Krüppel-homologue 1 Mediates Hormonally Regulated Dominance Rank in a Social Bee

Versatile, vigilance, and gut microbiome support the priority of high-ranking hens

Dominance hierarchy exists in social animals and shows profound impacts on animals' survival, physical and mental health, and reproductive success. Aggressive interaction, as the main indicator used to calculate social hierarchy, however, is not found in some female animals. In this study, we aimed to figure out the establishment of social hierarchy in hens that almost perform aggressive behaviors and investigated the interactions of social hierarchy with production performance and gut microbiome. Forty 49-day-old Qingyuan hens were randomly divided into four groups. The social hierarchy of hens was calculated by the relative position around the feeder. The rank 1 (R1), R2, R3, R4, R5, R6, R7, R8, R9, and R10 birds were determined in ascending order. Then, R1 and R2 birds (four duplicates, n = 8) were named as the high-ranking hens (HR) group, while R9 and R10 individuals were named as the low-ranking hens (LR) group (four duplicates, n = 8). The heart index (p = 0.01), number of visits per day, daily feed intake, and occupation time per day were higher in the HR group than LR group, but the LR group had a higher feed intake per visit than the HR group. The alpha diversity was significantly lower in the HR group than the LR group (p = 0.05). The relative abundance of phylum Firmicutes was higher while that of phylum Deferribacterota was lower in the HR group than LR group (p < 0.05). At the genus level, the relative abundance of Succinatimonas, Eubacterium hallii group, and Anaerostipes were higher in HR group than in LR group. The relative abundance of Bacteroides, Mucispirillum, Subdoligranulum, and Barnesiellaceae unclassified was higher in the LR group than HR group (p < 0.05). In conclusion, the rank of hens could be calculated by the relative position around the feeder when they compete for food. The dominant hens have a versatile. Moreover, they are more vigilant and have priority when foraging. Low-ranking hens adopt strategies to get enough food to sustain themselves. Hens of high-rank possess beneficial bacteria that use favorable substances to maintain the balance of the gut environment.

Integration of information from multiple sources drives and maintains the division of labor in bumble bee colonies

Bumble bees are eusocial bees in which the division of labor (DoL) in reproduction and in task performance changes during their annual lifecycle. The queen monopolizes reproduction in young colonies, but at later stages, some workers start to challenge the queen and lay their own unfertilized eggs. The division of colony maintenance and growth tasks relates to worker body size. Reproduction and task performance are regulated by multiple social signals of the queen, the workers, and the brood. Here, we review recent studies suggesting that bumble bees use multiple sources of information to establish and maintain DoL in both reproduction and in task performance. Juvenile hormone (JH) is an important neuroendocrine signal involved in the regulation of DoL in reproduction but not in worker task performance. The reliance on multiple signals facilitates flexibility in face of changes in the social and geophysical environment.

Kr-h1, a Cornerstone Gene in Insect Life History

Insect life cycle is coordinated by hormones and their downstream effectors. Krüppel homolog1 (Kr-h1) is one of the crucial effectors which mediates the actions of the two critical hormones of insects, the juvenile hormone (JH) and 20-hydroxyecdysone (20E). It is a transcription factor with a DNA-binding motif of eight C₂H₂ zinc fingers which is found to be conserved among insect orders. The expression of Kr-h1 is fluctuant during insect development with high abundance in juvenile instars and lower levels in the final instar and pupal stage, and reappearance in adults, which is governed by the coordination of JH, 20E, and miRNAs. The dynamic expression pattern of Kr-h1 is closely linked to its function in the entire life of insects. Over the past several years, accumulating studies have advanced our understanding of the role of Kr-h1 during insect development. It acts as a universal antimetamorphic factor in both hemimetabolous and holometabolous species by directly inhibiting the transcription of 20E signaling genes Broad-Complex (Br-C) and Ecdysone induced protein 93F (E93), and steroidogenic enzyme genes involved in ecdysone biosynthesis. Meanwhile, it promotes vitellogenesis and ovarian development in the majority of studied insects. In addition, Kr-h1 regulates insect behavioral plasticity and caste identity, neuronal morphogenesis, maturation of sexual behavior, as well as embryogenesis and metabolic homeostasis. Hence, Kr-h1 acts as a cornerstone regulator in insect life.