Biology subjects

Katzke, J.

Publications and source records attributed to Katzke, J..

6 recordsLinked to original sources

bioRxiv2026

Evolutionary diversification of the biological screw joint in weevils

Complex biomechanical innovations are often treated as discrete evolutionary breakthroughs, yet their diversification within large radiations remains poorly understood. Beetle leg joints provide a striking example: some weevils possess screw-like coxa-trochanteral articulations in which rotation and axial displacement are mechanically coupled, resembling engineered screw-and-nut mechanisms. Whether these joints represent isolated mechanical extremes, discrete adaptive types or part of a broader continuum of phenotypic variation has remained unknown. Here we combine synchrotron X-ray microtomography, landmark-free atlas-based morphometrics, quantitative functional morphology and phylogenetic comparative analyses to examine the mesocoxa-trochanteral joint in 68 specimens representing seven sampled family-level groups across early-diverging and derived weevil lineages. We show that screw joint evolution combines continuous variation in trochanteral shape with a restricted set of mechanically plausible joint-character combinations, rather than forming sharply separated morphological classes. True screw-and-nut joints are not confined to a distinct region of morphospace, indicating that overall form and mechanical configuration are not necessarily coupled. The occurrence of this configuration in the early diverging Caridae shows that it is not restricted to more derived families. Three-dimensional helix fitting revealed a mosaic geometry, with winding angle showing the clearest relationship with overall shape and joint architecture, whereas axial pitch varied largely independently of shape, size and lineage. Together, these patterns show that screw joint components diversified with different degrees of evolutionary integration. These results recast the weevil screw joint from a singular biomechanical curiosity into a diversified evolutionary system. They suggest that complex functional structures can evolve through the gradual recombination and differential persistence of structurally constrained and evolutionary flexible components, rather than through a single shift from simple to fully specialized designs.

zoology↗

bioRxiv2025

High-throughput phenomics of global ant biodiversity

The big data era in biology is underway, but the study of organismal form has been slow to capitalize on advances in imaging and computation. Modern imaging can digitize whole organisms, but low throughput has limited the effort to document morphological diversity. Within the open science initiative Antscan, we applied high-throughput synchrotron X-ray microtomography to capture phenotypes across a diverse and ecologically dominant insect group -- ants. We provide 2193 whole-body 3D ant datasets from 792 species to broadly cover the ant phylogeny with a global scope, also pairing phenomic data with genome sequencing projects. Scans acquired with standardized parameters facilitate automated analysis and free access to data can broaden the audience and incentivize methods development. Antscan presents a scalable approach to create libraries of diverse anatomies, heralding a new era of studies on the evolution, structure, and function of organismal phenotypes.

zoology↗

bioRxiv2025

Pumping Venom: Valvilli Architecture and Implications for Stinger Functionality

The internal structure of the insect stinger plays a central role in venom delivery, yet critical components in this process remain poorly understood. Of these, the valvilli, a pair of articulated structures within the valve chamber that act as flaps, have often been overlooked or described only superficially. Here, we use high-resolution micro-computed tomography (micro-CT), histological sectioning, and confocal laser scanning microscopy (CLSM) to characterize the fine morphology and material composition of the cuticle of ant valvilli. We report structural differentiation within the valvilli, including sharply delimited material zones that may correspond to distinct mechanical properties. CLSM imaging highlights variation in sclerotization, resilin distribution, and ultrastructure, indicating that the valvilli are not uniform flap-like elements but rather complex, partially deformable structures. Furthermore, comparative micro-CT scans of stingers fixed in different actuation states indicate the involvement of a non-antiphasic pattern of valvilli movement during stinger deployment, challenging the current understanding of valvilli-assisted pumping based on rhythmic, alternating movements, as inferred from European honeybees. These findings offer new anatomical insight into the architecture of the ant stinger and provide a refined morphological basis for future studies of venom delivery mechanisms in Hymenoptera; to also foster our understanding of the complex functionality of micro-scale injection and pumping systems in insects.

