Stage Sensitivity to Food Limitation for a Generalist Arthropod Predator, Pterostichus cupreus (Coleoptera: Carabidae)

Understanding the relationship between egg size, development time, and juvenile size is critical to explaining patterns of life-history evolution in marine invertebrates. Currently there is conflicting information about the effects of changes in egg size on the life histories of echinoid echinoderms. We sought to resolve this conflict by manipulating egg size and food level during the development of two planktotrophic echinoid echinoderms: the green sea urchin, Strongylocentrotus droebachiensis and the sand dollar, Echinarachnius parma. Based on comparative datasets, we predicted that decreasing food availability and egg size would increase development time and reduce juvenile size. To test our prediction, blastomere separations were performed in both species at the two-cell stage to reduce egg volume by 50%, producing whole- and half-size larvae that were reared to metamorphosis under high or low food levels. Upon settlement, age at metamorphosis, juvenile size, spine number, and spine length were measured. As predicted, reducing egg size and food availability significantly increased age at metamorphosis and reduced juvenile quality. Along with previous egg size manipulations in other echinoids, this study suggests that the relationship between egg size, development time, and juvenile size is strongly dependent upon the initial size of the egg.

Article Figures and data Abstract eLife digest Introduction Results Discussion Materials and methods References Decision letter Author response Article and author information Metrics Abstract How the nervous system internally represents environmental food availability is poorly understood. Here, we show that quantitative information about food abundance is encoded by combinatorial neuron-specific gene-expression of conserved TGFβ and serotonin pathway components in Caenorhabditis elegans. Crosstalk and auto-regulation between these pathways alters the shape, dynamic range, and population variance of the gene-expression responses of daf-7 (TGFβ) and tph-1 (tryptophan hydroxylase) to food availability. These intricate regulatory features provide distinct mechanisms for TGFβ and serotonin signaling to tune the accuracy of this multi-neuron code: daf-7 primarily regulates gene-expression variability, while tph-1 primarily regulates the dynamic range of gene-expression responses. This code is functional because daf-7 and tph-1 mutations bidirectionally attenuate food level-dependent changes in lifespan. Our results reveal a neural code for food abundance and demonstrate that gene expression serves as an additional layer of information processing in the nervous system to control long-term physiology. https://doi.org/10.7554/eLife.06259.001 eLife digest To maximize their chances of survival, animals need to be able to sense changes in the abundance of food in their environment and respond in an appropriate manner. The nervous system is able to sense cues from the environment and coordinate responses in the whole organism, but it is not clear how this leads to long-term changes in the organism's biology. In nematode worms, two genes called daf-7 and tph-1 appear to be involved in connecting the sensing of food availability with changes in the biology of the organism. The daf-7 gene encodes a hormone, while tph-1 encodes an enzyme that makes a neurochemical called serotonin. Here, Entchev, Patel, Zhan et al. found that daf-7 and tph-1 genes are active in three pairs of neurons in nematode worms. The experiments show that these neurons collectively form a circuit that carries information about the abundance of food, which leads to changes in how long the worms live. When this circuit was disrupted by removing these genes, the worms' ability to adjust their lifespan in response to changes in the availability of food was weakened, likely because they were unable to sense food. The experiments also show that the circuit regulates itself, largely because daf-7 and tph-1 are able to control each-other's activity. Together, these results suggest that changing the activity of certain genes in neurons enables nematode worms to alter their biology in response to changes in the availability of food. Neurons in the brain use electrical activity to communicate and process information and Entchev, Patel, Zhan et al.'s findings imply that gene activity can also perform a similar role. https://doi.org/10.7554/eLife.06259.002 Introduction All organisms need to accurately assess their environment to respond to changes that impact their survival. Environmental changes such as food availability can lead to alterations in organismal physiology, such as stress resistance and metabolic states that have consequences for clinically important outputs such as disease progression, health, fecundity and lifespan (Libert and Pletcher, 2007). Many conserved genetic mechanisms that govern these alterations to physiology have been identified (Libert and Pletcher, 2007; Berthoud and Morrison, 2008; Rother et al., 2008; Alcedo et al., 2010; Koch and Horvath, 2014). Yet, how these genetic pathways encode and process information about the environment to elicit physiological outputs in vivo is unclear at a quantitative and mechanistic level, despite their importance for health and disease. In animals, the nervous system is the central site for processing sensory information and coordinates organism-wide responses to changing conditions. Food availability is a critical environmental variable that modulates metabolism and other physiological outputs via neuroendocrine circuits (Berthoud and Morrison, 2008; Rother et al., 2008; Alcedo et al., 2010; Koch and Horvath, 2014). In contrast to well-studied sensory modalities such as vision and olfaction (Baier, 2013; Wilson, 2013), where neural processing occurs on short timescales using electrical signals, how food availability is internally represented across a broad range of inputs to regulate long-term, food-related physiological responses remains virtually unknown. A particularly interesting food-related response is the role of dietary restriction (DR) in modulating lifespan in diverse species (Bishop and Guarente, 2007; Mair and Dillin, 2008; Fontana et al., 2010; Alic and Partridge, 2011). DR occurs through changes that likely happen over long timescales (hours to days), unlike fast behavioral responses to visual or olfactory cues. Neural gene expression also occurs over long timescales (minutes to hours) and is thus well suited for functionally encoding food abundance during DR. In Caenorhabditis elegans, daf-7 and tph-1 are conserved components of neural TGFβ and serotonin signaling pathways, respectively, and are associated with food sensing and modulation of organismal physiology. daf-7 encodes a TGFβ family member (Ren et al., 1996), while tph-1 encodes tryptophan hydroxylase, the rate-limiting enzyme for serotonin synthesis (Sze et al., 2000). In C. elegans, TGFβ and serotonin signaling affect lifespan and metabolism, consistent