Lobster Molting Reading Worksheet
Marine Biology • Informational Reading Grade Level: 4–6
The Great Shell Escape
How Lobsters Shed, Grow, and Survive on the Ocean Floor
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Reading Passage Read carefully before answering the comprehension questions.
1 Down on the ocean floor, a lobster hides in a rocky cave. It picks and scratches at itself. Why does its dark blue-green shell seem so itchy? It’s time for the lobster to grow.
2 As a lobster grows bigger, it needs a new shell, just as you need new clothes and shoes as you grow bigger. How does it get one? First it has to molt, which means to shed its old shell.
3 Bend over and touch your toes. Do you feel your back stretch? That’s just how a lobster starts to discard its shell. But when it bends at the middle and stretches its back, its shell splits open.
4 Next it must pull itself free. It works hard to wiggle its big claws out through the tiny armholes of its shell. It struggles to pull out its eight skinny legs and long antennae. The many small paddles that stick out under its body have to come out, too. In all, the lobster has to tug twenty-eight body parts out of its narrow shell. Imagine pulling a tight turtleneck over your head twenty-eight times!
5 At last it has the front half of its body free. Then the lobster switches its tail back and forth to knock off the rest of the old shell. Now its body shines a bright blue-green. It is as smooth as silk and as soft as a sponge. With no hard shell to protect it, the lobster must stay concealed in its rocky cave. There, as it rests after the hard job of molting, its body begins to grow bigger. In two or three hours, a new shell starts to form.
6 Like your bones, the lobster’s shell contains a lot of calcium. Lobsters eat the old shell to get more calcium for the new one. You drink milk and eat vegetables to get calcium to build strong bones.
7 At first, the lobster’s new shell is rubbery. But in a few weeks it turns hard. Now the lobster can’t grow any larger until it molts again. Very young lobsters molt several times a year. An older lobster molts only once a year.
8 Unlike you, the lobster will never stop growing. Even as an adult lobster, it will outgrow its shell. Each time it gets a new shell, it will get a little bigger. If it lives about fifty years, it will grow into a giant lobster. Giant lobsters have bodies as long as baseball bats and claws the size of catchers’ mitts.
9 So if you see a lobster hiding in a rocky cave, don’t agitate it. It may be growing.
Vocabulary Clues in Context
Molt: Shedding an outer covering.
Discard: Cast off or get rid of.
Concealed: Hidden away from view.
Agitate: Bother, trouble, or disturb.
Incredible Fact
A lobster must pull 28 separate body parts through its narrow shell openings each time it molts!
Reading Comprehension & Vocabulary Check
Directions: Fill in the circle beside the best answer for each question based on the text.
Total Score: / 8
1 What is the main idea of this passage?
A. Lobsters are unique and amazing sea creatures. B. Lobsters’ shells contain a great deal of calcium. C. Lobsters shed their old shells in order to grow. D. Giant lobsters can grow as long as baseball bats.
2 Which sentence best explains why a lobster must molt?
A. "First it has to molt, which means to shed its old shell." B. "As a lobster grows bigger, it needs a new shell..." C. "Like your bones, the lobster’s shell contains calcium." D. "So if you see a lobster hiding in a cave, don’t agitate it."
3 When does a lobster first know that it needs a new shell?
A. It experiences intense growing pains in its claws. B. Its shell feels itchy and it scratches and picks at itself. C. Its shell splits accidentally against sharp sea rocks. D. It reaches fifty years of age on the ocean floor.
4 Why must a lobster seek shelter in a cave after molting?
A. It is actively stalking small fish and prey. B. Its body is soft and vulnerable with no hard shell to protect it. C. It is trying to escape freezing cold ocean waves. D. It is hiding to store food for the coming winter months.
5 What does the word discard most likely mean?
A. Get rid of B. Save for a long time C. Hide under rocks D. Chew and swallow
6 What does agitate most likely mean?
A. Bother B. Leave alone C. Ignore D. Feed
7 What does concealed mean?
A. Out in open B. Deep C. Hidden D. Sleeping
8 Written Response: Text Connections
2 Points
Explain how a lobster gets the calcium it needs to harden its new shell, and compare that to how humans get calcium for their bones.
Lobster Molt Quest • Student Reading Comprehension Worksheet Page 2 of 2
Lobster Molting Answer Key
Teacher Instructional Guide & Answer Key Lexile: ~780L • Grades 4–6
The Great Shell Escape • Teacher Key
Annotated Passage with Direct Text Evidence Citations
Standards: CCSS RI.4.1, RI.4.2, RI.4.4, RI.5.1
Topic: Marine Arthropod Biology (Ecdysis)
Annotated Text with Evidence Keys Colored highlights match specific questions on Page 2
1 Down on the ocean floor, a lobster hides in a rocky cave. It picks and scratches at itself. Why does its dark blue-green shell seem so itchy? It’s time for the lobster to grow. [Q3 Evidence]
2 As a lobster grows bigger, it needs a new shell, just as you need new clothes and shoes as you grow bigger. How does it get one? First it has to molt, which means to shed its old shell. [Q1 & Q2 Evidence]
3 Bend over and touch your toes. Do you feel your back stretch? That’s just how a lobster starts to discard [Q5: get rid of] its shell. But when it bends at the middle and stretches its back, its shell splits open.
4 Next it must pull itself free. It works hard to wiggle its big claws out through the tiny armholes of its shell. It struggles to pull out its eight skinny legs and long antennae. The many small paddles that stick out under its body have to come out, too. In all, the lobster has to tug twenty-eight body parts out of its narrow shell. Imagine pulling a tight turtleneck over your head twenty-eight times!
5 At last it has the front half of its body free. Then the lobster switches its tail back and forth to knock off the rest of the old shell. Now its body shines a bright blue-green. It is as smooth as silk and as soft as a sponge. With no hard shell to protect it, the lobster must stay concealed [Q7: hidden] in its rocky cave. [Q4 Evidence] There, as it rests after the hard job of molting, its body begins to grow bigger. In two or three hours, a new shell starts to form.
6 Like your bones, the lobster’s shell contains a lot of calcium. Lobsters eat the old shell to get more calcium for the new one. You drink milk and eat vegetables to get calcium to build strong bones. [Q8 Evidence]
7 At first, the lobster’s new shell is rubbery. But in a few weeks it turns hard. Now the lobster can’t grow any larger until it molts again. Very young lobsters molt several times a year. An older lobster molts only once a year.
8 Unlike you, the lobster will never stop growing. Even as an adult lobster, it will outgrow its shell. Each time it gets a new shell, it will get a little bigger. If it lives about fifty years, it will grow into a giant lobster.
9 So if you see a lobster hiding in a rocky cave, don’t agitate [Q6: bother] it. It may be growing.
Core Science Concept
Lobsters have an exoskeleton made of chitin and calcium carbonate. Because this rigid armor cannot expand, lobsters must shed it (ecdysis) to increase body volume.
