How food type and brood influence foraging decisions of Lasius niger scouts

We investigated how the type of food (sucrose or protein) and the presence of brood influence foraging decisions of Lasius niger L. scouts. In particular, we studied whether and how these parameters alter the drinking behaviour of scouts and the allocation of workers to food retrieving and recruiting tasks. We analysed drinking and recruiting behaviour of single scouts from nests with or without brood that encountered a proteinaceous or sucrose droplet. A substantial fraction of scouts encountering a proteinaceous droplet did not ingest it and did not then return to the nest whereas nearly all drank at sugar droplets; brood presence did not influence this decision. Once an ant started drinking, it needed to drink a critical volume before returning to the nest; this critical volume did not depend on the type of food and the presence of brood. Scouts laid a trail only if they returned to the colony. Food type and brood presence altered the proportion of individuals that laid a trail but not the individual trail-laying intensity. We discuss the consequences of this decision system through simple individual assessments and decision rules, with regard to the self-organized foraging patterns of this species and the efficient collective exploitation of natural resources.     

The flow of food in colonies of the fire ant, Solenopsis invicta: a multifactorial study

ABSTRACT. A study was conducted to determine the interaction of several factors in the trophallactic distribution of food in colonies of Solenopsis invicta Buren. Radioactive iodine (¹²⁵I) was used to quantify both the ingestion of test foods by foragers and the distribution of this food to nestmates. A multifactorial design tested the simultaneous effects of: (1) food-type (sugar water, casein hydrolysate, or oil), (2) temperature during foraging and food-sharing (25, 30 or 35°C), and (3) starvation period (colonies deprived for 0, 3, 7 or 14 days). The amount of food consumed by foragers was influenced by the interaction of food-type and starvation. Foragers from severely starved colonies ingested more aqueous foods than did those from slightly starved colonies, but oil was always taken in smaller quantities and its ingestion was least affected by starvation. Ingestion was generally lowest at 35°C, probably because of mutual interference of workers while feeding. Within the colony, food sharing varied with food type and increased with starvation. The sugar solution was utilized primarily by workers. Amino acids were shared throughout the colony, but were directed preferentially to the growing larvae. Soy oil was equally shared among workers and larvae and reached more colony members per initial unit volume than did the other foods. The test factors also interacted in their influence on trophallaxis. Starvation stimulated the dispersal of labelled foods, but at different intensities for different foods. The probability of the queen's receiving food increased when the labelled food was widely exchanged among her nestmates. Casein hydrolysate reached the queen in more cases than did the other tested foods.     

A comparison of two ATPase based schemes for histochemical muscle fibre typing in various mammals

Summary A comparative study was performed on the fibre populations in tibialis anterior muscles of mouse, rat, guinea pig, rabbit, cat and dog using the two different methods of histochemical staining for myofibrillar ATPase after acid (Brooke and Kaiser 1970) or alkaline preincubations (Guth and Samaha 1970). For all species a complete correspondence existed between type I (Brooke and Kaiser 1970) and fibres (Samaha et al. 1970). Gross correspondence (>85%) existed between IIA and IIB (Brooke and Kaiser 1970) and and fibres (Samaha et al. 1970) respectively in mouse, guinea pig, rabbit, cat and dog. In the case of mouse and dog, this high degree of correspondence was based on the assumption that mouse tibialis anterior contains no type I and the dog no type IIB fibres. For the rat, a pronounced overlap existed between IIA fibres on the one hand and and fibres on the other hand as well as between IIB fibres and and fibres. These observations lead to the conclusion that the two classification schemes are not interchangeable for all species and that the two terminologies should be used only in relation with the methods from which they were derived.     

Effect of nutritional condition on larval food requisition behavior in a subterranean termite Reticulitermes speratus (Isoptera: Rhinotermitidae)

Although optimal investment theory would be similarly applicable to eusocial insects to maximize colony reproductive outputs, directly distinguishing an amount of investment in each larva should be a difficult task for workers because of the characteristics of group living. Thus, it is expected that workers adjust brood care by using a cue or signal conveying information of larval status. In termites, which are typical group of eusocial insects, there are nevertheless few direct observations on worker brood care and little is known about cues inducing worker feeding. I show here that a Japanese subterranean termite Reticulitermes speratus uses an overt food solicitation by larva, “pecking”, as a cue for worker feeding. Direct observations demonstrated that workers feed larvae in response to larval pecking. Furthermore, nutritional experiments showed that larvae exhibited pecking more frequently when their nutrient status is lower; hence, pecking may be an honest reflection of larval hunger status. These results indicate that workers can feed more starved larvae than less starved ones because pecking honestly reflects larval hunger state. That is, feeding in response to pecking should standardize the total amount of food intake of each larva and help a termite colony make worker investment efficient.     