with conserved roles from invertebrates to mammals (Sze et al., 2000; Ashrafi, 2007; Murakami and Murakami, 2007; Petrascheck et al., 2007; Shaw et al., 2007; Brown and Schneyer, 2010; Oury and Karsenty, 2011). tph-1 and daf-7 are expressed in an environmentally responsive manner in specific neurons with food-related functions (Ren et al., 1996; Schackwitz et al., 1996; Sze et al., 2000; Zhang et al., 2005; Chang et al., 2006; Liang et al., 2006; Greer et al., 2008; Pocock and Hobert, 2010). daf-7 is expressed in the ASI sensory neurons, whose activities are responsive to bacterial food (Ren et al., 1996; Gallagher et al., 2013; Zaslaver et al., 2015). Starvation reduces daf-7 expression in ASI, and laser ablations of ASI extend lifespan, consistent with the role of daf-7 and other ASI-expressed genes in modulating lifespan (Ren et al., 1996; Alcedo and Kenyon, 2004; Bishop and Guarente, 2007). tph-1 is expressed in the NSM foregut neurons, the ADF sensory neurons, and the HSN motorneurons involved in egg-laying (Sze et al., 2000). Both serotonin signaling mutants and NSM ablation affect food-modulated locomotion, consistent with the idea that serotonin from NSM acts in this food-related response (Sawin et al., 2000). In the food-responsive ADF neurons (Zaslaver et al., 2015), tph-1 expression is responsive to pathogenic bacteria and starvation, to respectively mediate aversive olfactory plasticity and stress responses (Zhang et al., 2005; Liang et al., 2006). daf-7 and tph-1 are therefore strong candidates for mediating the link between environmental cues and longevity. Nonetheless, how these genes cooperate to quantitatively encode a broad range of food levels to modulate lifespan is unknown. Gene-expression responses to food cues have largely been studied as ON/OFF switches to the presence or absence of food (Zinke et al., 2002; Baugh et al., 2009). Because food abundance is a continuous variable, we sought to understand how expression of tph-1 and daf-7 could allow animals to distinguish multiple food levels. Furthermore, gene expression is inherently variable (Eldar and Elowitz, 2010), but this property is rarely studied in vivo in multicellular animals; thus we also sought to determine how gene-expression variability affects the ability of the worm to encode its environment. Here we show that daf-7 and tph-1 expression in three pairs of neurons forms a distributed circuit that quantitatively encodes food abundance and mediates dietary effects on lifespan in C. elegans. Specific disruptions to this circuit resulted in corresponding attenuation in the ability to discriminate between food levels in both the gene-expression code and lifespan output. We found that this circuit tunes its own accuracy, largely via the regulation of the dynamic range and variability of food-responsive gene expression by tph-1 and daf-7 signalling, respectively. Our work suggests that neural regulation of gene expression in conserved pathways can couple environmental sensation to physiological output, and highlights a novel mechanism for information processing by the nervous system to impact physiology. Results Two neuronal genes mediate bidirectional effects of DR on lifespan During DR, lifespan increases as food levels are decreased from ad libitum conditions until reaching a maximum, beyond which further food reduction lowers lifespan (Bishop and Guarente, 2007; Mair and Dillin, 2008; Fontana et al., 2010; Alic and Partridge, 2011). To fully understand the response to food levels that C. elegans might encounter in the wild (Felix and Duveau, 2012), we modified a well-established DR protocol (Greer et al., 2007) (Figure 1A) to measure the lifespans of wildtype animals shifted as day 2 adults to 19 concentrations of the Escherichia coli food source across ∼11 orders of magnitude (Figure 1B, Figure 1—figure supplement 1 and Figure 1—source data 1). We inhibited progeny production with egg-5(RNAi) (Figure 1A) to prevent matricide due to internal hatching at low food levels. This treatment does not affect the lifespan response to food; similar responses were observed in wildtype animals without egg-5(RNAi) (Figure 1—figure supplement 1), and are found in the literature where similar subsets of food ranges were tested using other DR protocols (below). Figure 1 with 2 supplements see all Download asset Open asset Two neuronal genes, daf-7 and tph-1, shape a complex, multiphasic relationship between lifespan and food availability. (A) Protocol for maintaining animals at different food levels for lifespan and imaging experiments. Effects of initiating different dietary restriction (DR) on different days are shown in Figure 1—figure supplement 1A,B. (B) Mean lifespan of wildtype worms subjected to 19 food levels ranging from 0–3.5 × 1010 bacterial cells/ml at 20°C. Points denoting key features in the food response and used as food conditions in subsequent experiments are highlighted. Figure 1—figure supplement 1D shows that these lifespan responses have similar shapes across different temperatures. The lifespan data are shown in Figure 1—source data 1. (C) Mean lifespans of wildtype and mutant animals across the six food levels indicated in (B) show that loss of tph-1 and daf-7 preserves the pattern but attenuates the range of the lifespan response. Genotypes are indicated by the legends below (E) and (F). The lifespan data are shown in Figure 1—source data 2, and statistical comparisons between the different genotypes and food levels are shown in Figure 1—source data 3. (D) tph-1 and daf-7 modulation of lifespan is bidirectional and their epistatic relationship is food-specific. The epistatic interaction between the two genes in the tph-1(−); daf-7(−) double mutant differs depending on food level. The double mutant resembled the tph-1(−) single mutant in the absence of a bacterial food source and resembled the daf-7(−) single mutant at a high bacterial food concentration. (E) Range of food-induced lifespan modulation for each genotype. Range is defined by the difference between the highest and lowest mean lifespan response across the six food levels. (F) Average of the mean lifespan responses across all food levels for each genotype reveals a consistent, food-independent baseline lifespan response. The schedule for transferring animals to different conditions in these lifespans are shown in Figure 1—figure supplement 2. https://doi.org/10.7554/eLife.06259.003 Figure 1—source data 1 Summary of wild type lifespan outputs under the full range of food levels tested. https://doi.org/10.7554/eLife.06259.004 Download elife-06259-fig1-data1-v1.xlsx Figure 1—source data 2 Summary of wild type and mutant lifespan outputs under six selected food levels. https://doi.org/10.7554/eLife.06259.005 Download elife-06259-fig1-data2-v1.xlsx Figure 1—source data 3 Statistical significance of lifespan modulation across food levels and genetic backgrounds. https://doi.org/10.7554/eLife.06259.006 Download elife-06259-fig1-data3-v1.xlsx We uncovered a multiphasic relationship between bacterial abundance and longevity that is more complex than