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Atmospheric hypoxia constrains skeletal growth and alters bone microstructure in hatchlings of the American alligator ( Alligator mississippiensis )
Author(s) -
Owerkowicz Tomasz,
Andrade Fernando,
Elsey Ruth M.,
Hicks James W.
Publication year - 2009
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.23.1_supplement.1031.3
Subject(s) - alligator , hatchling , american alligator , hypoxia (environmental) , biology , ontogeny , skeleton (computer programming) , growth rate , anatomy , medicine , endocrinology , ecology , oxygen , chemistry , geometry , mathematics , organic chemistry , hatching
Skeletal growth reflects whole‐body growth of the animal, and features of bone microstructure (vascular density, collagen arrangement) can be used to infer an animal's growth strategy. This relationship, however, may be altered by environmental change. Vertebrates are known to have endured large‐scale fluctuations in atmospheric %O 2 during their evolutionary history, but no study to date has tested the effect of atmospheric %O 2 on skeletal growth. We reared hatchlings of the American alligator under chronic hypoxia (12%O 2 ), normoxia (21%O 2 ) and hyperoxia (30%O 2 ). Animals were fed ad libitum every other day, and received injections of fluorescent dyes to determine bone deposition rates. The femoral midshaft shows no significant difference in bone formation rates (BFR) between normoxic and hyperoxic alligators, and an identical correlation with body mass growth rate (GRMb). Hypoxic animals, however, show a significantly higher ratio of BFR:GRMb, which results in a relatively robust skeleton. This is surprising, since hypoxia is thought to impair collagen and mineral deposition in new bone. We argue that any inference of growth rates of extinct vertebrates based on their bone microstructure (e.g., on the amount of bone deposited between seasonal growth rings) should take into account the prevalent atmospheric %O 2 contemporary for the species. Funded by NSF IOB 04445680 to JWH. TO supported by NIH 2T32AR047752.