Stingless Bee Scaptotrigona Postica Research Articles

Exposure to sublethal concentrations of imidacloprid, pyraclostrobin, and glyphosate harm the behavior and fat body cells of the stingless bee Scaptotrigona postica

Pesticide use in agriculture threatens non-target insects such as bees. Considering the ecological and economic relevance of native bees, such as Scaptotrigona postica, and the insufficient studies on the effects of pesticides on their behavior and physiology, improving the current knowledge on this issue is essential. Therefore, this study investigated the sublethal effects of imidacloprid, pyraclostrobin, and glyphosate on the behavior and fat body cells of S. postica. Pesticide ingestion decreased the walking distance and mean velocity of bees compared to the control and solvent control groups. The oenocytes of the control groups were spherical, with central nuclei containing decondensed chromatin, and the trophocytes presented irregular morphology, with cells varying in shape and the cytoplasm filled with vacuoles and granules. However, bees exposed to pesticides showed extensive cytoarchitectural disruption in the fat body, such as vacuolization and shape changes in oenocytes and altered nuclei morphology in trophocytes. Moreover, pesticide exposure increased the number of atypical oenocytes and altered trophocytes, except for the PYR group, which showed a lower number of atypical oenocytes. Caspase-positive labeling significantly increased in all exposed bee groups. Alternatively, TLR4 labeling was significantly decreased in the exposed groups compared to the control groups. There was a significant increase in HSP90 immunolabeling in all exposed groups compared to the control. These findings reinforce the importance of research on the sublethal effects of low pesticide concentrations on key neotropical pollinators and prove that these toxic substances can impair their detoxification and immune defense.

Toxicity of Imidacloprid to the Stingless Bee Scaptotrigona postica Latreille, 1807 (Hymenoptera: Apidae).

The stingless bee Scaptotrigona postica is an important pollinator of native and cultivated plants in Brazil. Among the factors affecting the survival of these insects is the indiscriminate use of insecticides, including the neonicotinoid imidacloprid. This work determined the toxicity of imidacloprid as the topical median lethal dose (LD50) and the oral median lethal concentration (LC50) as tools for assessing the effects of this insecticide. The 24 and 48hLD50 values were 25.2 and 24.5ng of active ingredient (a.i.)/bee, respectively. The 24 and 48h LC50 values were 42.5 and 14.3nga.i./µL of diet, respectively. Ours results show the hazard of imidacloprid and the vulnerability of stingless bees to it, providing relevant toxicological data that can used in mitigation programs to ensure the conservation of this species.

Impact of fipronil on the mushroom bodies of the stingless beeScaptotrigona postica

Studies on stingless bees are scarce, and little is known about these insects, especially regarding the effects of contamination by neurotoxic insecticides, which can cause damage to important structures of the insect brain. This study evaluated the morphological changes in the intrinsic neurons of the protocerebral mushroom bodies (Kenyon cells) of the stingless bee Scaptotrigona postica after exposure to different doses of fipronil, using light microscopy and transmission electron microscopy. This region of the brain was selected for analysis because of its importance as a sensory integration centre. In both oral and topical treatments, Kenyon cells presented pyknotic profiles, suggesting cell death. Statistical analysis showed significant differences among doses and exposure times. Transmission electron microscopy revealed changes in the nucleus and cellular organelles. Depending on the dose, the characteristics observed suggested apoptotosis or necrosis. This study demonstrates the toxic effects of fipronil. An increase in the number of pyknotic profiles of Kenyon cells of mushroom bodies was observed even at the sublethal doses of 0.27 ng AI bee(-1) and 0.24 ng AI µL(-1) in the topical and oral treatments respectively. Also, differences in the number of pyknotic profiles were dose and time dependent.

Olfactory attraction of Scaptotrigona mexicana drones to their virgin queen volatiles

Drone congregations are a ubiquitous phenomenon described in several species of stingless bees and extensively studied in the honeybee, Apis mellifera. In meliponaries of Scaptotrigona mexicana, it is usual to observe drones forming such congregations close to the nests, apparently waiting for a virgin queen for mating. We hypothesize that drones of this species, similarly to those of A. mellifera and the stingless bee Scaptotrigona postica, use olfactory signals to detect queens and evaluate their reproductive status. In both field and laboratory experiments, our results showed that S. mexicana drones were able to differentiate between virgin and physogastric queens. It seems that this ability to discriminate depends on the amount of 2-alcohols, since even though no differences were observed in the qualitative content between virgin and physogastric queens, these compounds were found in larger quantities in the virgin queens. Attraction is due to compounds found in the queen head, mainly 2-alcohols, where 2-nonanol is the most significant for drone attraction in field and laboratory bioassays and for eliciting a high drone antennal response.