Inspection and feeding of larvae by worker honey bees (Hymenoptera: Apidae): Effect of starvation and food quantity

Honey bee larvae are frequently inspected and, sometimes, provided with food by adult workers, but the stimuli that elicit the important task of food provisioning have never been investigated. Larvae with their food experimentally deprived received more frequent inspection and feeding visits from nurse bees than normally fed larvae, suggesting that there could be a hunger signal. Food-deprived larvae with artificially supplied larval food received the same rate of feeding visits from nurse bees as did normally fed larvae but still received more inspection visits. These results suggest that stimuli eliciting feeding are different from those for inspection. They also support the hypothesis that worker bees deposit food in a larval cell only when the quantity of food is below a certain minimum threshold that is perceived during larval inspections. A model is presented regarding the stimuli from larvae that result in worker feeding behavior.     

Infrared characterization of complex sandwich structures: Heparin immobilized on polyethylene surfaces

Surface modification to provide, e.g., a biocompatible surface is an important molecular engineering method. As an example the FTIR-Attenuated Total Reflection (ATR) method has been applied to follow the different steps in the immobilization process of heparin on polyethylene (PE). This chemical multicomponent modification process is based on van der Waals and electrostatic interaction between alternating layers of cross-linked polyethylene imine and dextran sulfate, and finally covalent attachment of partly nitrous acid degraded heparin. Modified PE sheets were withdrawn and analyzed after each reaction step in the process. The overall spectral agreement between the ATR spectra and the spectra obtained from the pure substances used is good, except for slight changes in position and relative intensities of the sulfate and amino peaks. This observation indicates that the amino and sulfate groups are important (electrostatic) binding sites between the alternating polyethylene imine and dextran sulfate layers. The amount of covalently attached heparin was determined according to the thin film model by Harrick. The surface concentration, , falls typically in the range of 2.4–2.7 g/cm², which is in good agreement with the result from a chemical analysis. The choice of peak areas used in the calculation of is also discussed.     

The assimilation and allocation of nutrients by symbiotic and aposymbiotic pea aphids, Acyrthosiphon pisum

The failure of a nutritionally balanced diet to ameliorate the impact of symbiont disruption in the pea aphid Acyrthosiphon pisum (Harris) was investigated using two approaches. The assimilation of dietary nutrients by aphids was investigated using chemically-defined diets containing ³ H-labelled inulin and ¹⁴C-labelled sucrose or amino acids. Symbiotic aphids (i.e., aphids containing their bacteria) had a high sucrose demand and assimilated 72% of sucrose ingested in the diet, whereas the assimilation of sucrose by aposymbiotic aphids (in which the bacteria had been disrupted), was significantly reduced to 47%. The assimilation of individual dietary amino acids by symbiotic aphids varied between 61 and 92%, and there was no impact on the feeding or assimilation rate when the aphids were fed a phloem sap-like diet containing a reduced amount of essential amino acids. Consequently, the absolute amount of each essential amino acid assimilated by symbiotic aphids feeding on a phloem sap-like diet was reduced by 36–59%. Aposymbiotic aphids consistently assimilated a lower proportion of ingested amino acids, and lysine in particular was poorly assimilated from the diet. In a second experiment, the allocation of free amino acids in the haemocoel to aphid embryos was investigated following microinjection of ¹⁴C-labelled amino acids. After 2 h, radiolabel could be detected at varying levels from the embryo complement of both symbiotic and aposymbiotic aphids, indicating rapid but selective uptake by the embryos. The essential amino acids phenylalanine and lysine were incorporated into the protein fraction of embryo tissues, but the rate of incorporation per unit biomass was approximately 4-fold higher in the embryos of aposymbiotic aphids, possibly reflecting increased demand due to the lack of amino acid provisioning from the symbiotic bacteria.     

