Sperm Whale's chronicles

A Weird Name: “Sperm Whale”

Spermaceti: Why Does the Sperm Whale Is Called “Sperm” Whale?

Sperm whales are odontocetes that have some usual cetacean characteristics, but some exclusive features [6]. Two of these features are the brain size and the spermaceti organ [6]. The Sperm whale’ brain is far the heaviest brain in Earth: 7.8 kg [6]. Despite of possessing the heaviest brain in the planet, the proportion of brain’s mass in comparison with the rest of their bodies is smaller than in other odontocetes or in humans (Table 1). Sperms’ specific name “macrocephalus” is derived from the Greek for “big head” [1].

Species

Brain Mass (kg)

Body Mass (kg)

Proportion Brain/Body

Sperm Whale (Male)

7.8

33,596

0.00023

Bottlenoise dolphin

1.6

154

0.01038

Killer Whale

5.6

5,448

0.00103

Fin Whale

6.9

81,720

0.00008

Human

1.5

64

0.02344

Table 1: Proportion of Brain Masses and Body Masses of Marine Mammals and a Human. Adapted from Whitehead, 2003 [6].

The spermaceti organ is sperm whales’ ‘more exclusive’ organ [6]. It occupies the biggest part of the animal’s head, and 25 to 33% of its body [6]. Its presence in animal’s head affects all the surrounding organs, mainly the skull, jaw, and nasal passages [6].

The spermaceti is an organ enclosured by mussels which contains a spongy tissue soaked in spermaceti oil [6], which received this name due to a misunderstanding: whalers thought this oil (or wax) [1] was the whale’s semen – that’s what gave sperm whale it’s common name [6].

I’ll explore the function of Spermaceti organ in a next post, since it’s speculated that this organ is related with echolocation and vocalisation.

 

Summarising… Their common name was given due a misunderstood: whalers thought their semen reservoir was in their heads. My personal opinion? A gonad in their heads would be really extreme and unique.

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