Selective preying of the sphecid wasp Trachypus boharti on the meliponine bee Scaptotrigona postica: potential involvement of caste‐specific cuticular hydrocarbons

The specialist digger wasp Trachypus boharti Rubio‐Espina preys exclusively on males of the stingless bee Scaptotrigona postica Latreille 1807, although the hunting attacks involve both male and worker bees of S. postica and members of its own species. To understand the mechanism of prey selection, the cuticular hydrocarbon patterns of workers and males of S. postica are analyzed in detail, and the mandibular secretion of males is examined. The cuticular profiles of males and workers are distinctively different. The major group of cuticular compounds, heptacosene isomers, is twice as abundant in workers as in males. There is no clear distinction between worker and male mandibular secretions. Such a distinct and straightforward caste‐specific difference in cuticular hydrocarbons could function as a recognition cue by which T. boharti distinguishes between workers and males of S. postica.

Morphological changes in the cephalic salivary glands of females and males of Apis mellifera and Scaptotrigona postica (Hymenoptera, Apidae)

The cephalic salivary glands of some species of bees are exclusive and well developed only in Apinae. These glands were studied with light and scanning electron microscopy in workers, queens and males from the honey bee Apis mellifera, and the stingless bee Scaptotrigona postica in different life phases. The results show that the cephalic salivary glands are present in females of both the species, and in males of S. postica. Nevertheless, they are poorly developed in young males of A. mellifera. In both species, gland growth is progressive from the time of emergence to the oldest age but, in A. mellifera males, the gland degenerates with age. Scanning electron microscopy shows that the secretory units of newly emerged workers are collapsed while in older workers they are turgid. Some pits on the surface of the secretory units correspond to open intercellular spaces. The possible functions of these glands in females and males of both species are discussed.

Unsuccessful attacks dominate a drone-preying wasp’s hunting performance near stingless bee nests

Bee males (drones) of stingless bees tend to congregate near entrances of conspecific nests, where they wait for virgin queens that initiate their nuptial flight. We observed that the Neotropical solitary wasp Trachypus boharti (Hymenoptera, Cabronidae) specifically preys on males of the stingless bee Scaptotrigona postica (Hymenoptera, Apidae); these wasps captured up to 50 males per day near the entrance of a single hive. Over 90% of the wasp attacks were unsuccessful; such erroneous attacks often involved conspecific wasps and worker bees. After the capture of non-male prey, wasps almost immediately released these individuals unharmed and continued hunting. A simple behavioral experiment showed that at short distances wasps were not specifically attracted to S. postica males nor were they repelled by workers of the same species. Likely, short-range prey detection near the bees' nest is achieved mainly by vision whereas close-range prey recognition is based principally on chemical and/or mechanical cues. We argue that the dependence on the wasp's visual perception during attack and the crowded and dynamic hunting conditions caused wasps to make many preying attempts that failed. Two wasp-density-related factors, wasp-prey distance and wasp-wasp encounters, may account for the fact that the highest male capture and unsuccessful wasp bee encounter rates occurred at intermediate wasp numbers.

Low mating frequency of queens in the stingless bee Scaptotrigona postica 1 and worker maternity of males

Kin selection models of intracolonial conflict over the maternity of males predict that social hymenopteran workers should favour the production of sons and nephews over brothers when the effective mating frequency (me) of the queen is low (me 2. Stingless bees have been used to support these models in that me within the group is considered low and workers are thought often to monopolise the parentage of males. We genetically analysed 20 worker and 20 male pupae from each of 10 colonies of the stingless bee Scaptotrigona postica (= Scaptotrigona aff. depilis) using six microsatellite loci and demonstrate queen monandry in eight nests and apparent low me in the other two. However, four colonies contained an additional matriline, possibly due to queen supersedure (serial polygyny), which complicated their genetic structure. Across colonies, workers were responsible for the maternity of 13% of all males. These data are broadly in agreement with predictions from kin selection theory, though the question remains open as to why workers do not secure a greater share of male maternity in this and other stingless bee species in which workers are more closely related to nephews than brothers.

