Patterns of lipid storage and utilization reflect the special life histories of the animal group. Poikilothermic vertebrates (fish, amphibians, reptiles) have evolved a number of life history patterns (smoltification, metamorphosis, hibernation) which present problems for lipid storage regulation. A general theme among poikilotherms is to store lipids among several sites (mesenteric fat, liver, muscle) as opposed to a single depot type (adipose tissue) as in homeotherms; lipids are stored primarily as triacylglycerols, but various other lipid classes also are stored and constituent fatty acids tend to be more complex (longer chain, polyunsaturated). Lipid storage is influenced by de novo lipid synthesis and by lipid deposition from various plasma lipoproteins. Lipid accumulation generally occurs in most poikilotherms during periods of feeding when plasma insulin levels are elevated. Lipid mobilization is controlled by an intracellular lipase enzyme. Lipid depletion occurs during transitional and non-feeding periods and is especially apparent during salmonid smoltification and amphibian metamorphosis.

Regulation of lipid metabolism in poikilothermic vertebrates

Lipids represent a biochemically efficient mechanism for storing energy to be used at a later date for maintenance and/or reproduction. This storage and utilization at different times results in seasonal patterns of lipid cycling. Reptiles exhibit a number of lipid cycling patterns which can be explained by seasonal patterns of food availability. Seasonality in food availability determines the quantity of lipids stored, when lipids are stored, and for what purposes these lipids are utilized. Lipid cycling patterns are in turn correlated with life histories.

https://www.jstor.org/stable/pdfplus/3882137.pdf

Lipid Storage and Utilization in Reptiles

Recent literature on the composition of milk lipids is reviewed and discussed. Many additional exotic fatty acids, mainly branched chain, keto, hydroxy and isomers containing double bonds, have been identified, often with the aid of mass spectrometry. It is estimated that ca. 500 fatty acids have been found in milk lipids. Components of lipid classes have been isolated and their structure determined, e.g., glucosyl and lactosyl ceramide, sphingomyelin, ether lipids, etc. The fatty acid composition of “protected” milk is discussed. This milk, obtained from cows fed polyunsaturated oils encapsulated with formaldehyde-treated casein, contains about five times more linoleic acid than regular milk. The future of research on milk lipids is promising, as there are still many intriguing problems of separation and identification.

Composition of bovine milk lipids.

Gas chromatography of amino acids.

Development of fatty acid analysis by high-performance liquid chromatography, gas chromatography, and related techniques

Gas chromatography of cyclopropane fatty acid methylesters prepared with methanolic boron trichloride and boron trifluoride.

1. 1. Male and female Cnemidophorus tigris caught in late August were studied for lipid and fatty acid content of carcass, liver and abdominal fat bodies. 2. 2. Fat bodies contained the highest percentage of lipids (66–97 per cent) while livers and carcasses contained 10–48 per cent and 2–14 per cent, respectively. 3. 3. Major fatty acids were myristic, palmitic, palimitoleic, stearic, oleic, linoleic, linolenic and arachidonic acids.

Buford L. Brian

Papers

Gas chromatography of cyclopropane fatty acid methylesters prepared with methanolic boron trichloride and boron trifluoride.

Fatty acid distribution of lipids from carcass, liver and fat bodies of the lizard, Cnemidophorus tigris, prior to hibernation

Analysis of acetylated and trifluoroacetylated phenylthiohydantoin amino acids by gas chromatography.