Friedrich G Barth

University of Vienna | UniWien · Department of Neurobiology

Engineered systems are typically based on a large variety of materials differing in composition and processing to provide the desired functionality. Nature, however, has evolved materials that are used for a wide range of functional challenges with minimal compositional changes. The exoskeletal cuticle of spiders, as well as of other arthropods suc...

A correction to this paper has been published: https://doi.org/10.1007/s00359-021-01497-z.

The work of the Nobel Laureate Karl von Frisch , the founder of this journal, was seminal in many ways. He established the honeybee as a key animal model for experimental behavioural studies on sensory perception, learning and memory, and first correctly interpreted its famous dance communication. Here, we report on a previously unknown letter by t...

Spiders show a broad range of motions in addition to walking and running with their eight coordinated legs taking them towards their resources and away from danger. The usefulness of all these motions depends on the ability to control and adjust them to changing environmental conditions. A remarkable wealth of sensory receptors guarantees the neces...

The measurement of cuticular strain during locomotion using foil strain gauges provides information both on the loads of the exoskeleton bears and the adaptive value of the specific location of natural strain detectors (slit sense organs). Here, we critically review available literature. In tethered animals , by applying loads to the metatarsus tip...

In the absence of minerals as stiffening agents, insects and spiders often use metal‐ion cross‐linking of protein matrices in their fully organic load‐bearing “tools.” In this comparative study, the hierarchical fiber architecture, elemental distribution, and the micromechanical properties of the manganese‐ and calcium‐rich cuticle of the claws of...

Non-nervous auxiliary structures play a significant role in sensory biology. They filter the stimulus and transform it in a way that fits the animal’s needs, thereby contributing to the avoidance of the central nervous system’s overload with meaningless stimuli and a corresponding processing task. The present review deals with mechanoreceptors main...

Some spiders are densely covered by an intriguingly large number of mechanoreceptive hairs on their exoskeleton, the wandering spider Cupiennius salei being the main example examined here. All of these hairs represent first-order lever arms, whose deflection triggers nervous impulses in the sensory cells ending at their base. Their sensitivities di...

In stingless bees (Meliponini) like in many other eusocial insect colonies food hoarding plays an important role in colony survival. However, very little is known on how Meliponini, a taxon restricted to tropical and subtropical regions, respond to different store conditions. We studied the impact of honey removal on nectar foraging activity and re...

Stingless bees (Hymenoptera, Apidae, Meliponini) are by far the largest group of eusocial bees on Earth. Due to the diversity of evolutionary responses to specific ecological challenges, the Meliponini are well suited for comparative studies of the various adaptations to the environment found in highly eusocial bees. Of particular interest are the...

We identify the presence of multiple vascular channels within the spider fang. These channels seem to serve the transport of zinc to the tip of the fang to cross-link the protein matrix by binding to histidine residues. According to amino acid and elemental analysis of fangs extracted shortly after ecdysis His-rich proteins are deposited before Zn...

Unlabelled: Highly sensitive lyriform organs located on the legs of the wandering spider Cupiennius salei allow the spider to detect nanometer-scale strains in the exoskeleton resulting from locomotion or substrate vibrations. Morphological features of the lyriform organs result in their specialization and selective sensitivity to specific mechani...

The spiders’ remarkable evolutionary and ecological success to a large extent is due to their highly developed sensory systems. Among these the cuticular hairs are the most obvious ones. They also provide the input stage for a spider’s sense of touch. As will be shown spider tactile hairs are surprisingly well “designed” to serve their particular s...

Synchrotron X-ray diffraction was applied to study the structure of biogenic α-chitin crystals composing the tendon of the spider Cupiennius salei. Measurements were carried out on pristine chitin crystals stabilized by proteins and water, as well as after their deproteinization and dehydration. We found substantial shifts (up to Δq/q = 9% in the w...

The metatarsal lyriform organ of the Central American wandering spider Cupiennius salei is its most sensitive vibration detector. It is able to sense a wide range of vibration stimuli over four orders of magnitude in frequency between at least as low as 0.1 Hz and several kilohertz. Transmission of the vibrations to the slit organ is controlled by...

Adding to previous efforts towards a better understanding of the remarkable diversity of spider mechanosensitive hair sensilla, this study examines hairs of Cupiennius salei most likely serving a proprioreceptive function. At the tibia-metatarsus joint of all walking legs, there are two opposing groups of hairs ventrally on the tibia (20 hairs) and...

A strain sensing lyriform organ (HS-10) on all legs of a Central American wandering spider (Cupiennius salei) detects courtship, prey, and predator vibrations transmitted by the plant on which it sits. It has been suggested that the viscoelastic properties of a cuticular pad directly adjacent to the sensory organ contribute to the organ's pronounce...

