[Smart Farmers] Picture Book | “Crab Encounter” Spectacular: What Do Ornamental Crabs Look Like?

Picture Book | “Crab Encounter” Spectacular: What Do Ornamental Crabs Look Like?

There are not only edible crabs, but also ornamental crabs. Ornamental crabs are classified differently from other aquatic organisms. Taxonomists divide crabs into six groups: Dromiacea, Archaeobrachyura, Oxystomata, Oxyrhyncha, Cancridea, and Brachyrhyncha.

In fact, it is a bit unfair to label crabs as "tyrannical and domineering". They are indeed tyrannical, but their tyranny is determined by their body structure. The 10 legs of crabs are all on both sides of their bodies. The two large claws are used for digging holes, defense and attack, and the remaining four pairs of claws are used for crawling. Since the body of a crab is wide and flat, walking sideways can reduce energy consumption, help crabs quickly enter caves, and avoid being chased by predators. This is why most crabs crawl sideways. In fact, if you observe carefully, not all crabs walk sideways. There is a kind of crab called the short-fingered monk crab that walks straight, and hermit crabs and spider crabs can also walk forward. Different lifestyles may lead to different ways of walking for crabs.

For this reason, we need to speak a fair word for crabs from another perspective. They are not only domineering, but also beautiful and charming. With the breakthrough of breeding technology and the improvement of people's living standards, some people will put beautiful, gentle and cute crabs in aquariums as ornamental crabs, which become a beautiful scenery in the home. Ornamental crabs are not expensive and easy to raise. More and more people are raising ornamental crabs. The ornamental crab industry, like the ornamental fish industry, has become an industry for fish farmers to get rich.

What are the main types of ornamental crabs?

Red clawed mantis crab. If the whole body of the mantis crab is red, its scientific name is red claw mantis crab. If only the claws are red, its scientific name is Chinese mantis crab. The cute part of the mantis crab is a pair of beautiful large claws.

Red claw crab, picture from the Atlas of Marine Life in China

The scientific name of the rainbow crab is Armed Round-axis Crab, which is native to West Africa. The rainbow crab is large in size and very aggressive. Rainbow crabs cannot be artificially bred at present, but the beauty of rainbow crabs is indeed as colorful as a rainbow after rain. I believe that if the artificial breeding technology is broken through, rainbow crabs will be loved by more people.

The purple crab wears an elegant purple coat and red gloves. It is said to be a close relative of the Christmas Island red crab, both of which are brightly colored crabs. It also cannot be artificially bred.

Purple crab, picture from "Atlas of Chinese Marine Life"

The leopard crab is also called the Sulawesi leopard crab, but it is not a devil crab and can be raised in deep water. Look at the leopard spots on its body. Does it look like a ferocious leopard?

The most commonly raised ornamental crab is probably the river crab. There are many types of river crabs, some of which are very beautiful, very ornamental, and can also be reproduced. River crabs have a very diverse diet and basically eat everything.

There are many more crabs like this. Here I would like to tell two short stories, one of which is about fiddler crabs.

Fiddler crabs are also one of the ornamental crabs. Its biggest feature is a pair of claws of different sizes. The large claws placed on the chest are like a warrior's shield. Fiddler crabs can make the action of dancing with their large claws, so they are called fiddler crabs. The purpose of this "fiddler" action is to use the large claws to intimidate the enemy or to seek a mate. In addition, fiddler crabs have a pair of protruding eyes like matchsticks, which are very special. When foraging, the two eyes stand up high to observe the surrounding movements. Once they find something, they will evacuate quickly. The biggest feature of male crabs is a pair of claws of different sizes. The large one is called the mating claw, which is brightly colored, has a special pattern, and weighs almost half of the body. The strange thing is that if the male body unfortunately loses its large claw, a small claw will grow in its place, and the original small claw will grow into a large claw instead, playing the same function.

Fiddler crabs are beautifully colored, with coral red, bright green, golden yellow and pale blue. They live on salt and brackish beaches, and there are many of them on the beaches near the Mauritanian desert in Africa.

Thick-legged green-eyed fiddler crab, picture from "Atlas of Chinese Marine Life"

The second story is about hermit crabs. Hermit crabs mainly live in snail shells, and the largest snail they live in can reach a maximum diameter of more than 15 cm. They are very ferocious and often use their claws to eat the meat of molluscs and shellfish, occupying their shells as their own, and never paying rent for their housing, hence their name. As hermit crabs grow, they will change to different shells to live in.

Author provided

The picture of the long-eyed hermit crab is from the Atlas of Marine Life in China.

Two years ago, I went to the Toronto Aquarium in Canada. There were many hermit crabs in the tanks, and the sign read: "Hermit crabs look for empty shells to shelter themselves. When they grow up, they will look for bigger shells as their new homes. For this reason, picking up shells on the beach is never a good idea!" I appreciate this entertaining way of popularizing science. If we can incorporate the advocacy and education of biodiversity conservation into every aspect of our lives and production and form our conscious actions, perhaps this work will be much easier!

Biodiversity provides us with colorful crabs, allowing us to enjoy their deliciousness and beauty. However, while enjoying them, we must always remember that although aquatic biological resources are renewable, they are not endless; no matter how prosperous the crab family is, once over-exploited, the resources will be difficult to sustain. The author hereby calls for the harmonious development of reasonable development and utilization and ecological protection!

Author: Liu Yadan (National Chief Science Communication Expert, former Assistant Secretary-General of the Chinese Society of Fisheries, Assistant Secretary-General of the China Rural Professional and Technical Association)

Audit expert: Dai Guoqing (Secretary-General of China Algae Industry Association)

Editor: Wu Yuetong

Proofreader: Jiang Ruiyi (internship)