View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Open Archive Toulouse Archive Ouverte Open Archive Toulouse Archive Ouverte (OATAO) OATAO is an open access repository that collects the work of Toulouse researchers and makes it freely available over the web where possible. This is an author-deposited version published in: http://oatao.univ-toulouse.fr/ Eprints ID: 11543 Identification number: DOI : 10.1007/s00114-013-1091-9 Official URL: http://dx.doi.org/10.1007/s00114-013-1091-9 To cite this version: Dejean, Alain and Revel, Messika and Azémar, Frédéric and Roux, Olivier Altruism during predation in an assassin bug. (2013) Naturwissenschaften, vol. 100 (n° 10). pp. 913-922. ISSN 0028-1042 Any correspondence concerning this service should be sent to the repository administrator: [email protected] Altruism during predation in an assassin bug Alain Dejean & Messika Revel & Frédéric Azémar & Olivier Roux Abstract Zelus annulosus is an assassin bug species mostly sticky substance of the sundew setae on their forelegs aids in noted on Hirtella physophora, a myrmecophyte specifically prey capture. Group ambushing permits early instars to cap- associated with the ant Allomerus decemarticulatus known to ture insects that they then share or not depending on prey size build traps on host tree twigs to ambush insect preys. The Z. and the hunger of the successful nymphs. Fourth and fifth annulosus females lay egg clutches protected by a sticky instars, with greater needs, rather ambush solitarily on differ- substance. To avoid being trapped, the first three instars of ent host tree leaves, but attract siblings to share large preys. nymphs remain grouped in a clutch beneath the leaves on Communal feeding permits faster prey consumption, enabling which they hatched, yet from time to time, they climb onto the small nymphs to return sooner to the shelter of their leaves. By upper side to group ambush preys. Long-distance prey detec- improving the regularity of feeding for each nymph, it likely tion permits these bugs to capture flying or jumping insects regulates nymphal development, synchronizing molting and that alight on their leaves. Like some other Zelus species, the subsequently limiting cannibalism. Communicated by: Sven Thatje Keywords Conspecific tolerance Predation Prey sharing Reduviidae . Zelus annulosus A. Dejean (*) Écologie des Forêts de Guyane, Campus agronomique, BP 316, 97379 Kourou cedex, France e-mail: [email protected] Introduction A. Dejean Group hunting followed by food sharing brings fitness bene- Université de Toulouse; UPS, Ecolab, 118 route de Narbonne, 31062 Toulouse, France fits to the participants through increased per capita food intake while minimizing the cost of capture. Indeed, in addition to M. Revel avoiding predation, preys are captured more effectively with National Research Council of Canada, 6100 Royalmount Avenue, less risk of injury. This is known in social spiders (Settepani Montreal, Quebec H4P 2R2, Canada et al. 2013; Yip and Rayor 2013) and some ant species (Cerda M. Revel and Dejean 2011) and, among vertebrates, in fishes (de Waal Centre INRS, Institut Armand-Frappier, Université du Québec, 2006), birds, cetaceans, otters, carnivorans, and chimpanzees Laval, Quebec H7V 1B7, Canada (see the synthesis in Bailey et al. 2013). Harris hawks coop- F. Azémar eratively hunt and rear young (Coulson and Coulson 1995). CNRS, Laboratoire Écologie Fonctionnelle et Environnement Hyenas, Lycaon, wolves, and lions also redistribute food (UMR-CNRS 5245), 31062 Toulouse, France between adults (Bailey et al. 2013), as do eusocial insects. Delayed benefits from food sharing occur in vampire bats F. Azémar Université de Toulouse; UPS, INP, Ecolab, 118 route de Narbonne, which regularly fail to obtain blood, their only food, and die 31062 Toulouse, France after 70 h if starved. Unsuccessful individuals can receive regurgitations from roost-mates, frequently relatives. Yet, re- O. Roux ceiving regurgitations depends mostly on having previously IRD; Maladies Infectieuses et Vecteurs, Ecologie, Génétique, Evolution et Contrôle (UMR-IRD 224), Équipe BEES, IRD 01, BP provided the helper with blood, resulting in the formation of 171, Bobo-Dioulasso, Burkina Faso food-sharing groups characterized by mutual allogrooming (Carter and Wilkinson 2013). A chimpanzee possessing food, decemarticulatus, shelter. Workers of this species build particularly meat, can share it with close relatives or in re- gallery-shaped traps permitting them to capture preys 1,800 sponse to harassment by beggars or obtain a delayed benefit times their weight (Dejean et al. 2005, 2013;Grangieretal. through grooming and forming coalitions according to dom- 2008a). Allomerus workers tolerate the fragile Z. annulosus inance (Silk et al. 2013). Altruistic motivation for food sharing first instar nymphs on their host plants (these nymphs are thus exists in bonobos which share their food with a stranger rather protected from other ants) and, later, the relatively large last than with a group mate, but