Biology subjects

Gorb, S.

Publications and source records attributed to Gorb, S..

8 recordsLinked to original sources

bioRxiv2025

Anatomy and mechanics of tsetse fly blood feeding

African trypanosomiasis is a neglected tropical disease transmitted by tsetse flies (Glossina spp.) in sub-Saharan Africa. The flys saliva carries parasitic unicellular trypanosomes, such as Trypanosoma brucei, leading to infections in humans, domestic animals, and wildlife. Tsetse flies feed on a broad spectrum of hosts, including humans, elephants, buffaloes, rhinos, hippos, turtles and monitor lizards. To understand how the insects can penetrate such diverse skin types, we detailed the anatomical structures involved in tsetse blood feeding, their mechanical properties and the forces exerted by the fly during probing. We found that the tsetse flys feeding apparatus does not rely on exceptionally unique structures or extraordinary forces. Instead, the tsetse fly has evolved subtle yet highly efficient adaptations, which include a labellum equipped with arrays of small teeth. When combined with a robust retraction movement of the proboscis, these structures create lesions on various types of skin, thus facilitating blood pool feeding on a broad host spectrum.

biophysics↗

bioRxiv2025

Tube feet dynamics drive adaptation in sea star locomotion

Sea stars use hundreds of tube feet on their oral surface to crawl, climb, and navigate complex environments--all without the coordination of a central brain. While the morphology of tube feet and their role as muscular hydrostats are well described, the dynamics underlying their locomotion remain poorly understood. To investigate these dynamics, we employed an optical imaging method based on frustrated total internal reflection to visualize and quantify tube foot adhesion in real time across individuals of Asterias rubens spanning a wide size range. Our results reveal an inverse relationship between crawling speed and the duration of tube foot contact with the substrate. This suggests that sea stars regulate locomotion by modulating foot-substrate interaction time in response to body load. To test this, we conducted perturbation experiments using 3D-printed backpacks that increased body mass by 25% and 50%, along with numerical simulations based on a mechanistic model incorporating decentralized feedback control of the tube feet. The added load significantly increased adhesion time, supporting the role of a load-dependent mechanical adaptation. We further investigated inverted locomotion, both experimentally and through simulation, and found that tube feet adjust their contact behavior when the animal is oriented upside down relative to gravity. Together, our findings demonstrate that sea stars adapt their locomotion to changing mechanical demands by modulating tube foot-substrate interactions, revealing a robust, decentralized strategy for navigating diverse and challenging terrains.

biophysics↗

bioRxiv2023

Mechanical and elemental characterization of ant mandibles: consequences for bite mechanics

Chewing with the mandibles is a food processing behavior observed in most current insect lineages. Mandible morphology has an essential role in biting behavior and food processing capacity. However, the mandible cuticle can have regional differences in its mechanical properties, associated or not with the accumulation of elements that increase cuticle stiffness. The effects of such a heterogeneous distribution of cuticle material properties in the mandible responses to biting loading are still poorly explored in chewing insects. Here we measured the elemental composition and material properties of workers of an ant species, Formica cunicularia, and tested the effects of the cuticular variation in Youngs modulus (E) under bite-loading with Finite Element Analysis (FEA). We divided worker mandibles into four regions that we expect would vary in elemental composition and material properties, namely the masticatory margin, mandible blade, ventral (VMA), and dorsal (DMA) mandibular articulations with the head. Specifically, we expect the masticatory margin will show higher cuticular hardness (H) and E values, followed by the mandibular joints and the mandible blade. We also predict that such cuticle material properties variation is functionally relevant under bite-loading, changing stress patterns when compared to the mechanical responses of a mandible with a homogeneous distribution of material properties. To measure elemental composition, we used energy disperse X-ray spectroscopy, while H and E were accessed through nanoindentation tests. Mandible mechanical responses to bite-loading were tested with FEA, comparing a mandible with a homogeneous versus a heterogeneous E distribution. As expected, the mandibular regions showed distinct proportions of relevant elements, like Cu and Zn, with the masticatory margin showing the higher levels of those elements, followed by the mandibular articulations with the head and the mandible blade. The same pattern was observed regarding the values of cuticle H and E. When incorporated into FEA, this variation in E effectively changed mandible stress patterns, leading to a higher concentration of stresses in the stiffer mandibular regions, letting the softer mandible blade with relatively lower stress levels. Our results demonstrated the relevance of cuticle heterogeneity in mechanical properties to deal with bite-loading demands and suggest that the accumulation of transition metals such as Cu and Zn has a relevant correlation with such mechanical characteristics of the mandible in this ant species.

