A Landscape Analysis to Understand Orientation of Honey Bee (Hymenoptera: Apidae) Drones in Puerto Rico.

Honey bees [Apis mellifera L. (Apidae, Hymenoptera)] show spatial learning behavior or orientation, in which animals make use of structured home ranges for their daily activities. Worker (female) orientation has been studied more extensively than drone (male) orientation. Given the extensive and large flight range of drones as part of their reproductive biology, the study of drone orientation may provide new insight on landscape features important for orientation. We report the return rate and orientation of drones released at three distances (1, 2, and 4 km) and at the four cardinal points from an apiary located in Gurabo, Puerto Rico. We used high-resolution aerial photographs to describe landscape characteristics at the releasing sites and at the apiary. Analyses of variance were used to test significance among returning times from different distances and directions. A principal components analysis was used to describe the landscape at the releasing sites and generalized linear models were used to identify landscape characteristics that influenced the returning times of drones. Our results showed for the first time that drones are able to return from as far as 4 km from the colony. Distance to drone congregation area, orientation, and tree lines were the most important landscape characteristics influencing drone return rate. We discuss the role of landscape in drone orientation.

Relative frequency of norovirus infection in children with acute gastroenteritis.

AIM: The aim of this study was to determine the prevalence of norovirus among children with acute gastroenteritis in 2009 and 2010. We also aimed that, to detecting the possible clinical and laboratory differences among cases in 2009 and 2010. METHODS: Fecal samples were collected from children under 16 years of age who were admitted for acute gastroenteritis. Norovirus was detected using immunochromatography. For the comparison of seasonal distribution, clinical manifestations, and laboratory results between cases, we divided subjects into two groups by year. RESULTS: Norovirus infection was detected in 112 of the 1027 collected samples (10.9%). In three cases with norovirus, other enteric viruses like rotavirus and adenovirus are detected concurrently, and these were excluded. After the exclusion of three cases with co-infections, statistical analysis was made in 109 cases. Most of the positive cases were between 1-24 months of age (N.=75, 67%). The rate of norovirus infection peaked in winter in 2010 (P<0.05). However, the rates were not significantly different between seasons in 2009 (P>0.05). We did not detect any positive cases in late summer and autumn in 2010. Diarrhea (97.2%), vomiting (95.4%), and abdominal pain (65.1%) were most frequently encountered symptoms of patients with norovirus. Leukocytosis and neutrophilia were significantly higher in 2010 than 2009 (P<0.05). CONCLUSION: The prevalence and clinical characteristics of norovirus in our study group is similar but seasonal distribution is different between two years. Most of the cases were <24 months of age. Like rotavirus, norovirus vaccine can be developed to prevent infection.

Physiological bases of genetic differences in cannibalism behavior of the confused flour beetle Tribolium confusum.

Physiological causes of genetic differences in cannibalism were examined to gain a better understanding of constraints on behavior evolution. Cannibalism has complex population level consequences in Tribolium confusum, including dramatic effects on population size. Laboratory strains with low and high cannibalism rates, obtained through inbreeding, have maintained distinct levels of cannibalism for over two decades even in the absence of artificial selection to maintain the differences. Why strains differ in their cannibalism rates was examined by measuring: (1) the nutritional benefit from cannibalism in both nutritionally good and poor environments, and (2) the possibility that eggs are an important source of water. How strains achieve differences in cannibalism was examined by testing for differences between strains in their ability to find eggs and in their tendency to eat eggs. Beetles from both strains survive equally well in a nutritionally good environment, but they accomplish this in different ways. The low cannibalism strain has high survivorship with and without cannibalism. The high cannibalism strain has low survivorship when not fed eggs and survivorship equivalent to the low cannibalism strain when fed eggs, suggesting it compensates for poor nutritional adaptation by eating eggs. The strains also differ in feeding behavior; beetles from the high cannibalism strain have a higher appetite for eggs. Beetles from the two strains did not differ in locomotor activity, search efficiency, or need for water. The observed behavioral and nutritional differences may contribute to the maintenance of different levels of cannibalism.

Expansion of the neuropil of the mushroom bodies in male honey bees is coincident with initiation of flight.

The mushroom bodies (MB), the insect brain structures most often associated with learning, have previously been shown to exhibit structural plasticity during the adult behavioral development of female worker and queen honey bees. We now show that comparable morphological changes occur in the brains of male honey bees (drones). The volume of the MB in the brains of drones was estimated from tissue sections using the Cavalieri method. Brains were obtained from six groups of drones that differed in age and flight experience. Circulating levels of juvenile hormone (JH) in these drones were determined by radioimmunoassay (RIA). There was an expansion of the neuropil of the MB that was temporally associated with drone behavioral development, as in female queens and workers. The observed changes in drones were maintained in the presence of low levels of JH, also as in females. These results suggest that expansion of the neuropil of the MB in honey bees is associated with learning the location of the nest, because this learning is the most prominent aspect of behavioral development common to all members (workers, drones, queen) of the honey bee colony.

Common endocrine and genetic mechanisms of behavioral development in male and worker honey bees and the evolution of division of labor.

Temporal polyethism is a highly derived form of behavioral development displayed by social insects. Hormonal and genetic mechanisms regulating temporal polyethism in worker honey bees have been identified, but the evolution of these mechanisms is not well understood. We performed three experiments with male honey bees (drones) to investigate how mechanisms regulating temporal polyethism may have evolved because, relative to workers, drones display an intriguing combination of similarities and differences in behavioral development. We report that behavioral development in drones is regulated by mechanisms common to workers. In experiment 1, drones treated with the juvenile hormone (JH) analog methoprene started flying at significantly younger ages than did control drones, as is the case for workers. In experiment 2, there was an age-related increase in JH associated with the onset of drone flight, as in workers. In experiment 3, drones derived from workers with fast rates of behavioral development themselves started flying at younger ages than drones derived from workers with slower rates of behavioral development. These results suggest that endocrine and genetic mechanisms associated with temporal polyethism did not evolve strictly within the context of worker social behavior.

Volume changes in the mushroom bodies of adult honey bee queens.

The volume of the mushroom bodies of the brains of honey bee queens (Apis mellifera) was estimated using the method of Cavalieri. Tissue sampled was obtained from queens in five different behavioral and reproductive states: 1-day-old virgin queens, 14-day-old virgin queens, 14-day-old instrumentally inseminated queens, 9- to 13-day old naturally mated queens, and 5-month-old naturally mated queens. There were significant volume changes within the mushroom bodies during the first 2 weeks of adult life. The volume occupied by the somata of the intrinsic neuronal population (Kenyon cells) of the mushroom bodies decreased by approximately 30% and the volume of the neuropil of the mushroom bodies increased between 25 and 50%. These volume changes are strikingly similar to those previously reported to occur for worker honey bees switching from hive activities to foraging (Withers, Fahrbach, & Robinson, 1993). However, in this study they were found even in queens that had no flight experience. In addition, queens exhibiting these volume changes were found to have low blood levels of juvenile hormone, while previous studies have shown that foraging worker honey bees have high hormone levels. These results suggest that some aspect of behavioral development common to both the queen and the worker castes is fundamental to protocerebral volume changes early in adulthood in honey bees. If juvenile hormone regulates this process, results from queens suggest that it may play an organizational role.