previously reported with smaller concentration ranges (Figure 1B) (Greer et al., 2007; Greer and Brunet, 2009; Ching et al., 2010). We found that lifespan increased and then decreased as bacterial concentration was reduced from the highest level, forming a DR response consistent with prior reports at high food ranges (Bishop and Guarente, 2007; Panowski et al., 2007; Greer and Brunet, 2009; Mair et al., 2009; Ching et al., 2010). Surprisingly, upon further reduction, lifespan increased again till a plateau was reached, suggesting that the initial decrease was not due to limiting nutrients. The longest lifespans occurred in the absence of bacteria, where the magnitudes of these effects were consistent with published dietary deprivation experiments (Kaeberlein et al., 2006; Lee et al., 2006). This relationship between lifespan and food abundance was maintained across temperatures (Figure 1—figure supplement 1), suggesting a robust food-sensing process. This multiphasic food response may reflect trade-offs between multiple food-regulated processes as previously discussed (Kaeberlein et al., 2006; Lee et al., 2006). Here we used the complex lifespan response as a functional basis for understanding how neuronal gene expression could encode food abundance. To understand how the multiphasic lifespan response to food abundance is regulated, we measured the lifespan of daf-7 and tph-1 null mutants across six bacterial concentrations that captured the complexity of broad-range DR (circled in Figure 1B). Prior studies suggested that daf-7 and tph-1 mediate lifespan extension (Murakami and Murakami, 2007; Shaw et al., 2007; van der Goot et al., 2012). We showed that their effects were in fact bidirectional: these genes could either extend or reduce lifespan in a food-specific manner (Figure 1C, Figure 1—source data 2, 3). Both single mutants had reduced lifespans at low food levels and increased lifespan at 6 × 108 cells/ml in comparison to wildtype; additionally, daf-7(−) mutants were long-lived at the highest food level (Figure 1C). The magnitude of lifespan changes we observed at high food levels (1 × 1010 cells/ml) were comparable to prior studies performed at ad libitum food conditions (Murakami and Murakami, 2007; Shaw et al., 2007). Intriguingly, tph-1 and daf-7 influenced the longevity response more strongly at low and high bacterial concentrations respectively (Figure 1D), suggesting that they act at different but overlapping ranges of food. Furthermore, the double mutant resembled the tph-1(−) mutant at low bacterial levels and the daf-7(−) mutant at high bacterial levels (Figure 1D), suggesting that these genes act in parallel rather than in a linear pathway. Together, these phenotypes indicate that daf-7(−) and tph-1(−) mutants were neither intrinsically long- nor short-lived; instead, their phenotypes and genetic interactions were modulated by extensive gene-environment interactions. Rather than altering the basic pattern of the lifespan response to food, loss of tph-1 or daf-7, either alone or in combination, dampened food responsiveness by bidirectionally attenuating extension and reduction of lifespan due to DR (Figure 1C,D). This effect was manifested in the diminished range of lifespans across all food levels in both the daf-7(−) and tph-1(−) single mutants, which was further reduced in the double mutant (Figure 1E). This result also supports the idea that these genes act in parallel pathways. Furthermore, the mean lifespan across all food levels were similar in all the genotypes tested (Figure 1F), suggesting that mutations in tph-1 and daf-7 lowered the food-responsive component of longevity around a consistent, food-independent lifespan that may be specified by other environmental parameters such as temperature (Figure 1E and Figure 1—figure supplement 1). This bidirectional dampening of the food response and preservation of an underlying lifespan differs from previously described DR regulators, such as aak-2, daf-16, pha-4 and skn-1, whose mutants abolish DR-mediated lifespan extension (Bishop and Guarente, 2007; Greer et al., 2007; Panowski et al., 2007). Thus, tph-1 and daf-7 mutants reveal a previously unobserved DR phenotype, and our results suggest that these genes mediate a bidirectional lifespan response to DR. Neuronal expression of daf-7 and tph-1 encodes food abundance tph-1 is expressed in the ADF sensory neurons, the NSM neurons within the foregut, and the hermaphrodite-specific HSN motor neurons (Sze et al., 2000). daf-7 is expressed in a single pair of ASI sensory neurons (Ren et al., 1996; Schackwitz et al., 1996). To determine whether tph-1 and daf-7 act in these neurons to modulate lifespan, we expressed these genes in specific neurons and tested their ability to rescue the lifespan phenotypes in the tph-1(−); daf-7(−) double mutant. Expression of tph-1 in either ADF or NSM neurons (Figure 2A–C) or of daf-7 in ASI neurons (Figure 2D,E) could rescue the lifespan phenotypes at low and high food levels, respectively. These results indicate that the activity of tph-1 and daf-7 in these respective neurons are relevant to lifespan modulation. Figure 2 Download asset Open asset Neuron-specific rescue of lifespan phenotypes. (A) Lifespan outcomes of wildtype, tph-1(−) and daf-7(−) single mutants and the tph-1(−); daf-7(−) double mutant indicates that the double mutant closely resembles the tph-1(−) mutant in the absence of a bacterial food source. (B) In the absence of bacterial food, restoration of tph-1 activity in the NSM neurons via the expression of a tph-1 cDNA driven by the ceh-2 promoter rescues the lifespan reduction observed in the tph-1(−); daf-7(−) double mutants. (C) Restoration of tph-1 expression in the ADF neurons via the srh-142 promoter also shows reversal of the lifespan reduction. (D) Lifespan outcomes of wildtype, tph-1(−) and daf-7(−) single mutants and the tph-1(−); daf-7(−) double mutant indicates that the double mutant closely resembles the daf-7(−) mutant at a high concentration of the bacterial food source. (E) At high food level, restoration of daf-7 expression in the ASI neurons via the expression of daf-7 under the gpa-4 promoter reverses the lifespan extension observed in the tph-1(−); daf-7(−) double mutants. All comparisons are drawn against non-transgenic siblings of animals bearing the extrachromosomal array of interest. https://doi.org/10.7554/eLife.06259.009 Previous studies showed that daf-7 and tph-1 expression are regulated by environmental cues (Ren et al., 1996; Schackwitz et al., 1996; Sze et al., 2000; Zhang et al., 2005; Chang et al., 2006; Liang et al., 2006; Greer et al., 2008; Pocock and Hobert, 2010). However, their expression profiles over a broad range of inputs remain unknown because manual studies limit the number of animals and environmental conditions that can be feasibly studied in a consistent way. To overcome these limitations, we used an automated, high-throughput microfluidic-based platform (Figure 3A and Figure 3—figure supplement 1) (Chung et al., 2008; Crane et al., 2012) for quantitative large-scale imaging of individual