Interesting facts about starfish

Such a familiar yet otherworldly organism, the starfish is a bizarre creature that inhabits a wide range of oceans. Their appearance matches the popular description of astronomical stars, but the bizarre bodies contain many surprises. What other creature might not have a brain and blood, but at the same time have unique eyes and the ability to digest food outside of its body? Get ready to learn some interesting facts about starfish that seem to ignore the laws of biology.

Star shape

The name "starfish" directly suggests the traditional five-point starfish that we usually see in the water, but the shape of the star can be very varied. There are also stars in the shape of the sun, with rounded bodies and numerous beams. The largest starfish in the Pacific Northwest can be up to 1 meter in diameter and weigh up to 5 kilograms, as well as have up to 20 arms. Solar stars are more active than many other species and are capable of rapidly pursuing prey. They are strong enough to tear the shells of molluscs and crustaceans. Such stars can form numerous groups in especially nutritious areas.

Lack of blood and brain

Starfish are complex and strange creatures in many ways, but their bodies are also quite primitive. They have a perfectly adapted digestive system and extremely advanced skin, but at the same time a clear lack of brain and lack of any blood. Lacking blood flow and gills, the starfish lives by pumping seawater through its body. Thus, it receives nutrients, oxygen and other important fluids. As a replacement for blood, seawater is distributed throughout their body through the so-called “water-vascular system”. Sea water is mechanically distributed throughout the body, with the help of muscles and lymphatic glands. In this case, the entire system works with maximum efficiency, even without the presence of blood. The body of the starfish is still shrouded in mystery, and we do not fully understand how it functions. The scientific study of the body of a starfish remains one of the most exciting challenges for scientists.

Starfish Suckers

You probably thought that the starfish has tentacles, but it's actually correct to call them hands. Look closely at the underside of the starfish and you will find that each hand can have up to 15, 000 tiny suction cups with which it can move very efficiently. During high tides, the suction cups allow the star to press against the rocks, otherwise the waves could shatter them to smithereens. The soft underbelly of the star will hug the rock, while the upper part of the star is covered in tough skin. Scientific research is constantly revealing new amazing facts about sea stars, and in the future we will definitely find out the secret of their magical suckers.


Most of us think of starfish as the bright pearls of the ocean, but in reality, they are more greedy predators. You will be surprised to know that cannibalism is a well-documented fact in the lives of these strange creatures. This cannibalistic behavior is often caused by a reduction in normal food supplies. They are very well equipped to attack their own species. Certain starfish do not mind feasting on small offspring, even of their own species.

Two stomachs

Starfish look attractive, but they are actually greedy predators with two stomachs. One of the more bizarre features is their ability to pull the stomach out. Using the pressure of the aquatic vascular system, one of the stomachs can be pushed out to digest the shellfish. After the starfish opens the shell of its prey, it places it in this outer stomach. He digests the victim in his shell and turns it into a thin soup. The stomach then returns to the starfish for the second stage of digestion. It is a rather complex mechanism with numerous enlargements of the intestinal system, distributing nutrients throughout the body. The entire digestive process of the starfish is one of the most incredible examples of evolutionary progress, especially considering how primitive these creatures are in other respects.

Crown of Thorns

There are very dangerous types of starfish. Common throughout the Indo-Pacific Ocean, the crown of thorns starfish is covered in venomous spines. They are dangerous not only for divers and swimmers, but also for coral reefs. These creatures can reach almost half a meter in length, threatening the ocean ecosystem. The doubling of phytoplankton levels resulted in a 10-fold increase in the population of these animals. Changes in ocean temperatures and currents, as well as declines in natural predators, are also cited as potential drivers of such a dramatic increase in population. The small population of this star contributes to the diversity of the reef, as it feeds on the fast-growing acropoid coral. This gives the slowly growing corals a chance to harden. On the other hand, the spines of these echinoderms can wreak havoc on coral reefs. One of the most serious cases involves damage to the Great Barrier Reef. The 50% decline in total coral cover on the surveyed reefs over the past 30 years has been extensively researched. It turned out that half of this decline can be attributed to the overgrowth of the poisonous starfish population.

Whimsical Pillow

As a group, starfish are named for their star shape, but some species have a completely different shape. Genetically true starfish, pillow stars (Culcita novaeguinea) have nothing to do with starfish at first glance. They have no arms, and their swollen body looks more like a pillow. Often covered with tiny vertebrae, these strange animals can grow to over 25 centimeters in length and come in a wide range of colors. While other starfish may prey on clams and open their shells, pillow stars are much gentler creatures with a less dramatic lifestyle. They mainly feed on algae, and sometimes on corals. The pillow stars also serve as a kind of home for other species of marine animals in a strange symbiotic system of relationships. The fish can live in the water-filled cavity of this star, while the invertebrates on the outside scrub the cushion's spiny vertebrae.

Diseases of Starfish

Recent news of the catastrophic extinction of starfish has drawn attention to this issue. The wasting starfish disease, which leads to mass extinctions and eventual fragmentation of the animal, has been potentially classified as a denzovirus. This is especially the case for the 2014 extinction along the Pacific Northwest coast. The problem of low resistance of the population to infections was discovered, threatening the existence of some types of stars. It turned out that different species of starfish show different levels of disease susceptibility. Scientists are now trying to determine the environmental impacts of declining starfish populations and their impact on marine biodiversity. They are also trying to figure out which environmental factors are increasing the spread of the infection. Potential root causes include environmental pollution.

Starfish Eyes

Due to the lack of blood and a typical central nervous system, it would be natural to assume that starfish also lack eyes. However, sea stars do have eyes, and they are located in a rather strange place: at the tips of their hands. These eyes collect visual information to guide the starfish in a direction of interest. They are similar in shape and structure to the eyes of arthropods, insects and crustaceans. Another question arises, how can they see without a brain? Recent research has shown how starfish use their eyes to move surprisingly precisely. An investigation by Anders Garm of the University of Copenhagen showed how a blue starfish travels 2 meters to a reef. Visually detecting the reef as a dim patch (the stars are color blind) they race towards their desired habitat.

Stars can change sex

It often happens that the simpler the animal, the more superpowers it has, such as regeneration of limbs, or the possibility of sex change. Certain starfish can change sex and then switch back. The reasons for the change are varied, and can include both the need for breeding and reactions to water quality, temperature and food availability. The gender differences in starfish are fairly subtle from an external point of view, although males are smaller than females. Some species have both male and female organs and can take on any role in mating. They carry their cubs on their backs until they are ready to set off on their own journey across the ocean floor.