New Technique for aging an octopus

[DWhatley]

Age validation in Octopus maya (Voss and Solís, 1966) by counting increments in the beak rostrum sagittal sections of known age individuals

Guadalupe Villegas Bárcenas,Catalina Perales-Raya,Aurora Bartolomé,Eduardo Almansa,Carlos Rosas - paper via subscription
Abstract

The present study was carried out to validate the daily deposition and age estimation by using beak rostrum sagittal sections increments of cultivated Octopus maya (Voss and Solís, 1966). This study validates for first time the periodicity of beak increments by using animals of known age. We analyzed the rostrum sagittal sections (RSS) of upper and lower beaks in 40 juveniles of O. maya divided into four age groups (63, 87, 105 and 122 days) with 10 individuals per group. The animals were fed with a soft diet allowing obtaining age estimations not affected by the beak erosion. At the same time 50 animals were sampled every 20 days until 120 days old to obtain an age-body wet weight (BW) curve which could be compared with the age-BW curve obtained using age estimations from beaks. Co-variance analysis showed no statistical differences between both curves. The number of increments present in the beaks corresponded with the number of days from hatchling. Therefore, it was possible to validate that a growth increment corresponds to a day of life in O. maya, confirming that, up to 122 days old, the beaks counts can be used to determine the age of O. maya.

 

[DWhatley]

Validation of growth increments in stylets, beaks and lenses as ageing tools in Octopus maya
Almendra Rodríguez-Domínguez,Carlos Rosas.Iván Méndez-Loeza,Unai Markaida

[h=2]Abstract[/h] Octopus hard structures have recently been used as ageing tools. Thirty-two Octopus maya were raised in captivity in four age groups, ranging from 124 to 233 days old. Their stylets, beaks and eye lenses were analyzed in order to validate the periodicity of growth increments during all the octopus life. Transverse sections of stylets were mounted in glycerin jelly, beaks were sagitally cut to analyze their lateral walls and eye lenses were processed by histological techniques and mounted in resin. Growth increments in each structure were observed and counted under a microscope. Stylet increments were successfully validated as their counts were closely related to age in days. Beak increments from the two younger age groups showed a close relationship with age, suggesting a daily deposition. However, persistence of lower increment counts strongly suggests that not all growth increments could be counted, probably due to erosion during feeding. Eye lens increment counts did not show a relation with age, although periodicity, if any, might be subdaily. The use of stylets is recommended for O. maya growth and ageing studies as they also showed a high precision in increment counts between readers.