worms bearing single-copy fluorescent transcriptional reporters for both tph-1 and daf-7 (Ptph-1::mCherry and Pdaf-7::Venus) across different food levels (Figure 3B). For brevity, we refer to these reporter activities as tph-1 and daf-7 expression. Our reporters contain the same regulatory regions as published reporters that have been well validated, and show identical expression patterns (Ren et al., 1996; Schackwitz et al., 1996; Sze et al., 2000; Zhang et al., 2005; Chang et al., 2006; Liang et al., 2006; Greer et al., 2008; Pocock and Hobert, 2010) (Figure 3B). Starvation, hypoxia, or pathogenic bacteria alter both tph-1 reporter expression and serotonin levels (Zhang et al., 2005; Liang et al., 2006; Pocock and Hobert, 2010), while corresponding changes occur in daf-7 RNA levels and daf-7 reporter expression (Ren et al., 1996). These published results indicate that tph-1 and daf-7 reporters are faithful readouts for the expression of their respective genes (see ‘Materials and methods’ for additional details on reporter validation). Figure 3 with 1 supplement see all Download asset Open asset High-throughput quantitative imaging of tph-1 and daf-7 fluorescent reporters reveals neuron-specific, graded expression responses to food level. (A) Microfluidic system enabling high-throughput, neuron-specific quantitative imaging of gene expression in a large number of individual animals. Animals are transferred from culture plates to a liquid suspension at day 6 of adulthood and then loaded into the device for imaging. Figure 3—figure supplement 1 shows an overview of this imaging system. (B) Representative merged fluorescent image of transgenic worm with red and green fluorescent reporters for tph-1 and daf-7 transcriptional activity. Shapes indicate locations and identities of specific neurons. (C) Mean expression profiles of tph-1 in NSM (Ptph-1NSM) and ADF (Ptph-1ADF), and daf-7 in ASI (Pdaf-7ASI) across six different food levels are neuron-specific and largely non-monotonic. Measurements are normalized to the highest mean expression response observed in each respective neuron; error bars are SEM. (D) Distribution of the expression responses of tph-1 in NSM and ADF and daf-7 in ASI at different food levels. Means are indicated by the solid lighter-shade lines behind the distributions. Dashed line denotes the highest mean expression for each neuron, which was used for normalization. https://doi.org/10.7554/eLife.06259.010 We measured tph-1 expression levels in both NSM and ADF, and daf-7 in ASI, in animals exposed to the same six food levels that define our complex DR response (Figure 3C). Remarkably, we found that each neuron type had a specific pattern of activity across the six food levels (Figure 3C). Even with respect to a single gene, tph-1, the expression response in NSM differed from that in ADF, suggesting non-redundant roles of NSM and ADF in encoding bacterial abundance. Consistent with low tph-1 expression in the absence of food (Figure 3C), serotonin levels were reduced in NSM and ADF after starvation (‘Materials and methods’ and Liang et al., 2006). Notably, the responses of tph-1 in NSM and daf-7 in ASI were non-monotonic, prohibiting unique representation of the food level using either of these readouts The dynamic range and variability of the three expression patterns also suggesting different the sensory from food in different neurons (Figure the of reporter for each neuron type shifted in a graded manner across the six bacterial concentrations (Figure that the expression of tph-1 and daf-7 could provide information about a continuous range of environmental inputs for individual animals. This graded response with pathways, such as signalling, that outputs with a number of where the population to changing environmental conditions by of from to 1996). gene expression may be used to internally environmental conditions and mediate long-term physiological outputs such as we to expression in individual neurons with lifespan across food levels. We found that the expression levels of the individual genes in each neuron alone were to either food inputs or lifespan outputs (Figure largely due to expression and lifespan responses 3C). However, encoding across multiple neurons can the by animals to use a combinatorial to internally environmental conditions with (Figure Figure Download asset Open asset The of all neuronal gene-expression readouts a unique internal representation of food levels. (A) between individual gene-expression profiles and the lifespan responses across the six food levels indicates that the individual readouts are to lifespan responses. (B) The of tph-1 in NSM (Ptph-1NSM) and ADF and daf-7 in ASI (Pdaf-7ASI) a encoding of both food inputs and lifespan (C) The ability of expression and lifespan readouts to respond to and food conditions can be by using the readouts of to the food conditions. The results can be represented by where the in each indicate the with which are for a food level. readouts result in high represented by a overlapping response profiles result in low represented by a (D) the of tph-1 and daf-7 readouts or in similar encoding to that of lifespan outputs in wildtype animals. To assess the accuracy of the internal representation of food levels on the graded combinatorial expression of tph-1 and daf-7 in wildtype animals, we a (Figure and the gene-expression we this to the food level that individual animals were exposed This into the of gene and thus both and variance to decreased between the from different food levels leads to increased accuracy (Figure We neuronal encoding with a to the population of expression data at each food level. We food on expression in and then to the food level to determine the accuracy of the gene-expression responses. The results were as the of each food the food for each population (Figure the expression were distinct across food levels, a was in a strongly (Figure the then the food level was and the in the were to the number of food conditions tested (Figure expression data from ADF or ASI we showed that each neuronal had (Figure When neuron pairs were and particularly all three neuron pairs were the accuracy (Figure This result suggests that non-redundant encoding by each neuron pair the accuracy of the this system was at the highest and lowest food levels, consistent with the and of C. elegans in the wild (Felix and Duveau, 2012). the bacterial level, 6 × 108 where we observed the lowest lifespan, also showed a the graded and encoding may allow certain food levels, the ability was also by in the responses. To determine the accuracy of gene expression was for modulating lifespan, we how accurately the lifespan could be used to the food level using a similar This is important because the accuracy of the for the accuracy in the internal the accuracy of both the representation and be that the representation carries information for the output. In this we whether lifespan could also be used to the food level by an using on the of our Remarkably, the accuracy of lifespan was similar to that of gene expression (Figure that

