Belgium

Research on the direct effects of capture and tagging on post-release behaviour is typically limited to short-term deployments. To investigate both immediate and longer-term behavioural responses, we deployed eight Cefas G7 tags (1Hz depth and temperature, and 20 Hz triaxial acceleration) for 21 - 94 hours and MiniPATs (depth, temperature, light and triaxial acceleration, each at 0.2 Hz) for 110 - 366 days on Atlantic bluefin tuna (ABT) in the English Channel. Post-release, ABT exhibited a highly active initial swimming response, aligning with previous pelagic fish tracking studies. Accelerometry tags revealed that activity (VeDBA), tailbeat amplitude and dominant strokefrequency were 2.4, 3.2 and 1.4 times greater respectively in the first hour post-release than the subsequent 24 hours, stabilising at lower levels within 5 - 9 hours. Long-term MiniPATs data revealed reduced activity for 11 ± 7.9 days (range: 2-26 days), with disrupted diel patterns of activity and fewer burst energy events (5 min/day vs. 14 min/day during “recovery” periods). Subsequently, activity levels stabilised, with increased high-magnitude acceleration events (potential feeding) and became more active during the day than at night. Year-long deployments revealed that consistent diel vertical migration, diurnal patterns of activity, and increased time allocation to fast starts are typical for ABT off the British Isles in summer months, and their absence at the start of data collection may be related to the effect of capture and tagging, which may be longer lasting, and more complex than previously appreciated.

SEB Conference 2025

Use of accelerometry to measure the dynamics of activity patterns of Atlantic bluefin tuna after tagging and release

recovery period

accelerometry

post-release behaviour

biologging

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technical paper

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Exposure to environmentally generated stressors during early development can profoundly shape physiology and behaviour. To which extent such organisational effects might be contingent on subsequent environmental circumstances, maximise physiological resilience and fitness outcomes remain unclear. Using a highly seasonal study system, the migratory Common quail (Coturnix coturnix), we tested the prediction that exposure to food uncertainty potentiate the expression of seasonal migratory fattening and that such a response is stronger in those birds previously exposed to the same environmental stressor during early post-natal growth. To this end, we combined known proxies of physiological energetics signalling the emergence of the migratory phenotype (including fat stores and nocturnal energy expenditure) with circulatory measurements of metabolic hormones (plasma corticosterone and plasma thyroid hormones), and gene expression measurements of candidate genes in the brain. Our results suggest that the impact of stress exposure on the migratory phenotype is dependent on early-life priming effects, and potential functional mechanisms will be discussed.

The influence of early life environmental conditions on seasonal energy turnovers in the Common quail

All birds have a remarkably efficient balance. This is particularly evident in their ability to maintain an upright posture when resting or sleeping. Unlike humans lineage, the different parts of the pelvic apparatus are not aligned perpendicular to the ground, so they cannot be held upright by the compressive force of gravity.
Our previous work has shown, using robotic simulation, that birds with this flexed posture can passively maintain a bipedal position via a tensegrity system. We use our previous model and vary its geometric parameters according to four bird species (Zebra Finch, Mallard, Egret and Macaw) representing different leg proportions. We check the generalisation of our model by applying it to the four species. For each case, we determine the requirements to reach a stable equilibrium.
Based on our results, we propose a new model to simulate a wide range of avian pelvic limb proportions and determine the associated stability zone, i.e. the area in which the Centre of Mass (COM) can evolve while maintaining balance. The aim is to compare, describe and identify the parameters that allow the bipedal equilibrium to be maintained in a stable passive manner. We have also identified new features in the maintenance of postural balance, such as the bony and supra-tendinous bridges located on the distal part of the tibiotarsus. Our results provide a better understanding of how birds maintain a stable bipedal posture, as well as providing elements for the future development of bipedal robots.

Robotics contribution to the understanding of passive bipedalism in birds, balance and stability explained by tensegrity

