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Animal bite force is an ecologically relevant performance trait, crucial for individual fitness through its impact on food ingestion and intraspecific agonistic interactions. Despite its popularity in vertebrates, bite force has only recently begun to be measured across the huge diversity of insects. Bite force studies generally use either in vivo measurements or forces modelled based on muscle physiological cross-sectional area (PCSA), and very rarely compare both. PCSA can be measured in a variety of ways, in particular in insects, which have never been thoroughly compared. Here we compare several digitally computed estimates of PCSA (and its components muscle volume and fiber length) in the major mandibular adductor muscle of Schistocerca gregaria, together with an experimental baseline estimate. This experimental estimate relies on dissecting out the muscles, weighing them, dissolving fiber bundles in acid and measuring fibre length. The digital estimates are based on CT scans of the heads, in which it is possible to measure muscle volume, fibre length, and muscle attachment area. After scanning the heads of the specimens and segmenting their mandibular apparatus, we used manual and automated approaches to measure the above mentioned values, to assess the comparability of the various PCSA methods and proxies, as well as the reliability of the automatization process. In addition, using the different PCSA estimates and muscle stress values from the literature, we model bite forces, which we compare to in vivo measurements from the same individuals.

SEB Conference 2022

Modelling bite force in insects: comparison of different PCSA approaches with in vivo measurements

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SEB’s Annual Conference is celebrated for creating the perfect composition of research, new discoveries and collaborative connections. Be creative and innovative by exchanging ideas and knowledge with masters of biology from all over the world.

2022 will find over 1500 experimental biologists from across the globe converging on the third-largest French city near the Mediterranean coast and the fastest-growing city in the country over the past 25 years.
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2022 found over 1500 experimental biologists from across the globe converging on the third-largest French city near the Mediterranean coast and the fastest-growing city in the country over the past 25 years - Montpellier, France.

Rice (Oryza sativa L.) is one of the important cereal grains and a staple food for more than 50% of the world’s population. Increases in global temperatures have a negative impact on crop productivity. Plants undergo a variety of physiological and biochemical changes as a result of temperature stress in order to adapt to higher temperatures. In this study, we have used 204 accessions from the Bengal and Assam Aus Panel (BAAP). A total of eight replicate plant per accession were grown. All plants were grown in the greenhouse until maturity; thereafter, five replicate plants were randomly selected, their panicles at anthesis stage marked and were transferred to large growth room at 38°C for 24 hours to assess high-temperature treatments. Three replicates plants were not heat treated. Fertility was assessed as the proportion of flowers filled. Heat treatment significantly (P&lt;0.0001) reduced fertility by 17.4% on average and there was a significant (P&lt;0.0001) differences among accessions. In addition to that, there was a significant (P&lt;0.001) interaction between accession and treatment. Heat tolerant cultivars have been identified including the aus reference cultivar DJ123. Genome Wide Association Studies (GWAS) using 2 million SNPs will be used to identify QTLs and candidate genes associated with heat tolerance in the BAAP.

Genotypic Variation in Heat Tolerance in Aus Rice During the Flowering Stage 

The Arabidopsis gynoecium is a complex structure composed of different tissues. Development is regulated by hormone interactions, especially auxin and cytokinin, as well as the spatiotemporal action of transcription factors and chromatin dynamics, including epigenetic modifications of core histones. SPT is bHLH transcription factor involved in gynoecium development, specifically affecting both auxin and cytokinin responses. GCN5 is a histone acetyltransferase with pleiotropic biological roles including auxin and cytokinin responses in the gynoecium. CLV1 is a receptor kinase, part of the CLAVATA signaling pathway which suppresses the expression of WUS in apical and floral meristems. Previous work has shown that clv1gcn5 double mutants exhibit a plethora of phenotypes including fasciated meristems and abnormal flowers with increased number of stamen and elongated gynoecia with enlarged apical regions and reduced ovaries. In the double mutants, the stem-cell-promoting transcription factor WUS is ectopically overexpressed in the gynoecia. To elucidate genetic interactions between SPT, CLV1 and GCN5 we created all genetic combination between spt, clv1 and gcn5 mutants. We show here that spt mutations largely suppress the phenotypes of clv1gcn5 gynoecia. The enlarged stigma and style and ovary formation are restored in sptclv1gcn5 plants compared to clv1gcn5 plants. The spt mutation also reverses the WUS ectopic overexpression in clv1gcn5 gynoecia. Interestingly spt gynoecia have also reduced WUS expression compared to wild type. These results suggest that SPT mediates the CLV1-GCN5 synergistic interaction during gynoecium development, potentially acting as a positive regulator of WUS expression in the gynoecium.