Foragers of several species of stingless bees (Apidae; Meliponini), a group of eusocial bees comprising more than 400 mainly tropical species, produce pulsed thoracic vibrations inside the nest when returning from a successful foraging trip. These vibrations do not provide navigational information on the direction and distance of a food source. Ins...

The spider fang is a natural injection needle, hierarchically built from a complex composite material comprising multiscale architectural gradients. Considering its biomechanical function, the spider fang has to sustain significant mechanical loads. Here we apply experiment-based structural modelling of the fang, followed by analytical mechanical d...

The perception of medium flows has received ever increasing attention during the last two decades and has increasingly been recognized as a sensory capacity of its own. A combination of experimental work and physical–mathematical modeling has deepened our understanding of the workings of airflow sensors, mainly represented by insect filiform hairs...

When hungry, the wandering spider Cupiennius salei is frequently seen to catch flying insect prey. The success of its remarkable prey-capture jump from its sitting plant into the air obviously depends on proper timing and sensory guidance. In this study, it is shown that particular features of the airflow generated by the insect suffice to guide th...

Spiders mainly feed on insects. This means that their fangs, which are used to inject venom into the prey, have to puncture the insect cuticle that is essentially made of the same material, a chitin-protein composite, as the fangs themselves. Here a series of structural modifications in the fangs of the wandering spider Cupiennius salei are reporte...

The hunting spider Cupiennius salei uses airflow generated by flying insects for the guidance of its prey-capture jump. We investigated the velocity field of the airflow generated by a freely flying blowfly close to the flow sensors on the spider's legs. It shows three characteristic phases (I-III). (I) When approaching, the blowfly induces an airf...

Three types of spider sensors responding to different forms of mechanical energy are chosen to illustrate the power of evolutionary constraints to fine-tune the functional "design" of animal sensors to the particular roles they play in particular behavioral contexts. As demonstrated by the application of computational biomechanics and a fruitful co...

Sensory perception is a biological phenomenon and should be treated as such. It has a long history, beginning in the early stages of the evolution of life. Even bacteria depend on information gained about their outside and inside world. Basic mechanisms of sensing have indeed already been invented by the simplest organisms. Among the rich diversity...

Sensory perception: mind and matter aims at a deeper understanding of the many facets of sensory perception and their relations to brain function and cognition. It is an attempt to promote the interdisciplinary discourse between the neurosciences and psychology, which speaks the language of cognitive experiences, and philosophy, which has been thin...

This chapter is about biological mechano-sensors embedded in the cuticular exoskeleton of arthropods and serving purposes analogous to those of technical strain gauges. Spiders have several thousands of such sensors providing them with a highly resolved picture of the mechanical events in their exoskeleton. The spider “strain gauges”, also called s...

Using measurements based on particle image velocimetry in combination with a novel compact theoretical framework to describe hair mechanics, we found that spider and cricket air motion sensing hairs work close to the physical limit of sensitivity and energy transmission in a broad range of relatively high frequencies. In this range, the hairs close...

Scanning white light interferometry and micro-force measurements were applied to analyse stimulus transformation in strain sensors in the spider exoskeleton. Two compound or 'lyriform' organs consisting of arrays of closely neighbouring, roughly parallel sensory slits of different lengths were examined. Forces applied to the exoskeleton entail stra...

In contrast to marking of the location of resources or sexual partners using single-spot pheromone sources, pheromone paths attached to the substrate and assisting orientation are rarely found among flying organisms. However, they do exist in meliponine bees (Apidae, Apinae, Meliponini), commonly known as stingless bees, which represent a group of...

Females are often thought to use several cues and more than one modality in selection of a mate, possibly because they offer complementary information on a mate's suitability. In the red mason bee, Osmia rufa, we investigated the criteria a female uses to choose a mating partner. We hypothesized that the female uses male thorax vibrations and size...

We describe male-male competition in a wandering spider living on plants (Cupiennius getazi, Ctenidae) and discuss it within the general context of the mating system. 1. Males produce vibratory courtship signals (duration about 20 s) and competition signals (2 s). Upon exposure to female silk, males produce almost exclusively courtship signals (98%...

Intracellular recordings from photoreceptor cells of all eyes of the spider Cupiennius salei Keys reveal 3 groups of cells with spectral sensitivity maxima in the blue (480 nm). green (520 nm), and UV (340 nm), respectively. The blue and green cells show secondary peaks in the UV at 340-380 nm. In the posterior median, posterior lateral and anterio...

Arachnids and insects use long, thin hairs as motion sensors to detect signals contained in the movement of the surrounding air. These hairs often form groups with a small spacing of tens to hundreds of micrometers between them. For air oscillation frequencies of biological interest, the potential exists for viscosity-mediated coupling among hairs...

