Duration Of Death-feigning Research Articles

Polygene control and trait dominance in death-feigning syndrome in the red flour beetle Tribolium castaneum.

Death-feigning behavior is an anti-predatory technique used in several animal taxa and often correlates with inhibited movements (i.e., death-feigning syndrome). We performed a reciprocal crossing among strains exhibiting a genetically longer (L-strain) and shorter (S-strain) duration of death feigning. Then, we investigated related heritable factors in F1 and F2 populations. We also evaluated movement activities, which negatively responded to artificial selection for death feigning in T. castaneum. Our results indicated that death feigning occurred more frequently and for shorter periods in the F1 population. However, in the F2 population, death feigning and movement exhibited continuous segregation. Although the distribution of each trait value in the F2 generation differed from that of the parental generation, no individuals transgressing the distribution of trait values in the parental generation emerged from the F2 generation. Besides, chi-square analysis of the observed death feigning and movement of F1 and F2 progenies rejected the hypothesis of mono-major gene inheritance. These results suggested that the death-feigning syndrome was polygenically controlled, indicating the usefulness of reciprocal crossing experiments in assessing the quantitative inheritance of behavioral traits.

Artificial selections for death‐feigning behavior in beetles show correlated responses in amplitude of circadian rhythms, but the period of the rhythm does not

AbstractOne of the most important survival strategies of organisms is to avoid predators. Studying one of such strategies, namely, death‐feigning behavior, has recently become more common. The success or failure of this antipredator strategy will be affected by the circadian rhythms of both prey and predator because death feigning sometimes has a diurnal rhythm. However, few studies have analyzed the effects of differences in circadian rhythms on predator‐avoidance behavior at the genetic level. Recently, the relationship between genes relating to circadian rhythm and death‐feigning behavior, an antipredator behavior, has been established at the molecular level. Therefore, in this study, we compared three circadian rhythm‐related traits, the free‐running period of rhythms, amplitude of circadian rhythms, and total activity of strains of three Tribolium species that were artificially selected for the death‐feigning duration: short (S‐strains) and long (L‐strains) durations. As a result, the amplitude of circadian rhythms and total activity were significantly different between S‐ and L‐strains, but there was no difference in the free‐running periods of the rhythm between the strains in T. castaneum, T. confusum, and T. freemani. Although the relationship between death‐feigning behavior and activity has been reported for all three species, a genetic relationship between the duration of death feigning and the amplitude of circadian rhythms has been newly found in the present study. It is important to investigate the relationship between antipredator strategies and circadian rhythms at the molecular level in the future.

Relationship Between the Duration of Death-Feigning and Temperature in Black and Red Elytral Types of a Polymorphic Ladybug, Harmonia axyridis

Relationship Between the Duration of Death-Feigning and Temperature in Black and Red Elytral Types of a Polymorphic Ladybug, Harmonia axyridis

Freezing or death feigning? Beetles selected for long death feigning showed different tactics against different predators.

Prey evolve antipredator strategies against multiple enemies in nature. We examined how a prey species adopts different predation avoidance tactics against pursuit or sit‐and‐wait predators. As prey, we used three strains of Tribolium beetles artificially selected for short (short strain) or long (long strain) duration of death feigning, and a stock culture (base population). Death feigning is known to be effective for evading a jumping spider in the case of the long strains, while the present study showed that the long‐strain beetles used freezing against a sit‐and‐wait type predator, Amphibolus venator, in this study. The short‐ strain beetles were more easily oriented toward predators. The time to predation was also shorter in the short strains compared to the long strains. The results showed that, as prey, the short strains displayed the same behavior, escaping, against both types of predators. Traditionally, death feigning has been thought to be the last resort in a series of antipredator avoidance behaviors. However, our results showed that freezing and death feigning were not parts of a series of behaviors, but independent strategies against different predators, at least for long‐strain beetles. We also examined the relationship between a predator's starvation level and its predatory behavior. In addition, the orientation behavior toward and predation rate on the prey were observed to determine how often the predatory insect attacked the beetles.