Single amino acids in sucrose rewards modulate feeding and associative learning in the honeybee

Obtaining the correct balance of nutrients requires that the brain integrates information about the body’s nutritional state with sensory information from food to guide feeding behaviour. Learning is a mechanism that allows animals to identify cues associated with nutrients so that they can be located quickly when required. Feedback about nutritional state is essential for nutrient balancing and could influence learning. How specific this feedback is to individual nutrients has not often been examined. Here, we tested how the honeybee’s nutritional state influenced the likelihood it would feed on and learn sucrose solutions containing single amino acids. Nutritional state was manipulated by pre-feeding bees with either 1 M sucrose or 1 M sucrose containing 100 mM of isoleucine, proline, phenylalanine, or methionine 24 h prior to olfactory conditioning of the proboscis extension response. We found that bees pre-fed sucrose solution consumed less of solutions containing amino acids and were also less likely to learn to associate amino acid solutions with odours. Unexpectedly, bees pre-fed solutions containing an amino acid were also less likely to learn to associate odours with sucrose the next day. Furthermore, they consumed more of and were more likely to learn when rewarded with an amino acid solution if they were pre-fed isoleucine and proline. Our data indicate that single amino acids at relatively high concentrations inhibit feeding on sucrose solutions containing them, and they can act as appetitive reinforcers during learning. Our data also suggest that select amino acids interact with mechanisms that signal nutritional sufficiency to reduce hunger. Based on these experiments, we predict that nutrient balancing for essential amino acids during learning requires integration of information about several amino acids experienced simultaneously.     

Mathematical models for some types of chemical information systems

Ant species on a high evolutionary level have evolved chemical recruitment systems such as mass recruitment or quality recruitment. The recruitment process from the nest to a food source may be damped by crowding effects at the source. For four patterns of behavior (mass/quality recruitment; with/without damping) we study mathematical models for the time development of the quantity of food at the source. Each of the models can be reduced to a second order time-delayed differential equation which will be studied in the equivalent form of a first order (nonlinear) functional differential equation. We discuss the complete exploitation of a given source. In case of mass recruitment there possibly remains a threshold quantity of food not worth exploiting. However, every source will be exploited completely (in finite time) provided that the volatility of the trail pheromone is small compared with the exploitation activities of the colony and the distance from the nest to the source. In addition, for the damped models the capacity of the crowded source must be large compared with the initial quantity of food offered. The efficiency of the exploitation activities of some species allows conclusions on their evolutionary development.     

Thyroid hormone regulation of Na,K-ATPase subunit-mRNA expression in neonatal rat myocardium

Summary Regulation of Na,K-ATPase mRNA isoform and mRNA expression by thyroid hormone (T₃) in neonatal rat myocardium was examined. In euthyroid neonates between ages of 2 and 5 days, mRNA₁, mRNA₃, and mRNA₁ abundances were nearly constant while mRNA₂ was undetectable. During the interval between postnatal days 5 and 15, mRNA₃ decreased to negligible levels and mRNA₂ became expressed and increased in abundance to account for 20% of the mRNA pool by the 15^th postnatal day. To examine the effect of T₃ on this developmental program, neonates were injected with 75 g T₃/100 g body weight or diluent alone on the second and third postnatal days and myocardial Na,K-ATPase subunit-mRNA abundances were determined on the third and fourth postnatal days. Because T₃ treatment increased the RNA/DNA ratios of myocardial tissue, the subunit-mRNA abundances were normalized per unit DNA. Following 24 and 48 hr of T₃ treatment, the abundances of mRNA₁, mRNA₃, and mRNA₁ increased, while mRNA₂ continued to remain undetectable during the 2-day interval between the second to fourth postnatal days. It is concluded that T₃ augments the abundance of Na,K-ATPase subunit mRNAs that are already being expressed in the neonatal rat myocardium. The results further suggest that T₃ does not act as a molecular switch in the developmental expression of the mRNA isoforms in rat myocardium during the first four postnatal days.     