zoology↗

bioRxiv2021

Denitrification in foraminifera has ancient origins and is complemented by associated bacteria

Benthic foraminifera are unicellular eukaryotes that inhabit sediments of aquatic environments. Several foraminifera of the order Rotaliida are known to store and use nitrate for denitrification, a unique energy metabolism among eukaryotes. The rotaliid Globobulimina spp. has been shown to encode an incomplete denitrification pathway of bacterial origin. However, the prevalence of denitrification genes in foraminifera remains unknown and the missing denitrification pathway components are elusive. Analysing transcriptomes and metagenomes of ten foraminiferal species from the Peruvian oxygen minimum zone, we show that denitrification genes are highly conserved in foraminifera. We infer of the last common ancestor of denitrifying foraminifera, which enables us to predict the ability to denitrify for additional foraminiferal species. Additionally, an examination of the foraminiferal microbiota reveals evidence for a stable interaction with Desulfobacteracea, which harbour genes that complement the foraminiferal denitrification pathway. Our results provide evidence that foraminiferal denitrification is complemented by the foraminifera-associated microbiome. The interaction of foraminifera with their resident bacteria is at the basis of foraminiferal adaptation to anaerobic environments that manifested in ecological success within oxygen depleted habitats. Significance StatementA substantial component of the global nitrogen cycle is the production of biologically inaccessible dinitrogen attributed to anaerobic denitrification by prokaryotes. Recent evidence identified a eukaryote - foraminifera - as new key players in this loss of bioavailable nitrogen. The evolution of denitrification in eukaryotes constitutes a rare event and the genetic mechanisms of the denitrification pathway in foraminifera are just starting to be elucidated. We present large-scale sequencing analyses of ten denitrifying foraminiferal species, which reveals the high conservation of the foraminiferal denitrification pathway. We further find evidence for a complementation of denitrification by the foraminiferal microbiome. Together, these findings provide novel insights on the early evolution of a previously overlooked component in the marine nitrogen cycle.

evolutionary biology↗

bioRxiv2021

Computational fluid dynamics provide evidence for a compensatory suction feeding like effect in the predatory strike of dragonfly larvae

Most fast-moving aquatic predators face the challenge of bow wave formation. Water in front of the predator alarms or even displaces the prey. To mitigate the formation of such a bow wave, a strategy aiming at pressure reduction via suction has evolved convergently in several animal groups: compensatory suction feeding. The aquatic larvae of dragonflies and damselflies (Insecta: Odonata) are likely to face this challenge as well. They capture prey underwater using a fast-moving raptorial appendage, the so-called prehensile labial mask. Within dragonflies (Odonata: Anisoptera) two basic shapes of the prehensile labial mask have evolved, with an either flat and slender or concave distal segment. While the former is a pure grasping device, the latter is also capable of scooping up smaller prey and retaining it inside the cavity by arrays of bristle-like structures. The hydrodynamics of the prehensile labial mask was previously unknown. We used computational fluid dynamic (CFD) simulations of the distal segment of the mask, to investigate for the first time how different shapes of the mask impact their function. Our results suggest that both shapes are highly streamlined and generate a low-pressure area, likely leading to an effect analogous to compensatory suction feeding. This presents a vivid example of how convergent evolution enables very different animal groups to successfully deal with the challenges of their environment. It may also be an interesting concept for technical application in small scale grasping devices; e.g. for simple sampling mechanisms in small-sized autonomous underwater vehicles (AUVs).

