Adipose Tissue Composition and Cell Size in Fall Migratory Thrushes (Turdidae)

Abstract

Fat deposition is one of the most important and constant physiological events associated with migration in birds (see reviews by King and Farner, 1956 and 1965; Farner, 1960; and Odum, 1960a, 1960b, and 1965). Odum, Rogers, and Hicks (1964) have advanced the hypothesis that before and during migration periods lipid deposition and depletion in adipose tissues occur without appreciable changes in the weight of water and other nonfat components in the body as a whole, in possible contrast to man, where changes in nonfat components may accompany obesity. In spite of the intensity of recent investigation of this subject, the morphology and histology of the storage adipose tissue have not been adequately described. In this study the gross morphology, composition, and histology of the easily dissectible fat bodies were investigated in samples of thrushes obtained during autumn migration. The special purpose of this effort was to determine if the changes of histology and composition of the adipose tissue are consistent with the hypothesis of the homeostasis of the nonfat components in migrating birds. As an index of possible concurrent changes in fatty acid composition, iodine numbers were also determined. METHODS AND MATERIALS Three species of migrant thrushes, Wood Thrush (Hylocichla m&e&a), Veery (H. fuxestens), and Swainson' s Thrush (H. ustzllata), were used in this study. All specimens were fall migrants killed between 14 September and 19 October 1963 in nocturnal collisions with a television tower near Tallahassee, Leon County, Florida. Personnel of the Tall Timbers Research Station collected the fallen birds daily at dawn and identified, weighed, and froze them sealed in plastic bags. This collection of migrant thrushes was assumed to he a random sample, since it represented the total kill for these three species during fall migration at this location. Wing length was measured to the nearest 0.5 mm from the proximal end of the carpometacarpus to the end of the longest primary with the primaries flattened on the measuring scale. Wet weights were taken at the time of dissection, but showed only insignificant variations from wet weights taken at the time of collection. Specimens were dissected while partially frozen so that their fat, which tends to melt at room temperatures, would remain solid for easier dissection. Feathers and skin were removed, leaving all subcutaneous adipose tissues attached to the carcass. These were then carefully lifted and teased away from the underlying structures. The smallest lobules were trimmed away with scissors until all visible lobular fat had been dissected. The abdominal cavity was then opened and the visceral fat masses carefully removed. Sex was determined by observation of the gonads. All the dissected lobular fat was then frozen for later analysis. After removal of the easily dissectible adipose tissue, carcasses were dried to constant weights in vacuum ovens at 40" C and 30 mm Hg. Most specimens reached constant weight after 72 hours of drying, some after 96 hours, and after...

Changes in adipocyte size during post‐embryonic growth in the female Aylesbury duck

“…The adipocyte size at this time is similar to that in the adult goose (Clara, 1929), thrush (Hicks, 1967), rat (Goldrick, 1967) and man (Bjorntorp and Martinsson, 1966) and is therefore probably close to the size finally reached in the fully adult bird.…”

Selective mobilization of fatty acids from adipose tissue in migratory birds

“…Johnston observed that migratory species tend to have more unsaturated fatty acids in adipose stores than non-migratory birds (Johnston, 1973), although Blem found no trend in saturation for migratory and non-migratory birds (Blem, 1976;Blem, 1980). Additionally, some researchers have noted a change in fatty acid composition leading up to migration, although this observation has not been consistent Hicks, 1967;McGreal and Farner, 1956) and does not seem to be the direct result of selective metabolism . Many authors have noted that adipose fatty acid composition tends to reflect dietary composition, and changes in bird diets leading up to migration can alter adipose stores (Bower and Helms, 1968;Conway et al, 1994;Morton and Liebman, 1974;West and Meng, 1968).…”

Fatty acid composition of pectoralis muscle membrane, intramuscular fat stores and adipose tissue of migrant and wintering white-throated sparrows (Zonotrichia albicollis)

“…Supporting this hypothesis, several studies have shown that migrants have a higher proportion of unsaturated FA than non-migrants, and further, that migrants increase the relative unsaturation of fat stores prior to migration (Johnston, 1973;Conway et al, 1994;Egeler and Williams, 2000). Nonetheless, this observation has been inconsistent, and other researchers have found no difference between migrants and non-migrants with regard to adipose tissue FA composition (Hicks, 1967;Blem, 1976;McWilliams et al, 2004). We sought to extend this previous work by examining the seasonal changes in adipose and muscle FA composition in white-throated sparrows.…”