The role of anchor-tipped larval hairs in the organization of ant colonies

The spatial organization within a social insect colony is a key component of colony life. It influences individual interaction rates, resource distribution, and division of labor within the nest. Yet studies of social insect behavior are most often carried out in artificial constructions, which may change worker behavior and colony organization. We observed how workers of the ant Pheidole rhea organized brood in nests with deep chambers and textured walls that were designed to mimic their natural constructions more closely. Instead of clumping larvae into piles on the chamber floor, workers suspended fourth-instar larvae from the vertical walls and ceiling of each chamber while young larvae and pupae were clumped at the base. Fourth-instar larvae possess five rows of anchor-tipped hairs on their dorsal side, and we predicted that these hairs functioned to attach larvae to the nest walls. We gave larvae "haircuts," where only the anchor-tipped hairs were removed, and then tested their ability to adhere to a textured surface raised to an angle of 90° and then 120° with respect to the horizontal plane. Larvae whose hairs had been clipped came unattached in almost all trials, while larvae whose hairs remained intact stayed attached. This confirmed that anchor-tipped hairs functioned to attach larvae to the walls of the nest. The presence of anchor-tipped hairs is widespread and has been documented in at least 22 genera from the ant subfamily Myrmicinae, including species that occur in a variety of environments and represent a broad range of nesting habits. Based on our results, it is likely that many species exhibit this larval hanging behavior, and this could impact colony characteristics such as spatial organization and the care of developing larvae by nurse workers.     

Consumption, digestion, and utilization of various grasses by fifth-instar larvae and adults of the migratory locust

Food consumption, digestion, and utilization were estimated in fifth-instar larvae and adults of the migratory locust by measurements of the weight of food ingested, the weight of faeces produced and the increase in body weight. The diet consisted of either rye, perennial rye-grass, cocksfoot, water meadow-grass, or reed-grass.Neither the general shape of the growth curve nor the duration of the developmental period are influenced by these diets.Considerable diet-specific differences in amounts of food consumed as well as digested are estimated. Although explanations for these differences cannot be given, some probable causes are discussed: water content of the food, and transition effect of dietary change.The approximate digestibility of the food is higher in larvae than in adults during their somatic growth, which will reflect a greater digestive capacity in larvae. This digestive capacity remains constant within each developmental period, but its absolute value may differ between the two periods investigated and is dependent on the kind of food offered. The efficiency of conversion of ingested food as well as digested food to body substance are greater for water meadow-grass and particularly for rye than for the other grasses.

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Zusammenfassung Im 5. Larvenstadium von Locusta migratoria und in den adulten Tieren wurden Aufnahme, Verdauung und Nutzbarmachen der Nahrung, die jeweils aus frischen Blättern der Species: Secale cereale, Lolium perenne, Dactylis glomerata, Glyceria maxima oder Phragmites communis bestand, durch Messungen von drei Parametern bestimmt: (1) Trockengewicht der aufgenommenen Menge an Gras, (2) an produzierten Fäces, und (3) Änderung des Körperfrischgewichtes.Weder die allgemeine Form der Wachstumskurve noch die Dauer der Entwicklungsperiode wurden von den Diäten beeinflusst.Beträchtliche Diät-spezifische Unterschiede in der Quantität des aufgenommenen sowie verdauten Futters wurden nachgewiesen. Obwohl es nicht möglich ist schon eine Erklärung dafür zu geben, sind mögliche Ursachen erwähnt: der Wassergehalt des Futters und der transition effect des Diät-Wechsels.Der A.D. (approximate digestibility)-Wert des Futters ist in Larven höher als in den adulten Tieren; dies deutet auf eine höhere Verdauungskapazität der Larven hin. Innerhalb einer Entwicklungsphase bleibt die Verdauungskapazität konstant; ihr absoluter Wert kann beim Vergleich der beiden untersuchten Entwicklungsstadien verschieden sein, und zwar abhängig von der Art des angebotenen Futters. Die efficiency of conversion of ingested food (ECI) wie auch digested food (ECD) in Körpersubstanz sind für G. maxima und besonders für S. cereale höher als für die übrigen Diäten.

