facilitate adaptations to dynamic foraging and life-history strategies.