Intra-specific differences in cognition: bumblebee queens learn better than workers

Species’ cognitive traits are shaped by their ecology, and even within a species, cognition can reflect the behavioural requirements of individuals with different roles. Social insects have a number of discrete roles (castes) within a colony and thus offer a useful system to determine how ecological requirements shape cognition. Bumblebee queens are a critical point in the lifecycle of their colony, since its future success is reliant on a single individual's ability to learn about floral stimuli while finding a suitable nest site; thus, one might expect particularly adept learning capabilities at this stage. I compared wild Bombus vosnesenskii queens and workers on their ability to learn a colour association and found that queens performed better than workers. In addition, queens of another species, B. insularis, a cuckoo species with a different lifecycle but similar requirements at this stage, performed equally well as the non-parasitic queens. To control for differences in foraging experience, I then repeated this comparison with laboratory-based B. impatiens and found that unmated queens performed better than workers. These results add to the body of work on how ecology shapes cognition and opens the door to further research in comparative cognition using wild bees.

Generalization of Foraging Experience Biases Bees Toward Flowers With Complex Morphologies

The importance of pollinators as selective agents for many floral traits is well established, but understanding their role in the evolution of complex floral shapes remains challenging. This is because pollinators often need much practice to efficiently handle morphologically complex flowers and extract their food rewards. What induces foragers to persistently visit and pollinate complex flowers despite their initial low profitability? We previously found that naive bumblebees, and unsuccessful feeding attempts of experienced ones, contribute to the pollination of complex flowers. Here we tested a complementary hypothesis, positing that successful foraging on flowers of one complex shape prepares pollinators to visit other species of different complex morphologies. We trained bumblebees to computer-controlled artificial flowers that were either simple, complex or both simple and complex. We then recorded their feeding choices and handling times on a second array of simple and complex flowers that had different shapes and required another handling technique. Bees trained on a single flower type (whether simple or complex) preferred flowers of the same type in the testing array. The foragers’ preferences after training on both flower types depended on the reward schedule during training: when both flower types rewarded equally, simple flowers were preferred at the test phase; when complex flowers provided higher reward during training, they became the preferred flower type during testing. These results suggest that successful foraging on complex flowers, especially when highly rewarding, can indeed induce insect pollinators to attempt additional flower species with other complex shapes.

Experience, but not age, is associated with volumetric mushroom body expansion in solitary alkali bees

In social insects, changes in behavior are often accompanied by structural changes in the brain. This neuroplasticity may come with experience (experience-dependent) or age (experience-expectant). Yet, the evolutionary relationship between neuroplasticity and sociality is unclear, because we know little about neuroplasticity in the solitary relatives of social species. We used confocal microscopy to measure brain changes in response to age and experience in a solitary halictid bee (Nomia melanderi). First, we compared the volume of individual brain regions among newly-emerged females, laboratory females deprived of reproductive and foraging experience, and free-flying, nesting females. Experience, but not age, led to significant expansion of the mushroom bodies—higher-order processing centers associated with learning and memory. Next, we investigated how social experience influences neuroplasticity by comparing the brains of females kept in the laboratory either alone or paired with another female. Paired females had significantly larger olfactory regions of the mushroom bodies. Together, these experimental results indicate that experience-dependent neuroplasticity is common to both solitary and social taxa, whereas experience-expectant neuroplasticity may be an adaptation to life in a social colony. Further, neuroplasticity in response to social chemical signals may have facilitated the evolution of sociality.

Prior Experience with Food Reward Influences the Behavioral Responses of the Honeybee Apis mellifera and the Bumblebee Bombus lantschouensis to Tomato Floral Scent

Bee responses to floral scent are usually influenced by both innate biases and prior experience. Honeybees are less attracted than bumblebees to tomato flowers. However, little is known about how tomato floral scent regulates the foraging behaviors of honeybees and bumblebees. In this study, the foraging behaviors of the honeybee Apis mellifera and the bumblebee Bombus lantschouensis on tomato flowers in greenhouses were investigated. Whether the two bee species exhibit different responses to tomato floral scent and how innate biases and prior experience influence bee choice behavior were examined. In the greenhouses, honeybees failed to collect pollen from tomato flowers, and their foraging activities decreased significantly over days. Additionally, neither naïve honeybees nor naïve bumblebees showed a preference for tomato floral scent in a Y-tube olfactometer. However, foraging experience in the tomato greenhouses helped bumblebees develop a strong preference for the scent, whereas honeybees with foraging experience continued to show aversion to tomato floral scent. After learning to associate tomato floral scent with a sugar reward in proboscis extension response (PER) assays, both bee species exhibited a preference for tomato floral scent in Y-tube olfactometers. The findings indicated that prior experience with a food reward strongly influenced bee preference for tomato floral scent.

