Biology subjects

Degen, J.

Publications and source records attributed to Degen, J..

4 recordsLinked to original sources

bioRxiv2026

Superposition eyes of diurnal and nocturnal hawkmoths are imperfect spheres and lack acute zones.

Superposition compound eyes improve sensitivity by pooling light from multiple facets and are widespread among nocturnal insects, including moths and beetles. Optical theory predicts that superposition eyes must be nearly spherical to form coherent images and therefore lack highly pronounced acute zones with high spatial resolution. To examine this, we imaged eyes of six hawkmoths (Sphingidae) spanning diurnal and nocturnal activity with high-resolution microcomputed tomography. Our automated pipeline created detailed eye maps quantifying morphological parameters. We measured local eye curvature (radial distance), interommatidial angle ({Delta}{varphi}), facet size and crystalline cone skewness (tilt of cone axes relative to the local surface normal). All species show more curvature in the dorso-ventral plane with flattening in the antero-posterior plane. However, their eyes still retain near-spherical curvature globally, with diurnal species showing greater distortion. For facet parameters, spatial acuity is generally highest (lowest {Delta}{varphi}) near the eye center and decreases gradually toward the periphery. However, overall variation in spatial acuity is low and these eyes lack distinct acute zones. Facet size gradually changes from center to periphery, increasing in some species and decreasing in the others. Cone skewness is present in all six species (0{degrees}-10{degrees}), but in two diurnal species of hummingbird hawkmoths it increases markedly in the posterior region (15{degrees}-30{degrees}) possibly compensating for regional eye flatness. This paper provides foundational data of ommatidial and eye shape measurements and advances our assumptions about how superposition eyes function.

animal behavior and cognition↗

bioRxiv2023

Regulation of pupil size in natural vision across the human lifespan

Vision is mediated by light passing through the aperture of the eye, the pupil, which changes in diameter from ~2 to ~8 mm from the brightest to the darkest illumination. In addition, with age, mean pupil size declines. In laboratory experiments, factors affecting pupil size can be experimentally controlled or held constant, but how the pupil reflects changes in retinal input from the visual environment under natural viewing conditions is not clear. Here, we address this question in a field experiment (N=83, 43 female, age: 18-87 years) using a custom-made wearable video-based eye tracker with a spectroradiometer measuring spectral irradiance in the approximate corneal plane. Participants moved in and between indoor and outdoor environments varying in spectrum and engaged in a range of everyday tasks. Our real-world data confirm that light-adapted pupil size is determined by light intensity, with clear superiority of melanopic over photopic units, and that it decreases with increasing age, yielding steeper slopes at lower light levels. We find no indication that sex, iris colour or reported caffeine consumption affect pupil size. Taken together, the data provide strong evidence for considering age in personalised lighting solutions and for using melanopsin-weighted light measures to assess real-world lighting conditions.

neuroscience↗

bioRxiv2022

Streetlights affect moth orientation beyond flight-to-light behaviour

One of the most dramatic changes occurring on our planet in recent decades is the ever-increasing extensive use of artificial light at night, which drastically altered the environment nocturnal animals are adapted to 1,2. One nocturnal species group experiencing marked declines are moths, which are not only of great importance for species conservation, but also for their key role in food webs and in ecosystem services such as nocturnal plant pollination 3,4. Light pollution has been identified as a driver in the dramatic insect decline of the past years 5-7, yet little is known about its impact on natural insect orientation behaviour. Using harmonic radar tracking, we show that the orientation of several species of moths is significantly affected by streetlights, although only 4 % of individuals showed flight-to-light behaviour. We reveal a species-specific barrier effect of streetlights on lappet moths whenever the moon was not available as a natural celestial cue. Furthermore, streetlights increased the tortuosity of flight trajectories for both hawk moths and lappet moths. Our results provide the first spatially resolved experimental evidence for the fragmentation of landscapes by streetlights and demonstrate that light pollution affects movement patterns of moths beyond previously assumed extend, potentially affecting their reproductive success and hampering a vital ecosystem service.

animal behavior and cognition↗

bioRxiv2021

ADAPs intrinsically disordered region is an actin sponge regulating T cell motility

Intrinsically disordered proteins (IDPs) play a vital role in biological processes that rely on transient molecular compartmentation1. In T cells, the dynamic switching between migration and adhesion mandates a high degree of plasticity in the interplay of adhesion and signaling molecules with the actin cytoskeleton2,3. Here, we show that the N-terminal intrinsically disordered region (IDR) of adhesion- and degranulation-promoting adapter protein (ADAP) acts as a multipronged scaffold for G- and F-actin, thereby promoting actin polymerization and bundling. Positively charged motifs, along a sequence of at least 200 amino acids, interact with both longitudinal sides of G-actin in a promiscuous manner. These polymorphic interactions with ADAP become constrained to one side once F-actin is formed. Actin polymerization by ADAP acts in synergy with a capping protein but competes with cofilin. In T cells, ablation of ADAP impairs adhesion and migration with a time-dependent reduction of the F-actin content in response to chemokine or T cell receptor (TCR) engagement. Our data suggest that IDR-assisted molecular crowding of actin above the critical concentration defines a new mechanism to regulate cytoskeletal dynamics. The principle of IDRs serving as molecular sponges to facilitate regulated self-assembly of filament-forming proteins might be a general phenomenon.

biochemistry↗