Did You Know? 21 Incredible Mangrove Horseshoe Crab Facts

Mangrove horseshoe crab facts may not bring you luck but knowledge is on your way.

A mangrove horseshoe crab (Carcinoscorpius rotundicauda) is a marine arthropod that evolved on earth several million years ago. Though they are known as crabs, they are closely related to scorpions and spiders. They hail from Asian countries like Hong Kong, Singapore, and Indonesia and are found living in sandy beaches, lagoons, sea waters, and mangrove regions.

Horseshoe crabs have blue blood while the color of a crab's blood is bright blue. The body anatomy of a horseshoe crab is more distinctly related to scorpions as they have six pairs of appendages whereas crustaceans like crabs have five pairs of legs. True crabs have antennae that are not present in the case of horseshoe crabs. True crabs have jaw-like structures or pincers in their mouth for cutting or biting their food, whereas, horseshoe crabs use their chelicerae or appendages for crushing their food and passing it to their mouth.

Horseshoe crabs have a hard shell in the shape of a horseshoe from which the species derived its name. They also have multiple eyes, 12 legs, and gills along with a round tail that helps them to flip in the waters. The Singapore Science Centre has researched and analyzed the geographical distribution and the morphometric features of the mangrove horseshoe crab, although their exact population is not known and hence is listed as Data Deficient on the IUCN Red List. More crab facts are on the way and it would be unwise to miss the spider crab and blue crab fun facts.

Mangrove Horseshoe Crab

Fact File

What do they prey on?

Insect larvae, small fish, crabs

What do they eat?


Average litter size?

2000-3500 eggs

How much do they weigh?

2.2-9.9 lb (1-4.5 kg)

How long are they?

14-19 in (35.5-48.2 cm)

How tall are they?


What do they look like?


Skin Type


What are their main threats?

Habitat loss, pollution, overfishing

What is their conservation status?

Data Deficient

Where you'll find them

Lagoons, mangroves, sea waters, sandy beaches


South-Eastern Asia, Hong Kong, Singapore, Indonesia





Scientific Name

Carcinoscorpius rotundicauda





Mangrove Horseshoe Crab Interesting Facts

What type of animal is a mangrove horseshoe crab?

A mangrove horseshoe crab is a marine arthropod that belongs to the subphylum of Chelicerata. Though it acquired the title of a crab, it is neither a true crab nor belongs to the community of the crustaceans but these crabs-like creatures are closely related to spiders and scorpions.

What class of animal does a mangrove horseshoe crab belong to?

A mangrove horseshoe crab belongs to the class of Arthropoda under the Animalia kingdom. Unlike true crabs, horseshoe crabs do not belong to the subphylum of Crustacea but hail from the Chelicerata subphylum.

How many mangrove horseshoe crabs are there in the world?

The exact population of the mangrove horseshoe crabs is not known due to their random distribution in marine waters. Although habitat loss, demands in the food market and biomedical industries have threatened this species.

Where does a mangrove horseshoe crab live?

A mangrove horseshoe crab is found living in the wetland regions of the mangroves. This species of horseshoe crabs are also found in the coastal wetlands, lagoons, shallow waters of the sea, as well as sandy beaches.

What is a mangrove horseshoe crab's habitat?

A mangrove horseshoe crab lives in the marine waters, coastal beaches, soft sandy ocean beds, lagoons, and the lowlands in the mangrove regions. The horseshoe crab species (Carcinoscorpius rotundicauda) are endemic to Southeast Asia and are found in countries like Hong Kong, Indonesia, and Singapore. They are found living in the shallow waters of the Indo-Pacific ocean.

Who does mangrove horseshoe crab live with?

Mangrove horseshoe crabs are generally found to live in a consortium (a group of two or more individuals) or a cast. Some horseshoe crabs may also be found living alone or in pairs similar to spiders and scorpions.

How long does a mangrove horseshoe crab live?

A mangrove horseshoe crab can live for more than 20 years of age. Although habitat loss, pollution, and overfishing have led to the untimely life loss of many individuals of the species.

How do they reproduce?

Female horseshoe crabs are one-third times larger in size than males.  The first pair of appendages of males are not only utilized for locomotion but serve an important role during mating; the first pair of walking legs that are situated right next to the prosoma (or the horseshoe-shaped front carapace or shell) is more enlarged and have hook-like tips that are used while mating. Horseshoe crabs have a pair of compound eyes that are primarily used to search for a mating partner. The reproducing organs for both males and females are situated between the last pair of pushing legs and the transverse appendages or the gills. Both male and female individuals are monogamous and engage in mating during high tides and the females lay about 2000-3500 pearl-like eggs. The eggs hatch after about a couple of weeks from the time of spawning, the eggs are laid by the females in nests or holes that they dig in the sands in the coastal areas. Juvenile horseshoe crabs (right after the hatching of the eggs) are teeny-weeny copies of the adult horseshoe crabs but lack the telson (or the round tail). Juvenile horseshoe crabs spend their infancy in their native beaches and after five to six times of sloughing of their shell, they acquire the size of an adult and gradually crawl towards the ocean.

What is their conservation status?

