Methodology and measurement of adenylate energy charge ratios in environmental samples

A method for measuring ATP, ADP and AMP levels in environmental samples was devised, and applied to seawater and bacterial cell extracts. This procedure is specifically designed for measuring the extremely low concentrations of total adenine nucleotides ([A_T]=[ATP]+[ADP]+[AMP]) that are apt to occur in most natural ecosystems (i.e., 10 ng A_T ml^-1 of sample extract). Although the current assay methodology can be used with purified firefly luciferase reagents, it has been suitably modified to accept crude luciferase preparations as well. ATP, ADP and AMP levels have been measured, and the corresponding energy charge (EC) ratios determined for seawater samples collected off the Southern California coast. The EC ratios ranged from 0.50 to 0.89, with peak values corresponding to the subsurface maxima in ATP and chlorophyll a concentrations, and the minimum values corresponding to the deepest water sampled (1500 m). The measurement of adenylate energy charge ratios in environmental samples can be a useful indicator of mean community metabolic activity and potential for cell growth.     

Effect of reduced salinity on adenylate energy charge in three estuarine molluscs

The value of adenylate energy charge as a biological indicator of the severity of departure from normal environmental conditions was examined in the gastropod Pyrazus ebeninus (Bruguière, 1792) and the bivalves Anadara trapezia (Deshayes, 1840) and Saccostrea commercialis (Iredale and Roughley, 1933). Mean energy charge for each species decreased by 17% or more when salinity was reduced from 35 to 10. Changes with reduced salinity were also found in the concentrations of individual adenylates and several adenylate ratios other than energy charge. Energy charge was calculated from the relative concentrations of adenosine 5-tri-, di- and monophosphate (ATP, ADP, AMP) in the columellar muscle of P. ebeninus and in the adductor muscle of A. trapezia and S. commercialis. Mean energy charge values for individuals in the low-salinity condition (10) were 0.61 for P. ebeninus, 0. 69 for A. trapezia and 0.53 for S. commercialis, compared with mean energy charge values in the control individuals (35 S) of 0.85 to 0.87 for P. ebeninus, 0.84 to 0.85 for A. trapezia and 0.64 to 0.76 for S. commercialis. The decrease in energy charge occurred within 24 h; no further change was found with exposure to low salinity for 48 h (A. trapezia) or no further change was found with exposure to low salinity for 48 h (A. trapezia) or 20 h (P. ebeninus, S. commercialis). Total adenylate concentrations (ATP+ADP+AMP) differed between the three species, with mean values (kg^-1 wet weight) of 5.0 mmol in P. ebeninus, 3.4 mmol in A. trapezia and 3.0 mmol in S. commercialis. No trends with time were found in total adenylate concentrations in any species. The changes in energy charge that occurred were not consistent with the differing sensitivity of the three species to reduced salinity, and do not support the use of energy charge as an absolute measure of stress in molluscs generally.     

Temperature adaptation in sea anemones: Physiological and biochemical variability in geographically separate populations of Metridium senile

Latitudinally separate populations of the sea anemone Metridium senile (L.) are very similar genetically by electrophoretic criteria, yet respond differently to temperature. Anemones from southern and northern California (USA) have different oxygen consumption patterns in response to acclimatory and acute changes in temperature. Northern anemones show a pronounced increase in Q₁₀ at temperatures just above the normal environmental range, but southern anemones do not. The two populations also differed in the extent of metabolic compensation to temperature following several weeks of acclimation. This acclimation regime resulted in changes in the activities of several enzymes of intermediary metabolism, yet the extent and direction of these changes did not display a consistent trend with regard to acclimation temperature or population. The biochemical concomitants of acclimatory and acute temperature effects were studied further by measuring the concentrations of adenylates (ATP, ADP, and AMP) in anemones from the two populations exposed to different temperature regimes. During cold acclimation for several weeks, total adenylate concentrations (A_T) increased in both the southern and northern populations, possibly due to metabolic rate compensation, since A_T is positively correlated with tissue metabolic rate in many species. Moreover, the extremely low weight-specific oxygen consumption rates of M. senile are probably related to its very low A_T values. Acute temperature decreases had no effect on adenylate concentrations and adenylate energy charge (AEC); in contrast, acute temperature increases led to large changes in adenylate concentrations. The effects of starvation on adenylate concentrations are pronounced, and the effect is temperature-dependent. In starved individuals held at 20°C, AEC values fell to 50% of normal values after 8 d, while those held at 10°C maintained normal AEC values.     