Influence of temperature and food availability on the biochemical composition and mortality of juvenile Mercenaria mercenaria (L.) during the over-winter period

Miguel Tejedo, Ricardo Reques, Effects of Egg Size and Density on Metamorphic Traits in Tadpoles of the Natterjack Toad (Bufo calamita), Journal of Herpetology, Vol. 26, No. 2 (Jun., 1992), pp. 146-152

The toxic activity of three novel compounds (Pyridalyl, Radical, Spinosad) and conventional insecticide (Lannate) against the second and fourth instars of the lab and field strains of Spodoptera littoralis were evaluated under laboratory conditions.The obtained 2 nd and 4 th instar larvae of the field and lab strains were fed for 48h on castor leaves, Ricinus communis were dipped for 15 seconds in series of concentrations of each tested compounds to determine the LC50 values.Radical was the most toxic one against both of 2 nd and 4 th instar larvae of the susceptible and resistance strains.The LC50 values were 1.1, 2.7 and 1.95, 4.4 ppm for both second and fourth instar larvae of the two susceptible and resistance strains, respectively While, Pyridalyl was the second one, the LC50 values were 1.8, 5 and 6.2, 9.4 ppm for the two instars of both strains, respectively.Whereas, Lannate was the third one, its LC50 values were 3.9, 6 and 11, 19 ppm of both instars for of both strains, respectively.While Spinosad was the fourth one, its LC50 values were 21, 62.5 and 31.3 and 130 ppm of both instars for both strains, respectively.The biological activities of larvae were affected with the treatment of the second and fourth instars of both lab and field strains with the four tested compounds.The effect varied according to the strain, larval instar and tested compound, therefore, the larval treatment for both instars of the both strains with the four tested compounds caused highly significantly effect led to pupation and adult emergence percentages decrease at the tested four treatments.While, Pyridalyl treatment had the highest effect in larval duration, pupal and adult malformations increase; adult fecundity, fertility and longevity decrease in case of larval treatment of the two instars of both strains with this compound and it had the highest effect in pupal duration increase and weight decrease in case of treatment of the second instar of the field strain with this compound and it was effective against the sex ratios, the males increase and females decrease, as respect to control, with the treatment of fourth instar of lab strain with it.Whereas, Radical had the greatest effect on adult fecundity and fertility with fourth instar treatment of field strain with it.Also, it was effective against the pupal weight with the treated second instar of field strain and it had the highest effect on larval duration and adult malformations in case of the treatment of the second and fourth instars of lab strain with it and it had an adversely effect on the sex ratio (it caused males decrease and females increase) with the treatment of fourth instar of field strain with it.However, Spinosad had the highest effect on both adult fecundity and fertility with the treated fourth instar of field strain and it was the effect on adult malformations with the treatment of both instars of lab strain with it and affect the sex ratio, lead to males increase and females decrease with the treatment of fourth instar of lab strain with it.While, Lannate, had the highest effect on pupal malformations with the larval treatment of both instars of both strains with it and it was effective on pupal weight and adult malformations with the treatment of either second or second and fourth instar together of field strain with it also, it was effective on adult fecundity, fertility and longevity with the treated fourth instar of field strain and it had the highest effect on larval duration with the treatment of the fourth instar of the lab strain with it.

