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Carnivorous Nepenthes pitcher plants normally use motionless pitfall traps with slippery walls to catch their prey. Nepenthes gracilis uniquely exploits rain drop impacts on the roof-like pitcher lid to flick insects into the pitcher. This mechanism relies on three independent adaptations of the lid: a horizontal orientation, an attachment-reducing wax crystal coating of the lower lid surface, and high stiffness of the lid itself combined with an elastic ‘hinge’ that facilitates a torsion spring-like impact response. Previously, it has been postulated that this elastic element is located in the ‘neck’ region between pitcher and lid.  We superimposed three serial micro-computerised tomography (µ-CT) scans with different lid positions to show an asymmetric deformation reaching far into the pitcher body. Downward lid displacement deformed two distinct areas in the neck and the pitcher body, while upward displacement stretched the entire dorsal spine of the pitcher uniformly. Cross-sectional slices and densities from the µ-CT scans  showed that areas of maximal deformation coincide with local minima of the second moment of inertia, while stiffer areas are geometrically and structurally reinforced. Load-displacement trials revealed strongly asymmetric spring properties, with 83% larger downward than upward lid displacement under equal loading. Our results point to a key role of pitcher geometry for effective ‘springboard’ trapping in N. gracilis.

SEB Annual Conference 2022

Disentangling the influence of geometry and material properties on the &#39;springboard&#39; trapping mechanism in carnivorous Nepenthes gracilis pitcher plants

Metabolic rate is closely related to body size (body mass), but when mass increases, metabolic rate usually increases less. This allometric scaling relationship between metabolic rate and body mass is fundamental to biology and widely applied, but also one of the most debated concepts in integrative and comparative physiology, ecology, and evolutionary biology.

Several theories and hypotheses have been put forward to explain why and how metabolic rate scales with body mass, and why there appears to be variation in how steep this scaling relationship is among different taxa and physiological or ecological conditions (e.g. 'surface area', 'cell size', 'fractal distribution network', ‘dynamic energy budget’, and ‘metabolic-level boundaries’ theories or hypotheses). However, the lack of consensus on these important topics is a major barrier to our understanding of the pace at which organisms of different sizes and species expend energy and need to consume resources such as food and oxygen from the environment. It also limits our ability to predict how metabolic rate and body size (co)evolves, and how climate change affects metabolic demands and body sizes, as metabolic scaling exponents are used to model how these key organismal traits are affected by changing temperature and oxygen levels. The importance of metabolic scaling is clear, yet it remains one of the most controversial concepts in biology.

The overall aim of this satellite meeting is to bring together researchers working with metabolic scaling, to: (1) bring the field up to speed on state-of-the-art knowledge and research on metabolic scaling; (2) help understand how the vastly different views and opinions on metabolic scaling can persist despite more than a century of research (e.g. scaling in proportion to surface area or not, universal ¾-power scaling or not, governed by ecological vs. physical or geometric factors); and (3) identify and help streamline specific areas of research on metabolic scaling that will be particularly important for our further understanding of why and how metabolic rate scales with body size.

The meeting is being organised as part of the Animal Section of the SEB and will therefore have a focus on metabolic scaling of animals, but work on other organisms is welcome where this can provide insight into metabolic scaling in general.

Why and how does metabolic rate scale with body size?

The overall aim of this satellite meeting is to bring together researchers working with metabolic scaling, to: bring the field up to speed on state-of-the-art knowledge and research on metabolic scaling; help understand how the vastly different views and opinions on metabolic scaling can persist despite more than a century of research (e.g. scaling in proportion to surface area or not, universal ¾-power scaling or not, governed by ecological vs. physical or geometric factors); and identify and help streamline specific areas of research on metabolic scaling that will be particularly important for our further understanding of why and how metabolic rate scales with body size.

Disentangling the influence of geometry and material properties on the 'springboard' trapping mechanism in carnivorous Nepenthes gracilis pitcher plants

poster

Discover the art of creating extraordinary science at SEB’s Annual Conference at Le Corum Conference Center     in Montpellier, France from 5 to  8 July 2022.

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.
	<br><br><br>


Please register for the conference by clicking on this link:

https://www.sebiology.org/events/seb-annual-conference-2022/registration.html

The site will be open for registered participants closer to the event.

