New Zealand hermit crab facts for kids

Quick facts for kids New Zealand hermit crab
Scientific classification

The Pagurus novizealandiae, also known as the New Zealand hermit crab, is a type of hermit crab. It belongs to the family called Paguridae. This crab is special because it is endemic to New Zealand. This means it is found naturally only in New Zealand. Its body can grow up to 16 millimeters (about 0.6 inches) wide.

About the New Zealand Hermit Crab

Hermit crabs are usually easy to spot. You can often tell them apart by the colors of their antennae. They also have smaller structures called antennules in front of their main antennae. The New Zealand hermit crab is about the size of a coin. It can be around 56 millimeters (about 2.2 inches) long. However, its size depends on the empty shells it can find.

The crab's abdomen (its back part) is spiral-shaped. It is also flexible and can twist. This helps the crab fit easily into different shells throughout its life. Hermit crabs protect themselves from predators and danger. They quickly pull back into their shell. They use their large pincer like a door. This pincer keeps them safe once they are inside their shell.

Throughout their lives, hermit crabs use empty shells. They often choose shells from snails or periwinkles. These shells protect their soft and easily hurt abdomens. The crabs carry their shells on their backs. They have small legs that help them grip inside the shell. They also use their stomach muscles to hold themselves securely. As hermit crabs grow, they must find new, larger shells. This is important for their protection.

Where New Zealand Hermit Crabs Live

Global Range

The Pagurus novizealandiae is found only in New Zealand. It does not naturally live anywhere else in the world. This is why it is called "endemic" to New Zealand.

New Zealand Locations

New Zealand is home to over 60 known types of hermit crabs. Most of these crabs live along the coastline. You can find them in tidal rock pools and estuaries. The Pagurus novizealandiae mainly lives in the intertidal zone. This is the area between high and low tide marks. You can find them all around both the North and South Islands. However, they are most common in the South Island. They also live on the Auckland Islands, which are south-east of New Zealand.

Preferred Habitats

The Pagurus novizealandiae lives only in ocean environments. They like rocky shorelines where the tide goes in and out. They also live on rocky reefs under the water. This type of hermit crab cannot live in fresh water. They need salty ocean water to survive. They are usually found in areas like estuaries. These places have strong tides. The water's saltiness stays high enough for the crabs to live there. You can find these crabs from the low tide line down to about 15 meters (about 49 feet) deep.

Life Cycle of the Hermit Crab

Moulting is a very important part of the Pagurus novizealandiae life cycle. It helps the crab grow and develop. Moulting also helps them fix any damaged legs or body parts. It is also a step in getting ready to reproduce. For a hermit crab to grow, it must shed its old exoskeleton (outer shell). The crab does this while still inside its current shell.

Underneath the old shell is a new, soft one. The crab must wait for this new shell to harden. This hardening process takes only a few days. Once the new shell is hard, it can protect the crab's abdomen. After moulting, the hermit crab is bigger. This means it needs to find a larger shell to live in. Their old shells also wear out or get damaged by predators. When searching for a new shell, there is a high demand for good homes. Crabs want to find a new shell quickly to stay safe from predators. Choosing the right time and place to moult is very important for them.

Male and female hermit crabs release special scents called sex pheromones. These scents attract each other. During breeding, male crabs can be quite strong and dominant. The Pagurus novizealandiae has its own way of transferring sperm. This process involves lining up parts on their legs. The male then passes sperm to the female.

When it's time to lay eggs, the female New Zealand hermit crab has two or three pleopods. These are small leg-like parts. The fertilized eggs stick to these pleopods. They are covered in a glue-like substance. The hermit crab keeps the eggs safe inside her shell. She protects them until the embryos are fully grown. When the eggs are ready to hatch, they release a scent. This scent makes the female move. Her movements help the eggs hatch. The tiny larvae are then released into the plankton. It takes weeks to months for the larvae to grow. They go through several stages. Finally, they reach a stage where they can live in a small piece of a broken snail shell. Eventually, they become young hermit crabs. Then they start their own search for a suitable shell.

What Hermit Crabs Eat

Hermit crabs are scavengers. This means they eat dead or injured animals. They often look for food at night. You can also see them moving around in rock pools during the day. Sometimes, they bury themselves partly in the sand or mud. There, they eat tiny bits of plants and animals. They also eat algae, slow-moving invertebrates, and tiny food particles from the water. They are known as detritus feeders. This means they eat a wide variety of decaying matter.

The hermit crab has one large, strong pincer (claw) and one smaller one. The large pincer is powerful enough to break tough outer parts. It can rip apart fish scales or skeletons. This helps the crab get to the soft, fleshy parts inside. It breaks the food into small pieces to eat. The large pincer usually removes the food. Then, the smaller pincer acts like a scoop. It collects the food and moves it to the crab's mouth. The crab uses its third maxillipeds (outermost mouth parts) to hold the food. This is because the larger pincer is often too big to do this job. Hermit crabs sometimes brace themselves over their food. They use their walking legs to make it easier to tear off pieces. They are true scavengers. They try to eat as much as they can quickly. This is before bigger scavengers come along and take their food.

Dangers for Hermit Crabs

Hermit crabs live at the bottom of rock pools and the ocean floor. Because of their small size, many animals hunt them. They are easy prey for fish and octopus. Other crabs are also known to eat smaller, unprotected hermit crabs. This is why having a shell is so important for their soft bodies. Hermit crabs often sift through the sand at the bottom of the ocean. Smaller invertebrates sometimes use this as a chance to find food for themselves.

Shell Trading Among Hermit Crabs

Hermit crabs show some very interesting behaviors when they trade shells. A trade usually involves two crabs. They might push, rock, and knock each other's shells. This behavior lets the crabs check the quality and size of each other's shells. Often, both crabs benefit from the trade. Many crabs can trade shells at once. This can happen very quickly. Once they trade, it doesn't take long for a crab to decide if the new shell is right for them.