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Feeding preferences of captive Morpho peleides at the Monteverde Butterfly Garden Beth Wright. Biology Department, Univer sity of Puget Sound ABSTRACT Morpho peleides is one of many tropical butterfly species that are fruit-feeding butterflies. In this paper, I will (1) explain the importance of biochemical compone nts in banana pulp including amino acids, sugar, and alcohol in the diet of M. peleides and how it affects the butterflies food choices, and (2) suggest how fermentation might encourage or discourage food preferences banana pulp with high or low concentrations of alcohol. Six combinations were tested in this study: mature pulp with amino acids, mature pulp with water, mature pulp with rum, overripe pulp with wate r, overripe pulp with amino acids, and overripe pulp with rum. There was no significant difference among average feeding durations (ANOVA: F ratio = 1.60; p value = 0.16; df = 5) or among frequencies of visits between each food type (Chi-square Goodness of Fit: 2 = 8.77, p > 0.05). The similarity between visit times and frequencies for banana pulp samples with higher concentrations of amino acids and rum can be explained by (1) previous research suggesting that it is more common for nectar-feeding butterflies to have preferences for amino acids than it is for fruitfeeding butterflies like M. peleides and (2) nutritional compensation of overripe bananas via (a) more amino acids released from the peel into the pulp or (b) higher sugar concentration peaks later on in the maturation process combined with stronger od or cues that attract the butterflies. RESUMEN Morpho peleides es una de muchas especies de mariposas tropicales que comen frutas. En este reporte explicar (1) la importancia de los compuestos bioqumicos en la pulpa de banano como amino cidos, azcar, y alcohol en el dieta de M. peleides y como lo afecta su eleccin de diferentes tipos de comida, y (2) explorar como el proceso de fermentacin puede animar o disuadir la eleccin por comida con ms o menos alcohol. Se probaron seis combinaciones en este estudio: pulpa de bananas maduros con agua, pulpa de bananas maduros con protena, pulpa de bananas ma duros con alcohol, pulpa de bananas ms maduros con agua, pulpa de bananas ms maduros con protena, y pulpa de bananas ms maduros con alcohol. No hubo una diferencia considerable entre el tiempo de alimentacin entre los tipos de comida o entre la frecuencia de visitas a los diferente tipos de comida. Esta homogeneidad entre los tiempos en los diferentes tipos de comida y frecuencias de visitas a pulpa con ms alcohol y ms protena se puede explicar de dos maneras. (1) Proyectos anteriores sugieren que es m s comn para mariposas que comen nctar a preferir comida con protena que para mariposas que comen frutas y (2) hay una compensacin de nutricional en la pulpa de bananos ms maduros en dos maneras: (a) ms protena fue transportado a la pulpa de la cscara y (b) ms azcar en la fruta durante fases ms tarde en el proceso de maduracin en combinacin con olores ms fuerte que atraen las mariposas. INTRODUCTION Tropical butterflies can feed on a number of sources such as nectar from flowers, and other sugar and mineral rich sources like diffe rent types of fruit, sap from trees, mud, carrion, dung, and pollen (Molleman et al. 2005). One of the larges t feeding guilds in butterfly species is the fruit-feeding guild, which includes Morpho peleides commonly known as the Blue Morpho butterfl y. In this paper, I will (1) explain the importance of different biochemical components in banana pulp including amino acids, sugar, and alcohol in the diet of M. peleides and how it affects the butterf lies food choices, and (2) suggest how fermentation might encourage or discourage food preferences between banana pulp with high or low concentrations of alcohol.