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 - Montpellier, France

Male mosquitoes detect and localise conspecific females by their flight tones using the Johnston's organs (JO), which detect antennal deflection under the influence of local particle motion. Acoustic behaviours of mosquitoes and their JO physiology have been investigated extensively within the frequency domain, yet the auditory sensory range and the behaviour of males at the initiation of phonotactic flights are not well known. In this study, we predict a maximum spatial sensory envelope for flying Culex quinquefasciatus by integrating the physiological tuning response of the male JO with female aeroacoustic signatures derived from numerical simulations. Our sensory envelope predictions were tested with a behavioural assay of free-flying male mosquitoes responding to a female-like artificial pure tone. The minimum detectable particle velocity observed during flight tests was in good agreement with our theoretical prediction formed by the peak JO sensitivity measured in previous studies. The iso-surface describing the minimal detectable particle velocity represents the quantitative auditory sensory range of approaching males and is directional with respect to the female attitude. Our results illuminate the intricacy of the mating behaviour dynamics and point to the importance of observing the attitude of flying mosquitoes to understand fully the sensory ecology of conspecific communication.

Auditory sensory range of male mosquitoes for the detection of female flight sound

Gene targeting (GT) is a method of precise genome engineering that can facilitate crop improvements that are central to meeting growing global food demands. Yet GT frequencies are very low in higher plants, mainly due to the low frequency of homologous recombination (HR) upon which GT relies, hindering realisation of the technology’s potential. Despite advancements, routine GT frequencies remain ~ &lt;1% and random integration of donor DNA and GT machinery causes problematic off-target effects; therefore, further improvements in GT frequency and accuracy are required. Here, a novel approach to address these problems is described, based on the application of DNA nanotechnology to GT in plants. In this approach random integration of the GT template will be prevented by concealing the free dsDNA ends of the repair template with nanostructure ‘caps’, as we propose that it is the free dsDNA ends that serve as the substrate for random integration. Here I report that capped structures containing a GFP reporter gene have been successfully transformed into plant cells via Agrobacterium and GFP expression detected on confocal microscopy. This demonstrates that these structures get into the plant cell nucleus and do not hinder enzymatic access to the gene, an important milestone in developing this technology. To test the nanostructure’s ability to improve GT efficiencies and reduce off target effects, an assay was established to measure GT rates with or without nanostructures. GT events have been successfully visualised by GFP expression in plant cells using confocal microscopy and flow cytometry. Next steps are to assay the rates of random integration using the nanostructure caps via qPCR-based assays and  to design, build and test the next generation of DNA nanostructures for prevention of random integration using DNA origami nanotechnology as a transgene delivery vehicle. Overall, this project brings together two exciting technologies to address the need for continued improvement in GT frequencies and preventing random integration. This will facilitate the improvement of plant genome engineering tools that can deliver vital improvements to crops required to bring sustainable agriculture into the 21st Century.
 



GM plants 2.0: Can DNA nanotechnology enhance plant genome engineering?

The structural integrity of biological armours derives in part from their geometric architectures. Armours often involve tessellations of self-similar structural elements, tiled together to form a shell-like surface. The boxfish carapace, for example, is comprised of polygonal mineralized dermal plates, called scutes, which are arranged in a complex geometric pattern. Unlike artificial armours, the exoskeleton grows along with the fish. Therefore, the relationship between the tessellation and the overall structure of the armour is critical to maintain protection throughout growth. Using high-resolution microCT data and segmentation algorithms, we quantify architectural aspects for each of the hundreds of scutes that build the armour, across an ontogenetic series of the longhorn cowfish Lactoria cornuta (from 1.7 cm to 13.6 cm body length), to investigate the maintenance of the tessellated structure throughout growth. We show that instead of adding scutes to enlarge the carapace surface, scute number remains constant, and carapace growth is achieved by scutes increasing in absolute volume, thickness, and especially width. Scutes also become relatively thinner and in areas of more complex topology (e.g. around fin insertions, mouth, anus) smaller scutes with more variable curvature are found. Besides providing insights into developmental constraints of this species related to carapace growth, our findings might also provide perspectives into natural strategies for construction of mutable tiled architectures.