ATP concentration and adenylate energy charge of tropical zooplankton from waters inside the great barrier reef

The adenylate energy charge ratio (EC) of 8 species of zooplankton ranged from 0.70 to 0.89. Eucalanus subcrassus had significantly (P<0.05) lower EC when captured during a 30-min tow than during a 3-min tow, indicating stress at capture. The concentration of ATP in the 8 species ranged from 9.1 to 36.0 g/mg protein and from 0.17 to 15.7 g/mg dry weight. Excluding a low value for the ctenophore Pleurobrachia sp., the average concentration was 8.1 g ATP/mg dry weight, which is equivalent to an approximate C/ATP ratio of 50.Contribution from the Australian Institute of Marine Science, Australia, and the Institute of Marine Biology, University of Bergen, Norway     

Metabolic activity and elemental composition of krill and other zooplankton from Prydz Bay,Antarctica, during early summer (November–December)

Oxygen uptake and ammonia excretion rates, and body carbon and nitrogen contents were measured in krill (Euphausia superba) and eight other zooplankton species collected during November–December 1982 in the Prydz Bay, Antarctica. From these data, metabolic O:N ratios (by atoms), body C:N ratios (by weight) and daily metabolic losses of body carbon and nitrogen were calculated as a basis from which to evaluate seasonal differences in metabolism and nutritional condition. Comparison of the present data with mid-summer (January) data revealed that early-summer E. superba were characterized by higher metabolic O:N ratios (58.7 to 103, compared with 15.9 to 17.5 for mid-summer individuals). Higher O:N ratios of early-summer E. superba resulted largely from reduced ammonia excretion rates and, to a lesser degree, from slightly increased oxygen uptake rates. Body C:N ratios of E. superba were low in early-summer (3.8 to 4.2) compared with mid-summer krill (4.1 to 4.7) due to lowered body-carbon contents in the former (42.6 to 43.6% compared with 43.2 to 47.5% dry weight of midsummer individuals); gravid females formed an exception, since no seasonal differences in body elemental composition were detected for these. No significant changes in water content (75.3 to 81.4% wet wt) and nitrogen content (9.9 to 11.1% dry wt) in E. superba were evident between the two seasons. Seasonal differences in metabolic rates and elemental composition were less pronounced in a salp (Salpa thompsoni), but a higher metabolic O:N ratio occurred in early-summer individuals. Interspecific comparison of the seven remaining zooplankton species studied with twelve species from mid-summer zooplankton investigated in an earlier study indicated that higher metabolic O:N ratios in early-summer are characteristic not only of herbivore/filter-feeders, but also of some carnivores/omnivores. No relationship between metabolic O:N ratios and body C:N ratios was apparent either intraspecifically or interspecifically, within or between early-summer and mid-summer seasons.     

Measurement of the adenylate energy charge in Nereis diversicolor and Nephtys sp. (Polychaeta: Annelida):

ATP-content and adenylate energy charge (AEC) ratios were determined in two polychaete species (Neries diversicolor and Nephytys sp.), sampled in ten stations along the heavily polluted Western Scheldt estuary (N. Belgium, S. Holland). The samples were taken between 27 December 1982 and 6 January 1983. Nereis diversicolor was also sampled in an unpolluted brackish water pond, and subjected to artificial stress by drying the organisms on filter paper. Adenine nucleotide levels were determined using the firefly bioluminescence reaction. The light emission was measured with the integration mode. As the Constant Light Signal reagent used contained AMP and probably ADP itself, both myokinase and pyruvatekinase had to be inactivated before the assay. The use of pepsin in acidic conditions to denaturate these enzymes is discussed. For both N. diversicolor and Nephtys sp., a significant relation between ATP-content and fresh weight is found in most samples. Within each species, ATP-content per g fresh weight is dependent on the sampling method, but it is not significantly different between stations. It is higher in Nephtys sp. from the W. Scheldt (130. 8 10^-5 g ATP/g fresh weight) than in N. diversicolor from the Dievengat (83.9 10^-5 g ATP/g fresh weight). This value in turn is significantly higher than that for N. diversicolor in the W. Scheldt (64.0 10^-5 g ATP/g fresh weight). In the drying experiment, AEC gradually decreases with increasing drying time. In the field, AEC is generally high and not significantly different between the three populations. AEC ratios also do not differ between stations within each population. It is argued that field monitoring of AEC in invertebrates is not valuable as a pollution assessment tool for two reasons. In polluted stations, only pollutant-resistant species will be found, and there is evidence that the maintenance of a stable population is impossible when the individuals constantly have low AECs.     

