Obtaining Specimens with Slowed, Accelerated and Reversed Aging in the Honey Bee Model

Summary

In honey bee workers, aging depends on social behaviors rather than on chronological age. Here we show how worker-types with very different aging patterns can be obtained and analyzed for cellular senescence.

Abstract

Societies of highly social animals feature vast lifespan differences between closely related individuals. Among social insects, the honey bee is the best established model to study how plasticity in lifespan and aging is explained by social factors.

The worker caste of honey bees includes nurse bees, which tend the brood, and forager bees, which collect nectar and pollen. Previous work has shown that brain functions and flight performance senesce more rapidly in foragers than in nurses. However, brain functions can recover, when foragers revert back to nursing tasks. Such patterns of accelerated and reversed functional senescence are linked to changed metabolic resource levels, to alterations in protein abundance and to immune function. Vitellogenin, a yolk protein with adapted functions in hormonal control and cellular defense, may serve as a major regulatory element in a network that controls the different aging dynamics in workers.

Here we describe how the emergence of nurses and foragers can be monitored, and manipulated, including the reversal from typically short-lived foragers into longer-lived nurses. Our representative results show how individuals with similar chronological age differentiate into foragers and nurse bees under experimental conditions. We exemplify how behavioral reversal from foragers back to nurses can be validated. Last, we show how different cellular senescence can be assessed by measuring the accumulation of lipofuscin, a universal biomarker of senescence.

For studying mechanisms that may link social influences and aging plasticity, this protocol provides a standardized tool set to acquire relevant sample material, and to improve data comparability among future studies.

Introduction

The complex colony structures of highly social animals are maintained through the interaction of a reproductive caste, and a helper caste of typically non-reproducing workers with different social task behaviors. In the different workers, specific physiological adaptations enable distinct sib care behaviors, and are also linked to extreme lifespan differences. Honey bees and mole rats represent the best-developed animal models to study how sociality is linked to patterns of accelerated, negligible or reversed aging^1-3.

In honey bee colonies, a single egg-laying queen is assisted by thousands of workers that tend the brood, forage....

Protocol

1. Decoupling Senescence from Chronological Age

This section describes the setup of double cohort colonies, which consist of a cohort of identified individuals that share the same chronological age ("single age cohort") and a cohort of nest bees. Same aged individuals of the single age cohort will eventually separate into different worker-types with different aging dynamics - these are nurse bees with slowed and forager bees with accelerated functional decline. All procedures are described for one experimental colony. We advise, however, to perform experiments for at least two colony replicates so that colony effects can be controlled for (tw....

Results

Protocol sections 1 and 2 detail how test groups can be obtained to study attributes of accelerated, slowed and reversed aging in colonies with a single age cohort. To monitor worker-type differentiation that accompanies the normal ontogeny we assessed forager counts ("entrance counts") for 6 colonies (Figure 1, compare section 1). The graphs show that considerable change from nurse to the forager state is typically not observed before individuals are more than 10 days old. Marked variability in forager .......

Discussion

We here adopt previously described approaches^{8,16,17,19,20}, and integrate them into a single workflow that will facilitate studying flexible aging in honey bees. Our aim is to provide scientists that are novice to this field with a standardized tool set to obtain relevant sample material, and to improve experimental reproducibility among different research teams. While our procedures are simplified and do not require special equipment as in earlier descriptions (compare for example⁸), some measures .......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Apifonda	Südzucker AG, Mannheim/Ochsenfurt, Germany
paraformaldehyde	Sigma-Aldrich	158127
phosphate-buffered saline	Sigma-Aldrich	P4417
Glycerol	Merck	1.04094.1000