Determining the Effect of Age on the Reproductive and Stress Physiology of Octopus Bimaculoides Using Dermal Hormones

Abstract Our goal was to validate the use of dermal swabs to evaluate both reproductive and stress physiology in the California two-spot octopus, Octopus bimaculoides. Our objectives were to: 1. use a biological stressor to validate glucocorticoid analysis; 2. compare the concentration of reproductive hormones (estrogen and progesterone in females; testosterone in males) of reproductive (N = 4) and senescent (N = 8) individuals to determine the effect of age on hormonal patterns; and 3. determine the relationship between glucocorticoid and reproductive hormone production. For the stress test, individuals were first swabbed and then chased around the aquarium with a net for five minutes. Afterwards, individuals were swabbed for 2 hours at 15-minute intervals to compare to a pre-stress test swab. Reproductive individuals responded to the stressor with a 2-fold peak of cortisol at 15 and 90 minutes. Six of eight senescent individuals did not produce a 2-fold increase in cortisol. Reproductive females had significantly higher sex hormone concentrations (progesterone, estrogen, and testosterone) compared to senescent females. Reproductive males also had significantly higher levels of testosterone compared to their senescent counterparts. After the stressor, only reproductive males produced a 2-fold increase in testosterone concentrations, while sex hormones in females showed no change. Dermal swabs provide an effective and non-invasive means for evaluating octopus hormones, which can provide indicators of both reproductive state and perceptions of acute stressors.