Genomic characterization between strains selected for death-feigning duration for avoiding attack of a beetle

Predator avoidance is an important behavior that affects the degree of adaptation of organisms. We compared the DNA variation of one of the predator-avoidance behaviors, the recently extensively studied "death-feigning behavior”, between the long strain bred for feigning death for a long time and the short strain bred for feigning death for a short time. To clarify how the difference in DNA sequences between the long and short strains corresponds to the physiological characteristics of the death-feigning duration at the transcriptome level, we performed comprehensive and comparative analyses of gene variants in Tribolium castaneum strains using DNA-resequencing. The duration of death feigning involves many gene pathways, including caffeine metabolism, tyrosine metabolism, tryptophan metabolism, metabolism of xenobiotics by cytochrome P450, longevity regulating pathways, and circadian rhythm. Artificial selection based on the duration of death feigning results in the preservation of variants of genes in these pathways in the long strain. This study suggests that many metabolic pathways and related genes may be involved in the decision-making process of anti-predator animal behavior by forming a network in addition to the tyrosine metabolic system, including dopamine, revealed in previous studies.

Transcriptomic comparison between beetle strains selected for short and long durations of death feigning

The molecular basis of death feigning, an antipredator behavior that has received much attention recently, was analyzed. We compared the gene expression profiles of strains with different behaviors, i.e., different durations of death feigning, in the beetle Tribolium castaneum. Beetles artificially selected for short (S) and long (L) durations of death feigning for many generations were compared thoroughly by RNA sequencing. We identified 518 differentially expressed genes (DEGs) between the strains. The strains also showed divergence in unexpected gene expression regions. As expected from previous physiological studies, genes associated with the metabolic pathways of tyrosine, a precursor of dopamine, were differentially expressed between the S and L strains; these enzyme-encoding genes were expressed at higher levels in the L strain than in the S strain. We also found that several genes associated with insulin signaling were expressed at higher levels in the S strain than in the L strain. Quantitative real-time PCR analysis showed that the relative expression levels of Tchpd (encoding 4-hydroxyphenylpyruvate dioxygenase, Hpd) and Tcnat (encoding N-acetyltransferase, Nat) were significantly higher in the L strain than in the S strain, suggesting the influence of these enzymes on the supply of dopamine and duration of death feigning.

Responses to relaxed and reverse selection in strains artificially selected for duration of death-feigning behavior in the red flour beetle, Tribolium castaneum

Divergent lines selected artificially for many generations make it possible to answer two questions: (1) whether genetic variation still exists within the selected population; and (2) whether the selection itself is costly for the selected strain. In previous studies, the red flour beetle Tribolium castaneum was divergently selected artificially for duration of death-feigning, and strains selected for longer (L-strain) and shorter (S-strain) durations of death-feigning have been established (Miyatake et al. 2004, 2008). Because the selection experiments have been conducted for more than 27 generations, genetic variation may be eroded. Furthermore, because another previous study reported physiological costs to L-strains, the L-strains selected artificially for longer duration of death-feigning may have suffered more costs than the S-strains. In the present study, therefore, we relaxed the selection pressure after the 27th or 30th generation of S- and L-strains. We also carried out reverse selection during the most recent eight generations of S- and L-strains. The results showed that each strain clearly responded to relaxation of selection and reverse selection, suggesting that (1) additive genetic variation still existed in both strains after long-term selection, and (2) selection for shorter and longer duration of death-feigning was costly. These results suggest that anti-predator behavior is controlled by many loci, and longer or shorter duration of death-feigning is costly in a laboratory without predators.

Genetic correlation between behavioural traits in relation to death‐feigning behaviour

AbstractIndividuals frequently behave in a consistent manner across time or in different situations. We examined the repeatability of duration of death‐feigning anti‐predator behaviour when attacked, and then carried out artificial selection for duration to calculate its heritability and examine correlated responses to selection in activity levels, in the confused flour beetle, Tribolium confusum. Three replicates of two strains were established by artificial selection for more than 17 generations: S strains exhibited shorter duration and lower frequency of death feigning while L strains exhibited longer duration and higher frequency of death feigning. Duration of death feigning clearly responded to selection, and significant value of realized heritability was detected in all replicates of the two strains. Examination of locomotor activity levels over a constant period showed that S strains had higher locomotor activity levels than L strains. No significant differences between the sexes were observed. Our study thus demonstrates heritability of death feigning and the existence of a negative genetic correlation between intensity of death feigning and activity level.