Anaerobic metabolism of the common cockle Cardium edule

Changes in the level of the adenylates (ATP, ADP, AMP), arginine phosphate, arginine, octopine, D-lactate, succinate, and aspartate were determined in the foot of Cardium edule, after 12 h of anoxia and after aerobic recovery for up to 12 h. Control levels of the adenylates, the calculated energy charge and the arginine phosphate content were restored after about 1 h of recovery. On the other hand, the recovery of the D-lactate, succinate, and aspartate pools was a slow process, taking place over about 12h.     

Elemental and biochemical composition of salps (Tunicata: Thaliacea)

Carbon and nitrogen content have been measured in the solitary and aggregate generations of 11 species of salps. Regression equations for each species and generation permit estimation of carbon or nitrogen content as a function of length of live individuals. Different species of the same length may have nearly tenfold differences in carbon content. Fractionation and biochemical analysis of some samples revealed that the organic content of salps is approximately 80% protein. Ash-free dry weights average 27% of dry weights; mean carbon content is 29% of ash-free dry weight. Excess ash-free dry weight not accountable as organic material is thought to be water of hydration.     

Adenosine nucleotide “energy charge” ratios as an ecophysiological index for microplankton communities

Energy charge (EC) ratios of microplankton samples have been measured from their adenosine triphosphate (ATP), adenosine diphosphate (ADP) and adenosine monophosphate (AMP) contents, according to a method based on enzymatic tranformations of ADP and AMP into ATP, and the subsequent quantitative analysis of the latter by the bioluminescent reaction of a firefly lantern extract (Photinus pyralis). Interference caused by other non-adenylic nucleotides and bioluminescence inhibition by various compounds were reduced, or estimated, by the use of internal standards for each sample. This was accomplished both by the injection of a small volume of a non-commercial extract of P. pyralis and by measurement of the bioluminescent flash at its maximal value. This standard method for preparation and analysis afforded good reproducibility and permitted the calibration of individual samples, thus allowing the comparison and treatment of data in the large series necessary in oceanographic studies. Studies were made on natural populations taken from a polluted marine area where phytoplankton communities live under the stressful influence of an urban sewer outlet, near Marseille (France). Three sampling strategies in surface waters (transects from the outlet, sampling during a 24-h buoydrift, and regular sampling for a day-night period) conducted at a point in front of the outlet revealed a decrease of EC in relation to urban activity or approaching proximity of the sewer outlet. These low EC values (0.2 to 0.5) were caused by a high AMP content, perhaps originating from degraded biogenic particles and dead or metabolically impeded bacteria of terrestrial orgin stressed by ecologic factors such as increased salinity and decreased temperature. Further away from the sewage outlet, the EC increased as the bacterial population decreased, and the phytoplanktonic communities reappeared parallel to the dilution of the effluent. Although in mature and unperturbed ecosystems EC values of 0.70 to 0.80 were recorded, the values were generally lower than those measured in growing bacterial or phytoplankton cultures. This fact may be related to differences in the various metabolic states of multispecific populations. Some EC measurements from deeper microplankton samples presented in this paper were difficult to interpret, reflecting perhaps unsolved problems concerning the treatment of samples. However, it was possible to associate the range of variation in EC values to differences in composition and structure of the ecosystem of microplankton populations in neritic surface waters.     

Adenosine triphosphate and adenylate energy charge in marine sediments

The determination of adenosine triphosphate (ATP), adenosine diphosphate (ADP), and adenosine monophosphate (AMP) concentrations in sediments from both Puget Sound and the Washington State continental shelf (USA) has been investigated. Major losses during the extraction procedure included sediment sorption, coprecipitation, and unreactivity of the soluble adenylates presumably through irreversible binding to solubilized sediment organics. Addition of phosphoric acid and the non-ionic detergent Triton X-100 to cold sulfuric acid significantly increased the extraction efficiency and sensitivity over that of sulfuric acid alone, although both methods yielded similar results when corrected for losses. Vertical profiles of ATP, total adenylates (A_T), and adenylate energy charge (EC) in sediments from both areas are presented. Profiles of A_T are similar in both areas, but EC values in the shelf sediments are significantly lower, which suggests a depressed physiological condition in the shelf population relative to that in Puget Sound.Contribution No. 513 from the University of Washington's College of Fisheries, and Contribution No. 1135 from the University of Washington's Department of Oceanography     

