Water contents and seasonal changes of the brain-weight in shrews

Abstract

Abstract The absolute and relative (in percentages of brain weight) lipids and fat-free dry rest contents in the brain of Sorex araneus were determined. The water content in the brain was determined from the difference between the sum of the above values and the weight of the fresh brain. Seasonal and age variations in the weight of the brain were found to occur really in material which had not been fixed. Variations in the weight of water, lipids, and dry rest were stated. These indices are smaller in the winter than in the summer by respectively 23.7, 11.8, and 6.8%. The water content exhibits a relation in direct proportion to the mass of brain, ie a significant loss in the winter (of 3.8%) and repeat increase in old adults (in spring) was found. The dry rest is in reverse proportion to variations in water content. The lipids content is lowest in young adults in the summer, increases in the winter and spring, and then decreases in old adults in the summer and autumn. These data indicate that seasonal variations in the brain weight of shrews are conditioned primarily by variations in water content, and also in fat-free dry rest and lipids contents.