Let’s crack into shellfish

We’re too far north to harvest oysters, at least for now. Ours come mostly for midcoast Maine. But our Downeast waters are famed for their scallops and other shellfish.

Last year, a Tendrils focused on lobsters, and I’m thinking of a few others in that vein looking ahead.

So today, let’s look at shellfish more broadly. You know, things like the fact they’re spineless and have hard shells. Now, for a few specifics, working around the fact that scientifically, they’re classified in three groups.

1. Mollusks include snails, clams, mussels, scallops, oysters, octopus, cuttlefish, squid, slugs, and abalone. They form the second-largest phylum of invertebrates, making up 23 percent of the named marine organisms and also widespread in freshwater and terrestrial environments. The oceanic ones are usually very tiny.
2. The expression of “happy as a clam” is more accurately understood in its fuller version, “happy as a clam at high water.” Or should that be “high tide”?
3. The chemistry of creating their calcium-rich calcareous shells remains largely mysterious. Chalk, for one, is comprised of their deposits.
4. But some of them, especially the larger species, have no bones at all. Can they even be considered shellfish?
5. The second group, crustaceans, includes lobsters, crabs, shrimp, crawfish, krill, and barnacles. They come with a segmented body, two pairs of antennae, and a tough, semitransparent exoskeleton. That chitinous covering is something they have in common with butterflies, crickets, beetles, and caterpillars.
6. A single shrimp can lay a million eggs. Of course, humans are far from alone in having a fondness for a shrimp dinner.
7. Crabs communicate by thumping their claws and drumming in a kind of Morse code.
8. And finally, echinoderms, which are found as adults on the sea bed at every depth. They include starfish, sand dollars, sea urchins, and sea cucumbers. They’re recognizable by their radial symmetry.
9. In general, shellfish blood is blue, not red, because it relies on copper, rather than iron. And many shellfish rely on plankton for their diet.
10. My favorite shellfish all seem to go well with melted butter and lemon.