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Atta Sexdens (Hymenoptera: Formicidae) Queens Perform More Selfgrooming Behaviors Than Broodcare Or Tending Fungus Garden Behaviors

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Atta Sexdens (Hymenoptera: Formicidae) Queens Perform More Selfgrooming Behaviors Than Broodcare Or Tending Fungus Garden Behaviors RESUMOXVIII Simpósio EXPANDIDO de Mirmecologia 032 385A THE BEST FOUNDING STRATEGY: ATTA SEXDENS (HYMENOPTERA: FORMICIDAE) QUEENS PERFORM MORE SELFGROOMING BEHAVIORS THAN BROODCARE OR TENDING FUNGUS GARDEN BEHAVIORS A melhor estratégia de fundação: rainhas de Atta sexdens (Hymenoptera: Formicidae) executam mais comportamentos de auto-limpeza do que comportamentos de cuidado com a prole ou com o fungo simbionte J.O. Augustin* & J.F.S. Lopes Universidade Federal de Juiz de Fora, Instituto de Ciências Biológicas, Campus Universitário Martelos, CEP 36036-330, Juiz de Fora, MG, Brazil; [email protected] An ant colony founding stage is defined as the behavioral acts performed by A. sexdens queens during earliest period of the colony life cycle, in which the both founding and early ergonomic stages. founding queen raises the first brood of workers up to Just after their nuptial flight in early november, 211 the moment the first adult individuals emerge. Once reproductive females of A. sexdens were collected in the first adults emerge, the colony begins to grow both pasture fields within the City of Juiz de Fora (21°46‘S– in biomass and number of individuals, what 43°21‘W, 678 m average altitude), southeastern Brazil. characterizes the ergonomic stage (HÖLLDOBLER & Queens were collected with the aid of tweezers and WILSON, 1990). individually placed in transparent plastic containers The few behavioral comparative studies between (12 cm of diameter and 10,5 cm of height) with a 1 cm the founding and ergonomic stages reveal that layer of dampened plaster at their base to keep humidity claustral queens spend more time with broodcare inside the chambers. With the aid of needle tip, small (CASSIL, 2002) and, in the particular case of the fungus holes on the chamber covers were made in order to growers, with the care of the fungus garden, relatively allow the entrance of oxygen in the colonies. Labelled to the ergonomic stage (AUTUORI, 1942; M ARICONI, 1970; containers permitted the identification of the colonies FERNÁNDEZ-MARÍN et al., 2003, 2004). However, there is to be observed every week. Laboratory conditions a lack of detailed information on the behavioral acts were kept in 25 ± 5° C, 70 to 80% of relative humidity performed by claustral Attini queens. Species of Atta and photoperiod of 12 hours. Fabricius, 1804, which initiate natural colonies from The Focal Animal Sampling method (ALTMANN, a single reproductive female and whose populations 1974) was conducted in 30 colonies, starting from the reach up to eight million individuals (RILEY et al., following day since the queens were collected. It took 1974; HÖLLDOBLER & WILSON, 1990), are particularly the colonies 11 weeks before the first workers emerged, interesting organisms from both the evolutionary and so that observations were extended for more 11 weeks behavioral point of view. This is mainly because such after workers emerged in each colony. Six colonies insects exhibit a mutualistic relationship with the were observed per day, during 30 uninterrupted fungus Leucoagaricus gongylophorus (Möller) Singer, minutes each. After 22 weeks, colonies had been 1986, which they obligatorily cultivate as their observed for 11 hours each, during both the founding essential food source (WEBER, 1972; HÖLLDOBLER & and the ergonomic stages. WILSON, 1990; CURRIE, 2001). Queens that eventually perished were replaced by Considering that the establishment of a new colony other ones from the same sample. may be a key feature to understand the evolutionary Behaviors were recorded as single occurrences adaptations by which many social insects went regardless of their duration. Data were found to be not through (HÖLLDOBLER & WILSON, 1990; PEETERS & ITO, normally distributed according to the Kolmogorov- 2001; BROWN & BONHOEFFER, 2003; FERNÁNDEZ-MARÍN et Smirnov modified by Lilliefors test. In order to evaluate al., 2003; FERNÁNDEZ-MARÍN et al., 2004; JOHNSON, 2006), differences in the absolute frequencies of the behavioural this study focuses on the behavior of A. sexdens queens acts both in different phases within the founding stage when establishing new colonies under laboratory as well as in between the founding and ergonomic conditions. The aim of this work was to compare the stages, all data were analyzed by means of c2 test. *Programa de Pós-Graduação em Comportamento e Biologia Animal. Biológico, São Paulo, v.69, suplemento 2, p.385-387, 2007 386 XVIII Simpósio de Mirmecologia Queens were found to perform four types of behaviors after 22 weeks since the queens’ nuptial flight, even in both the founding and ergonomic stages (Table 1). after 11 weeks since the first workers emerged. Being inactive was also considered a behavioral act for This study also shows the importance of the it may potentially function as a resting behavior. While selfgrooming behavior for founding A. sexdens queens, 83,84% of all behaviors were performed by the queens because it was far the most frequently recorded behavior. 