How vertebrates that ingest their prey whole and dissolve the skeleton can process high amounts of calcium and phosphorus passing through the intestine? This was assessed using captive Burmese pythons facing different diets: a normal diet (calcium and phosphorus provided from entire rodents); a low-calcium and phosphorus diet (rodents with no bones: ‘boneless prey’), and a calcium-rich diet (boneless rodents supplemented with intraperitoneal injection of calcium carbonate, CaCO3). The intestinal mucosa was analysed using microscopy techniques (alizarin red S and peroxidase staining, EDX analyses). Blood calcium and hormone levels (parathyroid hormone, PTH and calcitonin) were also analysed from fasting pythons and snakes repeatedly fed with either a normal prey or a boneless rat. Results revealed the presence of specialised cells along the intestine involved in the production of calcium and phosphorus particles (fed snakes). A multi-layered particle made of calcium, phosphorus and iron-rich nucleation elements in the centre is usually observed in the apical crypt of these cells. In fasting snakes, crypts are empty. When snakes are fed with a boneless prey, the particles are not observed, although iron elements are located within the crypts. When fed with a boneless meal supplemented with calcium, large particles fill the crypts. When snakes are fed repeatedly with a low-calcium diet, blood calcium level drops but calcitonin and PTH levels increase. So far this cell type was found in some Boidae, a Colubrid and the Gila monster, these vertebrates eating their entire prey. Therefore, a broader and thorough evolutionary analysis is needed.

A new cell type in the gut of Vertebrates ?

Cardiovascular diseases and protein malnutrition are public health problems that require attention. In this context, understanding the effects of low-protein diets on the heart and the therapeutic potential of TUDCA is essential. C57Bl/6 mice were divided into four groups: control (C), control + TUDCA (CT), restricted (R) and restricted + TUDCA (RT). For 16 weeks, they received normal-protein or low-protein diets and, in the last 15 days, were treated with TUDCA (300 mg/kg) or PBS. Animals in group R had lower body weight and lower serum concentration of total proteins. However, we did not observe any change in relation to heart/body weight. Morphometric analysis revealed cardiomyocyte hypertrophy in group R, which was reduced by TUDCA in group RT. Similar results were observed in interstitial and perivascular collagen deposition. The TUNEL assay indicated the highest rate of cell death in group R, reduced in RT. Structural alterations in the sarcomere and in the organization of type 2 myosin were evident. The length of sarcomeres, myofibrils and A and I bands was shorter in the R group, but in the RT group these structures presented measurements similar to those of the control. In addition, R mice exhibited greater structural disorganization and an increase in the termination points between the myofibrils. Thus, the low-protein diet induces hypertrophy, collagen accumulation, apoptosis and sarcomeric alterations in the heart, while TUDCA exerts a therapeutic effect by reducing these alterations.
Keywords:Cardiomyocytes; myosin type 2; fibrosis, hypertrophy, myofibrils.

TUDCA attenuates structural changes in the hearts of mice fed a low-protein diet

Silene nutans (Caryophyllaceae) is composed of 4 distinct genetic lineages which are strongly reproductively isolated: inter-lineage hybrids are chlorotic and exhibit high mortalities. The asymmetry in the reproductive isolation in reciprocal crosses suggested the involvement of cyto-nuclear incompatibilities in hybrid breakdown. Using hybrid capture and high-throughput DNA sequencing, we analyzed diversity patterns in the genic content of the organellar genomes in the four S. nutans lineages. Because organellar genomes are usually co-transmitted, we assessed whether both genomes could be involved in the speciation process.

What is the role of the organelles in the speciation process of Silene nutans?

Stomata arise during leaf epidermal development as specialised structures for gas-exchange. Stomatal numbers, apertures and distribution between leaf surfaces can affect plant water balance, growth and yield. While the mechanisms that govern the formation of stomata on the abaxial (lower) leaf surface are well-studied, how stomata develop on the adaxial (upper) leaf surface is poorly understood. How the distribution of stomata between leaf sides (stomatal ratio) is determined and adjusted in response to plant growth environment also remains unclear.
We addressed the effects of environmental conditions on adaxial and abaxial stomatal patterns in Arabidopsis thaliana. Acclimation to dry air or warm temperatures in Arabidopsis leaves manifests in substantial changes in stomatal density, small changes in stomatal ratio and minor, if any, changes in stomatal index. Thus, acclimation to growth environment may be mostly mediated by changes in cell expansion and less by alterations in leaf developmental program.
We also explored the relationships between stomatal anatomical traits and yield in crops. In spring wheat that has relatively more stomata on the adaxial leaf surface, higher adaxial but not abaxial stomatal density was negatively associated with yield, especially under dry and warm conditions. In tomato that has less stomata on the adaxial than abaxial leaf surface, higher stomatal ratios were positively associated with yield. Thus, manipulation of adaxial stomatal densities and stomatal ratios may increase yield in both monocot and dicot crops. Understanding how adaxial stomatal development is controlled and how stomatal ratios are regulated is necessary to achieve this goal.

