Age validation in common octopus Octopus vulgaris using stylet increment analysis

Abstract

Daily periodicity of growth increments in stylets was validated in wild-caught Octopus vulgaris maintained under controlled conditions. It was corroborated by staining the stylets either with oxytetracycline (OTC) or tetracycline (TC), and comparing the number of rings produced with the number of days elapsed. In all, 19 animals (10 males and 9 females; 680-1470 g body weight, BW) were injected with OTC in Vigo (mean 124 mg kg-1), and another six animals (1 male and 5 females; 248-570 g BW) with TC at Naples (mean 120 mg kg-1). The animals were successfully maintained in captivity until sacrificed for up to 6 (one animal), 9 (one animal), 18 (the six animals from Naples), and 21 (17 animals) days. The number of increments counted in transverse stylet sections was 18.9 ± 1.4 and 20.5 ± 1.5 for octopuses maintained for 18 and 21 d, respectively. The mean rate of increment formation was 1.02 increments per day, suggesting a periodicity of 1 increment per day in the stylet. Consequently, the results successfully validate daily increment deposition in O. vulgaris stylets in the size range analysed. © 2010 International Council for the Exploration of the Sea. Published by Oxford Journals. All rights reserved.