Surface ultrastructure and molecular phylogenetics of four unarmored heterotrophic dinoflagellates, including the type species of the genus Gyrodinium (Dinophyceae)

Small subunit rRNA gene sequences were determined for four unarmored heterotrophic dinoflagellates (Gyrodinium spirals, the type species of the genus Gyrodinium, as well as G. fusiforme, Gymnodinium rubrum and the freshwater species G. helveticum) using a single‐cell polymerase chain reaction (PCR) technique. For identification and record keeping, each cell was carefully observed and photographed using a light microscope under high magnification, prior to single‐cell PCR. G. rubrum and G. helveticum possess an elliptical apical groove and longitudinal striations similar to those of G. spirale and G. fusiforme, and molecular phylogenetic studies reveal that the four species form a single clade. We therefore propose the following new combinations: Gyrodinium rubrum (Kofoid et Swezy) Takano et Horiguchi comb. nov. and Gyrodinium helveticum (Penard) Takano et Horiguchi comb. nov.     

Movement of honey bee (Apis mellifera L.) queen mandibular gland pheromone in populous and unpopulous colonies

The mode of intranest transfer of the honey bee queen mandibular gland pheromone complex (QMP) was investigated in unpopulous and populous, slightly congested colonies, using synthetic QMP containing tritiated 9-keto-2(E)-decenoic acid, one of the QMP components. Radiolabel was rapidly transported from the center to the peripheral regions of the nest, and in a manner consistent with worker to worker transport. Population size and congestion had no effect on the relative rates of movement from the center to the periphery of the nest or on the mean amounts of radiolabel on individual bees. However, a significantly smaller proportion of the workers in the populous colonies received detectable amounts of radiolabel than in the uncongested colonies, and workers carrying especially large amounts of radiolabel were less numerous in the crowded colonies. It is suggested that, at the stage of colony development that the colonies were in, population size has more of an effect on intranest pheromone transmission than does crowding. Interference with pheromone transfer may occur only at higher levels of congestion than were created, and nearer to the reproductive phase of colony development. An alternative hypothesis is that colony crowding does not significantly affect QMP transport and that the onset of reproductive queen rearing may be associated more with changes in worker thresholds of response to QMP.     

Strain diversity and host specificity in a specialized gut symbiont of honeybees and bumblebees

Host‐restricted lineages of gut bacteria often include many closely related strains, but this fine‐scale diversity is rarely investigated. The specialized gut symbiont Snodgrassella alvi has codiversified with honeybees (Apis mellifera) and bumblebees (Bombus) for millions of years. Snodgrassella alvi strains are nearly identical for 16S rRNA gene sequences but have distinct gene repertoires potentially affecting host biology and community interactions. We examined S. alvi strain diversity within and between hosts using deep sequencing both of a single‐copy coding gene (minD) and of the V4 region of the 16S rRNA gene. We sampled workers from domestic and feral A. mellifera colonies and wild‐caught Bombus representing 14 species. Conventional analyses of community profiles, based on the V4 region of the 16S rRNA gene, failed to expose most strain variation. In contrast, the minD analysis revealed extensive strain variation within and between host species and individuals. Snodgrassella alvi strain diversity is significantly higher in A. mellifera than in Bombus, supporting the hypothesis that colony founding by swarms of workers enables retention of more diversity than colony founding by a single queen. Most Bombus individuals (72%) are dominated by a single S. alvi strain, whereas most A. mellifera (86%) possess multiple strains. No S. alvi strains are shared between A. mellifera and Bombus, indicating some host specificity. Among Bombus‐restricted strains, some are restricted to a single host species or subgenus, while others occur in multiple subgenera. Findings demonstrate that strains diversify both within and between host species and can be highly specific or relatively generalized in their host associations.     

Polymorphic microsatellite loci in Allodapine bees for investigating the evolution of social behaviour

Allodapine bees provide extraordinary systems for investigating the evolution of cooperation and particularly the division of reproduction in animal societies. We present the first microsatellite primers for two native Australian species (Exoneura nigrescens and E. robusta; Hymenoptera: Apidae: Xylocopinae) which allow the accurate determination of pedigrees, reproductive skew and relatedness in colonies. Up to 55 different alleles were observed per locus.     

Fine structural localisation of acetylcholinesterase activity in the compound eye of the honeybee (Apis mellifica L.)

Summary Acetylcholinesterase (AChE) activity was demonstrated histochemically at the electron microscopic level in the compound eye of the worker bee (Apis mellifica L.) by use of the method of Lewis and Shute (1969).All photoreceptor axons (short and long visual fibres) display AChE activity. The reaction product is located in the axoplasm and at the plasma membrane. Substantial amounts of the reaction product can be detected in the intercellular spaces between the visual fibres. Along the visual fibres, the enzyme activity is unevenly distributed. High AChE activity is present in the distal parts of the axons, in contrast to lower enzyme levels in the lamina. However, AChE is also present in the proximal terminals of the visual fibres as well as in the intercellular spaces between visual fibre terminals and the postsynaptic neurones (monopolar cells). Intracellular enzyme activity is almost absent in the monopolars.The authors assume the high AChE activity in the visual fibres to be indicative of acetylcholine as the transmitter at the first synapse of the compound eye. This hypothesis is discussed in view of the results of autoradiographic, electrophysiological and pharmacological investigations of the compound eye and of the ocellus. Our data are at variance with results of studies on the eyes of Diptera.     

Sterol utilization in honey bees fed a synthetic diet: Effects on brood rearing

The dietary sterols, cholesterol, campesterol, sitosterol, stigmasterol and 24-methylenecholesterol, were tested for their ability to support brood rearing in the honey bee, Apis mellifera L., by adding them singly to a chemically-defined worker bee diet. Diet supplemented with 24-methylenecholesterol supported the greatest survival of worker bees, but diet supplemented with either 24-methylenecholesterol or cholesterol supported the production of nearly equivalent amounts of sealed brood and more than any of the other three sterols tested. Diets containing stigmasterol, sitosterol, campesterol, or no supplement produced less sealed brood, in decreasing order.     

Vector navigation in walking bumblebees

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