The toxic activity of three novel compounds( Pyridayl, Radical, Spinosad) and conventional insecticide( Lannate)against the second and fourth instars of the Lab. and Field strains of Spodoptera littoralis. was evaluated under laboratory conditions through determination their LC50 values.` Radical was the most toxic one against both of 2nd and 4th instar larvae of the lab. and field strains . The LC50values were 1.1 , 2.7 and 1.95 , 4.4 ppm for both second and fourth instar larvae of the two lab. and field strains , respectively . Pyridalyl was the second one with the LC50values of 1.8 , 5 and 6.2 , 9.4 ppm for the two instars of both strains, respectively. Lannate was the third one ,its LC50values were 3.9, 6 and 11,19ppm for both instars of the strains , respectively. While , Spinosad was the fourth one, its LC50values were 21, 62.5 and 31.3 and 130 ppm for both instars of the strains, respectively. All the treated larvae were biologically affected by the four tested compounds . The effect varied according to the strain , larval instar and tested compound. Therefore ,the treated larvae were significantly affected and resulted in decreased pupation and adult emergence percentages. While , Pyridalyl treatment had the strongest effect in larval duration, pupal and adult malformations increase, adult fecundity ,fertility and longevity decrease in case of larval treatment of the two instars of both strains , and it had the highest effect in pupal duration increase and weight decrease in case of treatment of the second instar of the field strain with this compound, and it was effective against the sex ratios, it induced the males increase and females decrease, as respect to control, with the treatment of fourth instar of lab. strain . Whereas, Radical ,had the greatest effect on adult fecundity and fertility with the of fourth instar treatment of field strain .Also it was effective against the pupal weight with the treated second instar of field strain and it had the highest effect on larval duration and adult malformations in case of the treatment of the second and fourth instars of lab strain .However, it had an adversely effect on the sex ratio (it caused males decrease and females increase) with the treatment of fourth instar of field strain. Spinosad had the highest effect on both adult fecundity and fertility with the treated fourth instar of field strain and it induced the strongest effect of adult malformations with the treatment of both instars of lab. strain , and it affect the sex ratio, lead to males increase and females decrease with the treatment of fourth instar of lab .strain. Lannate , had the highest effect on pupal malformations with the larval treatment of both instars of both strains ,and it was effective on pupal weight and adult malformations with the treatment of either second or second and fourth instar together of field strain ,also, it was effective on adult fecundity, fertility and longevity with the treated fourth instar of field strain and it had the strongest effect on larval duration with the treatment of the fourth instar of the lab. strain .

The evolution of traits in hosts may be influenced by their parasites and vice versa and a coevolutionary arms race often develops between the two. As part of such an arms race, the common cuckoo mimics the eggs of its hosts to avoid egg rejection. Traits related to this arms race may also be influenced by climatic conditions, such as temperature, affecting, for example, food availability and, thus, female condition and egg size (therefore may reflect Bergmann’s rule or the resource rule). The potential interaction between coevolution and climate has rarely been studied. We investigated whether egg and body size of cuckoos and reed warblers from Britain and Denmark had undergone change between 1868 and 1956, and whether such changes were correlated with climatic factors. Cuckoo egg size decreased during the studied period while warbler egg size remained stable. Hence, cuckoo and warbler eggs have become more similar in size over time. Cuckoo egg volume decreased with increasing annual precipitation, but annual precipitation decreased over time. Warbler egg volume increased with spring temperatures (which could not reflect Bergmann’s rule, but may support the resource rule). Hence, it seems that the measured climatic indices did not affect cuckoo egg size but may in part affect warbler egg size. Therefore, the decrease in cuckoo egg size may be the result of the coevolutionary arms race. Body and egg sizes in the cuckoos were negatively correlated whereas warbler body and egg sizes were uncorrelated, suggesting that selection probably acted on egg size directly and not via selection on body size. Taken together, these findings may indicate that climate change, the coevolutionary arms race, or both, affected egg sizes. It is suggested that drawing conclusions regarding the arms race without taking into account other selective pressures (e.g., climate) may confound conclusions regarding parasite-host systems.

We tested alternative developmental hypotheses describing when during an insect oviposition cycle reproductive tactics are determined. Newly eclosed adult females of the grasshopper Romalea guttata were raised on eight different feeding treatments consisting of a low food diet, a high food diet, and changes from high to low food, or low to high food, at different times during the first oviposition cycle. When initial food availability was high, a decline in food availability >7 days after adult eclosion produced no significant increase in time to oviposition compared to constant high food. In contrast, when initial food availability was low, an increase in food availability as late as day 14 produced a significant decrease in time to oviposition compared to constant low food. Thus, time to oviposition is determined by feeding rate early in the oviposition cycle, but the time of this determination is later when food availability is lower. Masses of individual eggs were unaffected by these treatments. When initial food availability was high, a decrease in food availability on day 21 produced no significant change in numbers of eggs in a clutch compared to constant high food. In contrast, when initial food availability was low, an increase in food availability after day 7 produced no significant change in number of eggs in a clutch compared to constant low food. Changes in egg production resulted from oocyte resorption, which appeared to become unresponsive to food availability between day 14 and day 21. Our results refute the hypothesis that reproductive tactics are continuously flexible. Development toward oviposition seems to be structured so that reproductive tactics become independent of feeding late during the first oviposition cycle. Reproductive tactics become unresponsive to food at different times for groups initially receiving low or high food, suggesting that a particular developmental state, rather than some absolute time, marks the shift to development that is unresponsive to␣food. Plasticity in reproductive tactics appears to be␣controlled by hormones in a manner similar to the hormonal control of plasticity of metamorphosis in other insects.

