Size Matters: Body Size is Correlated with Longevity in Speckled Cockroaches (Nauphoeta cineria)

Abstract

Background: A relationship between body size and longevity has long been appreciated within eukaryotes, especially vertebrates. Introduction: In general, the large size is associated with increased longevity among species of mammals and birds but is associated with decreased longevity within individual species such as dogs and mice. In this study, we examined the relationship between measures of individual body size and longevity in a captive population of speckled cockroaches (Nauphoeta cineria). Methods: Newly molted adults of both sexes were removed from a mass colony housed in multiple terraria and housed individually with food and water provided ad libitum for the duration of their lifespan. Thrice weekly, the status (i.e., live/dead) of individual cockroaches was noted for the duration of the study. Individuals found dead were weighed and measured to obtain body mass and morphometric measures, and the age at the time of death was recorded. The relationship between body size and lifespan was assessed. Result: Contrary to what is commonly seen within vertebrates, large cockroaches were longerlived than their smaller counterparts. Specifically, body mass, body length, and pronotum width were all significantly correlated with the age at death in a mixed population of males and females (n = 94). In addition, we found that the longevity of a historically larger population in terms of both body mass and body length was significantly longer-lived than the population used in this study. Conclusion: These data indicate there is a significant interaction between body size and aging in this species and that increased size results in a survival advantage. There is evidence in the literature indicating that a positive relationship between size and longevity may be common in insects.