>To: email@example.com, firstname.lastname@example.org
>Subject: Whale embryos
>Date: Wed, Apr 11, 2001, 10:30 AM
> Dear Mr. Hoyt,
> I am a highschool biology teacher working on an evolution exhibit. It has
> come to my attention that at some stage in the development of whale embryos
> primitive hind legs are visible and then dissappear. Is this true? and can
> you tell me where to find a picture of this stage in a whales development?
> Dan Monahan
> LaSalle High School
> 3901 North Bend Rd.
> Cincinnati Ohio 45237
Dear Mr. Monahan,
There is nothing about this in the fairly comprehensive Biology of Marine
Mammals, published by the Smithsonian Institution Press in 1999. And the
various other whale scientists I asked knew nothing about this.
However, a developmental biologist I know who works on mice and chickens,
says that there is almost certainly a stage in very early whale development
when there are limb buds present but they don't develop. Even snakes have
limb buds and the capacity to grow limbs. But it wouldn't be a case of legs
appearing and then disappearing.
The early developmental biology of whales is not something that is really
studied, at least at present. As you can imagine, the difficulties of
studying embryos at sea, much less the early developmental biology, are
problematic, and experimental research is clearly impossible, so
embryologists and developmental biologists choose easier more accessible
animals such as mice, chickens, etc. It is possible that there is some data
on this buried in whaling records, especially for those trips when
scientists were involved; but you would have to go back into records more
than 25 years ago, when whaling was still being carried on.
It might be worth consulting the following book which has a section on
evolution of cetacea (which I don't have handy at the moment or I would
check it) :
Gaskin, D.E. 1982. The Ecology of Whales and Dolphins
In addition, I might add that there are some fascinating cases of whales
being found with vestigial legs. A humpback whale landed on Vancouver
Island, Canada, in 1919 had 4 foot long (1.2 m) legs.
Unfortunately, I don't have or know of any photos showing legs or even the
leg buds of whales.
Good luck with your exhibit.
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