Stomatal distribution between leaf surfaces and its relationships with yield

Sabre-toothed cats (Felidae: Machairodontinae†) are considered to have wide gape angles compared to conical toothed cats (e.g. lions, leopards, etc.). Intuitively, a wider gape may have allowed for larger prey to be dispatched with a neck bite. In this study, we took an experimental approach using 3D-printed skulls to investigate maximum gape angles in African cats from the Pliocene-to-Holocene (including conical and sabre-tooth cats). We tested whether representative skulls could physically fit around the neck, upper throat, and muzzle of high-quality taxidermed models of potential prey items (including suids, gazelle, antelope and bovids, rhinocerotids, and proboscideans). To account for soft tissue restrictions on maximum gape, we conducted a comparative study on fully-fleshed and de-fleshed heads of house cats (Felis catus), leopard (Panthera pardus), and lion (P. leo), examining both maximum myological (fully fleshed) and osteological gape angles. Osteological gape angles were larger across the specimens; we therefore used the highest, lowest, and mean differences in angles between osteological and myological gape angles as a range of conservative correction-factors for the gape angles of the 3D-printed skulls. Current results indicate comparable killing potential between medium-sized sabre-tooth cats (Dinofelis, Megantereon, Lokotunjailurus) and modern leopards and cheetahs. The extremely long sabres of Megantereon prevented the initiation of a killing bite on many medium and large ungulates, including adult alcelaphine, tragelaphine, and reduncine bovids (e.g. Kobus ellipsiprymnus). Finalising experimental results and applying prey-preference analyses will provide a more tangible range of prey which African sabre-tooths could have physically killed.

Wide is the gape that feeds - examining the physical constraints of biting in conical and sabre-toothed felids

Accurately distinguishing and classifying fibre types within composite bundles presents significant challenges, particularly for micro-scale fibres arranged in hierarchical structures. Biological fibre composites, such as spider silk or arterial walls, contain fibres that cannot be easily isolated, while their minimal mass makes characterisation through conventional techniques like mass spectroscopy, Raman spectroscopy, or proteomics time-consuming and, in some cases, impossible. In this work, we address this challenge by introducing a new method based on statistical classification and physically-constrained optimization. The approach exploits the ability of obtaining data both from the single fibres, e.g. through scanning electron microscopy, and from the composite fibre network, e.g. mechanical properties. The fibre-dependent data are used to run a labelling procedure using Gaussian Mixture Models. We use this first composition of the fibre sub-populations, as the start of a Mixed-Integer Linear Programming (MILP), to further categorize fibres based on their linear phase behavior, their mechanical properties, and their biological constraints. This integrated methodology proves particularly valuable for natural materials, where multiple fibre types with distinct mechanical functions coexist within a single structure. Through testing, we demonstrate robust classification performance when combining geometrical and mechanical properties. This method successfully distinguishes between overlapping distributions and resolves ambiguities that pure statistical approaches cannot address. To facilitate adoption across disciplines, we provide our implementation as an open-source Python package. By applying this method to other biological fibre networks, we could improve our understanding of how fibre bundles are organised in nature, and how they reach their optimal mechanical performance.

A Hierarchical Cluster-Separation Framework for Analysing Fibre-Based Biological Materials

Insect ovipositors and stingers have extensive variation in their morphology depending on the substrate they penetrate or probe. From an engineering perspective, stingers are micro penetration devices capable of penetrating a substrate and delivering a package. Understanding the role played by the microstructures and substrate property on the insertion and extraction forces will enable us to design efficient bioinspired micro needles and transdermal medical patches.
Quasi-static insertion and extraction experiments on honeybee stingers were conducted on artificial homogeneous substrate(humimic) and fibrous chicken muscle. The force required to remove the stinger from the fibrous substrate was 3 times more than that of in the homogenous substrate due to the rearward facing barb making it harder to pull out. The barbs, in addition to helping the stinger anchor, were found to significantly reduce the insertion forces. The increased stress concentration at the site of the barbs can contribute to the decreased insertion force.  Stingers with barbs were found to require one-third the insertion force in humimic and half the insertion force in the fibrous substrate, compared to modified barbless stingers. In biomedical applications, a reduced insertion force would translate to less pain and less tissue damage. Higher extraction forces could be beneficial in designing mechanically adhering patches.

Assessing the role of  barbs and substrate properties on insertion and extraction forces in worker honeybee stingers

This project explores how life science students' career trajectories and professional identities are shaped by their historical perspectives, curriculum experiences, and interactions with facilitators. Conducted at Imperial College London, it highlights the importance of recognising students' prior experiences and providing support to enhance their engagement with the life sciences discipline.

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The influence of early life environmental conditions on seasonal energy turnovers in the Common quail

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Physiological and behavioural responses to increased temperature in the Atlantic bluefin tuna

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