zoology↗

bioRxiv2020

Sand throwing in a pit-building antlion larva from a soil mechanical perspective

Sandy pitfall traps are an elaborate construction to capture prey and antlions are well-known representatives of this predation technique. From a soil mechanical perspective, antlions exploit the interactions between the particles of their habitat and engineer a stable trap. This construction is close to the unstable state, where a prey item will immediately slide towards the center - towards the ambushing antlion - when accidently entering the trap. This method is efficient, but requires permanent pit maintaining. According to the present knowledge, antlions throw sand at their prey, to distract it, and/or cause sand slides towards the center of the pit. Using sand throwing and escape experiments, as well as finite element analysis, we supported this hypothesis. Furthermore, we added new hypothesis about maintaining the pitfall trap. We showed that sand that accumulates in the center of the pit will be continuously removed, which lead to the slope maintenance close to an unstable condition. This avoids self-burial of the antlion, as well as decreasing the chance of prey item escapes by keeping the slope angle steep. This demonstrates the interaction of an insect larva with its abiotic environment from a novel perspective and adds further insights into longstanding entomological hypotheses.

zoology↗

bioRxiv2020

Hunting with catapults: the predatory strike of the dragonfly larva

Dragonfly larvae capture their prey with a strongly modified -extensible- mouthpart using a biomechanically unique but not yet understood mechanism. The current opinion of hydraulic pressure being the driving force of the predatory strike can be refuted by our manipulation experiments and reinterpretation of former studies. On this fact, we present evidence for a synchronized dual-catapult system powered by two spring-loaded catapults. The power output of the system exceeds generally the maximum power achievable by musculature. Energy for the movement is stored by straining a resilin-containing structure at each joint and possibly the surrounding cuticle which is preloaded by muscle contraction. To achieve the precise timing required to catch fast-moving prey, accessory structures are used to lock and actively trigger the system, ensuring the synchronisation of both catapults. As a proof of concept, we developed a bio-inspired robotic arm resembling the morphology and functional principle of the extensible mouthpart. Our study elucidates the predatory strike of dragonfly larvae by proposing a novel mechanism, where two synchronized catapults power the ballistic movement of prey capturing in dragonfly larvae – a so-called synchronized dual-catapult system. Understanding this complex biomechanical system may further our understanding in related fields of bio inspired robotics and biomimetics.One Sentence Summary The synchronized dual-catapult, a biomechanically novel mechanism for the ballistic movement of prey capturing in dragonfly larvaeCompeting Interest StatementThe authors have declared no competing interest.View Full Text

zoology↗

bioRxiv2019

The glue produced by Drosophila melanogaster for pupa adhesion is universal

Insects produce a variety of adhesives for diverse functions such as locomotion, mating, egg or pupal anchorage to substrates. Although they are important for the biology of organisms and potentially represent a great resource for developing new materials, insect adhesives have been little studied so far. Here, we examined the adhesive properties of the larval glue of D. melanogaster. This glue is made of glycosylated proteins and allows the animal to adhere to a substrate during metamorphosis. We designed an adhesion test to measure the pull-off force required to detach a pupa from a substrate and to evaluate the contact area covered by the glue. We found that the pupa adheres with similar forces to a variety of substrates (with distinct roughness, hydrophilic and charge properties). We obtained an average pull-off force of 217 mN, corresponding to 15 500 times the weight of a pupa and adhesion strength of 137-244 kPa. Surprisingly, the pull-off forces did not depend on the contact area. Our study paves the way for a genetic dissection of the components of Drosophila melanogaster glue that confer its particular adhesive properties. SUMMARY STATEMENTWe designed an adhesion test to measure the pull-off force required to detach drosophila pupae and found that Drosophila glue adheres similarly to various substrates of different chemical properties.

biophysics↗