The decrease in food availability as one of the indicators of food security in Europe has been noted since the beginning of the COVID-19 pandemic. The war in Ukraine caused a disruption in the supply chains of fertilizers, energy carriers and other resources needed by European and Ukrainian agricultural producers, which contributed to the increase in food prices. Thus, states as guarantors of food security must solve the task of ensuring the physical and economic availability of food products for the population. The purpose of the article is to highlight the dynamics of food availability in Ukraine and Europe, to identify the extent of the war's impact on the population's food supply, and to develop proposals for strengthening food security. In the research process, data from the Agroportal platform, the State Statistics Service of Ukraine, analytical reviews, research by domestic and foreign scientists, and the legal framework were used. In the research process, data from the Agroportal platform, the State Statistics Service of Ukraine, analytical reviews, research by domestic and foreign scientists, and the legal framework were used. A number of methods were used in the research process: comparison, index, generalization, formalization. A significant decrease in food availability was revealed both in Ukraine and in Europe as a whole. It has been established that the war in Ukraine caused a disruption in logistics, the removal of large tracts of land from agricultural use, an increase in the price of resources, and a complication in the export of food raw materials and its processing products. The main measures of the state policy to support food security are summarized, which differ in different countries, but have the same direction - elimination of social deprivation, protection of the poorest strata of the population, support of farmers' incomes, reduction of obstacles in the way of movement of food products. Proposals have been developed to improve the physical and economic availability of food products. The war became a serious trigger for the transformation of not only food security policy, but also foreign trade, tax, price, protectionist and other policies related to the performance of social functions of the state. The multifaceted nature of the problem of food availability makes it necessary to carry out research in these and other areas.

Aggression is an adaptive behavior that plays an important role in gaining access to limited resources. Aggression may occur uncoupled from reproduction, thus offering a valuable context to further understand its neural and hormonal regulation. This review focuses on the contributions from song sparrows (Melospiza melodia) and the weakly electric banded knifefish (Gymnotus omarorum). Together, these models offer clues about the underlying mechanisms of non-breeding aggression, especially the potential roles of neuropeptide Y (NPY) and brain-derived estrogens. The orexigenic NPY is well-conserved between birds and teleost fish, increases in response to low food intake, and influences sex steroid synthesis. In non-breeding M. melodia, NPY increases in the social behavior network, and NPY-Y1 receptor expression is upregulated in response to a territorial challenge. In G. omarorum, NPY is upregulated in the preoptic area of dominant, but not subordinate, individuals. We hypothesize that NPY may signal a seasonal decrease in food availability and promote non-breeding aggression. In both animal models, non-breeding aggression is estrogen-dependent but gonad-independent. In non-breeding M. melodia, neurosteroid synthesis rapidly increases in response to a territorial challenge. In G. omarorum, brain aromatase is upregulated in dominant but not subordinate fish. In both species, the dramatic decrease in food availability in the non-breeding season may promote non-breeding aggression, via changes in NPY and/or neurosteroid signaling.

ABSTRACT: Early life stages of Engraulis ringens were reared from hatch until yolk exhaustion. Weevaluated the effect of temperature on characteristics such as larval length and yolk volume at hatch,larval length at yolk absorption, duration of yolk-sac stage, yolk consumption rate and larval growthrate. Further, we determined the potential differences in these traits between populations located 13°of latitude apart (Antofagasta 23°S, Talcahuano 36°S). The results showed that egg size had an effecton the larval length at hatch, initial yolk volume and larval length at yolk absorption, since the val-ues obtained were always larger in larvae hatched from Talcahuano (from larger eggs) than fromAntofagasta (smaller eggs). These characteristics were also modified by the rearing temperature.Duration of yolk-sac phase, yolk consumption rate and larval growth rate until yolk exhaustionshowed high thermic dependence in both populations. However, these traits showed no differencebetween populations when larvae were reared at the same temperature in the range between 12 and20°C, despite their initial difference in egg size. When extrapolated from the environmental condi-tions in each nursery area (i.e. 15°C Antofagasta and 12°C Talcahuano), our results suggest that theanchoveta populations from Talcahuano compensate for their lower larval growth rates by increasingtheir initial egg and hatch sizes, as they are larger than Antofagasta larvae at the end of the yolk-sacstage. This increased larval length should enhance their chances of survival under adverse environ-mental conditions, such as high turbulence, lower temperature and lower food availability duringwinter, which is typical of the anchoveta southern spawning area.KEY WORDS: Anchoveta · Early life-history traits · Egg size · Growth · Latitudinal differences ·Temperature effects

