Marine Invertebrates

Sea stars

  • Scientific name: Asteroids or Asteroidea
  • Common Name: Starfish
  • Aquarium size: 400 liters
  • Temperament: Calm
  • Temperature: 22ºC to 25ºC
  • pH: 8.2
  • Diet: Carnivores, microphages …
  • Length: Between 10 and 40 centimeters

Description: What is a starfish?

The starfish or asteroids , are a well – known marine creatures worldwide, and although some think they are fish live in the sea, actually belong to the family of echinoderms , which are also part urchins sea ​​or sea cucumbers.
There are about 2,000 species of starfish , although very few species are raised in the aquarium, because they are quite delicate to maintain.

The most popular of all the species of starfish for aquariums are the Linckia laevigata which has very striking colors, blue, red or purple.

Morphology

When we think of sea stars, logically, we imagine stars with five arms, which is called pentarradial symmetry …

And it is that most sea stars have a flattened body, formed by a central disk and five arms, that is why He calls them “starfish.”

As a curiosity, at the end of their arms they have simple eyes that help them detect light, darkness and movement around them.

The skin of the sea stars is calcified, they have plates called ossicles in the form of granules or spines, which form the endoskeleton.

Their coloration is the most diverse, sometimes they seek to camouflage themselves and at other times their coloration is a way of deterring possible predators. The truth is that we can find starfish of blue, red colors …

Some specimens not only use mimicry as a form of protection, they also have stinging substances to protect themselves.
If they lose part or any of their arms, they have the ability to self-regenerate.

How do starfish move?

The way starfish move is as original as they are.

Their arms have feet called ambulantes , which are filled with suction cups that function as a lever, and which allow them to move on all kinds of surfaces, whether horizontal or vertical.

The feet are activated thanks to a very curious circulatory system, since not blood circulates through them, but sea water.
The direction is established by deciding which arm is the one that directs . If you want to change direction, you simply change the steering arm.

Types of starfish

In the world there are about 2,000 different species of starfish , which cover all the seas and oceans of the world, from tropical waters to those with much lower temperatures.

Most varieties of starfish have five arms, which is why they are called “stars”, but you can find species that have ten, twenty, even fifty arms , such as the spectacular Labidiaster Annulatus that lives in Antarctica.

Distribution and habitat

Starfish, as their name suggests, can only be found in the sea or in the oceans, some specimens can even survive in brackish waters, but there are no freshwater starfish.

Most species of sea stars are native to the Indian and Pacific oceans, which are very rich in their diversity, with tropical and temperate zones, which are ideal environments for most starfish.

They can be found in all types of habitats, from coral reefs, rock bottoms, mud, gravel or sand , even coexisting with seaweed and deep-sea bottoms, with very limited lighting.

Aquarium conditions

The aquarium conditions for starfish to be perfect can vary from one species to another.

Their acclimatization demands that we try to reproduce the aquarium they come from to the maximum, since sudden changes in density affect them a lot.

As average values, a marine aquarium in good condition for the starfish should have the following conditions:

  • Temperature between 22ºC and 25ºC
  • pH of 8.2
  • Water density between 1,020 and 1,026

Diet What do starfish eat?

If you are wondering, What does the starfish eat ?, I will tell you that the diet of starfish is so wide, as different species exist. Thus, we can find starfish:

  • Predatory, which feed mainly on mollusks or very slow fish.
  • Detritivores, feeding on decomposing animals or plant matter.
  • Microphages, which seek their food in plankton and suspended organic particles.

In the aquarium they are usually fed with mussels, pieces of fish or prawns, usually although they tend to adapt well to the change of diet.

Behavior and compatibility

They are animals that in the aquarium have no problem sharing spaces, obviously they do not usually compete with the rest of marine fish, but they can be a problem for certain mollusks , prawns or snails.

So we will not have problems in having them in a marine aquarium, as long as the right conditions are given and that they can be fed without problems.

Reproduction of the starfish

Starfish can reproduce sexually and asexually , although it is quite difficult to achieve this in the aquarium.

We have species in which there are males and females, although distinguishing them is almost impossible, we only know them when spawning begins.

But there are also simultaneous hermaphroditic species, that is, they have eggs and sperm at the same time… and there are also some species of starfish, which are sequential hermaphrodites, so that they are born males and become females.

Conclusion, if we want to reproduce starfish in the aquarium, we must first inform ourselves well of the species we have, and what are their conditions of sexual reproduction.
Another form of reproduction is asexual, although I would not put it into practice, unless it is spontaneously.

This form of reproduction occurs when part of the body of the starfish separates, either by an arm or by division of its central discs.

Depending on the species we also have everything, from species that with only 1 centimeter are capable of reproducing, while others need part of the central disk to be part of the excision.

Starfish images

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