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The canonical functions of the spleen e.g. immune function, blood filtering, and iron recycling overshadow its known role as a blood storage organ in mammals. Boreoeutherians or modern mammals, such as race horses and dogs, experience splenic contractions during exercise where a 30-40% increase in red blood cell availability is associated with an increase in oxygen consumption. Early data (pre-1960) suggest that splenic sequestration may be used in hibernators. Tenrec ecaudatus are basoendothermic mammals that possess numerous ancestral features such as a cloaca. We posit that tenrecs may provide evolutionary insight into the ancestral function of the spleen. Tenrecs may experience as much as a 25-fold variation in resting oxygen consumption as well as a 14-fold variation in spleen size. We contend that sequestration of red blood cells to the spleen in tenrecs controls oxygen consumption. Here, we present data that directly tests the association of spleen size and oxygen consumption using micro-computed tomography. We contend the boreoeutherian functions of the spleen may be a derived condition afforded by a heightened level of endothermy/homeothermy and its associated higher level of homeostasis. National Science Foundation, Department of Education. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Smith et al. (Wed,) studied this question.