Metabolic rates of epipelagic marine copepods as a function of body mass and temperature

Metabolic rates (oxygen consumption, ammonia excretion, phosphate excretion) have been calculated as a function of body mass (dry, carbon, nitrogen and phosphorus weights) and habitat temperature, using multiple regression. The metabolic data used for this analysis were species structured, collected from Arctic to Antarctic seas (temperature range: -1.7°C to 29.0°C). The data were further divided into geographical and/or seasonal groups (35 species and 43 data sets for oxygen consumption; 38 species and 58 data sets for ammonia excretion; 22 species and 31 data sets for phosphate excretion). The results revealed that the variance attributed to body mass and temperature was highest (93-96%) for oxygen consumption rates, followed by ammonia excretion rates (74-80%) and phosphate excretion rates (46-56%). Among the various body mass units, the best correlation was provided by the nitrogen unit, followed by the dry weight unit. The calculated Q₁₀ values varied slightly according to the choice of body mass units; overall ranges were 1.8-2.1 for oxygen consumption rates, 1.8-2.0 for ammonia excretion rates and 1.6-1.9 for phosphate excretion rates. The effects of body mass and temperature on the metabolic quotients (O:N, N:P, O:P) were insignificant in most cases. Although the copepod metabolic data used in the present analysis were for adult and pre-adult stages, possible applications of the resultant regression equations to predict the metabolic rates of naupliar and early copepodite stages are discussed. Finally, global patterns of net growth efficiency [growth (growth+metabolism)^-1] of copepods were deduced by combining the present metabolic equation with Hirst and Lampitt's global growth equation for epipelagic marine copepods.     

Effects of UV radiation of different wavebands on pigmentation, 15N-ammonium uptake, amino acid pools and adenylate contents of marine diatoms

Three marine diatoms Lauderia annulata Cleve, Odontella sinensis (Greville) Grunow and Thalassiosira rotula Meunier were exposed to ultraviolet (UV) radiation of different wavebands under controlled laboratory conditions (0.035 vol% CO₂, 18 °C). Several changes in the patterns of pigments in these organisms were seen depending on the waveband of UV radiation and species examined. UV-B and UV-B plus UV-A radiation led to a reduction in the overall pigment content of all three diatoms. The uptake of ¹⁵N-ammonium was less affected by 5-h UV-A (WG 320) but significantly reduced after UV-B and UV-B plus UV-A exposure. The pattern of free amino acid pools varied depending on the applied UV wavebands and the tested diatom. The main protein-bound amino acids of T. rotula decreased after 5-h UV irradiance except leucine. Contents of adenosine 5′-mono-, di-, and triphosphate (AMP, ADP and ATP) were affected differently by UV radiation; ATP values increased at the end of UV-B and UV-B plus UV-A exposure. These results have been discussed with reference to the impact of the different UV sources and the influence on the nitrogen metabolism in connection to pigments and supply with energy. Received: 13 May 1997 / Accepted: 11 October 1997     

Anaerobic metabolism in Arenicola marina and Nereis diversicolor during low tide

In order to observe the metabolic response of two marine polychaetes, Arenicola marina L. and Nereis diversicolor Müller, at various times during low tide, the concentrations of adenine nucleotides, phosphagens, D- and L-alanine, succinate, acetate, propionate and lactate were measured. During 8h of exposure ATP does not change significantly in the body-wall musculature of the lug-worm A. marina, whereas ADP and AMP concentrations double the first hour of exposure. Correspondingly, the energy charge falls from 0.91 to about 0.84. The concentration of the phosphagen phosphotaurocyamine decreases by about 20% during the first 2 h and after 6 h only about 50% of the initial concentration was measured. During exposure, aspartate decreases by approximately 6 mol g^-1 fresh weight within 6 h (from 23 to 17 mol g^-1 fresh weight). During the first 4 h of exposure succinate concentration doubles and within the next 4 h it reaches values about 10-fold the initial value. The concentrations of acetate and propionate only increase during the last 2 h (6–8) of exposure. After several hours of exposure typical changes in the concentrations of all these metabolites could also be demonstrated in N. diversicolor. The concentrations of the two phosphagens phosphoglycocyamine and phosphocreatine and of aspartate decrease by about 25% during 9 h of exposure, on the other hand succinate and especially D-lactate accumulate. In both species, the partial anaerobic energy production during exposure does not have a lasting detrimental effect. After one high tide the worms have fully recovered.     

