Biology of the Spermaceti Organ

Photo taken by Leslie Smith off Abaco Island, Bahamas of two Sperm Whales fluking before they go down for a dive.


Spermaceti oil contains lower molecular weight lipid molecules and the presence of wax esters (Morris 1973). When in contact with air the oil partially solidifies turning it white and giving it a semen like appearance, hence the name spermaceti oil (Carrier et al 2002). Spermaceti oil has a three-dimensional heterogeneous lipid composition that aids in ultra-sonic transmission and reception (Morris 1975, Morris 1973).


Diagram of a Sperm Whale Head

Adapted from Clarke 1978



The spermaceti organ is essentially 2 gargantuan oil filled sacs that make up 1/4 the body mass and 1/3 of the body length of a sperm whale (Clarke 1978; Carrier et al 2002). The upper sac is refered to as the spermaceti sac and the lower sac is referred to as junk (Clarke 1978; Carrier et al 2002). Both sacs are triangular in shape with the spermaceti organs larger side at posterior end of nose, and the junks larger side at anterior end (Clarke 1978; Carrier et al 2002).

The junk sac sits on top of the upper lip, and is filled with a denser oil than is found in the spermaceti organ and is organized into sections by partitions (Carrier et al 2002). It is thought to be derived from the odontoceti melon, a structure seen in other whales, while the affinity of spermaceti sac is unknown (Carrier et al 2002). The addition of the spermaceti sac causes the configuration of the junk to be different than melons of other Odontocetis in that it is not bilaterally symmetrical (Schenkkan and Purves 1973).

The spermaceti organ is considered the functional part of the right naris (Schenkkan and Purves 1973). The nares of most other whales are not separated as they are in the sperm whale. This separation is due to assymetrical development of the spermaceti organ (Schenkkan and Purves 1973). As a result the left naris passes outside the case containing the spermaceti oil, which the right naris passes directly below the spermaceti sac (Morris 1973).

Spermaceti oil, itself, is contained in minute sesicles held within a dense network of capillaries (Morris 1973). There is significant variation in lipid composition throughout both the junk and spermaceti, this variation allows for the termal and acoustic producing properties of the organ (Morris 1973).

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