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Defence in stingless bees
- 1. Safeena Majeed, A. A. II Ph.D. - Agril. Entomology PA1TAH082 Seminar - II
- 2. Introduction Types of defence Aerial defence Nest defence Fighting swarms Chemical defence Defence by soldiers Suicidal defence Conclusion Contents 2
- 6. Scaptotrigona depilis Trigona hyalinata Tetragonisca angustula 6
- 7. Tetragonisca angustula 11 colonies Predators 1 colony- Lestrimelitta limao/4 T. angustula Live insects- Melipona, Trigona, asilid fly Flight of T. angustula I. Aerial defence (Wittamann, 1985) Ta Ll Ta Ta Ta Ta Ta Ta Ta Ta Ta Ta 7
- 8. (Wittamann, 1985) Nest entrance of T. angustula The entrance tube guarded by group of hovering bees The groups of > 40 workers. The flanking flight corridor to the nest entrance from both sides. They rapidly attack flying insect invaders and force them to the ground Contd.... 8
- 9. 1. Males waiting for females They were workers (♀) Flight behaviour Males - zig zag Hovers - right angle to nest entrance Hypothesis on the hovering guards… Contd.... (Wittamann, 1985) 2. Young workers at orientation flight 3. Defensive bees 9
- 10. Hovering Stable positions without inspecting the surroundings of the nest site Nest entrance at 1cm slight below the opening Never observed facing in any other direction Stable at position even if hive moved Orientation flight Characterized by wide loops flown at rather low speed after the bees had hovered Facing the nest entrance at 30- 40 cm from it. After about 3-4 min the bees extended the range of loops Finally flew away on foraging trips Contd.... 2. Young workers at orientation flight (Wittamann, 1985) 10
- 11. 3. Defensive bees Dummy invaders passed in front of nest, Darted towards the invader repeatedly The bee attacked invaders vigorously. Landed on it, trying to grasp the wings or legs with its mandibles. L. limao stopped in the same way emits citral from mandibular gland Dead L. limao infront of nest with citral smell • Hovering bees are defensive guards • Aerial defense against flying predator • Citral is a alarm kairomone Contd.... (Wittamann, 1985) 11
- 12. 2 types of entrance guards 1. Hovering guards Main groups & Side groups Within 20cm of entrance Faces flight path 2. Standing guards 20-25cm from entrance To the right or left of entrance II. Nest defence (Gruter et al., 2011) 12
- 13. (Gruter et al., 2011) Tetragonisca angustula 15 colonies For 60 seconds Every 2hr 8.00 – 20. 00 hours 3 days Contd.... Number of standing & hovering guards • Standing guards (14.3) = 2 Hovering guards (4.64) • Standing - during day time & Hovering - intense during late afternoon • No guarding after 8pm 13
- 14. (Gruter et al., 2011) Will they close the door ???? Proportions of nest entrance tubes that are open at different times of the day and night Contd.... 14
- 15. (Gruter et al., 2011) Standing v/s hovering guard • Max. guarding duration – 20 days • Standing guard (91%) • Hovering by sub-groups of guards (9%) • 33% - both Contd.... 15
- 16. Low task switching between both Standing guards hovering guards Hovering guards- nest immunity against L. limao allospecific defence Standing guards- discriminate nestmate from conspecifics conspecific defence Long guarding duration of 20 days (LC- 21 days)--- guarding is specialized task Larger colony – more guards The study concludes…. allospecific intruder (Gruter et al., 2011) Contd.... 16
- 17. Tetragonula carbonaria Smith III. Fighting swarms (Gloag et al., 2008) 10m radius 10workers/colony DNA extraction Kinship analysis- max. likelihood ratios 17