The role of SPT as a mediator of CLV1 and GCN5 interaction in gynoecium development in Arabidopsis

Tessellated material systems, meaning self-similar subunits arranged to form surface structures, are found throughout various unrelated taxa as well as over a broad range of sizes. An especially interesting system constitutes the armadillo carapace, a rare example of mammal armor involving hard mineralized elements, so called osteoderms embedded in soft connecting tissue. Previous work focused on the structural integrity and histology of individual osteoderms. However, the larger scale organization of armadillo tilings has never been subjected to a larger scale comparative analysis, although the mechanics (e.g. overall fracture resistance) of a tessellation is linked to the geometrical arrangement of its subunits. In this study we digitally examined osteoderm carapaces from micro-CT scans of twelve armadillo species, representing all major lineages within the armadillo phylogeny, in order to quantitatively compare and describe osteoderm shape as well as arrangement and distribution within the entire carapace. Results show that five- and six-sided osteoderms are tied to positive Gaussian curvature similar to the patches on a soccer ball, where a comparable combination of pentagons and hexagons is used. Furthermore, osteoderm number per surface area of entire carapaces reflects a deep split in armadillo phylogeny, separating the two major groups Dasypodidae and Chlamyphoridae. Additionally, Chlamyphorinae display an outstanding carapace architecture that consists of bands comprising exclusively rectangular osteoderms, potentially related to functional adaptations to a specialized nocturnal and fossorial lifestyle that requires increased mobility compared to other armadillo species, while possibly also leading to a decrease in protective performance of the carapace. Our study reveals a hitherto understudied diversity of carapace structure and function in armadillos, a deeper understanding of which will yield further insight into the evolutionary history of the taxon. 

 Tessellated osteoderm carapaces in extant armadillos 

Basal metabolic rate (BMR) – the rate of energy use needed to perform basic, life-sustaining functions – is a universal measure of metabolic rate allowing for comparisons of energy expenditure between species. Many animals inhabit a vast array of challenging environments, an example being living in confined spaces where oxygen levels are likely to be low. Previously it has been shown that species can exhibit both geno- and phenotypic adaptations in metabolic rate to exploit such unique niches. Living for extended periods of time within an enclosed space – in a burrow, den or crevice – will likely require certain physiological and morphological adaptations, and thus influence the biology of the species that occupy them. In this study we are taking a global look at the mammalian kingdom to understand the relationship between BMR and burrow use (fossoriality) in mammals. In particular, we aimed to determine if there was a trait within BMR associated with fossoriality, versus species which live above ground. We used pre-existing data for mammalian BMR and body mass, and 24-life history traits. To account for variation in body size, residual BMR was used (RBMR), controlling for any phylogenetic trends through a phylogenetic least squares model (PGLS) and an MCMCglmm, to account for inter- and intra-specific variation. Overall, mammalian metabolic rate is dictated primarily by environmental temperature. Only aquatic mammals had a detectable trait in RBMR and there was no significant differences in RBMR of terrestrial, fossorial and subterranean mammals, suggesting that species occupying a subterranean niche do not pay any baseline metabolic costs on account of their burrowing lifestyle. This may possibly explain why certain species can live above ground whilst also occupying an underground shelter at night or during other periods of the day. Aquatic mammals, however, had a significantly higher RBMR to all other groups apart from flying mammals. This significantly high BMR may also be due to the energetically demanding thermoregulatory need to maintaining a constant body temperature in cold water, particularly the Arctic/Antarctic waters that the large aquatic mammals in the study will be visiting seasonally, if not occupying year-round. This study has shown that environmental temperature is an important factor when exploring differences in mammalian BMR. Temperature can be used to predict BMR and therefore strongly infers whether a mammal is physiologically suited to living in a particular place or habitat. Changes to the environmental temperatures that these species are experiencing are likely to have knock on effects and alter population spread and change, as well as persistence of populations in certain areas. This highlights the importance of climate change and the largescale effects that small changes in environmental temperature may have on the diversity and distribution of mammalian species on the planet.