Living organisms use composite materials for various functions, such as mechanical support, protection, motility and the sensing of signals. Although the individual components of these materials may have poor mechanical qualities, they form composites of polymers and minerals with a remarkable variety of functional properties. Researchers are now u...

Arachnid slit sensilla respond to minute strains in the exoskeleton. After having applied finite element (FE) analysis to simplified arrays of five straight slits (Hössl et al. J Comp Physiol A 193:445-459, 2007) we now present a computational study of the effects of more subtle natural variations in geometry, number and arrangement of slits on the...

The metatarsal lyriform organ of the spider Cupiennius salei is a vibration detector consisting of 21 cuticular slits supplied by two sensory cells each, one ending in the outer and the other at the inner slit membrane. In search of functional differences between the two cell types due to differences in stimulus transmission, we analyzed (1) the ad...

The micromechanical properties of spider air flow hair sensilla (trichobothria) were characterized with nanometre resolution using surface force spectroscopy (SFS) under conditions of different constant deflection angular velocities theta (rad s(-1)) for hairs 900-950 microm long prior to shortening for measurement purposes. In the range of angular...

Like ants and termites some species of stingless bees (Meliponini), which are very important pollinators in the tropics, use pheromone trails to communicate the location of a food source. We present data on the communicative role of mandibular gland secretions of Meliponini that resolve a recent controversy about their importance in the laying of s...

As recently found, in mechano-sensors of wandering spiders (Cupiennius salei) viscoelastic materials are important in signal filtering. We used atomic force microscopy to probe the time dependent mechanical behavior of these materials in live animals. We measured Young's modulus of a rubbery material located between a vibration receptor and the sti...

Since the seminal work of Lindauer and Kerr (1958), many stingless bees have been known to effectively recruit nestmates to food sources. Recent research clarified properties of several signals and cues used by stingless bees when exploiting food sources. Thus, the main source of the trail pheromone in Trigona are the labial, not however the mandib...

Bees generate thoracic vibrations with their indirect flight muscles in various behavioural contexts. The main frequency component of non-flight vibrations, during which the wings are usually folded over the abdomen, is higher than that of thoracic vibrations that drive the wing movements for flight. So far, this has been concluded from an increase...

In stingless bees, recruitment of hive bees to food sources involves thoracic vibrations by foragers during trophallaxis. The temporal pattern of these vibrations correlates with the sugar concentration of the collected food. One possible pathway for transferring such information to nestmates is through airborne sound. In the present study, we inve...

Does the food's sugar concentration affect recruitment behaviour in the stingless bee Nannotrigona testaceicornis? We recorded intranidal forager behaviour while offering sugar water of constant, increasing, or decreasing concentrations. Running speed was not correlated with sugar concentration but the jostling contacts/sec were. Food profitability...

Atomic force microscopy (AFM) and surface force spectroscopy were applied in live spiders to their joint pad material located distal of the metatarsal lyriform organs, which are highly sensitive vibration sensors. The surface topography of the material is sufficiently smooth to probe the local nanomechanical properties with nanometre elastic deflec...

Arthropods use fluid medium motion-sensing filiform hairs on their exoskeleton to detect aerodynamic or hydrodynamic stimuli in their surroundings that affect their behaviour. The hairs, often of different lengths and organized in groups or arrays, respond to particular fluid motion amplitudes and frequencies produced by prey, predators, or conspec...

The photoreceptor cells of the nocturnal spider Cupiennius salei were investigated by intracellular electrophysiology. (1) The responses of photoreceptor cells of posterior median (PM) and anterior median (AM) eyes to short (2 ms) light pulses showed long integration times in the dark-adapted and shorter integration times in the light-adapted state...

Arachnid strain sensitive slit sensilla are elongated openings in the cuticle with aspect ratios (slit length l / slit width b) of up to 100. Planar Finite Element (FE) models are used to calculate the relative slit face displacements, D c, at the centers of single slits and of arrangements of mechanically interacting slits under uni-axial compress...

Stingless bees of the species Trigona spinipes (Fabricius 1793) use their saliva to lay scent trails communicating the location of profitable food sources. Extracts of the cephalic labial glands of the salivary system (not the mandibular glands, however) contain a large amount (approx. 74%) of octyl octanoate. This ester is also found on the scent-...

Stimulus transformation in arthropod mechanoreceptive hairs is dominated by the mechanical properties of both the hair shaft and the hair’s articulation. Here a mathematical model of the hair’s articulation is developed based on simple relationships relevant for every anisotropic articulation. The mechanical behavior regarding deflection under load...