- 18. 1. Artificial introduction of worker – at midday 2. Exchange of nests -proxy of natural condition To induce fighting swarm… Control– 6 colonies Source – 6 colonies Receiver– 6 colonies (Gloag et al., 2008) Ho: Swarmrec. ǂ Swarmcntrl Contd.... 18
- 19. Black - proportion of workers from the nest closest to the fighting White & grey - % of workers from additional colony (identified in the collection) N - Sample sizes for each fighting swarm collection ( given to right of each bar) Number of colonies participating in 8 fighting swarm collections (Gloag et al., 2008) 19
- 20. (Cunningham et al., 2014) Who wins the fight then ???? Bees at war !!! • Tetragonula carbonaria v/s Tetragonula hockingsi • 5 year period • 260 stingless bee hive 20
- 21. (Cunningham et al., 2014) Behaviours observed during fights Fighting bees on ground near the hive Clusters of drones on nearby foliage Attacking worker dragging a callow 21
- 22. (Cunningham et al., 2014) 22
- 23. Callows ejected- 163 For 7 days T. hockingsi ejecting T. carbonaria Callows ejected- 1389 For 2-4 days All callows - T. carbonaria takenover (Cunningham et al., 2014) Fighting pairs, ejected callow bees collected outside focal T. carbonaria hive Contd.... 23
- 24. (Cunningham et al., 2014) Changes in resident species of stingless bee hive Year Hive species changes % change Tc to Th Th to Tc Tc Th X2 2008 10(253) 1(10) 4 10 ns 2009 8(268) 0(21) 3 0 ns 2010 9(252) 2(21) 4 10 ns 2011 8(253) 1(26) 3 4 ns 2012 6(274) 1(29) 2 3 ns Total 41 5 Hive change occupancy of 46 colonies Inter-colony battles in Tetragonula bees results in usurpation of the defeated hive by the winning colony Contd.... 24
- 25. Secured nest entrance Plant derived resins to form propolis T. carbonaria ----> propolis + Corymbia tree resin Entrance propolis : against Iridomyrmix mayri Nonpolar solvent - hexane Polar solvent - ethanol IV. Chemical defence Centre (brine) Barrier ( treatment) Outer 25
- 26. (Wang et al., 2018) • Nest entrance propolis deter ants • Nonpolar, nonvolatile chemicals of propolis acts as deterrent • Chemical composition varies wrt plant source • Sesqui & di –terpenoids, phlorogilcinols, flavonoids 26
- 27. Soldiers- rare in bees & absent in wasps Worker differentiation in 28 stingless bee species Captured workers Measured size, Head weight[ 𝐺𝑢𝑎𝑟𝑑𝑠 −𝐹𝑜𝑟𝑎𝑔𝑒𝑟 𝑆𝐷. 𝑜𝑓 𝑐𝑜𝑙𝑜𝑛𝑦 ] Quantified melanization, 𝑚 = 1 − 𝑔 r • g- average grey scale of specimen • r- reference grey scale Cuticle thickness - TEM V. Defense by soldiers Gruter et al. (2017) 27
- 28. Gruter et al. (2017) Contd.... 28
- 29. Gruter et al. (2017) Same ancestors Evolved ~ 20-25mya = predatory robber bees, Lestrimelitta 10 / 28 species – attacked by Robber bees Target species: Head 4x (70%) Contd.... 29
- 30. VI. Suicidal biting (Shackleton et al., 2014) 30
- 31. Attack bioassay (Shackleton et al., 2014) Aggression = 𝑃𝑁𝐷 𝐿 P – probability of attack N – number of attack D – log10 attack duration L – log10 latency Suicidal bioassay: flag test - 20 m from the nest brushed for 5 s using 5mm brush - no physical harm wings clamped using forceps – physical damage Choice btw disengage/ self sacrifice 31
- 32. (Shackleton et al., 2014) All 3 species of Trigona- highly aggressive & suicidal Most suicidal - Tr. hyalinata (83 %) Contd.... 32
- 33. (Shackleton et al., 2014) Contd.... 33
- 34. Conclusion Fighting individuals - sterile workers benefits by indirect fitness of protecting the colony Improved defence - outweigh the costs of dead workers Basic aerial defense to suicidal biting --- evolved defense Meliponinae are stingless, not defenceless 34
- 35. Thank you 35