A Nutritional Profile of the Social Wasp Polistes Metricus

A Nutritional Profile of the Social Wasp Polistes Metricus

Journal of Insect Physiology 56 (2010) 42–56 Contents lists available at ScienceDirect Journal of Insect Physiology journal homepage: www.elsevier.com/locate/jinsphys A nutritional profile of the social wasp Polistes metricus: Differences in nutrient levels between castes and changes within castes during the annual life cycle Timothy M. Judd a,*, Roxane M. Magnus a, Matthew P. Fasnacht b a Department of Biology, Southeast Missouri State University, Cape Girardeau MO, 63701, USA b Department of Chemistry, Southeast Missouri State University, Cape Girardeau MO, 63701, USA ARTICLE INFO ABSTRACT Article history: In wasps, nutrition plays a vital role for colony cohesion and caste determination. However, there is no Received 5 July 2009 baseline data set for the nutritional levels of wasps during the different stages of the colony cycle. Here Received in revised form 30 August 2009 we examined the levels of carbohydrates, lipids, protein, Ca, Cu, Fe, K, Mg, Mn, Na, and Zn in the wasp Accepted 9 September 2009 Polistes metricus at different stages of the wasp’s lifecycle. Individuals were collected at the following stages (1) spring gynes, (2) foundress colonies, (3) early worker colonies, (4) late worker colonies, (5) Keywords: emerging reproductives (gynes and males), (6) early fall reproductives, and (7) late fall reproductives. All Polistes eggs, larvae, pupae and adults were analyzed for their nutritional content to determine if there were any Nutrition differences between the nutrient levels in the different castes and how these nutrients changed within a Caste Cations caste during its lifetime. The results show there are differences in macro and micronutrient levels Macronutrients between the reproductive females and workers during development. Gynes showed changes in nutrient levels during their lifetime especially as they changed roles from a solitary individual to a nesting queen. Males also showed distinct nutritional changes during their lifetime. The implications for these nutritional differences are discussed. ß 2009 Elsevier Ltd. All rights reserved. 1. Introduction differences in gene expression within the developing castes (Evans and Wheeler, 2001; Kunieda et al., 2006; Wheeler et al., 2006). Understanding the nutritional needs and the nutritional state of Nutritional differences extend into adulthood in many of these an organism is important for understanding its physiology, devel- species. Reproductives tend to have higher lipid and storage opment, and behavior. Social insects provide a unique opportunity to proteins than workers in Hymenoptera (Peakin, 1972; O’Donnell, study the effects of nutrition on physiology because different 1998; Judd, 2006; Toth et al., 2009). Presumably these nutrients are functional components of a social insect colony have different important for ovarian growth, egg production and survival during nutritional needs much like different organs within an individual. In diapause and colony initiation. Much work has shown that addition, a single individual in a colony may change roles during its nutrients are distributed unequally through colonies such that lifetime which is potentially accompanied by physiological and individuals that need particular nutrients obtain more than those developmental changes (Robinson, 2009). As a result, the nutritional that do not (Peakin, 1972; Brian and Abbott, 1977; Sorensen and requirements may also change as well. Thus, a full understanding of Vinson, 1985; Sorenson et al., 1985; Hunt et al., 1987; Cassill and thenutritionalrequirementsandstates of individuals withinacolony Tschinkel, 1996, 1999a,b; Weeks et al., 2004; Hrassnigg and would provide insight into various levels of the biology of individuals Crailsheim, 2005; Judd, 2005; Judd and Fasnacht, 2007). within a colony and the biology of a colony as a whole. Behaviorally, workers of colonies can be influenced by the levels It has been known for a long time that nutrition plays a major of internal nutrient stores (Schultz et al., 1998; Blanchard et al., role in caste determination in many social insects (Wheeler, 1986; 2000; Judd, 2006) and down regulation of fatty acid synthesis (Toth Winston, 1987). In ants and honeybees the caste is influenced by et al., 2005). Workers with lower levels of nutrients are more likely the level of nutrition at a critical period during larval development. to forage (Blanchard et al., 2000; Kunieda et al., 2006). In addition, Termites (Roisin, 2000) and social aphids (Fukatsu and Ishikawa, the level of nutrition has been shown to influence colony cohesion 1992) also appear to have a nutritional component for caste in Polistes (Hunt and Dove, 2002; Karsai and Hunt, 2002). Polistes determination. These nutritional differences appear to trigger metricus larvae offer amino acid rich saliva to the adults (Hunt, 1991, 1994). If this saliva is artificially drained the colony will collapse (Hunt and Dove, 2002). Thus, nutrition is an important * Corresponding author. Tel.: +1 573 651 2365; fax: +1 573 651 2382. component for the maintenance of colonies in some eusocial E-mail address: [email protected] (T.M. Judd). insects. 