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The aim of the study was to analyse the intestinal microbiota of honey bees (Apis mellifera) treated with amitraz. In the present study, the microbiological profile of the honey bee intestines showed minor changes in the microbiota following the application of amitraz. A comparison of the numbers of bacteria and fungi revealed a positive downward trend in the number of fungi. The number of decreased bacteria, included E. coli and especially Clostridium spp., which were not isolated from the intestines of bees treated with amitraz. The number of lactic acid bacteria before and after treatment was at a similar level of 8.3 log cfu/g of intestinal contents.

Nowadays, cell cultures are a standard tool in animal biotechnology, but the problem with honeybees is the constant lack of appropriate cell lines to be used in in vitro research. Until the imperfections of bee tissue cultures are resolved, researchers have to conduct experiments on bees in laboratory cage tests (LCTs).

During the spring development of bee colonies, small-cell combs were found to create equally favorable conditions for worker bee rearing as standard-cell combs, since the workers reared in the small-cell combs did not differ significantly in the majority of morphometric traits, including the length of wings and the sum of the widths of the third and fourth tergites, from those reared in standard-cell combs. Moreover, they had a significantly longer and wider thorax. It can be assumed that the workers reared in small-cell combs collect nectar as effectively as those reared in standard-cell combs, as both groups did not differ in the proboscis length. It was confirmed that the body size of workers is relatively constant and is less influenced by the width of comb cells than was assumed previously, as the values of their morphometric parameters did not increase proportionally with the increasing cell width. The colony kept on small-cell combs provided worse rearing conditions for workers reared in standard-cell combs than the colony kept on standard-cell combs, which may have been related to the less abundant feeding of larvae by workers reared in small-cell combs. [ABSTRACT FROM AUTHOR]

For more than forty years, laboratory cage tests (LCTs) have been used in honeybee research. These tests facilitate the control of elements of the environment present in the laboratory, which allows the minimization of the impact of the changing environmental conditions and conditions in the bee colony nest on the studied features. Therefore, it is possible to estimate the content of the genetic component of a particular trait and to assess the impact of a specific substance or tested agent on the traits of bees.

Simple Summary: Honeybees live in two different environments that are affected by multiple factors, e.g., pathogens or weather conditions. Thanks to the construction of the nests and behavioral cooperation honeybees became independent from the influence of external conditions. Moreover, a single bee has barriers that maintain homeostasis in its body and protect it from harmful factors, such as pesticides, air pollutants, or pathogens, through a system of proteases and their inhibitors. In feral bee colonies, bee comb cells vary in their width, while in Europe, colonies are kept only on standard-cell combs (5.50 mm cell width) or small-cell combs (4.90 mm cell width). In apiary conditions, the activities of proteases and their inhibitors in the 1-day-old workers were always higher in workers reared in standard-cell combs than in workers reared in small-cell combs, and opposite results were observed in groups of older workers (aged 7, 14, and 21 d). However, evaluating the influence of the nest factor is complex and difficult in field tests. Therefore, we assessed the proteolytic system activity in the hemolymph of colonies kept simultaneously on standard and small-cell combs in laboratory cage tests. The use of two types of combs in bee colony nests is an innovative approach to the use of small-cell combs in beekeeping. Irrespective of the age of the bees, the workers reared in the small-cell combs had higher protein concentrations. In turn, the activities of proteases and their inhibitors in the hemolymph of 1-day-old workers were higher in the group reared in the standard-cell combs. In older workers (aged 7, 14, and 21 days), higher protease and inhibitor activities were detected in the group reared in small-cell combs. The comparison of the results of apiary studies with those of laboratory cage tests shows that functions performed in the nest have a greater influence than age on the activity of proteases and their inhibitors in the hemolymph of worker bees. The aim of the study was to compare the activities of proteases and their inhibitors in the hemolymph of honeybee workers reared in small-cell combs (SMC) and standard-cell combs (STC) in laboratory cage tests. The analyses conducted in laboratory conditions facilitated assessment of the impact of the comb cell width (small vs. standard) along with eliminating the influence of many environmental factors on the results. The width of the comb cells in which the workers were reared had a significant effect on the protein concentrations and proteolytic system activities in the hemolymph. Irrespective of the age of the workers, higher protein concentrations were found in the hemolymph of the SMC workers. In turn, the activities of proteases and their inhibitors in the hemolymph of 1-day-old bees were higher in the STC workers. In older bees, aged 7–21 days, activity was higher in the SMC workers. The role of the considerable cell width variability in natural combs that were built without the use of an artificially produced wax foundation is worth investigating. It is highly probable that the impact of the comb cell width on the features of workers reared in these combs modifies the age polyethism in the worker caste as well. The investigation results of one-season studies of honeybees could be seriously affected by random factors. To reduce the risk of these effects, it is advisable to continue experiments over a few consecutive years. [ABSTRACT FROM AUTHOR]

