Longevity and aging in insects: Is reproduction costly; cheap; beneficial or irrelevant? A critical evaluation of the "trade-off" concept.

The most prevalent hypothesis concerning the relationship between reproduction and longevity predicts that reproduction is costly, particularly in females. Specifically, egg production and sexual harassment of females by males reduce female longevity. This may apply to some short-lived species such as Drosophila, but not to some long-lived species such as the queens of ants and bees. Bee queens lay up to 2000 eggs a day for several years, but they nevertheless live at least 20 times longer than their sisters, the sterile workers. This discrepancy necessitates a critical reevaluation of the validity of both the trade-off concept as such, and of the current theories of aging. The widely accepted oxidative stress theory of aging with its links to metabolism and the insulin/IGF-I system has been disproven in Caenorhabditis elegans and mice, but not in Drosophila, necessitating other approaches. The recent spermidine/mitophagy theory is gaining momentum. Two major mechanisms may have been largely overlooked, namely epigenetic control of longevity by imprinting through DNA methylation as suggested by recent data in the honey bee, and especially, a mechanism of which the principles are outlined here, the progressive weakening of the "electrical dimension" of cells up to the point of total collapse, namely death.