0022-1910/$ – see front matter ß 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.jinsphys.2009.09.002 T.M. Judd et al. / Journal of Insect Physiology 56 (2010) 42–56 43 Surprisingly, apart from a few ant studies (Vinson, 1968, then initiate their own colony (Reeve, 1991). Little is known about Solenopsis invicta; Stein et al., 1990, Tschinkel, 1993, Pogonomyr- the nutritional fluctuations during the solitary phase of the Polistes mex badius; Tschinkel, 1998, Pheidole ceres, Judd, 2006), we know life cycle. Such information would bring new insight to the very little about natural nutritional levels and nutritional behavior of Polistes during the solitary phase of its life cycle. fluctuations of individuals within social insect colonies over the Our study was carried out to increase our understanding of the course of the colony cycle. The absence of fundamental data such role of nutrients in the regulation of social behavior and the as these has been discussed in several works (Tschinkel, 1991; nutritional needs of the reproductives during their solitary stage of Arrese et al., 2001; Hunt, 2007; Robinson, 2009). These papers life cycle. In this study, we looked at the nutritional content of suggest that much of the work with social insects has been focused individuals of P. metricus during different stages of the wasp’s life on testing specific theoretical ideas (Tschinkel, 1991), or for insects cycle, creating a nutritional profile for P. metricus. We included in general, investigating the roles of specific proteins or pathways collections from the pre-nesting period, three different phases of (Arrese et al., 2001). This has been especially true with the nesting and two collections post-nesting. Individuals were analyzed increasing advances in genomics research (Arrese et al., 2001). for their total carbohydrates, lipids, proteins, calcium (Ca), copper Recently, several new hypotheses have been put forth such as the (Cu), iron (Fe), potassium (K), magnesium (Mg), manganese (Mn), ‘‘diapause ground plan hypothesis’’ (Hunt and Amdam, 2005, Hunt, sodium (Na), and zinc (Zn). Thus, we were able to compare the same 2007) and the ‘‘dominance-nutrition hypothesis’’ (Markiewicz and caste during different stages of the life cycle and different castes O’Donnell, 2001; Molina and O’Donnell, 2008) emphasizing the within and between different stages of the life cycle. role of nutrition in the evolution and regulation of social behavior. At this juncture, the need for ‘‘nutritional profile’’ studies, the 2. Methods mapping out of natural nutritional levels in colonies at different stages of their life cycle, has become more evident than ever to 2.1. Study site complement the important advances in genomics and physiology to allow for a better understanding of the role of nutrition in the The study site was at Kelso Wildlife area owned by Southeast dynamics of social insect colonies. Missouri State University. The site consists of two adjacent fields Most nutritional ecology studies on insects have focused on the surrounded by woodlands. A wide path connects the fields to each levels of carbohydrates, proteins and lipids in the diets of other. The fields are close to a dirt road which has a number of organisms themselves. Other nutrients such as metal cations species of flowers blooming along the road side. Males and gynes could also have a potential effect on colony dynamics and caste frequented this spot during the fall (see below). determination. The role of micronutrients in the physiology of insects especially social insects has been largely neglected (Cohen, 2.2. Nest boxes 2004). Studies on non-social insects have found that several ions such as Ca, K, Na, Cu and Zn are important for growth, ovarian Nest boxes were 15.24 cm  15.24 cm  15.24 cm boxes con- development, and fecundity in insects (McFarlane, 1974, 1976, structed from wood. They were of similar construction as reported 1991). Judd and Fasnacht (2007) found that micronutrients are not in Gamboa et al. (1992). Two screws held the top of the box in distributed equally throughout the colony. Indeed, in most cases place. They were open in the front with a chicken wire screen to the micronutrients end up in the caste that has growing tissue. In protect the colony from bird predation. The box was mounted with addition, there is evidence that the levels of manganese differ baling wire onto a wooden stake about 1.3 m from the ground. A between pollen and nectar honey bee foragers (Ben-Shahar et al., total of 69 boxes were placed on the edge of the fields in the study 2004). This suggests that there may be a significant role for site. micronutrients in the regulation of caste determination but this has yet to be explored more fully. 2.3. Surveys and marking Primitively eusocial organisms such as Polistes provide an excellent model for nutritional profile studies because the life of a Colonies were monitored once a week and checked for number colony is restricted to one season.

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