Comparative analysis of queen and worker ovary morphology in the larval and pupal development of Frieseomelitta varia

• Grant number: 23/11435-0
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: October 01, 2023
• End date: July 31, 2025
• Field of knowledge: Biological Sciences - Zoology - Physiology of Recent Groups
• Principal Investigator: Flávia Cristina de Paula Freitas
• Grantee: Mariana Mayumi Yamashiro Delfino
• Host Institution: Centro de Ciências Biológicas e da Saúde (CCBS). Universidade Federal de São Carlos (UFSCAR). São Carlos , SP, Brazil
• Associated research grant: 20/13719-7 - Genomic signatures of plasticity and diversity in the phenotypic development, AP.JP

Abstract

Eusocial bees include the Apini and Meliponini tribes and offer an unique opportunity to unravel the genomic aspects of phenotypic plasticity as a diploid egg (one genome) is capable of originating a worker or a queen (two phenotypes), females with very different morphologies. In the stingless bee species (Meliponini) Frieseomelitta varia, monandric queens have an exclusively reproductive function and are responsible for copulation and egg laying, while workers are sterile and responsible for other colony maintenance activities, such as food and water foraging, nest cleaning and defense. In post-embryonic development, the ovarioles of Frieseomelitta varia worker bees undergo a process of programmed cell death that reduces the ovarioles to remnants without the basic structure for egg production. In queens, the reproductive system includes complete ovaries and the formation of spermatheca (a structure that stores sperm after copulation). These marked differences in the morphophysiology of workers and queens ovaries illustrate the main characteristic of eusocial bees, the division of reproductive labor. These and other morphological differences between workers and queens are triggered by differences in the amount of food ingested by the larvae during their development; so larvae destined to become queens eat about twice as much as larvae destined to become workers. In this caste determination strategy by massification of food supply in brood cells, all food is deposited at once inside the cell before egg laying. Next to the cell where the larva destined to become a queen will develop, an accessory cell is built to store the second portion of food. In this scenario, the objective of this project is to compare the morphological changes that occur in the ovaries during the development of workers and queens. For this, an in vitro rearing system of Frieseomelitta queens and workers will be implemented based on a protocol proposed in previous work. Ovaries of workers and queens at different stages of development will be dissected and prepared (nucleus labeling with DAPI and actin filaments with phalloidin) for visualization and photographic recording under a fluorescence microscope. The images obtained will be analyzed to characterize the development of the ovaries in workers and queens of F. varia. We believe that this approach will lead to the identification of the moment of development in which the apoptosis process (characterized by the fragmentation of the nuclei) is triggered in the bee destined to become workers. The identification of this moment is crucial to guide comparative analyzes whose purpose is to understand the molecular bases of phenotypic plasticity, in addition to revealing details of the biology of the native bee F. varia, and thus supporting the development of the research project of the Young Researcher Grant (2020/ 13719-7) to which this proposal is linked. A better understanding of native bees biology will support programs for the preservation and management of native bees and thus mitigate the consequences of the severe decline in wild populations of stingless bees in recent years.