Once Upon a Seashore:
A Curriculum for Grades K-6

Hermit Crabs Rent Shell Houses

Understandings
The children will be able to 1) label the parts of a hermit crab, 2) describe how a hermit crab finds a new shell house, 3) describe how a hermit crab protects itself from predators and from drying out when the tide goes out.

What Am I?
At the seashore, you can find me in tidal pools, hiding among moist seaweeds, and in shallow water on rocky and pebbly beaches.

I have a heavy coat of armor at the front of my body, but unfortunately for me, my lower abdomen is soft and curled and has no protection from hungry predators. You will never guess how I solved this problem. Believe it or not, I carry a borrowed empty snail shell to protect my delicate body from predators. As I grow older I must constantly find larger shells to protect my growing body. Changing snail shells is a dangerous task, and I often fight vicious looking battles with other hermits over empty snail shells.

I am very fussy when shopping for a new shell. If time permits, I will grasp the new empty shell, turn it around to see if it is the right shape and size, tap it with my antennae and look inside. The inspection completed, I quickly hop out of my old shell and slide tail first into the new one. I use my small hook-like legs for holding tight onto my "shell house." I have two pairs of antennae, or feelers, located between my eyes, my means of touching and tasting. My eyes are at the ends of long movable stalks so that I can see behind my shell and in every direction.

I have a pair of long, smooth claws. I can use my right claw, which is larger, like a nutcracker to crush small barnacles and other prey, and to defend myself from predators. I am a scavenger and feed on seaweed and dead and decaying animals. When I withdraw into my shell house, my large claw also acts like a door to block the entrance. This protects me from predators and keeps me from drying out in the hot sun.

Do You Know What I Am? (hermit crab)

Procedures
  1. Read the "What Am I" information for hermit crabs. After each paragraph ask the children to raise their hands if they think they know the mystery animal.
  2. Who has seen the hermit crab? Where was it? What was it doing?
  3. Use the transparency of a hermit crab without its borrowed shell. Give out cards with the following body parts written on them: claws, pincher, soft abdomen, small legs, antennae, eyes, mouth, hard crusty armor, snail shell. Can the students label the diagram with these names?
  4. How does a hermit crab know where it is going? (Its eyes on long stalks and antennae for touching and sensing its surrounding). Why are the eyes on long stalks? (It can see behind its shell and also can see when it is inside its shell).
  5. Why does a hermit crab carry an empty snail shell? (To protect its soft lower abdomen). Why is it dangerous for a hermit crab to change snail shells? What animals are predators? (Gulls, crows, fish). Describe how a hermit crab chooses a larger snail shell. How does a hermit hold on to its shell? (Its abdomen is curled to fit inside a snail shell, and it uses its small modified hook-like legs).
  6. How does a hermit protect itself from drying out? (It finds protection in moist crevices, among seaweeds, and in tidal pools. It can also withdraw into the snail shell and block the entrance with its large pincher, keeping the moisture inside).

Hermit Crab Comic Book
Imagine you are a hermit crab. Your shell is getting much too tight for your soft, delicate body. It's time you found a new more spacious shell. However, the community in which you live is over-populated with hermit crabs and low-cost housing is hard to find.

Preview Pages

cover

overview of each chapter
page 12, 13

sample lesson, hermit crabs
page 67, 68, 69

sample lesson, low tide
page 123, 124, 125

sample lesson, high tide
page 126, 127, 128

sample lesson, a trust walk
page 240