Make Your Own Hand Pluteus

We're all familiar with the hand turkey, that staple of second-grade Thanksgiving celebrations across America. (Though the enjoyment is apparently not limited to second grade.)

When I took an embryology course last summer, I decided to adapt the hand-tracing aesthetic to the illustration of marine larvae. The result? A Hand Pluteus in 10 easy steps!

PART I: The Body

Step 1. Trace your hand.

Step 2. Place your other hand over the traced hand, lining up the fingers. Trace only the thumb of this hand.

Step 3. Close the body along the bottom with a continuous curve from outside of pinky to outside of forefinger, cutting off both thumbs. Draw another line from inside of pinky to inside of forefinger, cutting off middle and ring fingers.

PART II: The Skeleton

Step 4. Get a new color. Start with the postoral skeletal rods.

Step 5. The outer branch of these skeletal rods is fenestrated, so add some holes.

Step 6. Now add the anterolateral skeletal rods. Don't forget to fenestrate!

Step 7. Finally, the posterodorsal skeletal rods. Note the lack of fenestration.

PART III: The Gut

Step 8. Get a new color. The digestive tract runs through the center of the pluteus, and its muscular wall is quite thick. The overall shape changes with peristalsis during feeding, so it's all right to take some liberties here.

PART IV: Finishing Touches

Step 9. Now that your pluteus has a gut, you can feed it. Green algal cells would be appropriate.

Step 10. Display your creation proudly!

What's that?

You don't know what a pluteus is?

Oh. Well. It's the larval form of echinoids (sea urchins and sand dollars) and ophiuroids (brittle stars). They acquire their arms in pairs as they develop, leading to progressively older two-arm, four-arm, six-arm, and eight-arm plutei. You've just drawn a six-arm pluteus, of course. Here's the six-arm pluteus of Dendraster eccentricus, the Western sand dollar, in two focal planes for enhanced 3D effect: