Age validation in early stages of Sepia officinalis from beak microstructure

This is the first study addressing validation of the early growth stages (including the first increment) in the beaks of juvenile cuttlefishes. The age validation in juveniles of Sepia officinalis was performed by comparison of the number of increments observed in the rostrum surface of lower jaws with their true age. A total of 159 individuals were reared at 18 ºC and 21 ºC, with ages up to 31 days from hatching. The number of growth increments in the beak was counted and contrasted with the days of life after hatching, validating the hypothesis of one increment of growth corresponding to one day of life. The mean coefficient of variation between readings (measuring precision) was 2.95 ± 5.98%. The growth of the reading area (rostrum surface) and the periodicity of increment deposition showed no difference between the two culture temperatures and therefore daily deposition was confirmed at these temperatures.