In contrast to nectar, fruit is known to contain higher amounts of necessary proteins, creating less dependen ce on the larval food reserves by fruit-feedi ng butterflies than the nectar-feeding butterf lies (Molleman et al. 2005). It was suggested that this difference could affect longevity, but there has been little supportiv e evidence of such a relationship in fruit-feeding bu tterflies. In contrast, there has been some evidence to the contrary demonstrating that neither longevity nor egg production was influenced by proteins in the diets of Bicyclus anynana a fruit-feeding butterfly species (Molleman et al. 2005). Tropical fruit-feeding butterflies typically feed on overripe or decaying fruit that are found on the ground in forests (Molleman et al. 2005). This could be due to the increase in sugar concentrat ions followed by a rapid decr ease as the ripening process occurs. As the amount of starch declines in bananas during ripening, the concentrations of sugar increase due to chemical conversions (Emaga et al. 2007). Varying sugar concentrations are confirmed by Zhang et al. (2005), who determined that pulp from a green banana contains 1.23% sucrose, which increases to 53.2% sucrose in a fully ripe banana. This conversion from starch to hi gher amounts of sugar could enable a female butterfly to acquire lacking amino acids, and the differentiation between food choices regarding sugar concentrations may be based on a fitness decision in an effort to gain more proteins. Alternatively, the nitrogen cont ent of the same fruit, required for the production of proteins and nucleic acids, wa s higher than known nitrogen amounts in nectar from flowers (Molleman et al. 2005). Fr uits, like bananas, also contain secondary compounds, alcohols (Molleman et al. 2005), sugar, starch, fiber, minerals such as potassium (Emaga et al. 2007), and amino acids such as leucine, valine, phenylalanine and threonine in consistent concentrations throughout fruit maturation (Emaga et al. 2007), which are often used by female butte rflies for egg production (O'Brien et al. 2003). As bananas mature, the amount of ethylene alcohol increases as well (Taiz & Zeigler 1991) via fermentation, a result of anaerobic processes (Biale 1964) and degradation processes. Fermentation should l ogically create shorter feeding spans, as it has been suggested that butterflies can beco me inebriated from high amounts of alcohol (Molleman et al. 2005), and might avoi d food sources with that component. In this study, I examined the food preferences of M. peleides based on two sources of banana pulpmature bananas a nd overripe bananas, as they have vastly different concentrations of alcohol due to natural fermentation. I also added rum (to increase the alcohol concentr ation in the samples) and amino acids (to supplement the pulp with more nutrients) to samples from each source to determine if there was a preference between different combina tions. Since my hypothesis was that M. peleides could recognize variances between the nutriti onal values of each food combination to choose pulp samples accordingly, I expected to see differences in both number of visits and time spent feeding at each sample. I predicte d that the visits to the pulp samples with rum and the pulp samples from the overripe bananas would have shorter and less frequent visits than the other samples, as Molleman et al. (2005) noted that butterflies generally do not like high amounts of alcohol. Additionally, I predicted that since amino acids provide necessary proteins to some species of bu tterflies, there would be longer and more frequent visits to the samples with amino aci ds. In decreasing order, I expected to see
longer visits to mature pulp with amino acids, mature pulp, mature pulp with rum, overripe pulp with amino acids, overrip e pulp, and overripe pulp with rum. MATERIALS AND METHODS Study SiteThe study was conducted at the Monteverde Butterfly Garden, in Monteverde, Costa Rica. There were a pproximately 70 adult individuals of M. peleides within the net-enclosed area that were reared in captivity. The butterf lies were fed banana pulp prior to each of the six observation days. Food Preparation The peels of two mature bananas and three overripe bananas were removed and the fruit was mashed with to a pu lp consistency and stor ed in two separate, labeled jars. All sample mixtures of matu re and then overripe bananas were mashed thoroughly to ensure homogeneity. Five ml of water, rum, or amino acids were added to 45 ml of both a mature banana pulp sample and 45 ml of an overripe banana pulp sample, making six combinations: mature pulp with water (10% by volume or 3.6 g of water and 90% by volume or 43.31 g of banana), mature pulp with amino acids (10% by volume or 3.08 g amino acids and 90% by volume or 44.13 g of banana), mature pulp with rum (10% by volume or 4.61 g of rum and 90% by vol ume or 45.9 g of banana), overripe pulp with water, overripe pulp with amino acids, and overripe pulp with rum. ObservationsOne set of three mature banana samples (mature pulp with water, mature pulp with amino acids, and mature pulp with rum) and one set of three overripe samples (overripe pulp with water, overripe pulp w ith amino acids, and overripe pulp with rum) were set on plastic lids, with the mature sa mples consistently on the left and overripe samples consistently on the right (Figure 1). Additionally, a replica of each set (as described above) was located on two nearby le aves. Prior to collecting data, all other bananas in the butterfly garden, typically left out for butterfly feeding, were removed for the duration of the observations to ensure that butterflies would have no other feeding options apart from the pulp. Since the juice from the banana pulp samples did travel from the point of origin, visits were recorded if the butterflies we re feeding on the juices from identifiable specific pulp samples. Data coll ection occurred for five hours in mornings from 9:30 AM to 1:30 PM due to peak butte rfly activity during th at time period. Two types of data were collected. First, for each feeding visit by a single individual, the start time and stop time were recorded as accurately as possible to calculate the amount of time per visit. On some occasions, estimates were made based on local position on the leaves or plates. Sample sizes for the timebased data on the six food types ranged from 15 visits for mature pulp with water to 46 visi ts for overripe pulp with rum. Alternatively, the frequency of feeding visits were reco rded for each pulp sample by utilizing scan sampling every five minutes to record the am ount of butterflies present on each sample. Sample sizes for the frequency-based data on six food types ranged from 28 visits for mature pulp with water to 46 visits to mature pulp with rum (Table 1). Three days of data collection were completed for each of the tw o types of data, and after over 100 visits observed for frequency data, observati ons were switched to timed visits. StatisticsAn ANOVA was run to compare the average lengths of time M. peleides spent feeding on each of the six different food t ypes. Additionally, a Chi-Square Goodness of Fit analysis was conducted on the frequency of visits to each of th e six pulp types to determine if some pulp samples were vi sited more frequently than others.
