Sea spiders, a species that has survived for 500 million years by "strength"

To live or die, this shouldn't be a question for sea spiders.

After all, they have paid too much for survival.

Sea spiders are found in oceans around the world, and there are over 1,300 known species in the class Araneae.

Their leg spans can range from 1 millimeter to more than 70 centimeters. Most sea spiders in shallow waters are only a few millimeters long, but in Antarctica or the deep sea they can become very large.

But this doesn't mean that their bodies are large. If you look closely at a sea spider, you'll find that they have nothing but legs.

For sea spiders, legs are far more than just a means of walking; they can be said to be the basis of their survival.

Next, let’s take a look at what unique functions the legs of sea spiders have evolved over hundreds of millions of years of development.

The surface area of ​​the sea spider's abdomen and thorax is so limited that the reproductive and digestive organs are directly allocated to the slender legs.

Of course, this is not the end.

Generally speaking, the circulatory system is responsible for transporting blood, and the digestive system is responsible for transporting food.

Just like the human body, the blood flows repeatedly in the heart and vascular system in a certain direction under the action of the heart pump, relying on the contraction of the ventricles.

It includes systemic circulation and pulmonary circulation, which are connected to each other to form a complete circulatory system.

However, as "minimalist" sea spiders, they seem to have abandoned their circulatory systems during the long process of evolution.

So how is their blood transported?

To answer this question, foreign researchers conducted an experiment in which they injected dye into the bodies of sea spiders to observe the direction of blood flow.

During this process, the researchers found that the creature's heart beat very weakly, while the digestive system in its legs contracted in a wave-like manner, and observed that food in the intestines and blood in the surrounding blood cavity (equivalent to veins and arteries) were moving.

As for why this work is undertaken by the digestive system, the reason is not yet clear, perhaps using intestinal contractions to transport food and blood can save energy.

In addition to using their digestive systems to transport blood, sea spiders have another "special" skill.

Most marine creatures like fish and shrimp breathe using their gills, or like whales, using their lungs.

But sea spiders are different from everyone else. Their respiratory system does not have its own name.

So how do sea spiders breathe?

It was not until 2018 that this problem that had long puzzled scientific researchers was solved.

What is it?

Yes, the legs again.

Researchers placed giant Antarctic sea spiders in a breathing chamber to observe how much oxygen they took in and found that they took in enough oxygen to keep their bodies functioning through small holes in their legs.

That is to say, their hard outer skin can not only be used for defense, but also provide them with breathing.

These special ways of survival allow sea spiders to live a low-key life in this world, and they have almost no natural enemies. After all, they look unpalatable, difficult to swallow, and hard to digest...

However, as they have no natural enemies, they have not caused much damage to the ecological environment. You know, in nature, creatures with very few natural enemies can easily affect the ecological environment.

For example, the carp that "smuggled" into the United States and the crayfish that "invaded" China.

Sea spider expert Dr. Claudia Arango said this may be related to the sea spiders' "eating habits."

Sea spiders have a long, thin proboscis that ends in a triangular mouth. Although they are carnivores, they only feed on bryozoans, leeches, or suck the body fluids of soft-bodied invertebrates.

Therefore, sea spiders do not affect other creatures. Instead, they are more like "undersea scavengers."