Carapace growth of the longhorn cowfish Lactoria cornuta: A tessellated armour through ontogeny

Metabolic rate is a fundamental trait that influences and constraints the behaviour and performance of animals. However, conventional measures of metabolic rate, based on whole-animal oxygen consumption, often fail to show the predicted relationships with measures of animal performance since it is unclear what proportion of consumed oxygen is associated with ATP production. Thus the efficiency with which the mitochondria convert oxygen into ATP can be a better determinant of an animal performance capacity. In this study we examined whether mitochondrial efficiency predicts sustained swimming performance in the European minnow (Phoxinus phoxinus), a riverine fish. We measured individual critical swimming speed (Ucrit) followed by a measurement of maximum metabolic rate (MMR), standard metabolic rate (SMR) and mitochondrial function, predicting that measures of mitochondrial performance such as the ATP produced per molecule O2 consumed will be positively related to Ucrit and that the variation in Ucrit explained by mitochondrial function will be greater than any explained by MMR and SMR. Maximal rates of oxidative phosphorylation at the mitochondrial level were positively correlated with maximal oxidative metabolism of the whole fish. However, contrary to our predictions, swimming performance was unrelated to both organism-level and our measures of mitochondrial level metabolism, with Ucrit, MMR and SMR being influenced by individual body mass only. This suggests that, while mitochondrial function predicts whole-animal metabolism, it does not necessarily constrain animal locomotor performance, and the maximum sustained swimming speed is not determined by energy or oxygen supply. Further research is needed to determine the limits to physical performance.

Sustained swimming performance is independent of organism-level and mitochondrial-level metabolism in European minnows.

Many animals experience periods of reduction in food quality and quantity. Metabolic responses of animals to periods of reduction in crucial nutrient and food deprivation may have positive and negative impacts on the animal performance. I will present results on the mitochondrial responses to reduction in omega-3 dietary availability in a marine fish, golden grey mullet (Chelon auratus) and naturally-occurring periods of food deprivation in brown trout (Salmo trutta). 
We show that mitochondria of fish fed on the low omega 3 highly unsaturated fatty acids (n-3 HUFA) diet had higher mitochondrial efficiency than those of fish maintained on the high n-3 HUFA diet. Yet, mitochondrial efficiency varied up about 2-fold among individuals on the same dietary treatment, resulting in some fish consuming half the oxygen and energy substrate to produce the similar amount of ATP than conspecific on similar diet.
In another study, after a 2-week period of fasting, brown trout increased their oxidative phosphorylation (OXPHOS) respiration and decreased proton leakage (LEAK) respiration, suggesting a selective increase in the capacity to produce ATP without a concomitant increase in energy dissipated through proton leakage. However, this was associated with an almost two-fold increase in mitochondrial H2O2 levels.
Our results emphasize that (i) shift in energy metabolism in response to food change may help preserve limited resources but potentially come at a cost of increased oxidative stress; (ii) individual variation in mitochondrial efficiency may explain intraspecific variation in response to food changes.







Mitochondrial responses to varying diet quality and quantity: shift in metabolic efficiency and capacity.

Thermal acclimation is a mechanism that ectotherms use to maintain performance across a range of temperatures. In variable environments, acclimating quickly may be as important as acclimation capacity. The phenotypic changes comprising acclimation require energy and nutrients that ectotherms obtain from their diet. Thus, diet may be a critical factor determining acclimation rate and capacity. Using a temperate omnivorous fish, opaleye (Girella nigricans), we tested the hypotheses that diet can impact thermal acclimation rate and capacity for cardiac performance. We offered juvenile opaleye an ad-lib herbivorous (algae), carnivorous (shrimp), or omnivorous (algae and shrimp) diet for two weeks at 12°C and measured the thermal performance curve (TPC) for maximum heart rate (fHmax) and cardiac thermal limits. Next, we raised the temperature in the holding tanks from 12 to 20ºC, mimicking an abrupt heatwave, and independently sampled fish on days 1, 3, 7, and 14 post-temperature change using the same cardiac test. Acclimation capacity for fHmax was sensitive to diet, with the herbivorous treatment displaying the smallest change in fHmax. However, acclimation rate and all cardiac thermal limits were insensitive to diet, with &gt;60% of acclimation capacity occurring in the first 3 days at 20°C. Our results indicate that for generalist species, like opaleye, variation in diet is an important determinant of thermal performance on environmentally relevant timescales. Our findings also add to growing evidence that it is essential to integrate acclimation time into our predictions of species responses to temperature change.

