Pressure effects on cholesterol and lipid synthesis by the swimbladder of an abyssal Coryphaenoides species

Abstract

SYNOPSIS. The swimbladder gas gland is recognized as a cholesterol synthesis site in abyssal rattail fishes, Coryphaenoides sp. (from 2000 m depth), and Galápagos Islands surface fish, Orthopristis forbesi, Seriola mazatlana, and Sphoeroides annulatus. This relates to high levels of cholesterol in the gas gland (up to 21% of lipid) and high cholesterol levels in the fatty swimbladder interior (up to 49% of lipid). The gas gland has more protein (45.4%) than the internal fatty mass (18%). Lipids synthesized include phospholipids and triglycerides in 2:1 ratio in the gas gland and 1:2 ratio in the liver. Deep fish have fatty livers (66%) compared to shallow fish (28%). Shallow fish incorporated five times as much acetate-l-14C into lipids as did deep fish, and seven to eight times as much acetate-l-14C into cholesterol. Pressure facilitation of cholesterol synthesis was observed in gas gland and liver of O. forbesi and Coryphaenoides, whereas total lipid synthesis was inhibited by higher pressures. Optimal acetate-l-14C incorporation into lipids occurred at 5000 psi and 2°C in Coryphaenoides; it occurred at 14.7 psi and 15° in O. forbesi. These conditions closely approximate the environment of the fish. © 1971 by the American Society of Zoologists.