There are constraints on the rate of energy intake of foraging animals, and allocation of energy, for example, to growth therefore must be at the expense of allocation to other purposes, such as energy storage. Moreover, the relative amount of energy allocated to different kinds of activities is likely to depend upon food availability. We have compared the patterns of energy allocation between adders, Vipera berus (L.), in populations inhabiting two different island groups in the Baltic Sea. These adders primarily feed on field voles, Microtus agrestis (L.), which undergo great population density fluctuations. In order to survive periods of low food supply adders allocate some energy to storage, and they can be expected to increase the proportion of energy devoted to storage when food levels and rate of energy intake decrease. Individuals allocating much energy to storage have less energy available for growth, reproduction and maintenance, and one can expect a trade-off between growth and energy storage, especially during resource shortage. Since the size of energy reserves influences fasting endurance, while body size influences future reproductive success, the pattern of energy allo- cation between growth and storage might have important fitness consequences for these animals. We compared the size of energy reserves (body mass in relation to body length) and the growth rates of individual male adders from two localities with different densities of field voles. Relative body mass was similar to both adder populations, but individuals grew faster where vole density was higher. This suggests that the pattern of energy allocation changed with resource availability. We also investigated the relationships between rela- tive growth rate and relative mass within the two adder populations. We found a significant nega- tive relationship where prey density was low, and a negative but non-significant relationship where prey density was high, indicating a trade-off between growth and energy storage in male adders that changes with food availability.

With the aim of integrating the physiology and evolutionary ecology of Lymnaea stagnalis (Linnaeus, 1758), we studied the effects of day length and food availability on the energy budget. Snails were assigned to two different photoperiods and three levels of food availability. The snails were kept individually, and food consumption, growth, and egg production were measured for about 2 months. Snails could nearly compensate for a one-day starvation period by increasing the rate of food-intake. However, food-intake rates did not increase further after a starvation period of 2 days. Growth was well described by the Von Bertalanffy growth equation. The ultimate size of snails kept under medium-day conditions (MD; light:dark = 12:12 h) was not affected by food availability. By contrast, the ultimate size of snails kept under long-day conditions (LD; light:dark = 16:8 h) depended on food availability; those fed the lowest quantities grow the least. Dry-weight densities (dry weight/wet weight) of MD snails were considerably above those of LD snails. In MD snails, food availability did not appreciably affect dry-weight density. By contrast, in LD snails, dry-weight density decreased with decreasing food availability. The reproductive output of LD snails declined with declining food availability, but was 2 to 4 times that of MD snails. The difference in reproductive output was largely accounted for by the difference in stored energy, i.e. dry-weight density. To gauge the extent to which the conclusions from our laboratory work applied to free-living snails, a field study was conducted. The wild-caught snails' dry-weight density was also lowest in long-day conditions when most eggs were laid. However, the dry-weight densities during medium and short days were lower than the dry-weight densities of laboratory animals under LD conditions. Thus, in the field, snails stored less energy than in the laboratory.

The current year's growth of Douglas fir contains galactose, unusual in that this carbohydrate makes up 78.7% of the total carbohydrate fraction. An agar diet study was undertaken to determine the effects of galactose, other carbohydrates, and terpenes on western spruce budworm larval mortality, growth rate, and adult biomas production. All concentrations of the carbohydrates and terpenes tested, as well as other mineral elements not tested, were typical of the current year's foliage of Douglas fir. In experiment I, the diet containing 5.61% total carbohydrate did not significantly affect larval mortality when compared to the control diet. However, diets containing 9.45% and 15% total carbohydrate concentrations significantly increased larval mortality 64% and 96.1%, respectively, when compared to the control. Also in experiment I, terpenes alone (78.9% morality) and terpenes in combination with 9.45% and 15% total carbohydrates significantly increased larval mortality (97.2% and 100%, respectively) when compared to mortality on the control diet (44%). To determine which carbohydrate was causing the adverse effect, 6% glucose, 6% fructose, and 6% galactose were placed individually and in combination with terpenes in diets in experiment II. The 6% galactose diet significantly increased larval mortality and reduced growth rate when compared to the control, glucose, and fructose diets. Glucose resulted in 16% less larval mortality, significantly enhanced female larval growth rate and pupal weight, but did not affect male larval growth rate and pupal weight, when compared to the control. Fructose resulted in a significant decrease in larval mortality and a general trend of enhanced female and male larval growth rate and pupal weight. Larval mortality on terpenes alone was not significantly different from the control, but terpenes with 6% galactose increased larval mortality and decreased female and male growth rate and pupal weight significantly when compared to glucose-terpene and fructose-terpene diets. No significant interactions were found between carbohydrates and terpenes in either experiment.

Egg size affects larval size, growth rate, survival and fecundity with maternal fitness being maximized by a trade-off between egg size and fecundity. Production of a small number of large eggs maximizes female fitness under poor food conditions, as does a large number of small eggs under rich food conditions. Gnathopogon caerulescens (Honmoroko) spawns over a wide range of water temperature from spring to summer. Thus, we determined whether or not egg size varied with water temperature and how egg size influenced hatchling size at different water temperature. Changes in egg size strongly correlated with seasonal changes in water temperature around the lake, regardless of time and area. An experiment using eggs from the lake indicated that hatchling size has a significant positive relationship with egg size in water temperatures of 24 °C. On the other hand, a lower incubation temperature, similar to that likely to be encountered at the beginning of the spawning season, resulted in a smaller hatchling size, eggs requiring a longer time to hatch. At the beginning of the spawning season, therefore, egg size may have a lesser impact on hatching size in the natural environment of Honmoroko because of the relatively lower temperatures. Although fish larvae below a certain threshold of effective body size are generally not expected to have a high early survival rate due to, for example, a lower competitive ability or a high susceptibility to predation, seasonal egg size variation in Honmoroko may be adaptive so as to enhance the likehood of early survival by establishing an effective body size under changing water temperature conditions.