Wednesday, February 20, 2008

Inside Moby Dick.

The white object in this picture is about three feet tall and seven feet long. It is lying on a beach in Bermuda and reeking to high heaven. Any guesses?

Correct. The skull of a young sperm whale. The whale was found floating, dead, believed to have been struck by a ship. The corpse was towed to a small island and, in the hot sun and amid the most gag-inducing of stenches, dissected down to its skeleton, which eventually, I think, ended up at the Bermuda Aquarium, Museum and Zoo. But for the better part of a summer the skull and other large skeletal elements were left out --in the elements, to let nature digest away the remaining soft tissue.

Oh lord did it stink.

Sperm Whale skull. Drawings from Lawlor, T.E. 1979. Handbook to the Orders and Families of Living Mammals. 2nd Edition. Mad River Press, Inc. Eureka, CA. 327 pp.

Above are drawings of a sperm whale skull, which has been described as “asymmetrical and compressed, having been deformed by evolution more than the skull of any other mammal.” The same site illustrates how the flattened skull is related to the well-known, towering, Moby Dick sperm whale brow. The lengthy concavity supports a body of segmented tissue, known as “junk,” and above that the massive spermaceti organ, which may be functionally related to the control of buoyancy. Whether spermaceti organ or junk is homologous to the melon in other toothed whales, and thus likely involved in echolocation, is uncertain, although, apparently (i.e., I haven’t read them), at least two studies (Heyning, 1989; Cranford et al. 1996) support junk (anatomically speaking).

Refs (as cited in Tree of Life Web Project: Cetacea)

Cranford T. W., Amundin M., and K.S. Norris. 1996. Functional morphology and homology in the odontocete nasal complex: implications for sound generation. J. Morph. 228:223-285.

Heyning, J. E. 1989. Comparative facial anatomy of beaked whales (Ziphidae) and a systematic revision among the families of extant Odontoceti. Cont. Sci. Nat. Hist. Mus. Los Angeles 405:1-64.

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