zoology↗

bioRxiv2024

A vestibulospinal pathway for context-dependent motor control of the mouse tail

The tail movement is critical for maintaining balance during locomotion in many animal species, yet its underlying neuro-muscular control remains poorly understood. In this study we investigated what are the neuronal substrates responsible for tail control in mice. Using high-resolution microCT scans and retrograde labeling, we lay out the neuro-muscular organization of the tail and identified distinct pools of motoneurons in the spinal cord that innervate proximal and distal muscles. We further show that the spinal vestibular nucleus (SpVN) in the brainstem sends direct projections to the same spinal cord segments where tail motoneurons are located. The activation of these vestibulospinal neurons using optogenetics results in more accurate tail movements during challenging balance tasks. Our results reveal that the vestibular systems influence on tail control is context-dependent, enhancing balance performance under uncertain sensory conditions. These findings provide novel insights into the neural circuits responsible for maintaining balance, highlighting the role of the vestibulospinal pathway in context-dependent modulation of tail movement to maintain stability during complex locomotor tasks.

neuroscience↗

bioRxiv2024

A new leaf sensing organ in a predatory insect group, the praying mantises (Mantodea)

Animals sensory systems enable them to navigate and interact with their environments. Adaptive specializations of these systems can generate novel structures or organs that support highly unique niche adaptations. We report the discovery of a novel sensory organ in a group of praying mantises (Insecta, Mantodea, Nanomantoidea), which have an unusual "leaf-planking" ecomorphic life strategy, laying against the undersides of broadleaf vegetation. Histology, scanning electron microscopy, and x-ray computed tomography all support the novelty of this distinct morphology while electrophysiology reveals that the sensory organ, herein designated the gustifolium organ, detects plant volatiles. The location of the gustifolium organon the ventral thoracic surface of these mantises appears to facilitate the chemical detection of the leaves on which it resides. The gustifolium is a novel plant volatile-detecting sensory structure in an obligate predatory insect, directly linked to a newly-identified, highly-adapted life strategy.

zoology↗

bioRxiv2023

Parallel and divergent morphological adaptations underlying the evolution of jumping ability in ants

Jumping is a rapid locomotory mode widespread in terrestrial organisms. However, it is a rare specialization in ants. Forward jumping has been reported within four distantly related ant genera: Gigantiops, Harpegnathos, Myrmecia, and Odontomachus. The temporal engagement of legs/body parts during jump, however, varies across these genera. It is unknown what morphological adaptations underlie such behaviors, and whether jumping in ants is solely driven directly by muscle contraction or additionally relies on elastic recoil mechanism. We investigate the morphological adaptations for jumping behavior by comparing differences in the locomotory musculature between jumping and non-jumping relatives using x-ray micro- CT and 3D morphometrics. We found that the size-specific volumes of the trochanter depressor muscle (scm6) of the middle and hind legs are 3-5 times larger in jumping ants, and that one coxal remotor muscle (scm2) is reduced in volume in the middle and/or hind legs. Notably, the enlargement in the volume of other muscle groups is directly linked to the legs or body parts engaged during the jump. Furthermore, a direct comparison of the muscle architecture revealed two significant differences between in jumping versus non-jumping ants: First, the relative Physiological Cross-Sectional Area (PCSA) of the trochanter depressor muscles of all three legs were larger in jumping ants, except in the front legs of O. rixosus and M. nigrocincta; second, the relative muscle fiber length was shorter in jumping ants compared to non-jumping counterparts, except in the front legs of O. rixosus and M. nigrocincta. This suggests that the difference in relative muscle volume in jumping ants is largely invested in the area (PCSA), and not in fiber length. There was no clear difference in the pennation angle between jumping and non-jumping ants. However, the length of hind legs relative to body length was longer in jumping ants. Based on direct comparison of the observed vs. possible work and power output during jumps, we surmise that direct muscle contractions suffice to explain jumping performance, in two species, but elastic recoil is likely important in one. We suggest that increased investment in jumping-relevant musculature is a primary morphological adaptation that separates jumping from non-jumping ants. These results elucidate the common and idiosyncratic morphological changes underlying this rare adaptation in ants.

evolutionary biology↗