     

The composition of larval food and the significance of exocrine secretions in the bumblebee Bombus terrestris

Summary: This paper describes a study on the relation between the composition of larval food and the development of female castes in bumblebees. The first aim was to evaluate the significance of glandular secretions in the larval diet as a possible factor involved in larval feeding and caste differentiation. Small amounts of proteinaceous secretions were found to be added during the ingestion of sucrose but not while discharging food to the larvae. It is discussed that these secretions are digestive in function rather than food additives that would possibly play a role in the process of caste differentiation.¶Secondly, a comparative analysis was made of the general composition of food samples obtained from larvae of different castes and ages and from various periods in the social development of the colony. No significant differences in the total amount of pollen, sucrose and protein were detected between the castes or different age groups. Unlike honeybee workers, individual bumblebee workers did not change the composition of the diet they supplied to the brood in relation to their own age, nor to the social development of the colony. These findings suggest that all larvae receive the same nourishment during their total development and indicate that differences in development between queen larvae and worker larvae are neither caused by variations nor by a qualitative modification of their food with respect to the amount of pollen, protein and carbohydrates.     

Mating Triggers Queen Elimination by Workers of Japanese Harvester Ant (<Emphasis Type="Italic">Messor aciculatus</Emphasis>)

During reproduction, ant colonies produce winged queens. These new queens usually leave the nest to mate and can then establish a new nest. If the new nest is close to an existing colony, it will be in competition with the existing colony. Therefore, workers will kill any mated queens they find outside the colony during the reproductive season. In this study, factors that might determine whether workers eliminate queens were investigated. Mating status (mated or unmated), colony origin (same or different to tested workers) and mating partners (inbred or outbred) of the queens of Japanese harvester ants (Messor aciculatus) were manipulated and the workers’ behavior towards the queens was observed. Mated queens were always attacked by workers, though this was not affected by either colony origin or mating partners. These results suggest that mating status triggers elimination of queens by workers, and that the colony origin and mating partner are unlikely to be important roles in elimination of queens.     

Nectar feeding and body size in the ant Camponotus mus

Summary: Feeding behavior and worker polymorphism were studied in the ant Camponotus mus. Individual workers were conditioned to visit an arena in which an ad libitum food source of 60% (w/w) sucrose solution was offered. Individual feeding time, crop load, and intake rate were recorded. Worker head width and pronotum width were measured. Behavioral and morphometric variables were analyzed in relation to ant weight. C. mus workers of the laboratory nest have an elemental polymorphism with monophasic allometric growth. Worker size affected feeding dynamics. Load weight and intake rate were positively correlated with ant weight, whereas feeding time was independent of ant weight. Size related differences in intake rate could not be attributed to differences in pumping frequency, and could be attributed to differences in the volume ingested per pumping cycle.     

Feeding behavior ofRhagoletis pomonella flies (Diptera: Tephritidae): Effect of initial food quantity and quality on food foraging,handling costs,and bubbling

Under seminatural conditions feeding and postfeeding behaviors of individual apple maggot flies, Rhagoletis pomonella(Diptera: Tephritidae), were recorded after flies were presented with yeast hydrolysate or sucrose droplets, varying in either concentration, amount of food solute, or total droplet volume. The objectives were (a) to establish, at a constant level of previous food deprivation, food ingestion thresholds in relation to food quality and quantity and (b) to study the effect of initial food quantity and quality on food handling time and subsequent food foraging behavior. For both carbohydrate and protein substrates, fly foraging time after feeding on a tree branchlet was positively related to total amount of food solute previously encountered on a leaf surface, though largely independent of food volume or concentration. The volume and concentration of food presented, however, significantly affected food handling and processing time and therefore foraging time. In fact, total branchlet residence time was more closely linked to food handling and processing time than to foraging time. Less time was needed for uptake of liquid than dry food, the latter requiring liquification by salivary secretion and eliciting considerable intermittent cleaning of mouthparts by feeding flies. Similar to the situation in other fluid feeders, uptake time in R. pomonelladecreased with increasing dilution, although below a threshold of a 30% concentration of solute, the rate of nutrient intake decreased rapidly. When the level of dilution and total volume of food ingested were great enough, engorged flies entered extended quiescent postfeeding periods during which they extrude orally droplets of liquid crop contents (bubbling). After this they reinitiated feeding, followed by more bubbling and feeding bouts. Multivariate logistic regression analysis suggested that bubbling behavior is determined by liquid food volume and degree of dilution, hunger, and temperature. Although thresholds triggering bubbling decreased with increasing temperature, higher temperature by itself did not result in bubbling behavior. This suggests that bubbling is not primarily a mechanism to achieve evaporative cooling as has been suggested but, rather, a behavior to eliminate excess water, thereby enabling engorged flies to continue feeding on diluted food sources.     