3 during the founding stage, only 16,16% of them were Indeed, selfgrooming contributed with more than /4 of performed during the ergonomic stage. Selfgrooming, the behaviors performed by the queens. This result broodcare and tending fungus garden were differs from what has been found for newly mated significantly more frequent in the founding than in the monogyne Solenopsis invicta Buren, 1972 queens, which ergonomic stage. On the other hand, being inactive was spent most of their time on broodcare during colony significantly more frequent in the ergonomic stage. In founding (CASSIL, 2002). Providing round-the-clock order to evaluate when the queens were comparatively broodcare has been interpreted as a compensatory more active, either in the founding or in the ergonomic strategy for rearing brood without workers‘ help once stage, we suppressed the frequencies previously it guarantees a quick development of the offspring recorded for being inactive. We found that the queens (CASSIL, 2002). However, Attini queens face a challenge performed 85,02% of the behaviors in the founding that goes beyond the care of offspring: they must cultivate stage and 14,98% of the behaviors in the ergonomic their ancient symbiotic partner, the fungus garden stage. This result shows that the queens were Leucoagaricus gongylophorus (Möller) Singer, 1986. It comparatively more active during the founding stage has been demonstrated however that the fungus garden than during the ergonomic stage (c2 = 51,127; p <0,001). is the host of the specialized parasite Escovopsis The most frequently recorded behavior, relatively to all (Ascomycota: Hypocreales) which is only known from behaviors in both the founding and the ergonomic Attini gardens (SEIFERT et al., 1995; CURRIE et al., 1999a). stages, was selfgrooming, which contributed with more Because the symbiotic fungus is their main food source 3 than /4 of the behaviors performed by the queens. (QUINLAN & CHERRET, 1979), the ants were favored with The fact that the frequencies of selfgrooming, a series of selfgrooming and garbage disposal behaviors broodcare and tending fungus garden were that protect the colony against parasites (WILSON, 1980; significantly higher in the founding stage compared to CURRIE & STUART, 2001; FERNÁNDEZ-MARÍN et al., 2003). the ergonomic stage together with the fact that being Besides, attine queens have been found to live in a inactive was significantly more recorded in the mutualistic association with the filamentous bacteria ergonomic stage than in the founding stage strongly Streptomyces, which produces specific antibiotics indicate that, despite being incipient, young colonies of against Escovopsis (CURRIE et al., 1999b). In A. sexdens exhibited one of the most distinctively phylogenetically derived ants such as Mycocepurus, characteristics that is formally used to define eusocial Cyphomyrmex, Trachymyrmex and Acromyrmex the insects: reproductive division of labor (HÖLLDOBLER & mutualist bacteria was found on the ventral plates of WILSON, 1990; CROZIER & PAGE, 1996). Although were the propleura, while in the phylogenetically basal neither the queens’ egg laying behavior nor the workers’ Myrmicocrypta and Apterostigma ants, the filamentous behaviors recorded in this study, our results show that bacteria was found under the forelegs. Although not the queens were comparatively more active in the visible on the exoesqueletum of any Atta species, founding stage than in the ergonomic stage, suggesting Streptomyces has been isolated from both workers and that, once workers had emerged, the queens gradually queens of Atta colombica and A. cephalotes (CURRIE et al., refrained from working at the colony maintenance so 1999b). Thus, performing selfgrooming behaviors at a that to spend their time solely on laying eggs, what high frequency possibly indicates the presence of characterize the reproductive division of labor in the Streptomyces on the exoesqueletum of A. sexdens queens, insects societies (HÖLLDOBLER & WILSON, 1990). Further who would probably perform selfgrooming in an investigations should elucidate how gradually A. attempt to spread Streptomyces over their bodies so that sexdens queens rely on workers to perform the behaviors to minimize colony contamination by pathogens. If this related to colony maintenance. Such work is in progress is the case, then selfgrooming may be understood as a (J. DE O. AUGUSTIN & J.F.L. SANTOS, in prep.). prophylactic behavior adopted by A. sexdens queens to The fact that during the ergonomic stage
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