Fatty acid composition of the triacylglycerols of the cypris larva of the barnacle Balanus balanoides during metamorphosis

In the free-swimming cypris larva of Balanus balanoides, the mean level of triacylglycerols (triglycerides) was 8% of the ash-free dry weight. During metamorphosis into the juvenile barnacle, the triacylglycerol level in the newly settled non-feeding cypris larva fell to a mean of 2% of the ash-free dry weight. The ratio of fatty acids in the triacylglycerols remained constant throughout metamorphosis, indicating that all species of fatty acids were used as energy sources. There was no evidence for the selective utilisation of particular fatty acids.     

Seasonal respiration changes in Pomatoschistus microps and Palaemon adspersus: an experimental simulation

In an attempt to reduce the effort involved in measuring seasonal variations in oxygen consumption, a simulation experiment was conducted with the goby Pomatoschistus microps (Krøyer) and the shrimp Palaemon adspersus (Rathke). Comparison of the results obtained by monthly conventional measurements on individuals taken directly from the biotope with those obtained from individuals after long-term adaptation to temperature and light conditions representative of the different seasons showed that the standard metabolic rates yielded by the two methods for both species are astonishingly similar, although slight differences appeared particularly during the early summer and early autumn. In contrast, the routine metabolic rates shown by the seasonal and simulated seasonal measurements differed considerably, the differences being particularly striking when considering the scope of the individuals for routine work and their metabolic expansibilities. In view of this, routine data obtained by experimental simulation of conditions appear to be of doubtful value.     

The prevalence of heavy metals in Cladophora glomerata L. from Farahabad Region of Caspian Sea – Iran

The presence of toxic heavy metals in the environment is considered as a risk factor for adverse human and environmental health effects. Farahabad Region is a tourist center in the southern coast of Caspian Sea in Mazandaran Province of Iran. Environmental monitoring of this site is important for public health for individuals visiting and residing in this region. Although numerous biomonitoring data are available globally, very few if any apparent investigations have been conducted in this region. In this study, concentration of three heavy metals chromium (Cr), lead (Pb), and cadmium (Cd) was determined for one year in Cladophora glomerata, the predominant macroalga species present in this region. Detection of heavy metals was performed with atomic absorption spectrophotometer using standard methods. Results showed that the range of Cr metal in various algal samples was 29–55 ppm/g dry weight. The levels of Pb in algal samples (Cladophora) ranged from 2 to 8 ppm/g dry weight. The Cd concentrations in C. glomerata biomass ranged from 1.5 to 8.2 ppm/g dry biomass. In view of potential threats of such high metal concentrations in coastal waters and in algal tissues, it is necessary to adopt conservation measures to ensure public health safety.     

Energy storage and dynamics in bay anchovy Anchoa mitchilli

The energy of the body components and the energy costs of spawning and overwintering in the bay anchovy Anchoa mitchilli, the most abundant fish in Chesapeake Bay, were studied to determine seasonal variability during the different stages of its life cycle. Bimonthly samples were collected by trawl from April 1990 through October 1991. Fish condition and body energy levels fluctuated seasonally, and were related to anchovy size. Energy equivalents (cal g^-1 dry wt) was highest in December, before the overwintering period. The somatic weight component increased by 32 to 33% and total body weight by 26% during the spawning season, indicating that feeding not only met energy requirements of daily spawning but also provided surplus energy for growth. The overwintering loss of energy was 33 to 35% of total body calories, and was primarily derived from deposit fat in somatic and visceral tissues.     

Spatial and seasonal variation of polychlorinated biphenyls in Songhua River, China

The spatial and seasonal variation of polychlorinated biphenyls (PCBs) were investigated in water and sediment samples collected from Songhua River, China, from 2007 to 2008. The total concentration of PCB congeners ranged from 1.1 to 14 ng/l in water and 0.26–9.7 ng/g dry weight (dw) in sediment. The results of seasonal variation may suggest an impact to PCB concentration in water from its atmospheric input, the dilution to PCBs concentrations of high stream in summer, and a general trend towards increased volatilization in warmer conditions. From PCBs concentrations comparison between upstream and downstream of industrial urban cities, it was obvious that industrial urban cities reflect an important pollutant source for PCBs in our study, also with the evidences of high concentrations of PCBs occurring in high development industry and residential areas. Meanwhile, the homologue profile of PCBs in Songhua was analyzed, whose comparison with published data indicates that the sources of PCBs accumulated in the sediment may also came from the residue of PCBs production in China. Total five dioxin-like PCBs (CB-77, 81, 105, 114, and 126) and nine (CB-77, 81, 105, 114, 118, 123, 126, 156, and 167) were found in Songhua water and sediment.     

