Can Patience tell time?

I always feed my tank critters around the same time; midnight. We got in the habit long ago, when my big polychaete worms would not come out to feed in daylight. I liked to watch them, so the diurnal animals got used to it, too, and I haven't made any changes, even though the worms are gone.

Almost every night, now, starting a few minutes before midnight, I find my grainy-hand hermit, Patience, with her "nose" up to the glass in the front of the tank, waiting. At other times, she's roaming, but she knows supper time.

And, since I handled her so much when she was sick, she takes bits of food directly from my fingers. (All the other hermit crabs either hide or run if my hand gets too close.)

Patience, completely over her illness, eating a dried fish steak.

I find myself wondering, these days, about animal intelligence, about memory. How much of the behaviour of a crab or a shrimp, or of Patience, the hermit, is instinctual, and how much is based on what they have learned about the world? It seems that every few days I find some article about the intelligence of apes, dogs, horses, crows, whales, dolphins, and even little fish. How far down does the chain go?

Did my polychaete worms adjust to me as much as I adjusted to them? Were they waiting for the daily handout, down in their burrows?

Questions, questions.