Morphological Aspects and the Ecological and Mechanical Consequences of Fat Deposition in Wild Vertebrates

"Interstitial and depot fat is by far the most variable constituent of the body and the one most clearly related to nutrition" (148). Fatty tissue can amount to half or more of the live weight of the animal (173, 269, 304) or can be so reduced as to be undissectible; this feature of it so impressed the 18th century anatomist John Hunter that he regarded fat as "not animal substance" because "the animal is the same with as without it" [kited in (214)]. It is now universally accepted that much (but not all) body fat serves as an energy reserve, but its other "functions" and the consequences of its presence on the anatomy and physiology of the whole animal have not been the subject of critical review since the work of Shattock (247) and Auerbach (10). As long ago as 1940, Wells (294) described the anatomy of adipose tissue as a "neglected subject" in humans and in other animals. Statements made in elementary texts (78, 201, 248, 288) are extremely brief; they stress aspects that are in fact of minor importance in many species-e.g. the role of fat in thermoregulation. Indeed, 20th Century opinion on the subject is well summarized by Langebartel (157), who devoted one of the 510 pages of his standard textbook of veterinary anatomy to adipose tissue and concluded that "little more seems necessary to be said about the subject." Comparative anatomists have long treated the subject with suspicion; the most recent systematic attempt to apply the concept of homology to fat masses across classes and orders of vertebrates was that of Butler (49). Many anatomy texts do not mention the subject at all (103, 135, 137); others dismiss the subject very briefly (201, 214) or refer only to biochemical aspects of the tissue (78, 248).