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

Abstract

Guerra, Á., Rodríguez-Navarro, A. B., González, Á. F., Romanek, C. S., Álvarez-Lloret, P., and Pierce, G. J. 2010. Life-history traits of the giant squid Architeuthis dux revealed from stable isotope signatures recorded in beaks. – ICES Journal of Marine Science, 67: 1425–1431. 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 δ15N ranged from 5.5 to 13.4‰ and of δ13C from −14.4 to −17.8‰. Nitrogen isotope profiles differed significantly in shape among the four animals analysed, but δ15N increased along each profile, with lowest values around the rostral tip. The difference between the lowest and the highest δ15N values was ∼5.8‰, slightly less than a two-level difference between the trophic position of small and large A. dux. The increase in δ13C values was not as pronounced as for the δ15N 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 δ13C 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 δ13C 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.

Mitochondrial genome diversity and population structure of the giant squid Architeuthis : genetics sheds new light on one of the most enigmatic marine species

“…By using t, the estimated mode of the mismatch distribution, and an estimated generation time of 3 years, we estimated the time of expansion by the relationship t ¼ 2ut, where u ¼ 2mk (t is the generation time, m the mutation rate and k is the length of the DNA fragment used for the analysis; in this case 14 976 bp). A generation time of 3 years was chosen as it lies in the mid-range of suggested maximum ages of giant squid [9,22,23]. As mentioned earlier, three potential mutation rates were explored.…”

“…Long generation time is also an unlikely cause. While Architeuthis generation time remains uncertain, most published estimates based on statolith growth rings, isotope analyses and growth models suggest 1-6 years [9,22,24,55,56], and the FAO species catalogue suggests a maximum of 14 years [19], far below that needed to significantly decrease the mutation rate.…”

“…Under such a model, we hypothesize that they would prey on pelagic zooplankton and smaller animals, until reaching a sufficiently large size, after which they would descend to their closest nutrient-rich deep habitat (e.g. a continental upwelling zone [9,70]), where they would remain until maturation. The global ocean currents (see the electronic supplementary material, figure S6) powered by the thermohaline circulation, also known as the Great Ocean Conveyor, could drive the continual homogenization of the giant squid global population by transporting the juveniles.…”

Stock identification of neon flying squid (<em>Ommastrephes bartramii</em>) in the North Pacific Ocean on the basis of beak and statolith morphology

“…Hard structures, including the statolith, beak (mandibular) and gladius (pen), which contain a series of ecological information during its mysterious life history, have gradually been used for their stable and constant configuration (Bizikov and Arkhipkin 1997, Piatkowski et al 2001, Ikeda et al2003, Jackson and Domeier 2003, Guerra et al 2010, Ruiz-Cooley et al 2013. As calcified structures embedded in cartilage, a pair of statoliths is an indispensable part of the acceleration receptor system that controls the movement and direction of the cephalopod (Hanlon andMessenger 1996, Arkhipkin andBizikov 2000).…”

Uso de la morfometria de las mandibulas de cefalopodos en estudios de contenido estomacal

“…Además, de servir para estudios de crecimiento (Perales-Ray, 2010;Hernández-López et al, 2001), maduración (Mercer et al, 1980), alimentación (Pérez-Gándaras, 1983;Pérez-Gándaras & Guerra, 1978a), distribución geográfica y batimétrica e identificación de especies (Clarke, 1986;Roper et al, 1988;Pineda et al, 1996), entre otros aspectos de su biología y ecología (Clarke et al, 2002;Guerra et al, 2010). En Chile, estas estructuras obtenidas de estómagos o directamente de ejemplares, en general son poco utilizadas con fines taxonómicos, ya que la información sobre sistemática, taxonomía y biogeografía de los cefalópodos del mar de Chile, sigue siendo escasa (Ibáñez et al, 2009;Vega, 2009).…”