Abstract:Here we examine growth rates of lamellae in the cuttlebones of Sepia pharaonis reared at different stages and temperatures (20, 25 and 30 °C). Juveniles showed a faster and more stable increase in the number of lamellae than hatchlings. Different temperatures affect the widths of increments; these decrease as the temperature increases from 20 to 30 °C. Our results suggest that in S. pharaonis the pattern of growth of the cuttlebone's structure does not follow a ‘daily’ increment, and that increments of lamellae vary between life stages. The growth of the cuttlebone is therefore considered to be affected by a combination of physiological and environmental factors.