Biology subjects

Robert, D.

Publications and source records attributed to Robert, D..

5 recordsLinked to original sources

bioRxiv2026

Regional connectivity and partial residency of capelin (Mallotus villosus) in the Gulf of St. Lawrence inferred from otolith chemistry

Capelin (Mallotus villosus), a key forage fish in the Northwest Atlantic, links zooplankton to predators including commercial fishes, seabirds, and marine mammals, yet its life-cycle movements in the Gulf of St. Lawrence (GSL) remain poorly understood. Between 2022 and 2024, otoliths from 927 individuals collected during and after spawning were analysed by Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS). Building on previous work on regional structuring, seven trace elements (Li, B, Mg, K, Zn, Sr, Ba) were used to discriminate three regions. Early-life regional signatures were inferred through an edge-to-core approach, assigning otolith core chemistry to one of these regions using quadratic discriminant analysis. The core was treated as an integrated early-life signal (late-larval to early juvenile period) rather than a strictly natal signature. Spatial variation in core chemistry was consistent across cohorts, mirroring the stability documented on the otolith edge. Results revealed widespread dispersal alongside partial regional residency: individuals with northeastern early-life signatures showed the strongest correspondence between early-life and capture regions, whereas other regions were more connected. Fish sampled during spawning were more often reassigned to their inferred early-life region than post-spawning fish, a regional-scale homing-like pattern consistent with regional spawning fidelity. This coexistence of dispersive and resident strategies likely generates a portfolio effect buffering the population against environmental variability and localised reproductive failures.

ecology↗

bioRxiv2026

Electrostatic facilitation of odorant capture in insects

Olfaction is a sensory modality common to most organisms. In insects, the primary olfactory organ is the antenna, where sensilla house olfactory receptor neurons adapted to detect volatile organic compounds (VOCs). Whilst olfaction is well-understood at molecular and neural levels, questions remain as to how, biophysically, airborne VOCs reach sensilla. Transport through passive diffusion and active antennal motion is empirically supported but cannot entirely explain the remarkably rapid VOC sampling rates. We present evidence that the insect antennae exploits electrostatic forces that amplify VOC transfer from bulk air to sensilla. In effect, charged antennae capture more ambient VOCs than neutral ones, also evoking an enhanced electrophysiological (EAG) response to VOCs. Experimentally altering the charge of isolated antennae modulates EAG responses and olfactory sensitivity. Multiphysics modelling incorporating electrostatic and fluid dynamic mechanisms supports empirical evidence. Altogether, this work reveals the existence of a previously unknown and complementary biophysical mechanism supporting olfaction. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=147 SRC="FIGDIR/small/703773v1_ufig1.gif" ALT="Figure 1"> View larger version (23K): org.highwire.dtl.DTLVardef@1917cc3org.highwire.dtl.DTLVardef@962075org.highwire.dtl.DTLVardef@2ce4b3org.highwire.dtl.DTLVardef@15ada3a_HPS_FORMAT_FIGEXP M_FIG C_FIG

physiology↗

bioRxiv2025

Warming, but not acidification, increases metabolism and reduces growth of redfish (Sebastes fasciatus) in the Gulf of St. Lawrence.

Understanding the effects of global change, including temperature, pH, and oxygen availability, on commercially important species is crucial for anticipating consequences for these resources and their ecosystems. In the Gulf of St. Lawrence (GSL), redfish (Sebastes spp.) have been under moratorium from 1995 to 2024, with a massive recruitment observed in 2011-2013. However, little is known about their metabolic and thermal physiology, making predictions of their response to changing GSL conditions challenging. To address this, we quantified the effects of four acclimatation temperatures (2.5, 5.0, 7.5, and 10.0 ) and two pH levels (7.35 and 7.75) on standard and maximum metabolic rates (SMR and MMR), aerobic scope (AS), hypoxia tolerance (O2crit), food consumption, and growth in redfish. SMR, MMR, and AS increased with temperature, but growth decreased at the highest temperature, likely due to increased metabolic demand, with food consumption similar across 5.0 to 10.0 {degrees}C treatments. O2crit was lower for fish acclimated to 2.5 and 5.0 , making redfish less hypoxia-tolerant at higher temperatures. Except from SMR, no significant effect of pH was observed. These results suggest that future changes in the GSL will challenge redfish, with potential long-term effects on their growth due to increased energy requirements.

physiology↗

bioRxiv2021

Tree canopy influences ground level atmospheric electrical and biogeochemical variability

Static electric fields in the atmosphere are increasingly recognized to interact with various organisms over several levels of biological organization. Recently, a link between atmospheric electrical variations and biogeochemical processes has been established in the context of open fields, yet biological structures like trees produce substantial alterations in atmospheric electric properties. Here, we assess whether these structural changes affect the dynamics of both biogenic and abiotic electrical landscapes and their relation to geochemical processes. To this end, we theoretically assess how trees alter their surrounding electric fields and empirically compare the temporal dynamics of atmospheric potential gradients, positive ions in the near-ground level atmosphere and soil electrochemical properties in an open field and under a tree. The developed model of electric fields around trees provides insight into the extent to which trees shield underlying electric landscape, revealing that a substantial increase in atmospheric potential gradient only marginally affects the electric field under the canopy. We further show that soil electrochemical properties are tied to temporal dynamics of positive ions in the near-ground level atmosphere, and that the presence of a tree reduces the temporal variability in both ground level positive ions concentrations and soil redox potential. This suggests that a tree can have a stabilizing effect on drivers of temporal variability in atmospheric electricity and soil electro-chemistry, thereby likely indirectly influencing soil microorganisms and processes as well as electro-sensitive organisms that perceive and utilize atmospheric electric fields.

biophysics↗

bioRxiv2021

A Tad-like apparatus is required for contact-dependent prey killing in predatory social bacteria

Myxococcus xanthus, a soil bacterium, predates collectively using motility to invade prey colonies. Prey lysis is mostly thought to rely on secreted factors, cocktails of antibiotics and enzymes, and direct contac with Myxococcus cells. In this study, we show that on surfaces the coupling of A-motility and contact-dependent killing is the central predatory mechanism driving effective prey colony invasion and consumption. At the molecular level, contact-dependent killing involves a newly discovered type IV filament-like machinery (Kil) that both promotes motility arrest and prey cell plasmolysis. In this process, Kil proteins assemble at the predator-prey contact site, suggesting that they allow tight contact with prey cells for their intoxication. Kil-like systems form a new class of Tad-like machineries in predatory bacteria, suggesting a conserved function in predator-prey interactions. This study further reveals a novel cell-cell interaction function for bacterial pili-like assemblages.

microbiology↗