Diet effects on acclimation rate and capacity for maximum heart rate in a temperate fish (Girella nigricans)

All animals must acquire food for energy, but there is a vast diversity in how different species and even different individuals approach this task. Individuals within a species appear to fall along a bold-shy continuum, whereby some fish acquire food aggressively and with seemingly high risk, while others appear more opportunistic and cautious. Greater food consumption generally results in faster growth, but only if the energy acquired through food is more than enough to compensate for heightened metabolism associated with a more active lifestyle. Fast-growing phenotypes also tend to have elevated baseline metabolism – at least when food is plentiful – which further complicates the link between food consumption and growth. The net energy gained from a meal (as calculated from the specific dynamic action (SDA) coefficient) is optimised with larger meal sizes, but the digestion of large meals can erode the aerobic metabolic scope available for other critical activities such as predator avoidance. Thus, it is expected that fish in predator-rich habitats should regulate meal sizes to maximise growth efficiency without dangerously compromising aerobic capacity, and this balance may differ between individual metabolic phenotypes. This presentation will discuss these complicated interplays with a goal to better understand what drives intraspecific differences in growth performance.

Why some fish grow faster than others: examining the interplay between metabolic phenotype, predator threat and growth performance

Mammalian cell culture is widely used for discovery and development. Recently, increasing
attention has been paid to the importance of maintaining physiologically-relevant conditions in cell
culture. Although oxygen level is a particularly important consideration, it is rarely regulated by
experimentalists. The atmospheric O2
levels commonly used in cell culture are significantly higher
than those experienced by most mammalian cells in vivo, leaving cells susceptible to oxidative damage, senescence, transformation, and otherwise aberrant physiology. A barrier to incorporating O2
regulation into most cell culture workflows has been the expense of investing in new equipment, as
the vast majority of laboratory CO2
incubators do not regulate O2
. Here, we describe an inexpensive
(<CAD 1000), portable and user-friendly O2/CO2
incubator that can establish and maintain physiological O2
, CO2
, and temperature values within their physiological ranges. We used an Arduino-based
approach to add O2 and CO2 control to a temperature-regulating egg incubator. Our incubator
was tested against a commercial laboratory O2/CO2
incubator. Using Presens OxoDish technology, we demonstrate that at a setpoint value of 5% gas-phase incubator O2
, media O2 averaged
5.03 (SD = 0.03) with a range of 4.98–5.09%. MCF7, LNCaP and C2C12 cell lines cultured in the
incubator displayed normal morphology, proliferation, and viability. Culture for up to one week
produced no contamination. Thus, our incubator provides an inexpensive means of maintaining
physioxia in routine mammalian cell culture.

An Inexpensive Incubator for Mammalian Cell Culture Capable of Regulating O2, CO2, and Temperature

Phosphate sensing SPX proteins control arbuscule life-time in Medicago

Contagious cancers are somatic cell lineages that are transmitted between individuals via the transfer of living tumour cells, meaning that they can survive beyond the host that spawned them. In other words: they are tumours that metastasize across different hosts. For this reason, they represent an interesting and unique model to illuminate insights into the general mechanisms of cancer development and metastasis. Since 2016, we have collected 6,300 common cockles from 33 locations covering all the Atlantic Coast of Europe, from Morocco to Russia. 342 cockles (5.4%, 350/6,300) from 5 different countries were diagnosed with cancer by cytological and histological methods. The contagious nature of these cancer samples was assessed with sequencing data as it has been previously done in dogs and Tasmanian devils that also suffer from contagious cancers. Phylogenetic analyses based on variants from mitochondrial DNA revealed nine paraphyletic clonal cancer lineages, some with a distribution extending over thousands of miles. The analysis of nuclear structural variants, however, does not reveal nine cancer lineages, seeming to suggest a maximum of two independent origins of the disease. Multiple captures of the mitochondria from the host cells by the cancer lineages, throughout the long-term evolution of these two cancer lineages, may explain these contradicting observations. This work represents the most comprehensive analysis of a marine contagious cancer performed to date and reveals that mitochondrial and nuclear DNA of cockle transmissible cancers tell slightly different evolutionary stories that are part of the same book.

Disentangling the influence of geometry and material properties on the 'springboard' trapping mechanism in carnivorous Nepenthes gracilis pitcher plants

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