Histology and ultrastructure of pericardial cells of Scaptotrigona postica Latreille (Hymenoptera, Apidae) in workers and queens of different ages

Genotoxic effect of two environmentally safe doses of cadmium on the hepato-nephrocytic system of Bombus atratus forager workers

Eusocial bees are declining due to anthropogenic actions. Individuals can be exposed to contaminants like Cd, which have been found in pollen. Thus, we evaluated the potential genotoxicity of Cd to the hepato-nephrocitic system of Bombus atratus foraging workers exposed to environmentally safe doses of Cd (0.001 mg/kg and 0.003 mg/kg) during 72 h. To assess the genotoxicity of Cd, we conducted an alkaline comet assay. Doses of 0.001 mg/kg of Cd caused comets of levels 2 and 3, and 0.003 mg/kg of Cd induced comets of level 4, while controls exhibited regular nucleoids. Also, 0.003 mg/kg doses caused higher Damage Index, Damage Frequency, and Total Damage. Our results bring new evidence that 0.003 mg/kg Cd exerted genotoxicity to the HNS cells of B. atratus, probably affecting secondary metabolism and the detoxification capability of bees.

The rate of DNA synthesis in ovaries, fat body cells, and pericardial cells of the bumblebee (Bombus terrestris) depends on the stage of ovarian maturation

Bumblebees are important pollinators of plants worldwide and they are kept for commercial pollination. By studying the process of oogenesis, we can understand their ontogenetic developmental strategy and reproduction. We describe the anatomy of the ovary of the bumblebee Bombus terrestris using 3D reconstruction by confocal microscopy. We found that an oocyte is accompanied by 63 endopolyploidy nurse cells. The number of nurse cells nuclei decreased during oogenesis and the cells are finally absorbed by the oocyte. We monitored the rate of DNA synthesis in vivo during 12 h in ovaries, fat body, and pericardial cells in B. terrestris queens and workers of different ages. The DNA replication activity was detected on the basis of visualization of incorporated 5-ethynyl-2'-deoxyuridine. DNA synthesis detected in differentiated nurse cells indicated endoreplication of nuclei. The dynamics of mitotic activity varied among different ages and statuses of queens. In 3- to 8-day-old virgin queens, intense mitotic activity was observed in all tissue types investigated. This might be related to the initial phase of oogenesis and the development of the hepato-nephrotic system. In 15- to 20-day-old mated pre-diapause queens, DNA synthesis was exclusively observed in the ovaries, particularly in the germarium and the anterior part of the vitellarium. In 1-year-old queens, replication occurred only in the peritoneal sheath of ovaries and in several cells of the fat body. The similar DNA synthesis patterns in the ovaries of mated pre-diapause queens, ovipositing workers, and non-egg-laying workers show that mitotic activity is related not only to age but also to the stage of ovarian maturation and is relatively independent of caste affiliation.

The Basic Plan of the Adult Heart Is Conserved Across Different Species of Adult Mosquitoes, But the Morphology of Heart-Associated Tissues Varies

The heart is a pivotal organ in insects because it performs a number of different tasks, such as circulating nutrients, hormones, and excreta. In this study, the morphologies of the heart and associated tissues, including pericardial cells (PCs) and alary muscles (AMs), in the hematophagous mosquitoes Anopheles aquasalis Curry (Diptera: Culicidae), Aedes aegypti L. (Diptera: Culicidae), and Culex quinquefasciatus Say (Diptera: Culicidae), and the phytophagous Toxorhynchites theobaldi Dyar & Knab (Diptera: Culicidae) were compared using different microscopy techniques. Mosquito hearts are located across the median dorsal region of the whole abdomen. Paired incurrent openings in the heart wall (ostia) are found in the intersegmental regions (segments 2-7) of the abdomen, while an excurrent opening is located in the terminal cone of Ae. aegypti. The sides of the heart contain PC that are more numerous in An. aquasalis and Th. theobaldi. In these two species, PC form a cord of as closely aggregated cells, but in Ae. aegypti and Cx. quinquefasciatus, PC occur in pairs with two or four PC pairs per intersegmental region. In Th. theobaldi, AM binds to all regions of the heart, whereas in other mosquitoes they only bind in the intersegmental regions. The basic plan of the adult heart was conserved across all the adult mosquitoes investigated in this study. This conserved organization was expected because this organ plays an important role in the maintenance of individual homeostasis. However, the species had different PC and of AM morphologies. These morphological differences seem to be related to distinct physiological requirements of mosquito circulatory system.

Hepato-Nephrocitic System: A Novel Model of Biomarkers for Analysis of the Ecology of Stress in Environmental Biomonitoring

Bombus presents a serious global decline of populations and even loss of species. This phenomenon is complex and multifactorial: environmental degradation due to increasing cultivation and grazing areas, indiscriminate use of agrochemicals, and a plethora of xenobiotics daily discharged in the environment. We proposed that bees have an integrated cell system, which ensures protection against chemical stressors up to a certain limit. Therefore, this hypothesis was tested, exposing workers of Bombus morio to cadmium, a harmful trace metal nowadays widespread in our society. The workers were kept in BOD (26°C, RH 70%, in the dark), fed ad libitum, and divided into a control group (n = 20) and an experimental group (n = 20). For the first group, we offered 2 mL of distilled water; for the experimental groups, 2mL of cadmium at 1 ppb. In relation to the control group, exposed bees showed that their fat body and hemocytes responded in synchronization with pericardial cells in a topographical and temporal cascade of events, where the fat body is the first barrier against xenobiotics, followed by pericardial cells. The immune cells participate throughout the process. To this system, we proposed the name of hepato-nephrocitic system (HNS), which may explain many phenomena that remain unclear in similar research with Apis mellifera and other species of bees, as shown in this paper. The bee’s HNS is a system of highly responsive cells to toxicants, considered a novel parameter for the study of the ecology of stress applied in environmental management.