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Age‐related changes in hematocrit in the Galápagos sea lion ( Zalophus wollebaeki ) and the Weddell seal ( Leptonychotes weddellii )
Author(s) -
Trillmich Fritz,
Rea Lorrie,
Castellini Michael,
Wolf Jochen B. W.
Publication year - 2008
Publication title -
marine mammal science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.723
H-Index - 78
eISSN - 1748-7692
pISSN - 0824-0469
DOI - 10.1111/j.1748-7692.2007.00177.x
Subject(s) - zalophus californianus , sea lion , fur seal , foraging , biology , hematocrit , harbor seal , predation , zoology , ecology , marine mammal , ontogeny , oxygen transport , phoca , fishery , oxygen , chemistry , genetics , organic chemistry , endocrinology
In mammals, hematocrit (Hct) is optimized between the divergent requirements of blood flow characteristics and oxygen transport and storage capacity. This trade‐off plays a particularly major role in marine mammals, in which oxygen demand during sustained diving requires high Hct levels. Galápagos sea lions ( Zalophus wollebaeki ) need a long time after birth to develop from terrestrial life to the state of an independent forager at sea. We here show that pups were born with high Hct of 45%, then reduced Hct during the first 40 d of life to 31% while they remain constantly ashore, and increased Hct again until the adult level (57%) is reached at 1 yr of age when they begin to dive for foraging at sea. A similar, but much more rapidly changing pattern is seen in Weddell seal pups, but not in northern elephant seals, where no reduction in Hct is seen after birth. These and similarly changing patterns in terrestrial mammals likely reflect species specific functional adjustments during development due to a trade‐off between the costs of circulation and the changing need to store and transport oxygen.