Ovary Development in Honeybee (Apis Mellifera L.) Workers Under Co₂ Narcosis, Caged Outside of the Colony

Abstract

A b s t r a c t Exposure of A. mellifera workers to CO 2 has been reported to decrease life span, induce behavioral changes, and inhibit the development of some glands and the ovaries. However, the use of CO 2 is currently practiced among beekeepers and how the development of workers' ovaries are affected is unknown. The present work aimed to evaluate the effect of CO 2 on the ovaries of A. mellifera workers, using a morphological approach. Newly emerged, and 3, 5, and 10-day-old workers were exposed to saturated CO 2 for 30 seconds, more than once. The ovaries were examined under light (LM) and transmission electron microscopy (TEM). The ovaries of narcotized, 5-day-old workers exhibited long ovarioles with well-developed germarium, although oogenesis showed little development. While in the control group, the ovaries already exhibited cysts with cystocytes forming rosettes. At 10-days-old, the ovaries feature was variable; some of the ovaries showed ovarioles with many rosette cysts while others showed a high intensity of disorganization due to the beginning of cell death. The ovarioles of the ovaries of 15-day-old treated workers were morphologically varied as oogenesis showed little or no advance. In others cases, a complete disorganization with swollen cells and cell death features were observed. Germ cells of the ovaries of CO 2 -treated workers exhibited well-structured organelles, such as the Golgi complex, and larger amounts of mitochondria in the cytoplasm than the control group, but there was disorganization of the endoplasmic reticulum membranes. Our fi ndings revealed that the exposure of workers to CO 2 promotes impairment of oogenesis and ovarian degradation.

Impacts and mechanisms of CO2 narcosis in bumble bees: Narcosis depends on dose, caste and mating status and is not induced by anoxia

“…Understanding these mechanisms can also clarify why the impacts of CO 2 are caste dependent in both bumble bees (current study) and honey bees (15, 25, 59). If CO 2 activates network of genes related to hormones and vitellogenesis that have decoupled during the evolution of social behavior (60–62), then the downstream effects on worker and queen reproduction are easier to explain.…”

“…CO2 narcosis has pleiotropic impacts on insect physiology and behavior. These effects have been documented in multiple orders including Orthoptera (8), Diptera (9,10), Hemiptera (11), and Hymenoptera (12)(13)(14)(15). CO2 narcosis in Drosophila melanogaster resulted in changes in fecundity and longevity (10) and reduced climbing behavior (16).…”

“…However, these impacts are not limited to stimulation and may also include suppression of reproduction in some species. For example, exposure to CO 2 led to a reduction in insemination frequency in Glossina females (19), suppressed ovarian development in adult Tribolium castaneum (20), reduced egg laying in Pyrrhocoris apterus (21), and inhibited ovary activation in honey bee workers (14, 15, 22). Similar changes following CO 2 were found in the gene expression profile of multiple species, demonstrating changes in genes related to vitellogenesis (23–25), insulin and juvenile hormone (JH) signaling pathways (23) and oxidative stress (14, 23).…”

No evidence that DNA methylation is associated with the regulation of fertility in the adult honey bee Apis mellifera (Hymenoptera: Apidae) worker ovary

“…CO 2 narcosis is known to inhibit ovary activation in A. mellifera workers (Harris et al 1996;Koywiwattrakul et al 2005;Berger et al 2015) but how it does so is unclear. Thus we were interested to see if narcosis would change methylation patterns.…”

Beekeeping practice: effects of Apis mellifera virgin queen management on ovary development

“…Given the conditions for colony organization, three types of controls can influence queen ovarian function: an intrinsic control due to genetics and physiology; a colony environment control derived from interactions between castes and colony conditions, such as colony age demography, the number of cells available for egg laying and available food; and the beekeeper's management practice, such as fumigation that exposes bees to CO 2 that has an effect on the ovary of workers and queens (Berger and Cruz-Landim 2012;Berger et al 2015;Butler and Simpson 1965;CruzLandim et al 2006;Hamilton 1964;Hartfelder 2000;Page and Ericksons 1988;Patrício and Cruz-Landim 2003). Although Cobey (2007) found that the colony environment is indispensable for the start of oogenesis in the ovaries, the results herein showed that even in queens maintained outside of the colony environment, follicle differentiation can advance until separation of the oocyte and pre-nurse cells, which is just one step short of the ovarian development seen in queens maintained inside a colony.…”