Reconstructing life‐time reproductive histories using steroid hormones in cephalopod beaks

Abstract Reproductive data are vital for fisheries and conservation management. For cephalopods, reproductive data are usually obtained by analyzing gonads, which only provide data on an individual at a given time and require whole deceased specimens. We developed a novel method for extracting reproductive hormones from along the growth axis of a chitinous structure which could thus provide lifetime reproductive histories. We tested our method on two octopus species by taking small subsamples (> 2 mg) of beak tissue along the growth axis. Estradiol and progesterone were detected in both sexes and species, but testosterone was not. Hormonal peaks were observed, likely indicating the timing of sexual maturity; however, peaks were not matched to absolute age. This is the first study to analyze hormones in the accretionary tissues of a marine invertebrate and could be used to collect vital reproductive data, such as age at maturity, on poorly understood species.