Life-history traits of the giant squid Architeuthis dux revealed from stable isotope signatures recorded in beaks

Angel Guerra, Alejandro B. Rodriguez-Navarro, Angel F. Gonzalez, Chris S. Romanek, Pedro Alvarez-Lloret, Graham John Pierce

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Carbon and nitrogen isotope profiles constructed from the upper beaks of four giant squid Architeuthis dux from the Bay of Biscay and Namibian waters provided a time-integrated record of their diet. Values of delta N-15 ranged from 5.5 to 13.4% and of delta C-13 from 214.4 to 217.8%. Nitrogen isotope profiles differed significantly in shape among the four animals analysed, but delta N-15 increased along each profile, with lowest values around the rostral tip. The difference between the lowest and the highest delta N-15 values was similar to 5.8%, slightly less than a two-level difference between the trophic position of small and large A. dux. The increase in delta C-13 values was not as pronounced as for the delta N-15 profiles, but the changes suggest an ontogenetic shift in diet early in life from smaller prey of relatively low trophic status to larger prey of higher status. Fluctuations in delta C-13 values observed near the rostral tip may be associated with a greater intrinsic variability in the carbon isotope composition of relatively small prey, and/or transient migratory behaviour early in life. The relative stability of the delta C-13 profiles over the remainder of their lifespan is consistent with the hypothesis that adult giant squid inhabit relatively small, well-defined, and productive areas, where food resources have a constant carbon isotope composition.

Original languageEnglish
Pages (from-to)1425-1431
Number of pages7
JournalICES Journal of Marine Science
Issue number7
Early online date4 Aug 2010
Publication statusPublished - Oct 2010


  • beak
  • cephalopods
  • giant squid
  • stable isotopes
  • trophic relationships
  • nitrogen isotopes
  • including giant
  • Southern-Ocean
  • fatty-acid
  • carbon
  • diet
  • ratios
  • ecology


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