Friday mystery object #128 answer

Happy New Year!

On Friday I gave you this piece of an animal to identify:

As expected, you managed to work out what it is in fairly short order.

Jake recognised it as skin, Denis Copilas as scales and Rhea as carapace – all of which are right at least in part. Henstridgesj and Barbara Powell’s friend Alison spotted that the section of carapace came from a Cowfish or Boxfish. There wasn’t really enough information available to identify it any further than that.

Fortunately this specimen had a label associated with it, so I can tell you that the section of carapace is from the Scrawled Cowfish Acanthostracion quadricornis (Linnaeus, 1758).

Juvenile scrawled cowfish ( Acanthostracion quadricornis ). Gulf of Mexico. Credit: NOAA/NMFS/SEFSC Pascagoula Laboratory; Collection of Brandi Noble, NOAA/NMFS/SEFSC

This group of tropical reef fish have gone down the route of using bony armour in the skin to deter predators. They have two little protuberances that protect their eyes and because they look like horns, they give the Cowfish their name. The rest of the armour makes the body form a rigid triangular(ish) box, which is sufficiently strong to prevent most predatory reef fish from being able to get at the tasty bits of Cowfish inside.

Of course, this rigid box means that the Cowfish can’t swim like a regular fish, with undulations along the body. Instead they use just their fins for propulsion (described in scientific detail in this pdf), which gives them a bit of an odd appearance when they move. The older larger individuals just look stiff, but the small young Cowfish look a bit like a balloon caught in a breeze. Very cute!

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