Protein requirements in larvae and adults of Scaptotrigona postica (Hymenoptera, Apidia, Meliponinae): midgut proteolytic activity and pollen digestion

The number and degree of digestion of pollen grains in the midgut and rectum, the midgut proteolytic activity and the time of pollen grain passage through the digestive tract in the stingless bee Scaptotrigona postica (Latreille) have been analyzed. The results show similar protein requirements among larvae, nurse bees and queens, as well as between forager bees and old males, but these requirements are higher in individuals from the former groups than in those from the latter. Although protein requirements have been demonstrated to vary according to a bee's activity in the colony, they are similar among bees from different castes or sexes. These changes in feeding behavior are related to the bee's function and to less competition for nourishment among individuals of the colony. It is also noted that pollen grains took between 6 and 28 h to pass through the digestive tract. Pollen grains are irregularly accumulated in the various regions of the midgut, which may reflect functional differentiation throughout the midgut.

Distribution of acid phosphatases in the hypopharyngeal glands from workers, queens and males of a Brazilian stingless bee Scaptotrigona postica Latreille: an ultrastructural cytochemical study.

The present study reports the localization of acid phosphatase in the hypopharyngeal gland cells from workers (newly-emerged, nurse and forager), queens (newly-emerged and laying) and males (newly-emerged and mature for mating) of the Brazilian stingless bee, Scaptotrigona postica. The phosphatase activity varied in intensity and localization depending on the individual class, physiological age and the substrate used. In newly-emerged workers, the phosphatase-positive sites suggest the involvement of the enzyme with cellular differentiation that occurs in the presecretory phase, in nurse workers with protein synthesis and in forager workers with changes in cellular activity or glandular regression. In males mature for mating and laying queens, the positive sites are related to secretory activity, showing that the gland maintains some activity in spite of the regressive aspect. Of the substrates used, beta-glycerophosphate gave the least specific localization.

Genetic structure of colonies and a male aggregation in the stingless bee Scaptotrigona postica , as revealed by microsatellite analysis

Stingless bee queens have for long been assumed to mate once on a nuptial flight, early in life. To evaluate critically monandry in one stingless bee, Scaptotrigona postica, worker offspring (adults or brood) were genetically analysed with microsatellite loci, five of which were developed specifically for the species. Marker loci were highly variable; unbiased estimates of heterozygosity were > 0.5. "Foreign" workers, either those having drifted from other colonies (circa 2%) or those of a replacement queen, were identified with the genetic markers and removed from further analysis. Worker genotypes were consistent with some queens having mated once and others having mated with up to six different males. Scaptotrigona postica queens are therefore facultatively polyandrous. Effective mating frequencies, m e , were generally lower than the number of patrilines observed. Relatedness estimates of nestmates from individual colonies concurred with those derived from direct counts of the number of patrilines and their proportional representation. Putative genotypes of a colony's queen and her mates were deduced from those of her workers. Queens were generally not related to their mates. For one polyandrous queen, her six mates were related to each other, possibly because of numerically biased representation of males from different colonies at mating sites. However, males at an aggregation outside a colony came from numerous colonies.

Ontogeny of cephalic volatile patterns in queens and mating biology of the neotropical stingless bee, Scaptotrigona postica

Summary Chemical communication is an ancient yet still immensely important part of reproduction. Amongst all invertebrates, the most sophisticated “chemical languages” are used by social insects. Here the sex- and caste-specific pheromonal messages consist of multicomponent mixtures. In the neotropical stingless bee Scaptotrigona postica, an inhabitant of dense tropical rain forests, the cephalic volatiles of a queen transmit information on her reproductive status to males. A distinct ontogenetic pattern of the queen pheromone composition allows drones to discriminate receptive virgins which are then chased during the short nuptial flight through the forest understorey. By means of gas chromatographic/mass spectroscopic analyses, the numerous volatile compounds found in pentane extracts of individual bee heads could be identified. Qualitative as well as quantitative changes of these volatiles in the course of imaginal development could be determined, and bioassays with synthetic compounds were undertaken in order to decode the chemical signals used during the short encounter of a young queen and her mate.