RESULTS There was no significant difference in th e average feeding times between the six locations (Figure 2), though th e range of time spent feedi ng at the banana pulp ranged from less than one minute to 47 minutes at mature pulp with water. Additionally, though there was no significant difference in frequencies of vis its between the banana pulp samples, the number of visits received for each food type ranged from 28 to 43 (Table 1). 0 2 4 6 8 10 12 14 Mature Banana Pulp with Water Mature Banana Pulp with Amino Acids Mature Banana Pulp with Rum Overripe Banana Pulp with Water Overripe Banana Pulp with Amino Acids Overripe Banana Pulp with Rum Type of Food n 15 n 29 n 33 n 33 n 25 n 46 Figure 2. Average time spent feeding on six different combinations of banana pulp: mature banana pulp with water, mature banana pulp with amino acids, mature banana pulp with rum, overripe banana pulp with wate r, overripe banana pulp with amino acids, and overripe banana pulp with rum. Timed observations were run at the Monteverde Butterfly Garden. There was no significant difference in the average feeding times between the six food types (ANOVA: F ratio = 1.60; p value = 0.16; df = 5). Therefore, the butterflies were not spending more or le ss time on a given type of food. Sample sizes (visits) for each food type were as follows: n = 15 (Mature Banana Pulp with Water), n = 29 (Mature Banana Pulp with Amino Acids), n = 33 (Mature Banana Pulp with Rum), n = 33 (Overripe Banana Pulp with Water), n = 25 (Overripe Banana Pulp with Amino Acids), n = 46 (Overripe Banana Pulp with Rum). Standard error bars are shown. Table 1. Amount of feeding visits received by each food type. There were no significant differences between the frequencies of vis its to each of the food types (Chi-square Goodness of Fit: 2 = 8.77, p > 0.05). Food Type Frequency of Visits Mature banana pulp with water 28 Mature banana pulp with amino acids 29 Mature banana pulp with rum 46 Overripe banana pulp with water 34 Overripe banana pulp with amino acids 29 Overripe banana pulp with rum 43
DISCUSSION My hypothesis regarding M. peleides detecting varying nutriti onal values and choosing a food source accordingly was not supported by my results. Morpho peleides butterflies did not spend a longer or shorter length of time on a given type of food as was predicted (Figure 2). Additionally, they did not visit any specific pulp sample with higher or lower frequencies (Table 1). The results indicate that amino acids were not favored nor were the overripe samples with rum avoided (Figure 2) There are multiple possibilities for this outcome. First, amino acids may not have been preferred because female M. peleides individuals either had received enough nutriti on as larvae or because amino acids do not affect fecundity in this particular spec ies. Referring to the former reason, the M. peleides individuals at the Monteverde Butterfly Garden likely received sufficient amounts of food and high quality nutrients during their larval stage. In regards to the latter reason, Mevi-Shutz & Erdhart (2003) noted that there was a female preference for amino acids in some species for nectar-feeding butterflies and that food choice in these species was dependent on larval food quality (caterpillar s, like other herbivores gain nutrients by consuming various plant parts (Mattson 1980) of their host plant). Additionally, some female butterflies oviposit their eggs on the sa me plant that they feed on (Janz et al. 2005) indicating that perhaps there is a dietary quality in the plant ( like amino acids) that the butterflies can detect and actively d ecide to lay eggs on that plant. Since M. peleides are fruit-feeding butterflies, it is less likel y that female individuals would exhibit a preference for amino acids due to the observation that preferences for amino acids seems to be found only in nectar-feeding butterfli es. This is supported by the fact that relationships between amino acids in adult butterfly diets, longevity and egg production have not been found for fruit-feeding bu tterflies (Molleman et al. 2005). Second, banana peels contain many nutrients