Xiphosura, also known as horseshoe crabs, is an ancient arthropod that has existed for over 450 million years. Because these wonders of the natural world have remained relatively unchanged since their appearance in the fossil record, many people call them living fossils.
It’s important to note that the only possible difference is the abdominal segments in the present species fused into a unit. Also, when Xiphosura first appeared, there were several species. However, currently, there are only four living species. In this article, we will look at Xiphosura’s appearance, diet, habitat, reproduction, threats, and other interesting facts to give you a clear picture of how this wonderful sea animal looks its significance in the ecosystem, and other essential details.
Appearance
Xiphosuras are mainly distinguished by a hard exoskeleton that covers their entire bodies. They have a horseshoe-shaped shell that protects their cephalothorax (the fused head and thorax) and a long, spiky tail known as a telson.
The body of the fascinating animal is divided into three sections: the prosoma, or head; the opisthosoma, or abdomen; and the telson, located on the back.
The first pair of Xiphosura legs are modified into pincers called chelicerae, which they use for feeding and defense. Walking and swimming are done with the remaining eight legs. At the same time, they have compound eyes on the sides of their heads that are light-and-motion sensitive.
The modern Xiphosurans are typically approximately 60 cm, though some species can be far smaller. You can find some adult ones measuring one to three cm long.
Diet
Xiphosura eats worms, mollusks, and other small invertebrates. They use the chelicerae to crush and tear their prey, which they then consume with mouthparts.
Experts have also observed Xiphosura scavenging on dead or decaying animals. They may consume small fish or other vertebrates.
Habitat
Xiphosura can be found in shallow coastal waters worldwide, from the tropics to the temperate zones. They prefer sandy or muddy bottoms where they can burrow and hide from predators.
You can also find Xiphosura on rocky beaches and seagrass beds. They can find food and shelter in these places easily.
Reproduction
Xiphosura has a unique reproductive process in which the female lays eggs, and the male fertilizes them externally. Whenever mating, the male grasps the female with his chelicerae, and the female digs out a depression on the wet ground to prepare for fertilization. She lays between 200 and 300 eggs. Once done, the male covers them with sperm.
After that, the two partners part ways. The male looks for another female and feeds, while the female remains behind to protect the eggs. She buries them with sand carefully and then leaves them to hatch.
Before moving to the next section to talk about threats, let’s add that Xiphosura larvae are free-swimming and undergo several molts before adulthood. Besides, Xiphosura can take up to ten years to reach sexual maturity, and they can live for decades afterward.
Moreover, note that during the early days of the larvae’s life, they feed on zooplankton and some phytoplankton.
Threats
Various factors threaten Xiphosura, including habitat loss, overfishing, and pollution.
They are particularly at risk of being caught and used as bait for commercial fishing, severely harming their populations.
Furthermore, Xiphosuras are harvested for their blue blood and used in the medical industry to test vaccines and medical equipment for bacterial contamination, threatening their survival. So, while Xiphosuras are not endangered today, their populations have declined in some areas because of these reasons.
The good news is that these animals are legally protected in many countries.
Facts About Xiphosura
- Xiphosura are one of the oldest groups of arthropods, dating back more than 450 million years.
- Xiphosura are often called living fossils because they have remained relatively unchanged since their discovery in the fossil record.
- Xiphosura have blue blood, used in the medical industry to test vaccines and medical equipment for bacterial contamination.
- Xiphosura are not true crabs but rather relatives of spiders and scorpions.
FAQs
Are Xiphosura extinct?
No, Xiphosura isn’t extinct. Xiphosura, also known as horseshoe crabs, are still alive and well in shallow coastal waters worldwide. While their populations in some areas have declined due to threats such as habitat loss, overfishing, and pollution, they are not considered extinct. Remember that they are often referred to as “living fossils” because they have remained relatively unchanged since their discovery in the fossil record over 450 million years ago.
Are Xiphosura spiders?
No, while Xiphosura has long legs and a hard exoskeleton, they are not spiders. They belong to a different group of animals called Chelicerata, which includes arachnids. Xiphosura has a distinct body structure, including a large, horseshoe-shaped carapace (shell), a long tail, and four pairs of legs. Unlike spiders, these animals are not venomous and do not spin webs.
Where are Xiphosura found?
Xiphosuras are commonly found in the Atlantic Ocean along North America’s eastern coast, from Maine to Florida and the Gulf of Mexico. They can also be found along Asia’s eastern coast, from Japan to Indonesia, and in the Indian Ocean. Xiphosura prefers sandy or muddy bottoms where they can burrow and hide from predators. You can also find them on rocky beaches and in seagrass beds, where they can find food and shelter.
Can Xiphosura hurt humans?
No, Xiphosuras are usually not harmful to humans. While they have a hard exoskeleton and a long, pointed tail, their primary defense mechanism is to flip themselves over and push themselves back into the water with their legs. However, remember that treating horseshoe crabs with care and respect is critical. They may use their tail to defend themselves when provoked, potentially injuring a human or another animal. Furthermore, some people may be allergic to horseshoe crabs.
Why is Xiphosura’s blood so valuable?
Xiphosura blood is valuable because it contains Limulus amoebocyte lysate (LAL), a substance used to test for bacterial contamination in medical equipment, vaccines, and other pharmaceutical products. So, they are frequently captured, and their blood is harvested for use in the pharmaceutical industry due to their ability to produce LAL. However, this practice has the potential to harm Xiphosura populations.