do not give food if a social instar nymphs do not attack these ants (Revel et al. 2010). interaction is impossible (Tan and Hare 2013). Although several authors have provided information on the In insects, egg clutching, in addition to improving egg predatory behavior of different harpactorine species (Edwards survival by preventing desiccation, is often associated with 1966;Inoue1982, 1985;Haridassetal.1987, 1988; Weirauch toxicity or impalatability and favors larval/nymphal aggrega- et al. 2012; Zhang and Weirauch 2013), we aimed to verify if tion (Janz 2002) which frequently permits early instars to clutch laying by females is followed by nymph clustering with organize a group defense (Jolivet 2008). Feeding efficiency the subsequent possibility of group hunting and prey sharing is improved when larval aggregation is associated with com- by examining the modalities of their hunting behavior. munal feeding in the herbivore larvae of sawflies, chrysomelid beetles, and lepidopterans (Wilson 1971; Grégoire 1988). Communal feeding is infrequent among predatory insects that Materials and methods lay their eggs in clutches. Group hunting and prey sharing were noted in the first instar larvae of aphidophagous Study site and models ladybirds (Moore et al. 2012), in the nymphs and adults of a predacious pentatomid (Heteroptera) (Ables 1975), and in This study was conducted between 2009 and 2013 at the field some harpactorine assassin bug nymphs (Heteroptera; station at Petit Saut, Sinnamary, French Guiana (5°03′39″ N; Reduviidae) (Inoue 1982;Haridassetal.1988; Jackson et al. 53°02′36″ W) and in the forest around the station; also, some 2010). Z. annulosus individuals were gathered from La Montagne Except for the vertebrate blood-feeding Triatominae, other des singes (5°04′19″ N; 52°41′42″ W), ca. 50 km away from reduviid subfamilies are almost exclusively composed of ar- Petit Saut. The climate is tropical moist, with 3,500 mm of thropod predators (Hwang and Weirauch 2012; but see annual precipitation distributed over 280 days. Bérenger and Plutot-Sigwalt 1997). Prey capture success in Z. annulosus was only found on pubescent plants, mostly most harpactorine species, related to prey size (Inoue 1985; H. physophora. The females lay egg clusters under the leaves Cogni et al. 2002), is enhanced by the presence of a sticky and deposit a sticky secretion on them that seems sufficient to substance that coats their legs. “Resin bugs” gather this sub- ward off predators and ants. They then fly away, leaving the stance from certain plants (Forero et al. 2011). In some species eggs to develop unattended. Between 10 and 22 first instar of the genus Zelus, the substance is secreted by specialized nymphs hatch from these egg clusters (Revel et al. 2010;AD, dermal glands and sticks to the “sundew setae” (so-called MR, and OR, personal communication). because they resemble the trichomes of sundew carnivorous plants) that cover the tibiae of the forelegs (Werner and Reid The hunting zones and preys of different instars of Z. 2001; Betz and Kölsch 2004; Weirauch 2006; Zhang and annulosus nymphs Weirauch 2013). Because they lack these sticky glands, the first instars use the sticky secretions deposited by females on We surveyed 65 Hirtella trees on which we had noted the their egg mass to increase their predation success (Weirauch presence of Z. annulosus nymphs, representing ca. 240 h of 2006; Law and Sediqi 2010). Also, Agriosphorus dohrni focal samplings distributed over 80 non-consecutive days nymphs (Harpactorinae) allocate short periods to active for- during the rainy season in which individuals were observed aging where they form search groups of ten or more individ- continuously for periods of time of more than 2 h (generally uals of different origins (not necessarily siblings); small preys limited by the rain or nightfall). In addition, during a series of are eaten selfishly, whereas large preys are shared (Inoue observations permitting us to cover the 24 h of the 1982, 1985). nycthemeron, we verified each hour if the nymphs were The nymphs of the assassin bug Zelus annulosus are effi- hunting or sheltering under the leaves (35 to 43 diurnal con- cacious predators that develop mostly on Hirtella physophora trols; 16 to 48 nocturnal controls). (Chrysobalanaceae) (Revel et al. 2010). This is an In both approaches, we noted if, depending on the instar, understorey-dwelling myrmecophyte (i.e., a plant housing the nymphs stayed under the leaf where they hatched or left to ants in hollow structures) whose long-lived leaves bear hunt on its upper side, whether they remained grouped or not, extrafloral nectaries and a pair of pouches at the base of each and finally if they moved to a different leaf. We also noted lamina where colonies of the myrmicine ant, Allomerus what insects were captured by these nymphs plus information on their size and the period of the year. Using a quartz crystal frequencies between behavioral acts, presented as percentages, microbalance, we weighed several live preys and Z .