Species-specific variation in cuttlebone δ13C and δ18O for three species of Mediterranean cuttlefish

Stable carbon (delta C-13) and oxygen (delta O-18) isotopes in cuttlebones of three species of Mediterranean cuttlefish (Sepia elegans, S. officinalis, and S. orbignyana) with different life histories were contrasted. Cuttlebone delta C-13 and delta O-18 were quantified at both the core and edge (representing early life and recent deposition, respectively) for all three species sampled from the southern Adriatic Sea in 2010 (n = 28). For S. officinalis, cuttlebone delta C-13 and delta O-18 values were both lower relative to S. elegans and S. orbignyana at the core by approximately 1.0-2.0 and 3.0 aEuro degrees, respectively. Differences between core and edge in cuttlebone delta C-13 and delta O-18 were also observed for S. officinalis with observed values at the cuttlebone edge (recent) exceeding core (early life) values by 2.5 aEuro degrees for delta C-13 and 1.4 aEuro degrees for delta O-18. Differences in isotopic composition across S. officinalis cuttlebones are possibly reflective of ontogenetic migrations from nearshore nurseries (lower seawater delta C-13 and delta O-18 values) to offshore overwintering habitats (higher seawater delta C-13 and delta O-18 values). Overall, results from this study suggest that cuttlebone delta C-13 and delta O-18 hold promise as natural tags for determining the degree of spatial connectivity between nearshore and offshore environments used by cuttlefish.