such as amino acids that may seep into the banana pulp as the outer peel erodes away (Emaga et al. (2007). Since the overripe bananas had the peels on longer than the mature bananas, the overripe bananas may have gained more amino acids from the peel than the mature bananas. This increase in amino acids in overripe bananas could bala nce out the decreased appeal of the higher concentrations of alcohol, by adding enough nut ritional value to the overripe bananas so that visitation lengths of times and freque ncies between the banana pulp samples were more equivalent. However, it appears that amino acids are not attractive by themselves as there was no preference for this in overripe samples or amino acid samples, refuting the banana peel theory. Third, as noted by Molleman et al. (2005), butterflies use cues such as food odors to find food. Stronger odors of alcohol via fe rmentation present stronger signals than food sources with less alcohol (Molleman et al 2005). The previous suggestion by Molleman et al. (2005) that fermented fruits causes but terflies to become inebriated (possibly making fermenting fruits less desirable as food) is contrary to the results presented in this paper. Molleman et al. (2005) also found that mature bananas did receive a large amount of feeding visits, but not as many visits as the overripe, fermenting banana (reportedly due to volatiles likely ethylen ein the fruits). Molleman et al. (2005)s results support the notion that there is some biochemical compound in overripe bananas that make it attractive, even with the less desirable highe r concentration of alc ohol. This additional important compound could be sugar, and the combination of higher amounts of sugar and
alcohol could explain the compensation (demons trated in longer and more feeding times than expected) for the less desirable possibility of becoming inebriated. Biologically, then, the butterflies are attracted to the strong odors and feed on the relatively higher amounts of sugar. As a side note, there is a weaker odor in mature pulp with rum than in the overripe pulp due to the early stage of maturation and a relatively smaller amount of sugar. Therefore, the hypothesis th at butterflies would make decisions between food choices based on detectable nutritional valu es was not supported in this study, but it is logical to think that choosi ng food sources with higher suga r and protein concentrations would prove beneficial for egg production (O'Brien et al. 2003 ) longevity as a result of adult dietary intakes (Mevi-Schutz & Erdhardt 2005), body size, and development, especially if the butterfly did not receive enough nutriti on as a larva (Mevi-Schutz & Erdhardt 2005; Mevi-Shutz & Erdhart 2003). In the future, it would prove beneficial to address questions to increas e the understanding of how M. peleides decides which food sources to consume, such as (1) how amino acid supplements affect fecundity or longevity in M. peleides (to determine if they are fora ging adaptively) as well as (2) examining how different odors affect the ability of M. peleides to detect food. There is a sufficient amount of information still unknow n about butterfly feeding choices. The answers to these questions could assist res earchers in determining what exactly is the deciding factor in food choices, which coul d prove to be important for butterfly conservation. Acknowledgements Thanks to Karen and Alan Masters for the inspiration for this project. Thanks to Mark Wainwright who led a butterfly diversity field problem in Santa Rosa, which encouraged me to conduct research with butterflies. Thanks to Jim Wolfe and the Monteverde Butterfly Garden for letting me conduct my project there. Thank you to the staff at the Monteverde Butterfly Garden for being so friendly. Thanks to Karen Masters, Camryn Pennington and Kalle Larson for reading drafts and offering suggestions for improvement. Thanks to Pablo Allen for helping me get the Power Point presentation ready. Thanks to the Estacin Biolgia de Monteverde for access to co mputers and the hospitality. Literature Cited: BIALE, J. 1964. Growth, maturation, and senescence in fruits. Science: New Series. 