Age Estimation from Teeth in Longman’s Beaked Whales (Indopacetus Pacificus) Stranded in New Caledonia (South Pacific)

Type Article
Date 2021-05
Language English
Author(s) Lockyer Christina1, Garrigue Claire2, 3
Affiliation(s) 1 : Age Dynamics, Huldbergs Alle 42, 2800 Kongens Lyngby, Denmark
2 : Institut de Recherche pour le Développement UMR9220 ENTROPIE (IRD, Université de La Réunion, CNRS, Université de la Nouvelle-Calédonie, IFREMER, Laboratoire d’Excellence–CORAIL, BPA5, 98848 Noumea, New Caledonia)
3 : Opération Cétacés, BP12827, 98802 Noumea, New Caledonia
Source Cetacean Population Studies (CPOPS) (2434-5571) (Publication Committee for Cetacean Population Studies), 2021-05 , Vol. 3 , P. 189-197
DOI 10.34331/cpops.2020F010
Keyword(s) Age estimation, Ziphioid whales, Indopacetus pacificus, teeth.

Seven Longman’s beaked whales mass stranded in New Caledonia in November 2013, of which 4 ultimately died, in a first worldwide event reported for this poorly known Ziphioid species. Teeth were extracted, collected and thoroughly cleaned of gum tissue from 3 females ranging from juvenile to adult and one adult male. These were sectioned (crown-root) and prepared using two different methods and examined under microscope magnification when Growth Layer Groups (GLGs) in both dentine and cement were successfully identified. The methods employed for aging included 1) sectioning centrally at approx. 150 µm through crown and root on an Isomet circular diamond saw and examining under a microscope using both transmitted polarised light and plain light; and, 2) thick sectioning (wafering) at approx. 2.5 mm and subsequent decalcifiation in RDO™ (a proprietory brand, Illinois, USA) and then thin sectioning the wafer at 10–25 µm and staining with Ehrlich’s acid haematoxylin. GLGs were investigated in both dentine (25 micron) and cementum (10–15 µm). Layering was evident in both tissues but higher counts were more evident in thin stained sections of cementum. Although dentinal GLGs in untreated tooth sections have been used successfully for aging in Ziphioid species Hyperoodon ampullatus (Christensen 1973, Feyrer et al., 2020), it is believed this is the first time that teeth have been used for estimating age from GLGs in this tropical species.

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