Social insect colonies represent distinct units of selection. Most individuals evolve by kin selection and forgo individual reproduction. Instead, they display altruistic food sharing, nest maintenance and self‐sacrificial colony defence. Recently, altruistic self‐removal of diseased worker ants from their colony was described as another important kin‐selected behaviour. Here, we report corroborating experimental evidence from honey bee foragers and theoretical analyses. We challenged honey bee foragers with prolonged CO2 narcosis or by feeding with the cytostatic drug hydroxyurea. Both treatments resulted in increased mortality but also caused the surviving foragers to abandon their social function and remove themselves from their colony, resulting in altruistic suicide. A simple model suggests that altruistic self‐removal by sick social insect workers to prevent disease transmission is expected under most biologically plausible conditions. The combined theoretical and empirical support for altruistic self‐removal suggests that it may be another important kin‐selected behaviour and a potentially widespread mechanism of social immunity.

Some social insects exhibit an exceptionally high degree of polyandry. Alternative hypotheses exist to explain the benefits of multiple mating through enhanced colony performance. This study critically extends theoretical analyses of the hypothesis that enhanced division of labour confers fitness benefits to the queen that are sufficient to explain the observed mating frequencies of social insects. The effects of widely varying numbers of tasks and matings were systematically investigated in two alternative computer simulation models. One model was based on tasks that have to be performed to maintain an optimal trait value, while the other model was based on tasks that only have to be sufficiently performed to exceed a minimum trait value to confer full fitness returns. Both model versions were evaluated assuming a broad and a narrow response threshold distribution. The results consistently suggest a beneficial effect of multiple mating on colony performance, albeit with quickly diminishing returns. An increasing number of tasks decreased performance of colonies with few patrilines but not of more genetically diverse colonies. Instead, a performance maximum was found for intermediate task numbers. The results from the two model versions and two response threshold distributions did not fundamentally differ, suggesting that the type of tasks and the breadth of response thresholds do not affect the benefit of multiple mating. In general, our results corroborate previous models that have evaluated simpler task/patriline scenarios. Furthermore, selection for an intermediate number of tasks is indicated that could constrain the degree of division of labour. We conclude that enhanced division of labour may have favoured the evolution of multiple mating but is insufficient to explain the extreme mating numbers observed in some social insects, even in complex task scenarios.

Honey bee queens are exceptionally promiscuous. Early in life, queens perform one to five nuptial flights, mating with up to 44 drones. Many studies have documented potential benefits of multiple mating. In contrast, potential costs of polyandry and the sensitivity of queens to such costs have largely been ignored because they are difficult to address experimentally. To consider one aspect of mating costs to queens, the difficulty of flight, we compared flight behavior and success among a group of control queens and two experimental groups of queens that carried lead weights of two different sizes. For each queen, we assessed the number and duration of all flights and, after egg‐laying commenced, the amount of stored sperm and the number of mates in terms of the offspring’s patrilineal genetic diversity. Added weights quantitatively decreased the number of flights, the mean duration of flights and consequently the total time spent flying. Mating success in terms of sperm quantity and patrilines detected among the queens’ offspring was also negatively impacted by the experimental manipulation. Thus, it can be concluded that the flight effort of honey bee queens during their mating period is adjusted in response to an experimentally increased cost of flying with multiple consequences for their mating success. Our results suggest that queen behavior is flexible and mating costs deserve more attention to explain the extreme polyandry in honey bees.

In many organisms, homolog pairing and synapsis at meiotic prophase depend on interactions between chromosomes and the nuclear membrane. Male Drosophila lack synapsis, but nonetheless, their chromosomes closely associate with the nuclear periphery at prophase I. To explore the functional significance of this association, we characterize mutations in nuclear blebber (nbl), a gene required for both spermatocyte nuclear shape and meiotic chromosome transmission. We demonstrate that nbl corresponds to dtopors, the Drosophila homolog of the mammalian dual ubiquitin/small ubiquitin-related modifier (SUMO) ligase Topors. We show that mutations in dtopors cause abnormalities in lamin localizations, centriole separation, and prophase I chromatin condensation and also cause anaphase I bridges that likely result from unresolved homolog connections. Bridge formation does not require mod(mdg4) in meiosis, suggesting that bridges do not result from misregulation of the male homolog conjunction complex. At the ultrastructural level, we observe disruption of nuclear shape, an uneven perinuclear space, and excess membranous structures. We show that dTopors localizes to the nuclear lamina at prophase, and also transiently to intranuclear foci. As a role of dtopors at gypsy insulator has been reported, we also asked whether these new alleles affected expression of the gypsy-induced mutation ct 6 and found that it was unaltered in dtopors homozygotes. Our results indicate that dTopors is required for germline nuclear structure and meiotic chromosome segregation, but in contrast, is not necessary for gypsy insulator function. We suggest that dtopors plays a structural role in spermatocyte lamina that is critical for multiple aspects of meiotic chromosome transmission.A SSOCIATIONS between chromosomes and the nuclear envelope during meiotic prophase are a widely conserved phenomenon important for proper chromosome transmission. In many species, such interactions are required for bouquet formation, an arrangement in which telomeres cluster in association with the nuclear envelope to facilitate homolog pairing and synapsis (reviewed in Scherthan 2007). In Caenorhabditis elegans, analogous interactions between nuclear envelope proteins and chromosomes are mediated by zinc finger proteins that connect chromosomespecific pairing sites to integral nuclear membrane proteins ). These connections establish bridges across the nuclear envelope and allow for interactions between meiotic chromosomes and cytoskeletal actin. Chromosome movements dependent on these connections are important for homolog pairing (Sato et al. 2009).The association of meiotic chromosomes with the nuclear periphery is particularly striking in Drosophila males, in which paired homologs occupy discreet domains closely apposed to the nuclear membrane. The relevance of this organization to meiotic chromosome segregation in this organism, however, has not been explored. Drosophila males have an unconventional meiosis in which homologs pair but do not assemble synapto...

<b><i>Objectives:</i></b> We set out to evaluate the risk for severe coronavirus disease 2019 (COVID-19) infection and subsequent cerebrovascular disease (CVD) in the population with a prior diagnosis of CVD within the past 10 years. <b><i>Methods:</i></b> We utilized the TriNetX Analytics Network to query 369,563 CO­VID-19 cases up to December 30, 2020. We created 8 cohorts of patients with COVID-19 diagnosis based on a previous diagnosis of CVD. We measured the odds ratios, relative risks, risk differences for hospitalizations, ICU/critical care services, intubation, mortality, and CVD recurrence within 90 days of COVID-19 diagnosis, compared to a propensity-matched cohort with no prior history of CVD within 90 days of COVID-19 diagnosis. <b><i>Results:</i></b> 369,563 patients had a confirmed diagnosis of COVID-19 with a subset of 22,497 (6.09%) patients with a prior diagnosis of CVD within 10 years. All cohorts with a CVD diagnosis had an increased risk of hospitalization, critical care services, and mortality within 90 days of COVID-19 diagnosis. Additionally, the data demonstrate that any history of CVD is associated with significantly increased odds of subsequent CVD post-COVID-19 compared to a matched control. <b><i>Conclusions:</i></b> CVD, a known complication of CO­VID-19, is more frequent in patients with a prior history of CVD. Patients with any previous diagnosis of CVD are at higher risks of morbidity and mortality from COVID-19 infection. In patients admitted to the ED due to COVID-19 symptoms, these risk factors should be promptly identified as delayed or missed risk stratification and could lead to an ineffective and untimely diagnosis of subsequent CVD, which would lead to protracted hospitalization and poor prognosis.