Monday, November 11, 2013

Moon snails and the biggest foot ever

Lunatia heros.  Moon god.  Quite a name for quite an animal.

Last week my marine bio lab ventured out into the mudflats.  Besides being our messiest lab, it's often the one where we find the most interesting things, despite my students' trepidation beforehand.

I give a prize for the muddiest student.  This year there were several contenders, although the winner went above and beyond by both losing her boots and falling over; completely encasing her bottom half in thick, anaerobic mud.  She was a good sport and smiled about it as we hosed her off afterwards. 

I also give a prize for the student who finds the coolest organism.  Really, I'm always rooting for someone to find us a moon snail.  Some years it happens; most years it doesn't.  Imagine my excitement when I myself came across a nice little 1 1/2 inch moon snail; just sitting on the surface with its operculum mostly closed up.  I grabbed that bad boy and proclaimed I might just give the prize to myself.  My students weren't too impressed though; it didn't look like much since its operculum was almost completely closed.  Just a hint of the foot peeked out.  Little did they suspect what a moon snail is really all about.

My students met that challenge though.  Not five minutes later one of them called over "What's this?"  She was striding towards the class in her boots, holding up a monster moon snail; dripping wet and trailing a giant foot under it.  That foot got their attention.  It was as big as my palm, and when we put the snail in a bucket it started to march around, antennae out and foot taking up most of the small pail.

Moon snails are tremendous predators.  They move just under the surface, with only the top of their shells exposed, searching for their prey -- preferably a nice soft-shell clam; Mya arenaria.  When it finds a clam, the snail grips it in a deadly embrace with its enormous foot, and begins to drill a hole in the clam using its rasp-like tongue (called a radula) and some acidic spit.  Once the shell is breached, the snail releases a digestive enzyme right into the clams shell, turning it into soup, and sucking up the delicious chowder.

Now I have two very nice moon snails in my teaching tanks, and a bunch of soft-shell clams I collected for feeding them.

What's the prize you ask?  Gift certificates to Gelato Fiasco!  Too bad I didn't win after all . . . . Dory would have loved a cup.

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