GUSTATORY REACTION TIME AND TIME INTENSITY MEASUREMENTS OF TREHALOSE AND SUCROSE SOLUTIONS AND THEIR MIXTURES

Dynamic sweetness perception of commercial food grade trehalose, sucrose solutions and their mixtures were studied for a wide range of concentrations. For gustatory reaction time (GRT), concentrations ranged from 2.3 to 13.8% for sucrose and up to 23.0% for trehalose. For time intensity (T-I) sucrose or trehalose solutions (concentration range 2.3–36.8%) and their combinations (23.0 and 36.8% total solids) were analyzed. Trehalose had bigger GRT along the studied range. Both sugars presented similar values for persistence and times of plateau and to maximum intensity, while a significant difference was observed in intensity and GRT at equal concentrations. Trehalose had longer persistence than sucrose in equi -sweet solutions. Overall sweetness profile of some sucrose solutions (i.e., 29.9% sucrose solution and 0.6 sucrose/trehalose ratio mixture at 36.8% total solids) were perceived as similar to mixtures of sucrose/trehalose or single trehalose solutions, which suggests the possibility of sugar replacement without completely modifying sweetness perception.

PRACTICAL APPLICATIONS

It has been suggested that trehalose may be a potential substitute for sucrose and other sugars used in food formulation because, although its chemical structure is very similar to that of sucrose, it is more stable at low pH and high temperatures. It is not involved in caramelization and does not participate in Maillard reaction with amino acids/proteins. In order to fully establish the potential of trehalose as a functional replacement of sucrose we have determined the sweetness dynamic profile (gustatory reaction time and time-intensity curves) of trehalose solutions and sucrose/trehalose solutions; this aspect is needed for adequately replacing (partially or totally) sucrose in food systems.     

Cooperation during prey digestion between workers and larvae in the ant, Pheidole spadonia

Digestion and distribution of nutrients are central to the growth and reproduction of social insect colonies, just as they are to individual organisms. In the case of eusocial insect species, different components of food handling and processing can be distributed among castes. This paper reports on an ant species, Pheidole spadonia, in which the adult workers butcher prey and 4^th instar larvae dissolve prey for distribution among other colony members including workers, larvae and queens. To characterize the process, six groups, each composed of twenty-five workers and thirty larvae, were provisioned with a fruit fly carcass, and then video-taped continuously for 24 hours. On average, five adult workers and twenty-two 4^th instar larvae invested 12.8 labor hours into butchering and predigesting one fly carcass. Workers contributed a mean total of 3.3 labor hours to butcher the carcass into small fragments. Fourth instar larvae contributed a mean total of 9.5 labor hours to pre-orally dissolve the solid fragments. Surprisingly, larvae did not ingest during the dissolving process. Instead, workers ingested the dissolved prey tissue into their crops and then regurgitated it to colony members, larvae and workers, that solicited for feedings. The cooperative interactions reported here between workers and larvae extend the mechanistic and evolutionary explanations for eusociality. Received 13 January 2005; revised 22 April 2005; accepted 25 April 2005.     

Prey kills predator: Counter-attack success of a spider mite against its specific phytoseiid predator

Success of counter-attack by the spider mite,Schizotetranychus celarius (Banks), against its specific phytoseiid predator,Typhlodromus bambusae Ehara, was examined under experimental conditions. The success of counter-attack by prey females (mothers) against a predaceous larva depended upon the former's density per nest. About 30% of the predaceous larvae were killed when they intruded into a nest containing eight females and their offspring. On the other hand, the prey males (fathers) effectively killed the predators, i.e. one male in the nest killed ca. 40% of the predators while two or three males destroyed up to 80%.The presence of prey parents in a nest considerably enhanced the success of the counter-attack. One male and two young females could kill 70% of the predator's larvae, while two males and two females killed 90% of such larvae. This suggests a kind of cooperative brood defence amongstS. celarius parents.Although more robust, protonymphs of the predator also suffered damage by the prey's counter-attack. However, prey male and female could not destroy the predator's eggs and adult females, whilst the latter often killed spider mite adults.From these as well as previous experiments, it is concluded thatS. celarius has evolved some kind of biparental care for its offspring. It is further proposed that the predator—prey interactions observed in this study provide a unique contribution towards understanding predator—prey coevolution.