What do sea urchins eat?

We know as sea urchins more than 1 000 species of animals that are characterized by having their bodies covered with thorns. All these species form the class Echinoidea, a group of animals closely related to stars, cucumbers, and sea lilies, as well as to starfish. Together they form the phylum Echinodermata, which means "prickly skin" due to its ornate skeleton..

As in many echinoderms, sea urchins have a very powerful chewing apparatus. Around their mouth you can see 5 teeth that serve to chew and scrape, but ¿what do sea urchins eat exactly? ¿Are they carnivores or herbivores? We will tell you about it in this article about the feeding of sea urchins.

You may also be interested in: What do starfish eat? Index
  1. Is the sea urchin a carnivore?
  2. Types of sea urchin diet
  3. What do omnivorous sea urchins eat?
  4. What do herbivorous sea urchins eat?
  5. What do carnivorous sea urchins eat?

Is the sea urchin a carnivore?

The best known relatives of sea urchins are stars. These, as we explained in the article on What do starfish eat, are voracious predators. Due to this and the terrifying appearance of their serrated mouth, there is a belief that sea urchins are carnivores. The reality is that, although there are some carnivorous species, the biggestía They are omnivorous.

Most of the sea urchins they base their diet in the algae, although they supplement their diet with small live or dead animals that are on their way. But, ¿what exactly do sea urchins eat? Let's see it.

Types of sea urchin diet

The feeding of sea urchins it depends on each species, of its geographical location and, above all, of the food available. Most sea urchins are opportunistic and consume the most abundant foods in the ecosystem: algae. When these are not very numerous, they often consume other types of food, being able to have a quite varied diet.

What sea urchins eat also depends on the presence of predators. They often forage at night when their predators rarely appear. Also, to avoid exposing themselves too much, they don't stray too far from their shelter (cracks in rocks, corals, etc.). For this reason, they only consume what is close of the place where they rest during the day.

However, this is not true for all species. Therefore, according to their diet, sea urchins are usually classified into three types:

  • Omnivorous sea urchins
  • Herbivorous sea urchins
  • Carnivorous sea urchins

What do omnivorous sea urchins eat?

Omnivorous sea urchins are the most common and numerous. They often have a favorite food and consume it in large quantities when it is abundant near their shelter. For most omnivorous hedgehogs, this preferred food is the leafy brown algae. However, when these are scarce, they do not move much for fear of being predated. That is when they have a more varied diet, which can include:

  • Red algae
  • Green algae
  • Diatoms
  • Barnacles
  • Polychaetes
  • Sponges
  • Tunicates
  • Bryozoans

Here are some species of omnivorous sea urchins:

  • Crowned sea urchinCentrostephanus coronatus)
  • Green hedgehogTOrbatia dufresnii)
  • Long-spined sea urchin (Savignyi headband)
  • Black sea urchinArbacia lixula)
Image: black sea urchin

What do herbivorous sea urchins eat?

Very few sea urchins are considered herbivorous animals. Normally, they are specialized in consuming a single type of algae, That can make up up to 90% of your diet. This is the case of the purple sea urchin (Strongylocentrotus purpuratus), which feeds mainly on geniculate coralline algae. They can also consume fleshy brown and red algae when they are abundant.

Another herbivorous sea urchin is the pink-flowered urchin (Toxopneustes roseus), whose diet is based on rhodoliths, that is, non-geniculate coralline algae. It's pink because her body is covered in rhodoliths, allowing it to camouflage itself while feeding. In addition to coralline algae, this sea urchin eats green algae and diatoms in small quantities. Very rarely eats bryozoans.

Image: purple sea urchin

What do carnivorous sea urchins eat?

Carnivorous sea urchins are those that base their diet on the consumption of other animals. They are very few species and feed mainly on sessile invertebrate animals, that is, they live fixed to a substrate. As in herbivores, carnivorous sea urchins often specialize in consuming a single type of food.

An example of a carnivorous hedgehog is the slate pencil hedgehog (Eucidaris tribuloides), specialized in the consumption of sponges, although it can eat other organisms in small amounts. Some carnivorous sea urchins are so skilled that they can consume mobile animals, such as clams and even other sea urchins. This is what sea urchins of the species eat Arbacia spatuligera, who can even practice the cannibalism when other foods are not very abundant.

Now that you know the different types of diet of sea urchins, do not miss this other article in which we talk about all the characteristics of the sea urchin.

Image: hedgehog slate pencil

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