Segmentation of the subcuticular fat body in Apis mellifera females with different reproductive potentials

Abstract Evolution has created different castes of females in eusocial haplodiploids. The difference between them lies in their functions and vulnerability but above all in their reproductive potentials. Honeybee queens are highly fertile. On the other hand, the workers are facultatively sterile. However, rebel workers, i.e. workers that develop in a queenless colony, reproduce more often than normal workers. As a result, the fat body of these bees, which apart from acting as the energy reserve, is also the site of numerous metabolic processes, had to specialize in different functions perfected over millions of years of eusocial evolution. Assuming that the variety of functions manifests itself in the pleomorphic structure of the fat body cells, we predicted that also different parts of the fat body, e.g. from different segments of the abdomen, contain different sets of cells. Such differences could be expected between queens, rebels and normal workers, i.e. females with dramatically different reproductive potentials. We confirmed all these expectations. Although all bees had the same types of cells, their proportion and segmental character corresponded with the caste reproductive potential and physiological characteristics shaped in the evolutionary process. The females with an increased reproductive potential were characterized by the presence of oenocytes in the third tergite and high concentrations of compounds responsible for energy reserves, like glucose, glycogen and triglycerides. Queens had very large trophocytes, especially in the third tergite. Only in workers did we observe intercellular spaces in all the segments of the fat body, as well as high protein concentrations—especially in the sternite. As expected, the rebels combined many features of the queens and normal workers, what with other findings can help understand the ways that led to the origin of different castes in females of eusocial Hymenoptera

Body-Surface Compounds in Buckfast and Caucasian Honey Bee Workers (Apis Mellifera)

Body-surface chemical compounds were studied in 1-day-old nest workers and foragers both in Buckfast and Caucasian bees. The workers of these two age-castes were sampled twice in each of two consecutive years. Body-surface lipids were determined by means of gas chromatography, with a GCQ mass spectrometer. Protein concentrations and activities on the body surface were examined in bee cuticle rinsings obtained from worker bees according to the methods of Lowry, of Anson, and of Lee and Lin. Protease and protease inhibitor activities were determined. Polyacrylamide gel electrophoresis was performed. Caucasian bees, particularly foragers, had more lipids, but Buckfast bees (two age-castes) had more proteins on their body surfaces. A total of 17 alkane types (C17 - C33), 13 alkene types (C21 - C33), 21 esters (C12 - C32), and a phenol (C14) were detected in both races. Alkene C33 was detected only in Caucasian bees. More alkanes, esters, and phenols were found in Caucasian 1-day-old nest workers and foragers than in these age-castes of Buckfast bees. The protein concentration and protease inhibitor activities were lower in Caucasian bees that had higher protease activities. These values corresponded with specific numbers and widths of the electrophoretic bands

Insights into the biochemical defence and methylation of the solitary bee Osmia rufa L: A foundation for examining eusociality development.

We examined age-related biochemical and histological changes in the fat bodies and hemolymph of Osmia rufa males and females. We analysed solitary bees during diapause, in October and in April; as well as the flying insects following diapause, in May and June. The trophocyte sizes, as well as the numbers of lipid droplets were the greatest at the beginning of diapause. Subsequently, they decreased along with age. Triglyceride and glucose concentrations systematically decreased in fat body cells but increased in the hemolymph from October to June. Concentrations/activities of (enzymatic and non-enzymatic) antioxidant and proteolytic systems, as well as phenoloxidase, aspartate aminotransferase, alanine aminotransferase and alkaline phosphatase levels were constant during the diapause, usually lower in the males than the females. Prior to the diapause/overwintering, the concentrations/activities of all the compounds were higher in the fat bodies than in the hemolymph. Later in the spring and in the summer, they increased in the hemolymph and on the body surfaces, while decreasing in the fat bodies. The global DNA methylation levels increased with age. Higher levels were always observed in the males than in the females. The study will promote better understanding of bee evolution and will be useful for the protection and management of solitary bees, with benefits to the environment and agriculture

Morphology of Nasonov and Tergal Glands in Apis mellifera Rebels

Social insect societies are characterized by a high level of organization. This is made possible through a remarkably complex array of pheromonal signals produced by all members of the colony. The queen’s pheromones signal the presence of a fertile female and induce daughter workers to remain sterile. However, the lack of the queen mandibular pheromone leads to the emergence of rebels, i.e., workers with increased reproductive potential. We suggested that the rebels would have developed tergal glands and reduced Nasonov glands, much like the queen but contrary to normal workers. Our guess turned out to be correct and may suggest that the rebels are more queen-like than previously thought. The tergal gland cells found in the rebels were numerous but they did not adhere as closely to one another as they did in queens. In the rebels, the number of Nasonov gland cells was very limited (from 38 to 53) and there were fat body trophocytes between the glandular cells. The diameters of the Nasonov gland cell nuclei were smaller in the rebels than in the normal workers. These results are important for understanding the formation of the different castes of Apis mellifera females, as well as the division of labor in social insect societies

Cuticle, fat body and hemolymph protein concentrations in <i>Osmia rufa</i>.

<p>Various lowercase letters indicate that the month averages differ significantly for comparisons made within each sex and tissue at P ≤ 0.05. The <i>asterisks</i> indicate significant differences (P ≤ 0.01) difference between sexes compared for the each month separately. The comparison was made separately within each of the tissue. Males were not found in June.</p

Phenoloxidase (PO) activities in the fat bodies and hemolymph in <i>Osmia rufa</i>.

<p>Various lowercase letters indicate that the month averages differ significantly for comparisons made within each sex and tissue at P ≤ 0.05. The <i>asterisks</i> indicate significant differences (P ≤ 0.01) difference between sexes compared for the each month separately. The comparison was made separately within each of the tissue. Males were not found in June.</p

Activities of aspartate aminotransferase (AST), alanine aminotransferase (ALT) and alkaline phosphatase (ALP) in the fat bodies and hemolymph in <i>Osmia rufa</i>.

<p>Various lowercase letters indicate that the month averages differ significantly for comparisons made within each sex and tissue at P ≤ 0.05. The <i>asterisks</i> indicate significant differences (P ≤ 0.01) difference between sexes compared for the each month separately. The comparison was made separately within each of the tissue. Males were not found in June.</p

Concentrations of non-enzymatic antioxidants in the fat bodies and hemolymph in <i>Osmia rufa</i>.

<p>Various lowercase letters indicate that the month averages differ significantly for comparisons made within each sex and tissue at P ≤ 0.05. The <i>asterisks</i> indicate significant differences (P ≤ 0.01) difference between sexes compared for the each month separately. The comparison was made separately within each of the tissue. Males were not found in June.</p

Levels of the total antioxidant potential (FRAP) in the fat bodies and hemolymph in <i>Osmia rufa</i>.

<p>Various lowercase letters indicate that the month averages differ significantly for comparisons made within each sex and tissue at P ≤ 0.05. The <i>asterisks</i> indicate significant differences (P ≤ 0.01) difference between sexes compared for the each month separately. The comparison was made separately within each of the tissue. Males were not found in June.</p

Activities of acidic, neutral and alkaline protease inhibitors on the cuticles and also in the fat bodies and hemolymph in <i>Osmia rufa</i>.

<p>Various lowercase letters indicate that the month averages differ significantly for comparisons made within each sex and tissue at P ≤ 0.05. The <i>asterisks</i> indicate significant differences (P ≤ 0.01) difference between sexes compared for the each month separately. The comparison was made separately within each of the tissue. Males were not found in June.</p