Senescence and food limitation in a slowly ageing spider

Abstract

Summary Evidence for reproductive senescence in invertebrate natural populations is scant probably because most groups are short‐lived or because they lack natural markers of age. Lycosa tarantula (L.) (the Mediterranean Tarantula) (Araneae, Lycosidae) is a slowly ageing burrowing wolf spider, in which females can reproduce for two consecutive seasons. Females in their first reproductive season (1Y) can easily be distinguished from females in their second reproductive season (2Y) because the lack of pilosity in the latter. The diet of 1Y and 2Y females was supplemented and their reproductive performance was compared with that of control, non‐food supplemented females. The predictions were that senescent 2Y females would show a worse reproductive performance than 1Y females, and that they would not be able to improve their performance relative to 1Y after food supplementation. The predictions were met. Older females gained less mass, laid smaller egg sacs, produced fewer spiderlings and, if food supplemented, invested a smaller fraction of their mass in egg sacs. Although 2Y females foraged less actively than younger females, 2Y did not improve their performance relative to 1Y following food supplementation. This pattern of changes provides evidence for reproductive senescence in a natural spider population.