Honeybee nests constructed without man-made wax foundation have significantly more variability of cell widths/sizes than those in commercially-kept colonies. The effects of this natural variability in comb cell widths on individual and colony traits have not been explained to date. The investigation of this problem can lead to new findings about the biology, physiology, and possibly, the evolution of the honeybee. The aim of the study was to compare the catalase and superoxide dismutase activities and the total antioxidant capacity levels in the hemolymph of honeybee workers reared in small-cell combs and standard-cell combs in colonies kept simultaneously on standard- and small-cell combs. The ratio of the small-cell combs to the standard-cell combs in the nest was 1:1. The workers reared in small-cell combs were characterized by higher antioxidant activities in the hemolymph than those reared in standard-cell combs. Consequently, their hemolymph had a greater antioxidant capacity, which indicates that they may be better predisposed to be foragers than workers reared in standard-cell combs. To describe the physiological differences between worker bees reared in small- and standard-cell combs in the same colony, the role of the considerable variation in the cell width in natural combs built without the use of artificially produced wax foundation is worth elucidating. The comparison of the apiary and cage experiments indicated that changes in antioxidant activities predominantly result from worker activities, especially those requiring the intensification of metabolism, rather than the age of the worker bees. To reduce the impact on the results of random environmental factors potentially present in one-season studies of honeybee research, investigations should preferably be carried out over a few consecutive years. [ABSTRACT FROM AUTHOR]

Based on the research conducted by Maggi et al. [[29]], who reported a significant variation in the width of comb cells in a bee colony nest constructed without a wax foundation, we decided to combine small-cell combs and standard-cell combs in a nest of the same bee colony. This study is a continuation of our innovative research on the impact of simultaneous maintenance of bee colonies on standard- and small-cell combs on the traits of worker bees and bee colonies [[36], [39]]. Apis mellifera, proteases, hemolymph, proteolytic system, protease inhibitors, bee comb, small-cell combs Keywords: Apis mellifera; hemolymph; proteolytic system; proteases; protease inhibitors; bee comb; small-cell combs EN Apis mellifera hemolymph proteolytic system proteases protease inhibitors bee comb small-cell combs N.PAG N.PAG 13 04/26/22 20220415 NES 220415 1. [Extracted from the article]

Nowadays, cell cultures are a standard tool in animal biotechnology, but the problem with honeybees is the constant lack of appropriate cell lines to be used in in vitro research. Until the imperfections of bee tissue cultures are resolved, researchers have to conduct experiments on bees in laboratory cage tests (LCTs). At the turn of the 21st century many new hazards for beekeeping appeared. An early recognized problem was the Colony Collapse Disorder and Honey Bee Depopulation Syndrome, which were associated with the harmfulness of pesticides and strictly linked with a decline in bee immunity. Such problems in LCTs were attempted to be resolved through research on the interactions between biostimulators and antiparasitic drugs. LCTs allow the relationship between the dose of a specific factor and its impact to be determined, which can be used in the establishment of reference values. Furthermore, LCTs may be a useful tool in understanding the function and role of bee gut flora. Using the honeybee as an animal model is possible thanks to knowledge of the honeybee genome and bee biology and the similarity between some physiological and biochemical processes and those occurring in humans. So far, LCTs have been used to understand better human aging, learning and gene expression regulating. This is facilitated by the advanced development of medicine and molecular genetics, and in the future the use of honeybees may become a standard in biochemical or gerontological research. [ABSTRACT FROM AUTHOR]

Simple Summary: Honeybee workers are able to detect dead or infected brood in comb cells and remove it outside the nest before the infection spreads onto the colony. Such a phenomena is called an hygienic behaviour. Colonies with efficient hygienic behaviour are more resistant to diseases. Bee comb cells may vary in width. In Europe, standard-cell combs (cell width approx. 5.50 mm) and small-cell combs (cell width approx. 4.90 mm) are used. Typically, colonies are kept only on standard- or small-cell combs. We assessed the dead brood removal efficiency in colonies kept on both comb types. Simultaneous keeping of a colony on standard- and small-cell combs is a novel approach to the use of small-cell combs in beekeeping. The removal from small-cell combs was significantly more efficient than in the case of the standard-cell combs, which indicates that bees find dead brood in small-cell combs faster or devoted more attention to the removal. Better understanding of the effect of the simultaneous keeping of colonies on standard- and small-cell combs on the efficiency of hygienic behaviour may contribute to enhancement of the resistance of bee colonies to diseases. The efficiency of the hygienic behaviour in bee colonies towards dead brood was assessed in small-cell combs (SMCombs) and in standard-cell combs (STCombs). Each colony had both types of combs in the nest on a permanent basis. Simultaneous keeping of a colony on standard- and small-cell combs is a novel approach to the use of small-cell combs in beekeeping. The number of killed pupae removed within 24 h was the measure of the hygienic behaviour efficiency. Regardless of the year, the brood in the SMCombs was uncapped and removed significantly more efficient (p ≤ 0.01) than in the STCombs (number of non-uncapped cells: in 2020 SMCombs = 3.79, STCombs = 11.62; in 2021 SMCombs = 2.34, STCombs = 5.28 and completely removed cells: in 2020 SMCombs = 87.46, STCombs = 80.04; in 2021 SMCombs = 96.75, STCombs = 92.66). In colonies kept simultaneously on standard- and small-cell combs, the width of the comb cells has a significant effect on the efficiency of removal of dead brood, which is removed more efficient from small-cell combs than from standard-cell combs. [ABSTRACT FROM AUTHOR]