Experimental studies on the effects of copper on a marine food chain

Effects of copper sulphate on a marine food chain were investigated in large tanks at Loch Ewe on the west coast of Scotland. The food chain consisted of phytoplankton, the bivalve Tellina tenuis da Costa, and O-group plaice (Pleuronectes platessa L). During initial months after settlement, T. tenuis siphons are an important food for juvenile plaice, which feed by grazing the siphon tips; these subsequently regenerate. Copper dose rates of 10, 30 and 100 μg Cu/1 were investigated; the distribution of added copper was monitored and its metabolic effects were determined. Copper levels in water, sand, in algae on tank walls, in T. tenuis shell and flesh, and in plaice muscle and viscera were measured by atomic absorption spectrophotometry. Copper accumulated in sand, T. tenuis flesh and shell, and plaice viscera. Accumulations were dose-dependent and in no case was a plateau concentration reached. Most of the added dose was taken up by the sand; accumulations in T. tenuis shell were small — less than twice background in all cases. High levels were found in T. tenuis flesh, where concentrations after 100 days were 270, 470 and 1100 μg Cu/g dry flesh for dose concentrations of 10, 30 and 100 μg Cu/1, respectively. The mean control concentration was less than 50 μg Cu/g dry flesh. There was no accumulation of copper in plaice muscle. Visceral accumulations after 100 days were 71, 147 and 567 μg Cu/g dry flesh for dose concentrations of 10, 30 and 100 μg Cu/1, respectively. The mean control level was 30 μg Cu/g dry flesh. The effect of copper on phytoplankton metabolism was investigated by measuring plant pigment levels and rates of primary photosynthetic fixation of C¹⁴-labelled bicarbonate. All dose concentrations reduced both the standing crop and the rate of photosynthesis per unit of chlorophyll a. The effects of copper on growth and condition of T. tenuis and P. platessa were investigated. All dose concentrations adversely affected T. tenuis condition (dry flesh weight for standard individual). The effect was most marked during deposition of winter reserves. In the absence of plaice predation, there was a decrease in the mean siphon weight for T. tenuis exposed to 30 and 100 μg Cu/1. For plaice, all dose concentrations of copper resulted in reduced growth, but there was no significant change in condition or biochemical composition. The ash weight of fish exposed to copper was significantly higher than for controls.     

Shifts in foraging behavior by a Battus philenor population: field evidence for switching by individual butterflies

Summary A bivoltine east Texas population of the pipevine swallowtail butterfly (Battus philenor) exhibits a seasonal shift in the shapes of non-host leaves upon which ovipositing females land. Field mark-recapture studies and analysis of the behavior of wild females of different ages were used to distinguish between two alternative mechanisms for the shift in the populations's predominant leaf-shape search mode: seasonal differences in the outcome of learning for successively emerging naive foragers which exhibit one preference for most of their lives vs. synchronous switching by experienced foragers from one learned preference to another. Results supported each hypothesis: (1) Since wild butterflies are short-lived, the seasonal shift in searching behavior must reflect at least partly the successive emergence of naive females that learn to prefer host species with different leaf shapes. The leaf-shape preferences of older females were, in fact, stronger and less variable than those of younger individuals. About 80% of 51 marked individuals maintained stable leaf-shape search modes over recapture events, exhibiting slightly stronger preferences in later observation periods. (2) Almost 16% of marked females switched search modes across recapture events. Unmarked females sometimes switched search modes within an observation period; switching occurred only after the discovery of the host species with a leaf shape differing from that originally preferred. Switching by individual butterflies was generally more frequent at the time an adult brood shifted from one dominant search mode to another. Individual switching within an adult brood was more common in those years in which the population's shift in predominant search mode occurred during that brood.The evolution of rapid learning by naive females and conservative switching by experienced females is discussed in relation to a quantitative model of switching dynamics.