We examined the ability of Trigona recursa, a scent trail-laying stingless bee, to allocate foragers to the more profitable of two food sources. Imbibing time and imbibed volume of individuals were the same at feeders containing 20% or 40% w/w (weight in weight) sugar solution. However, sugar intake rate and sugar per crop load were significantly h...

An element common to the recruitment communication of eusocial bees (honey bees, stingless bees and bumble bees) are pulsed thorax vibrations generated by successful foragers within the nest. In stingless bees, foragers vibrate during the unloading of the collected food. In the present study on Melipona seminigra we demonstrate that during trophall...

Foragers of many species of stingless bees guide their nestmates to food sources by means of scent trails deposited on solid substrates between the food and the nest. The corresponding trail pheromones are generally believed to be produced in the mandibular glands, although definitive experimental proof has never been provided. We tested the trail...

How does the sugar concentration of the food source affect the recruitment of Scaptotrigona aff. depilis? We offered sugar water of either constant, increasing, or decreasing concentrations. Simultaneously, we recorded the number of recruits and the recruiters' running speed, jostling contacts, and vibrations inside the nest. Neither the number of...

The present study introduces a new preparation of a spider vibration receptor that allows intracellular recording of responses to natural mechanical or electrical stimulation of the associated mechanoreceptor cells. The spider vibration receptor is a lyriform slit sense organ made up of 21 cuticular slits located on the distal end of the metatarsus...

Dragline use by an orb web spider (Nephila clavipes) was analysed by observing both intact spiders and those prevented from producing a dragline. The behaviours observed were those associated with returning to the web hub and prey capture. Upon returning to the hub, spiders resume the resting position by rotating within the hub, producing several n...

Slit sensilla are sensory organs which measure strains in the exoskeleton of arachnids. They occur as isolated slits, in loose groups and in close parallel arrangements known as lyriform organs or compound slit sensilla. The deformations of the slits' faces induced by far-field strains acting on groups of slits are studied using Kachanov's analytic...

When coming across the term “bee communication”, almost automatically an image of the legendary “figure-of-eight movements” of the honey bee (Apis mellifera) crosses most people’s minds. Expressions like “dance language” or “bee language” are associated with the name of the Austrian scientist Karl von Frisch (1886-1982), who observed that the body...

Arachnids and insects use long, thin hairs as motion sensors to detect signals contained in the movement of the surrounding air. These hairs often form groups with a small spacing of tens to hundreds of micrometers between them. For air oscillation frequencies of biological interest, the potential exists for viscosity-mediated coupling among hairs...

In order to examine whether Nannotrigona testaceicornis deposits chemical attractants at a food source we made the bees choose between a feeder where nestmates had fed before and a clean unused feeder. 86 ± 5% of the bees chose the used feeder over the clean one. The attractiveness of the used feeder was reduced but not lost when the sugar water it...

Footprint secretions deposited at the nest entrance or on food sources are used for chemical communication by honey bees, bumble bees, and stingless bees. The question of the glandular origin of the substances involved, however, has not been unequivocally answered yet. We investigated the morphology and structure of tarsal glands within the fifth t...

Spiders have highly developed mechanosensory systems, some of which provide access to forms of stimulation alien to our own sensations. Studies of hair-shaped air movement detectors (trichobothria) and tactile sensors have uncovered an outstanding refinement of the processes of stimulus uptake and stimulus transformation, which reflect details of b...

Our previous studies on spider tactile hairs concentrated on the mechanical behavior of the hair shaft and the electrophysiological properties of the sensory cells. Here we focus on the structure and mechanical properties of the coupling of the hair shaft and the sensory terminals. 1. The functional "design" of the coupling provides for a combinati...

An important question in stingless bee communication is whether the thorax vibrations produced by foragers of the genus Melipona upon their return to the nest contain spatial information about food sources or not. As previously shown M. seminigra is able to use visual flow to estimate flight distances. The present study investigated whether foragin...

Using a laser vibrometer we studied the influence of the food's sugar concentration on different parameters of the thorax vibrations produced by foragers of Melipona seminigra during trophallaxis in the nest. The concentrations tested (20-70% sugar w/w) were within the biologically relevant range. They substantially influenced different parameters...

By depositing scent marks on flowers, bees reduce both the search time and the time spent with the handling of nonrewarding flowers. They thereby improve the efficiency of foraging. Whereas in honey bees the source of these scent marks is unknown, it is assumed to be the tarsal glands in bumble bees. According to histological studies, however, the...

The pheromones used by several species of stingless bees for scent trail communication are generally assumed to be produced by the mandibular glands. Here we present strong evidence that in Trigona recursa these pheromones originate from the labial glands, which are well developed in the heads of foragers. Analysis of the behavior involved in scent...