An Analysis of the Fluid Contents in the Postanal Sac of the Gray Whale, Eschrichtius robustus
A distinctive, thick walled, postanal sac is found midventrally on the caudal peduncle of most gray whales. The structure appears to be unique to this cetacean and is a relatively unknown organ, with no known function. This study describes partial physicochemical characterization of the fluid contents in the sac. The major chemical component is a unique glycoprotein of molecular weight greater than 150,000 daltons, as determined by gel filtration, analytical ultracentrifugation, acrylamide gel electrophoresis, and colorimetric analyses. A second component of lesser molecular weight, appears to be predominantly protein.
Beierle, John W.; Degnen, Chris; Beierle, Joseph J.; Patten, Donald R.; and Durham, Floyd E.
"An Analysis of the Fluid Contents in the Postanal Sac of the Gray Whale, Eschrichtius robustus,"
Bulletin of the Southern California Academy of Sciences:
Available at: https://scholar.oxy.edu/scas/vol75/iss1/3