Thermal niches of specialized gut symbionts: the case of social bees

Responses to climate change are particularly complicated in species that engage in symbioses, as the niche of one partner may be modified by that of the other. We explored thermal traits in gut symbionts of honeybees and bumblebees, which are vulnerable to rising temperatures. In vitro assays of symbiont strains isolated from 16 host species revealed variation in thermal niches. Strains from bumblebees tended to be less heat-tolerant than those from honeybees, possibly due to bumblebees maintaining cooler nests or inhabiting cooler climates. Overall, however, bee symbionts grew at temperatures up to 44°C and withstood temperatures up to 52°C, at or above the upper thermal limits of their hosts. While heat-tolerant, most strains of the symbiont Snodgrassella grew relatively slowly below 35°C, perhaps because of adaptation to the elevated body temperatures that bees maintain through thermoregulation. In a gnotobiotic bumblebee experiment, Snodgrassella was unable to consistently colonize bees reared at 29°C under conditions that limit thermoregulation. Thus, host thermoregulatory behaviour appears important in creating a warm microenvironment for symbiont establishment. Bee–microbiome–temperature interactions could affect host health and pollination services, and inform research on the thermal biology of other specialized gut symbionts.     

Electroantennogram responses of the American cockroach to germacrene D sex pheromone mimic

Electroantennogram responses of adult American cockroaches were recorded from the sex pheromone mimic, germacrene D, and its related analogs. Germacrene D stimulated male antennae much greater than females, whereas other compounds produced significant responses of similar intensity with both male and female antennae. In the biological assay, only germacrene D induced the typical sexual behavior of males. The bioassay results imply that the conjugated system and isopropyl group of germacrene D are necessary chemical moieties for the sexual response in male cockroaches.     

Nutritional and metabolic studies in humans with 1,3-butanediol.

Three studies of the role of 1,3-butanediol (BD) in human nutrition are described. Isocaloric substitution of BD for starch in the diets of volunteers caused less negative nitrogen balance. Ingestion of urea also decreased negative nitrogen balance, and the effect of BD plus urea in the diets seemed to be additive. No effects were detected on many blood parameters measured during and after the study, except that BD feeding decreased blood glucose significantly. 1,3-Butanediol was shown to be a nontoxic metabolite providing a source of calories for human nutrition. In a second study, ingestion of BD was shown to cause slight increases in serum insulin and growth hormone concentrations in the fasting state. We next studied the effects of prior ingestion of BD on serum insulin, growth hormone, glucose, and lipids during glucose tolerance tests. No significant differences in these parameters were noted when prior ingestion of sucrose or an isocaloric quantity of BD were compared. Possible mechanisms whereby ingestion of BD spared nitrogen and caused decreased blood glucose are discussed.     

The ambrosia beetle Anisandrus maiche (Stark) is repelled by conophthorin and verbenone and attracted to ethanol in a dose-dependent manner

1. Anisandrus maiche (Stark) (Coleoptera: Curculionidae: Scolytinae) is a non-native ambrosia beetle recently detected in northwestern Indiana. There is a critical need for advanced methods to detect and manage this potentially destructive beetle. Identifying semiochemicals that function as attractants or repellents can inform management practices to protect high-value plantings of hardwood trees.
2. We evaluated the extent to which (S)-(−)-verbenone, (E)-(±)-conophthorin and ethanol influence trap capture of A. maiche using two trap types and heights. We also investigated the effect of ethanol release rate on trap capture.
3. Traps baited with ethanol alone captured the most beetles, while traps baited with (S)-(−)-verbenone or (E)-(±)-conophthorin alone captured few A. maiche, and each compound decreased capture when paired with ethanol lures.
4. There was no difference in mean capture of A. maiche between trap types across treatments, and the height of ethanol-baited traps did not influence the capture rate suggesting this species is widely distributed throughout the canopy.
5. Our results suggest that (S)-(−)-verbenone and (E)-(±)-conophthorin are effective repellents for A. maiche and a release rate of at least 3 g/day of ethanol enhances trap to capture.

     

Distribution of developmentally regulated hemoglobins in embryonic erythroid populations.

Both cellular and molecular mechanisms regulate the expression of globin genes during development and differentiation.When a change occurs in the type of hemoglobin synthesized, it may be the result of a substitution of erythroid stem cell lineages or may arise through a modulation of globin gene expression after cells become committed to erythroid differentiation. We have investigated the relationship between the early to late embryonic hemoglobin switch and the primary to definitive erythrocyte change in chick embryos. Using double-label fluorescent antibody technique, we find the simultaneous presence of early and late hemoglobins in single erythrocytes of the definitive cell type. Synthesis of early embryonic hemoglobin is not restricted to the primary cell lineage. This evidence is most compatible with the hypothesis that erythroid cells become committed to the synthesis of specific globins after they have become committed to hemoglobin synthesis in general.