Intra-skeletal variability in phosphate oxygen isotope composition reveals regional heterothermies in marine vertebrates

[摘要] Strategies used by marine vertebrates to regulate theirbody temperature can result in local variations, and the knowledge of theseregional heterothermies is crucial for better understanding thethermophysiologies of extant and extinct organisms. In order to investigateregional heterothermies in vertebrates, we analysed the oxygen isotopecomposition of phosphatic skeletal elements ( δ 18 O p ) of twoendothermic fishes ( Thunnus thynnus and Xiphias gladius ) and three dolphins (two Delphinus delphis delphis and one Cephalorhynchus commersonii kerguelensis ). We observed aconsistent link between δ 18 O p variations and temperatureheterogeneities recorded by classical methods. Our δ 18 O p data indicate that: (i) bone hydroxylapatite of the axial skeleton ofdolphins mineralise at a warmer temperature than that of the appendicularone, (ii) the skull is the warmest body region in X. gladius , and (iii)  T. thynnus possesseshigh body temperature in the skull and visceral mass region. These resultsdemonstrate the possibility of tracking regional heterothermies in extantmarine vertebrates using the δ 18 O p , paving the way todirect assessment of thermophysiological specificities of both living andextinct vertebrates. From a palaeoenvironmental perspective, the significantobserved δ 18 O p variability questions the use of some taxaor random skeletal elements for the reconstruction of palaeoceanographicparameters such as seawater temperature and δ 18 O.

[学科分类] 大气科学