A stingless bee (Melipona panamica) indicates food location without using a scent trail

The study of location specification in recruitment communication by bees has focused on two dimensions: direction and distance from the nest. Yet the third dimension, height above ground, may be significant in the tall and dense forest habitats of stingless bees. Foragers of the stingless bee Scaptotrigona postica recruit to a specific three-dimensional location by laying a scent trail. Stingless bees in the genus Melipona are thought to have a more sophisticated recruitment system that communicates distance through sounds inside the nest and direction through pointing zig-zag flights outside the nest. However, prior research on Melipona has not examined height communication or even established that foragers can recruit newcomers to a specific location. We used identical paired feeders to investigate recruitment to food in M panamica on Barro Colorado Island, Panama. We trained foragers from an observation hive to one feeder and monitored both feeders for the subsequent arrival of newcomers. We changed the relative positions of the feeders to test for correct direction, distance, and canopy-level communication. A 40-m canopy tower located inside the forest enabled us to examine canopy-level communication. We found that M. panamica foragers can recruit to a specific (1) direction, (2) distance, and (3) canopy level. To test the possibility that foragers accomplish this by means of a scent trail, we placed the colony on one shore of a small cove and trained bees over 116 m of open water to a feeder located on the opposite shore. We also placed a second feeder on this shore, equidistant from the colony but 20 m from the first feeder. Significantly more newcomers consistently arrived at the feeder visited by the foragers. Thus foragers evidently do not need a scent trail to communicate direction. Inside the nest, a forager produces pulsed sounds while visibly vibrating her wings after returning from a good food source. She is attended by other bees who cluster and hold their antennae around her, following her as she rapidly spins clockwise and counterclockwise. Locational information may be encoded in this behavior. However, foragers may also directly lead newcomers to the food source. Further experiments are planned to test for such piloting and other communication mechanisms.

Rates of juvenile hormone synthesis control caste differentiation in the stingless bee Scaptotrigona postica depilis.

In social insects the expression of caste-specific characters is controlled by juvenile hormone (JH) during definite sensitive periods in preimaginal development. For a number of stingless bee species the existence of such a JH-sensitive period has already been demonstrated. Queen development can be induced by topical JH applications during the cocoon spinning phase of the last larval instar. Neither JH titers nor rates of JH synthesis were known so far for this subfamily of eusocial bees distinguished by a pronounced caste dimorphism. As the pantropically distributed stingless bees with approximately 400 recent species are the largest group of social bees, JH synthesis was studied in one of the species that can be kept under laboratory conditions. An in vitro radiochemical assay was used to measure stage- and caste-specific activities of the corpora allata (CA). For the first time in a eusocial hymenopteran species it was demonstrated how the endocrine system is reacting to trophogenic stimuli capable to induce caste differentiation during larval development. Generally JH synthesis in queen CA was found to be 30-80% higher than in workers during the penultimate and last larval instar, but a strong and distinct caste-specific modulation of JH synthesis was only observed right before the onset of a JH-sensitive period in the cocoon spinning phase of the fifth instar.

Variation in cephalic volatile substances in relation to worker age and behavior in the stingless bee, scaptotrigona postica

Head extracts of adult workers of the Brazilian stingless bee Scaptotrigona postica (Trigonini, Meliponinae: Apidae) were analysed for volatile substances by gas chrom atography/ mass spectroscopy. Individual worker bees performing clearly defined tasks and representing five age groups were collected. A total of 36 compounds was identified, 22 of which had not been previously described for a Trigona species. The major components are 2-heptanol, 2-tridecanone, 2-pentadecanone, Z-5-tetradecenylbutanoate and Z-7-hexadecenylbutanoate. 11 of the 36 compounds increase in concentration with age, but only 2 decrease. The other substances are present in more or less constant concentrations. These data are discussed assuming more complicated pheromone-m ediated interactions within an age-dependent polyethism between old workers acting inside and outside the nest than between young house bees

Differences in quantity of food in worker and male brood cells ofScaptotrigona postica (Latr. 1807) (Hymenoptera, Apidae)

Workers and males of the stingless beeScaptotrigona postica emerge from morphologically similar cells. Normally only one bee is reared in each brood cell, but we found that some of the cells, interspersed throughout the brood comb, contained more than one egg. Because these additional eggs produced adult males, they were probably laid by nurse bees (workers) after the queen had oviposited in the cells concerned. Although there is no morphological difference between male and worker cells a significant difference was found in the amount of food inside them. The cell where the male is reared shows less food than the worker cell, difference that is statistically significant at 1% level. This fact suggests that: the worker might recognise the cell before oviposition and that this recognition is based on the difference of food quantity.