SEA BISCUITS: THEY REALLY DO CONTAIN DOVES – AND MORE!

Recently I posed the question whether sea biscuits, like sand dollars contain ‘doves’. I had one in my hand, it rattled, I took a photograph through its ‘mouth hole’ and the question was answered. Biscuits do indeed contain doves – see HERE for details and comparisons with dollar doves.

However, I spinelessly* failed to break open the biscuit to check out the contents more closely. I theorised that, because of the 5-way symmetry of these creatures, there would be 5 doves (which are in fact segmented mouth parts) in a biscuit exactly as with a dollar, and amiably challenged anyone to disprove it. [* biscuits and dollars are types of sea urchin – see what I did there?]

Dollar dove in close-up – one of 5 segmented mouth parts inside the ‘test’ (skeleton)

Melissa Ann Guinness from Hope Town has a far more robust attitude to these things and, taking up the challenge, she heartlessly smashed open a sea biscuit from her collection to investigate further. I said I’d publish a correction if my theory was wrong. This is it – though in one arguable sense the theory holds good. It just didn’t go far enough…

In the above picture you can see (a) 4 quarters of a sea biscuit skeleton (b) 10 demi-doves (rather than 5 whole doves) and (c) a small mummified 5-limbed brittle star that was presumably in the creature’s digestive system when it died.

10 ‘demi-doves’  (or, when assembled, 5 doves that (unlike sand dollars) are in 2 parts

Complete doves

The final reconstruction – 5 doves and a bonus brittle star

Photo Credits: Keith Salvesen (1, 2, 3, 10); Melissa Ann Guinness (4, 5, 6, ,7 ,8 ,9)