Young bumblebees may rely on both direct pollen cues and early experience when foraging

An adequate supply of macro- and micronutrients determines health and reproductive success in most animals. Many bee species, for example, collect nectar and pollen to satisfy their demands for carbohydrates, protein and fat, respectively. Bees can assess the quality of pollen by feeding on it, but also pre-digestively by means of chemotactile assessment. Whether they additionally use larval nutritional experience, as has been shown for Drosophila melanogaster and Bombyx mori , is unknown. In this study, we tested whether pollen selection of bumblebee foragers is affected by nutritional experience (acquired before the onset of foraging) or solely by food quality. Bumblebee larvae were fed with one out of three different pollen blends. As adults, they were offered all three blends when they started foraging for the first time. We found all treatment groups to prefer one out of the three blends. This blend provided the highest nutritional quality and increased the bees' lifespan, as shown by feeding studies with microcolonies. Besides, bees also chose the pollen blend fed during their larval stage more often than expected, indicating a significant effect of pre-foraging experience on adult pollen foraging behaviour. The combination of both direct pollen quality assessment and pre-foraging experience (i.e. during the larval phase or as early imagines) seems to allow foraging bumblebees to efficiently select the most suitable pollen for their colony.

Orientation to polarized light in tethered flying honeybees

ABSTRACTBehavioral responses of honeybees to a zenithal polarized light stimulus were observed using a tethered animal in a flight simulator. Flight direction of the bee was recorded by monitoring the horizontal movement of its abdomen, which was strongly anti-correlated with its torque. When the e-vector orientation of the polarized light was rotated clockwise or counterclockwise, the bee responded with periodic right-and-left abdominal movements; however, the bee did not show any clear periodic movement under the static e-vector or depolarized stimulus. The steering frequency of the bee was well coordinated with the e-vector rotation frequency of the stimulus, indicating that the flying bee oriented itself to a certain e-vector orientation, i.e., exhibited polarotaxis. The percentage of bees exhibiting clear polarotaxis was much smaller under the fast stimulus (3.6 ° s-1) compared with that of the slow stimulus (0.9 or 1.8 ° s-1). The bee did not demonstrate any polarotactic behavior after the dorsal rim region of its eyes, which mediates insect polarization vision in general, was bilaterally covered with black paint. The bees demonstrated a high preference for e-vector orientations between 120 to 180°. Each bee exhibited similar e-vector preferences under clockwise and counterclockwise stimuli, indicating that each bee has its own e-vector preference, which probably depends on the bee’s previous foraging experience. Our results strongly suggest that the flying honeybees utilize the e-vector information from the skylight to deduce their heading orientation for navigation.Summary statementTethered flying bees exhibited polarotaxis under a zenithal rotating e-vector stimulus, in which their right-and-left abdominal movements were coincident with the rotation of the stimulus.

Neuroethology of the Waggle Dance: How Followers Interact with the Waggle Dancer and Detect Spatial Information

Since the honeybee possesses eusociality, advanced learning, memory ability, and information sharing through the use of various pheromones and sophisticated symbol communication (i.e., the “waggle dance”), this remarkable social animal has been one of the model symbolic animals for biological studies, animal ecology, ethology, and neuroethology. Karl von Frisch discovered the meanings of the waggle dance and called the communication a “dance language.” Subsequent to this discovery, it has been extensively studied how effectively recruits translate the code in the dance to reach the advertised destination and how the waggle dance information conflicts with the information based on their own foraging experience. The dance followers, mostly foragers, detect and interact with the waggle dancer, and are finally recruited to the food source. In this review, we summarize the current state of knowledge on the neural processing underlying this fascinating behavior.

Investigating high seas foraging conditions for salmon in the North Pacific: insights from a 100-year scale archive for Rivers Inlet sockeye salmon

The high seas phase of Pacific salmon life history remains particularly data-limited, and the potential implications of climate impacts on ocean productivity for salmon condition and reproductive success is poorly understood. We used carbon and nitrogen stable isotopes (SI) from salmon scales to reconstruct aspects of the marine environment experienced by Rivers Inlet sockeye salmon (Oncorhynchus nerka) over the last century (1915–2016). Time series of SI compositions of salmon scales showed a greater variability after 1950, probably linked to more dynamic high seas environmental conditions. However, climate indices (e.g., Pacific Decadal Oscillation, El Niño Southern Oscillation) did not explain the SI variability. We assessed the time series with respect to changes in food web dynamics, including shifting trophic baselines, changes in prey–salmon diet, and changes in salmon foraging location. A significant correlation (r = 0.53) between sea surface temperature and δ13C enabled us to define the area of potential salmon distribution in the open ocean for approximately 9 months prior to sampling. This method shows high potential for stock-specific high seas distribution mapping that could be combined with prey isotope values to inform stock-specific foraging experience.