The conservation status of the two horseshoe crab species, namely, the Chinese horseshoe crab (Tachypleus tridentatus) and the Atlantic horseshoe crab (Limulus polyphemus, from the family limulidae), is Endangered and Vulnerable, respectively. However, the conservation status of the mangrove horseshoe crab lacks sufficient information and is listed as Data Deficient on the IUCN Red List.

Mangrove Horseshoe Crab Fun Facts

What does mangrove horseshoe crab look like?

The horseshoe-shaped prosoma of its carapace earned mangrove horseshoe crab its name.

Mangrove horseshoe crabs (C. rotundicauda) are crab-like arthropods and resemble crustaceans in terms of anatomy but they actually belong to the subphylum of Chelicerata and hence are not true crustaceans. Horseshoe crabs (from the family Limulidae) have a carapace with a unique horseshoe shape that has earned them their name as horseshoe crabs. Horseshoe crabs (mostly found in Asian countries like Hong kong) have their body divided into three main parts, namely, the head (the first part of the body) that consists of the carapace with the hard shell cover, the anterior part of which is the prosoma that is round in shape, the middle part of the body contains the six pairs of legs and the end part that consists of one round telson or tail. However, juveniles lack the tail. The occiput of the carapace of a horseshoe crab consists of spines; the spines are moveable and mostly used for protection. Among the four extant species, the mangrove horseshoe crab is the smallest in size. The two chelicerae or a couple of appendages in the front are used by horseshoe crabs to nibble on their food and passing the same to their mouth. The prosoma of the horseshoe crab has a pair of compound eyes along with the other eight eyes. The telson or the tail has photoreceptors and is used by horseshoe crabs to make them flip when upturned.

How cute are they?

Horseshoe crabs do not really fit being called as cute. The shell of their prosoma along with their telson or tail may make them look creepy and scary as scorpions. However, horseshoe crabs are harmless and meek creatures and prefer to live in their group.

How do they communicate?

Horseshoe crabs are arthropods and lack specialized communicating mechanisms. However, adult horseshoe crabs communicate through chemical signals. Males receive chemical signals from the females to communicate during breeding.

How big is a mangrove horseshoe crab?

A mangrove horseshoe crab is smaller in size when compared to the Atlantic (Limulus polyphemus) species of the horseshoe crab and the other Asian species scientifically called  Tachypleus gigas. A mangrove horseshoe crab measures about 14-19 in (35.5-48.2 cm) in body length including its tail. The size of the juvenile's body is much tinier yet they grow about 33% times during each session of sloughing their shell and their body takes about five to six sloughing sessions to grow fully as an adult. They are much bigger than a green crab.

How fast can a mangrove horseshoe crab move?

Horseshoe crabs can swim on their back but are poor and slow swimmers; they can crawl at a moderate pace on the sea bed or coastal lowlands.

How much does a mangrove horseshoe crab weigh?

Mangrove horseshoe crabs weigh about 2.2-9.9 lb (1-4.5 kg).

What are the male and female names of the species?

There is no specific name by which males and females of the species are called. However, males that do not attach themselves with females during breeding are called 'satellite males'.

What would you call a baby mangrove horseshoe crab?

A baby mangrove horseshoe crab is often referred to as a juvenile.

What do they eat?

The food of mangrove horseshoe crabs comprises sea worms, insect larvae, small crabs, and small fishes.

Are they poisonous?

The presence of the chemical tetrodotoxin in some individuals of mangrove horseshoe crabs has resulted in few cases of poisoning after being eaten, although other species like the Limulus horseshoe crabs are not poisonous.

Would they make a good pet?

These meek creatures are not usually fostered and are found living in their marine natural habitats.

Did you know...

The horseshoe crab is also called the 'living fossil' and is very closely identical to its earliest ancestors that evolved on earth several years ago even before the dinosaurs have lived.

The mouth of a horseshoe crab is situated in the middle of its abdomen and they prefer to crawl over swimming. Surprisingly, their reproductive cycles are dependent on the tidal cycles.

Why is the horseshoe crab's blood important to humans?

The blue blood of a horseshoe crab acts as an indicator of bacterial infections in the human body. The Atlantic species of horseshoe crab's blood contains the substance 'Limulus amebocyte lysate' that coagulates around the bacterial invasion. The rising demand for horseshoe crabs' blood in the pharmaceutical and biomedical industries has led to their mass killing and high cost.

What is unique about horseshoe crabs?

The species of horseshoe crabs (C. rotundicauda) have been one of the oldest living species on earth, they hail from an era even before the existence of the dinosaurs. Horseshoe crabs evolved into existence a million years ago and since then they have managed to survive the climatic changes that the earth has been through. The multiple sets of eyes, upside-down swimming style, chemical sensitivity, photoreceptive mechanism, large-scale litter size have made these creatures secure Darwin's concept of being the fittest. The role of their blue blood in biomedical researches has also made these creatures unique. They are also extensively used as baits by fishermen. The eggs of horseshoe crabs are great sources of food for several migratory birds, turtles, and other marine creatures living in the sea and hence the horseshoe crabs justly contributed to preserving the balance of the earth's ecosystem.

Here at Kidadl, we have carefully created lots of interesting family-friendly animal facts for everyone to discover! For more relatable content, check out these grass spider facts and limpet facts pages.

You can even occupy yourself at home by coloring in one of our free printable Lot Of Crabs coloring pages.



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