Pleiotropic antipredator strategies, fleeing and feigning death, correlated with dopamine levels in Tribolium castaneum

A prey animal has the alternative of fleeing or feigning death to survive when it encounters predators. We found that fleeing by an artificial threat, locomotion and feigning death are pleiotropically correlated with a genetic factor related to a biogenic amine in the red flour beetle, Tribolium castaneum. Walking distance of adults was significantly lower in strains artificially selected for longer (L strains) than shorter duration (S strains) of death-feigning. Crosses showed that S-strain adults were dominant in the frequency and duration of death-feigning and locomotor activity compared to those of L strains, suggesting that death-feigning and activity have the same genetic basis. S-strain adults fled, but L-strain adults feigned death, when they encounter artificial threat. Not only adults that were directly selected for the duration of death-feigning, but also the larvae of L strains frequently showed tonic immobility, when they were dropped onto the ground: the larvae of S strains showed this behaviour less often. This suggests that chemical modulators of behaviour present in these insects before and after metamorphosis control both general locomotor activity and death-feigning. Brain levels of the candidate neuromodulator dopamine were, in fact, found to be significantly higher in S strains compared to L strains in the two selection replications. Thus, we suggest that two alternative behaviours related to antipredator strategies, fleeing or feigning death, are associated with the pleiotropic effects of a neuroactive substance in T. castaneum.

Drop or fly? Negative genetic correlation between death-feigning intensity and flying ability as alternative anti-predator strategies

A prey animal may have the alternative of flying away or feigning death when it encounters predators. These alternatives have a genetic base as anti-predator strategies in the adzuki bean beetle, Callosobruchus chinensis. A negative genetic correlation between death-feigning intensity and flying ability was found in C. chinensis, i.e. lower flying ability is genetically connected to escaping by dropping from a perch and then feigning death, whereas higher flying ability does not correspond to death-feigning behaviour. Two bidirectional artificial selections for death-feigning duration and flying ability were conducted independently in C. chinensis. The strains selected for shorter (longer) duration of death-feigning had higher (lower) flying ability, while the strains selected for lower (higher) flying ability showed longer (shorter) duration of death-feigning. When the two traits were compared in 21 populations of C. chinensis derived from different geographical regions, a significant negative correlation was found between death-feigning intensity and flying ability. Based on these results, the choice between alternative escaping behaviours in animals is discussed from two points of view: phenotypic plasticity, an individual with two tactics; and pleiotropic genetic correlation, different individuals with opposite strategies.

Body-Size Dependent Difference in Death-Feigning Behavior of Adult Callosobruchus chinensis

Size-dependent differences in death-feigning behavior, an anti-predator defense, was examined in the adult adzuki bean beetle, Callosobruchus chinensis (Coleoptera: Bruchidae). A positive correlation was observed between the duration of death-feigning and adult body weight in two replicated experiments. Moreover, under starved condition, beetles reared under high (= lighter beetles) larval density showed significantly shorter longevity and a shorter duration of death-feigning than those reared under low (= heavier beetles) larval density. The body-size-dependent difference in the duration of death-feigning is discussed from the viewpoint of the difference in survival strategies between small and large beetles. Because small beetles don’t live as long, they have less time in which to reproduce and so any loss of that short time might be a greater proportion of their fitness lost. This is the first report on the body-size-dependent difference in death-feigning behavior in the adult holometabolic beetle.

The Critical Cues for Diurnal Death Feigning in Young Chicks: A Functional Analysis

The critical determinants of extended diurnal death feigning were assessed in a refinement experiment in which visual and tactile cues during rearing and/or testing were systematically eliminated. Ninety-five domestic chicks were reared in either a social environment or physical (tactile) isolation, and half in each rearing condition were reared and/or tested under conditions of visual restriction. As expected, social rearing was prerequisite to the manifestation of extended death feigning; however, the incidence and duration of death-feigning was attenuated by functional visual isolation of socially reared chicks during either rearing or testing. It was concluded that visual novelty of the environment is the minimal condition for sustained death feigning by young chicks in the daylight hours.