白鱀豚额隆油、下颌油及皮脂油的脂肪酸组成

在齿鲸类的头部,有两个特殊的富含油脂的构造,即额隆和一对下颌脂肪体。在全身的皮下有很厚的皮脂层。Litchfield等(1974,1975)对齿鲸类中近20个属的额隆、下颌脂肪体和皮脂的脂质类型作比较研究,发现不同类群的油脂组分有差别,任何类群的额隆和下颌脂肪体的油脂--头脂的组分,与皮脂油的组分有明显区别,而额隆和下颌脂肪体的油脂组分是相近的。

FATTY ACID COMPOSITION OF THE MELON,JAW AND BLUBBER FATS OF THE BAIJI (LIPOTES VEXILLIFER)

Melon, jaw and blubber fats from an adult female Lipotes vexillilfer were analyzed for lipid composition and for iodine value. The melon was sectioned into 10 parts and the blubber samples were cut from the throat, navel and the dorsal median part.Wax esters and triglycerides are the major lipid class in the head fats, only triglycerides are found in the blubber fats. The main fatty acids of the melon fats are isoC_12:0(9-26%), nC12:0(13-17%) and isoC_13:0(12-22%). The fatty acid composition of the jaw fats resemble those of the melon but with higher isoC_12:0(40.36%) content. In the blubber fats, the main fatty acids are C_18:1(37.08-40.31%), C_16:1(16.73-20.51%),C_16:0(10.9-15.56%) and small quantities of nC_12:0 and isoC_13:0,but no isoC_12:0 have been found. The blubber fats also differ from the melon and jaw fats in having higher unsaturated acids levels and very low iso-acids levels.No isovalerate acids are found in the melon, jaw and blubber fats of Lipotes vexillifer. Therefore, Lipotidae is referred as nonisovalerate family, the same as Platanistidae, Iniidae, Ziphiidae and Physeteridae are.According to the view point of comparative anatomy, the melon and mandibular fat bodies respectively were produced by the fatty degeneration of the maxillolabial and mandibular muscles of the head. Consequently, the chemical compositions of the melon and mandibular fats are alike and they are different to that of the blubber fats.The dividing of four types of lipid composition in odontocete melon and jaw fats (Litchfield et al., 1975) cannot be identical with the classification of odontocetes at superfamily rank. Previously published data and our results indicate that three types of lipid composition can be identified in odontocete blubber fats,In Physeteroidea, wax esters or wax esters and triglycerides are the major lipid class present, no isovalerate acids are found. The major lipid class of blubber fats in Platanistoidea is triglycerides and dees not contain isovalerate acids. Wax esters are absent. In Delphinoidea, the major lipid class of blubber fats is triglycerides and characterized in the presence of isovalerate acids. Wax esters are absent or have very slifht airount. We infer from the analysis of the blubber lipids that the ancestor of extant odon-tocete groups protably differentiated into two lineages:isovalerate and noniso-valerate groups. The former is considered ancestral to Delphiroidea. The latter branched into wax ester lacking and wax ester contairirg grouts, i.e. Physeteroidea and PlataniEtoidea. This evolutionary reaticrship is in general agreement with that based on morphological studies.