What do starfish eat?

Surely you have seen a starfish, either in photographs or when you have visited a beach. They are among the most widely distributed marine animals in the world, although most of them live in the depths, so their habits are unknown to many people..

¿Know what do starfish eat? If you are interested in knowing this and other curiosities about these striking marine inhabitants, you cannot miss the following article. ¡Keep reading!

You may also be interested in: What do sea urchins eat? Index
  1. Starfish characteristics
  2. Where do starfish live?
  3. Reproduction of starfish
  4. Types of starfish
  5. Starfish feeding
  6. What do sea urchins eat?
  7. What do sea sponges eat?

Starfish characteristics

Starfish belong to the Asteroidea class and are invertebrate animals that inhabit the deep sea. They are characterized by presenting a flattened body from which they protrude multiple arms, whose quantity varies according to the species, but which is located between five and fifty extremities. These limbs possess suction cups used to move, catch their prey, defecate and breathe. Due to their way of moving, by locomotion, these suction cups are called "tube feet ".

In addition to the arms, they have a mouth which is located in the flattened part of the body, that is, in the center. Another curiosity about their morphology is that they lack blood, they use a hydrovascular system that pumps water.

The skin of the starfish is composed of calcium and it can present a grainy, rough, smooth texture and even with hard thorns. Most of them are distinguished by their bright colors (blue, red, white), although many species also have simple hues to blend in with the seabed.

Where do starfish live?

¿Do you know where starfish live? They are distributed in oceans around the world, that is, it is possible to find them in the Arctic, Antarctic, Atlantic, Indian and Pacific. In these oceans, most species prefer to live to 6,000 meters deep, although some inhabit the sandy bed found on the coasts.

These stars only survive in salty and brackish environments, so it is not possible to find them in fresh waters. In the ocean, his favorite areas are around coral reefs, kelp forests, and anywhere on the bottom where he finds rocks or muddy sands. Due to their nocturnal habits, they can carry out their lives to perfection in low-light environments such as the ocean floor.

Reproduction of starfish

Considering the curious appearance of these invertebrates, one wonders how starfish are born, ¿sure? Actually, it does not have much mystery: they present a sexual reproduction and an asexual reproduction.

Sexual reproduction

Although it is difficult for humans to distinguish, in most species of starfish there are individuals male and female. Many of them are capable of changing gender as they age, that is, they are born males or females and an exchange occurs when they reach adulthood or old age.

When it's time to breed, a starfish release gametes (sex cells) through the gonads in your arms. As the eggs are released, another starfish release sperm to fertilize them. It is even possible that both parts of the process are carried out by the same individual in the case of a hermaphrodite species.

Once the eggs are released, there are several options: they will develop as part of the plankton, the mother will incubate them and the will protect with your body, or they will grow stuck to a rock. When they reach the right size, the eggs give way to the larvae, which swim or float in the sea. As they become adults, their body morphology changes and they inhabit the seabed.

Asexual reproduction

Other species of starfish have an asexual reproduction cycle. Some do not need the intervention of another individual, because at the end of their arms they have the male and female gonads, thanks to this, they are able to reproduce when some of their arms are detached for whatever reason, even if the separated piece measures one centimeter.

Another asexual method is gemmation. This process consists of the creation of an individual that grows attached to the parent and only separates when it is developed. This method is common in starfish larvae found in environments with abundant food.

Types of starfish

In the world there are around 2000 kinds of starfish, so its characteristics are varied.

  • Order Paxillosida: includes 255 species. They do not have suction cups on the tube feet. They prefer to live half-buried in sand or sea mud. They usually appear in abundance of individuals in the areas that inhabit.
  • Valvatida Order: it is made up of 695 species. They have around five arms with suction cups, in addition to a visibly calcified body.
  • Order Velatida: includes 210 species. They have a hexagonal shape with fifteen arms with suction cups. The body is decalcified and they inhabit cold waters, such as the polar and subpolar regions.
  • Order Spinulosida: it is made up of 120 species. They have a weak skeletal body and arms with suction cups. In addition, they have a rough texture full of thorns.
  • Order Forcipilatida: includes 300 species. They present a body made up of three pieces and arms with flattened suction cups. They have powerful serrated jaws, making them great predators. They prefer cold waters.
  • Brisingida Order: includes 111 species. They have between six and twenty arms without suction cups. They prefer deep waters.
  • Order Notomyotida: includes 75 species. They can have arms with or without suction cups, accompanied by a muscular body. They inhabit areas of great depth.

Starfish feeding

Now that you know how these curious animals of the oceans carry out their life cycle, it is time to tell you all about the feeding of starfish.

Most starfish are carnivorous and predatory, this means that they hunt their prey. Their main source of food is crustaceans, sea urchins, smaller fish, plankton, clams., mussels, snails, sea cucumbers, coral polyps, anemones, and basically any animal slow enough to be able to ingest.

However, ¿How can seemingly white-bodied and defenseless starfish devour such a variety of prey? The stomach of these invertebrates has the quality of being evagible, which means that they are able to "expel" it out of the body. When faced with prey, the star surrounds her with his arms, whether or not they have suction cups, and then expels the stomach so that the prey is covered with digestive juices. This process starts the decomposition of the victim. Then they simply fold their stomachs and swallow the prey..

Other species, however, feed only on decomposing matter, whether of plant or animal origin. The species that are not able to suck what remains of the prey after pouring out the gastric juices, simply devour the whole animal and then the star expels the inedible parts.

In this video from @ n2oBlazer on YouTube you can see how a starfish ingests a crustacean:

What do sea urchins eat?

The sea ​​urchins are echinoderms which is usually found in places where stars also inhabit, so they are preyed upon by them. They are characterized by having a round body full of rigid spikes.

However, ¿do sea urchins eat? Most of them are herbivorous animals, so they feed on algae found on the seabed. Others, however, are detritivores, which means they eat decaying matter. In the same way, some of them are predators and feed on smaller and slower animals than they are..

What do sea sponges eat?

The sponges of the sea are invertebrates poriferous (phylum Porifera). There are about 9000 species and for a long time they were thought to be marine plants, due to their peaceful life and their appearance that lacks recognizable structures, such as eyes, mouth, etc. They are incredibly simple animals, but at the same time you surprise by the strange and unique forms that their bodies take.

Regarding food, ingest nutrients in a cellular way, through the phagocytosis (cells surround the food particle and break it down to absorb it) and the pinocytosis (It is the same process, but it is carried out with fluids instead of solids). Thanks to these processes, they feed on small particles of decomposing matter, microscopic algae and marine bacteria..

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