146: 3646. 880-888. EMAGA, T., R. ANDRIANAIVO, B. WATHELET, J. TCHANGO, AND M. PAQUOT. 2007. Effects of the stage of maturation and varieties on the chemical composition of banana and plantain peels. Food Chemistry. 103: 590-600. JANZ, N., A. BERGSTROM, AND A. SJOGREN 2005. The role of nectar sources for oviposition decisions of the common blue butterfly Polyommatus icarus. Oikos. 109 : 3: 535-538. MATTSON, W. 1980. Herbivory in Re lation to Plant Nitrogen Content. Annual Review of Ecology and Systematics. 11. pp. 119-161. MEVISCHUTZ, J., AND A. ERDHARDT. 2003. Larv al nutrition affects female nectar amino acid preference in the Map Butterfly ( Arashchnia levana ). Ecology. 84 (10):2788-2794. MEVI-SCHUTZ, J.AND A.ERDHART. 2005. Amino acids in nectar enhance butterfly fecundity: A longawaited link. The American Naturalist. 165: 4. MOLLEMAN, F. M. VAN ALPHEN, P. BREAKEFORD, AND B. ZWAAN. 2005. Preferences and food quality of fruit-feeding butterflies in Kiba le Forest, Uganda. Biotropica 37: 4. 657-663 O'BRIEN, D., C. BOGGS, AND M. FOGEL. 2003. Pollen feeding in the butterfly Heliconius charitonia : isotopic evidence for essential amino acid transf er from pollen to eggs Proceedings: Biological Sciences. 270: 2631-2636.
TAIZ, L. AND E. ZEIGLER. 1991. Plant Physiology Benjamin/ Cummings Publishing Company Inc. USA. ZHANG, P., R. WHISTLER, J. BEMILLER, AND B. HAMAKE R. 2005. Banana Starch: production, physiochemical properties and digestibilitya review. Carbohydrates Polymers. 59: 443-458. Appendix OR OAA O MR MAA M Figure 1. Diagram of banana pulp samples. Th e left plate is from mature bananas while the right plate is from overripe bananas. M = Mush with water, O = Mush with water, MAA = Mush with amino acids, OAA = Mush with amino acids, MR = Mush with rum, OR = Mush with rum.
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Las preferencias de alimentacin de Morpho peleides en el Jardn de Mariposas Monteverde
Feeding preferences of captive Morpho peleides at the Monteverde Butterfly Garden
Morpho peleides is one of many tropical butterfly species that are fruit-feeding butterflies. In this paper, I will (1) explain the importance of biochemical components in banana pulp including amino acids, sugar, and alcohol in the diet of M. peleides and how it affects the butterflies food choices, and (2) suggest how fermentation might encourage or discourage food preferences banana pulp with high or low concentrations of alcohol. Six combinations were tested in this study: mature pulp with amino acids, mature pulp with water, mature pulp with rum, overripe pulp with water, overripe pulp with amino acids, and overripe pulp with rum. There was no significant difference among average feeding durations (ANOVA: F ratio = 1.60; p value = 0.16; df = 5) or among frequencies of visits between each food type (Chi-square Goodness of Fit: 2 = 8.77, p > 0.05). The similarity between visit times and frequencies for banana pulp samples with higher concentrations of amino acids and rum can be explained by (1) previous research suggesting that it is more common for nectar-feeding butterflies to have preferences for amino acids than it is for fruit-feeding butterflies like M. peleides, and (2) nutritional compensation of overripe bananas via (a) more amino acids released from the peel into the pulp or (b) higher sugar concentration peaks later on in the maturation process combined with stronger odor cues that attract the butterflies.
Morpho peleides es una de las muchas especies de mariposas tropicales que comen frutas. En este reporte explicar (1) la importancia de los compuestos bioqumicos en la pulpa de banano incluyendo el amino cido, la azcar, y el alcohol en la dieta de M. peleides y como le afecta su eleccin de diferentes tipos de comida, y (2) sugiere en como el proceso de fermentacin puede animar o disuadir las preferencias de pulpa de banano con concentraciones altas o bajas en alcohol.
Text in English.
Tropical Ecology 2007
Ecologa Tropical 2007
Mariposas que se alimentan de frutas
Mariposas que se alimentan de nctar
t Monteverde Institute : Tropical Ecology