Skeletochronology and isotopic analysis of a captive individual of Alligator mississippiensis Daudin, 1802
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Abstract
In the present study, bone histology and isotope composition (C, N, O) of a femur and
three postcranial osteoderms from an approximately 23–25 year-old captive female Alli gator mississippiensis Daudin, 1802 were analyzed to infer the recorded life history. The
number of visible annual growth marks in the femur cross-section is less than the known
age for the individual concerned, this information clearly shows that skeletochronology
has certain limits. However, bone histology reflects very well the traceable life history of
this individual and its slow growth in early ontogeny. Bone histology on the basis of the
osteoderms shows massive remodeling and an only incompletely preserved growth re cord, reflecting the egg-laying status of this individual. Interestingly, the carbon and espe cially the nitrogen isotope compositions of the osteoderms differ from those of the femur.
This presumably reflects dietary changes and/or differences in resorption and remodeling
processes during tissue formation of these bones. The N, C, and O isotope composition of
the femur is consistent with the food and water the alligator had ingested during the last
years of its life. Thus, contrary to the osteoderms, the femur yields reliable data for the
reconstruction of an individual’s dietary and environmental history.