No evidence for a signal in mammalian basal metabolic rate associated with a fossorial lifestyle.

The enlarged brains of homeotherms bring behavioural advantages, but also incur high energy expenditures. The ‘expensive brain’ (EB) hypothesis posits that the energetic costs of the enlarged brain and the resulting increased cognitive abilities (CA) were met by either increased energy turnover or reduced allocation to other expensive organs, such as the gut. We tested the EB hypothesis by analysing correlated responses to selection in an experimental evolution model system, which comprises line types of laboratory mice selected for high or low basal metabolic rate (BMR), maximum (VO2max) metabolic rates and random-bred (unselected) lines. The traits are implicated in the evolution of homeothermy, having been pre-requisites for the encephalization and exceptional CA of mammals, including humans. High-BMR mice had bigger guts, but not brains, than mice of other line types. Yet, they were superior in the cognitive tasks carried out in both reward and avoidance learning contexts and had higher neuronal plasticity (indexed as the long-term potentiation) than their counterparts. Our data indicate that the evolutionary increase of CA in mammals was initially associated with increased BMR and brain plasticity. It was also fuelled by an enlarged gut, which was not traded off for brain size.

Brain size, gut size and cognitive abilities: the energy trade-offs tested in artificial selection experiment

Scorpion venoms contain different types of proteins, peptides, and molecules that can be used against predators or to immobilize prey. Toxins of venom are used for pharmaceutical purposes that require maintaining scorpions in captivity as long as possible for venom extraction purposes.
In this survey, four scorpion species from four genera; Androctonus, Buthus, Hottentotta, and Scorpio, were put in environments that vary in three variables: Diet, Temperature, Humidity. And it Was conducted to discover the influence of the captivity conditions on the venom quantity. During this research, we aim to explore these interactions, to optimize captivity conditions for more venom secretion efficiency. 
In the Light of this study, the results are very promising. This proves the huge impact of the environment on the scorpions. It could be the main key to studying other species or other venomous animals.











Performance of scorpion venom secretion in response to different captive conditions: diet, temperature and humidity on different genera of scorpions

Early-life conditions are important in shaping variation in individual quality and rates of ageing. Our understanding of this relationship between early-life conditions and late-life outcomes is particularly lacking in the context of age-related functional declines, which are often overlooked in favour of age-specific mortality and reproduction. Flight is a metabolically costly trait in insects and is closely associated with fitness in wild burying beetle populations, including Nicrophorus vespilloides. Therefore, flight represents an interesting avenue along which to examine ageing in an expensive functional trait that is closely related to fitness. We manipulated early-life environments through adjusting food availability to explore the role early-life-environments play in shaping lifespan and ageing in flight. Preliminary results find that individuals from higher quality early-life environments (abundance of food) exhibited superior peak flight-speed that was maintained across all assayed ages (10-99 days old). Peak flight speed was seen to decline only in the oldest-aged beetles (90+ days old), an age-range which exceeds that of most studies of ageing performed on this species . However, poorer-quality early-life environments (dearth of food) was associated with increased survival in later life. Beetles displayed a decreased propensity to fly at increasing ages, but no accompanying decrease in time spent in flight was detected . We show that high-quality early-life environments can contribute to improved measures of peak flight performance but have a less pronounced role in shaping patterns of age-related declines in flight. Furthermore, these early-life benefits may also be associated with reduced adult lifespan.

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Genotypic Variation in Heat Tolerance in Aus Rice During the Flowering Stage

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