Starfishes are echinoderms, having no vertebrae. They possess an internal skeleton and five arms. The eyes are placed at the end of each arm.
Starfish has been a subject of interest, since a long time. They also have the unique capability of regeneration of arms.
The body doesn’t have any blood and they eat with their stomach inside out.
Starfishes have a lifespan of about 100 years, in average, surviving mostly on algaes and snails.
They have managed to intrigue the masses and the researchers alike. There are a huge variety of species of starfishes. They are each different from each other, based on the number of arms, feet, natural habitat and more.
Some has distinct physical features that help them be easily recognizable. However, these characteristic features are very minute and can be detected only if the starfish is studied carefully. The naked human eye cannot spot the differences and hence it all seems same at the first glance.
There are nearly 1900 species of starfish. They are mainly categorized into seven types or orders. They are closely related to sea urchins and sea lilies.
- This kind have tubular arms, tube feet and possess conspicuous ossicles.
- Conspicuous ossciles are individual structures found in the dermis of the skin that provides protection and rigidity to the starfish.
- They are characterized by paxillas and pedicellars.
- This order umbrellas around 14 families and 600 species of starfish.
- The species that are most commonly found around the world are Heterozonias alternatus, Protoreaster nodosus, Linckia guildingi, Diabocilla clarki and Pentaster obtusatus
- These species have five or more arms, possessing paxillas. These paxillas protect the starfish from getting sand stuck in the rain.
- The upper part of the body features granule like structures.
- While some species of this order live in deep depths of the sea, some live on the surface.
- It has nearly 250 species of starfishes categorized under it, the major ones being
- Luidia bellonae, Ctenodiscus australis, Abyssaster planus, Gephyreaster Fisher, Astropecten acanthifer.
- These types of starfish lack pedicellars in the body, pedicellars are replaced by spines in these cases.
- They tentacles have suction cups.
- They survive in varied climatic conditions such as deep water, polar and tropical conditions. This order of starfish includes the Echinasteridae family and nearly 100 species of starfishes.
- The most commonly found species are Odontohenricia violaceous, Echinaster colemani, Rhopiella hirsute, Henricia sanguinolenta and Metrodira subulate.
These starfishes are found in deep sea water, usually living in the sea bed, about 1800m to 2400m deep.
- Though they are found all around the world, they are mostly found in Newzealand, Carribean Sea and Pacific Ocean.
- The ocean currents often leave them on the shores and one may spot them hanging from cliffs or just laying in the sand on the shore.
- They have about 6 to 20 arms, depending on the species they belong to.
- This order incorporates Brisingidae and Freyellidae family.
- 100 species of starfishes are included in these two families, the common ones being Freyella elegans, Colpaster edwardsi, Brisinga endecacemon, American novodina, Hymenodiscus coronate
- These starfishes are easy to spot and can be recognized by their opening and closing pincars. Pincars are much similar to pedicellars and has three skulls like structures alongside a short stem.
- They have tube feet with flat tipped suckers. They are found all across the globe and survives equally well in both cold and tropical climates.
- It comprises of three families of starfish and more than 300 species.
- Some of the most common species include Asterias rubens, Bythiolophus acanthinus, Coscinasterias tenuispina, Allostichaster capensis, Labidiaster annulatus and Ampheraster alaminos.
- These starfishes have suction cups at the end of each of its tube feet.
- The pedicellars maybe replaced by thorns or spines.
- They are essentially found in deep waters.
- Notomyotida has a single family, Benthopectinidae, which has 75 species.
- Some of the species that are common are Pectinaster agassizi, Acontiaster bandanus, Myonotus intermedius,Benthopecten acanthonotus and Cheiraster echinulatus.
- They are small in size ranging from 0.5 and 2 centimeters, though some species that are 30 centimeters in size are also found.
- Deep waters provide them natural habitat.
- Pedicellars are replaced in this species, by uniformly placed thorns.
- This order comprises of five families and over 200 species of starfishes.
- The most known starfishes of this category are Euretaster attenuates, Belyaevostella hispida, Asthenactis australis, Caymanostella phorcynis and Korethraster hispidus.
There are a few species of starfish which are founf globally in deep waters and on the shores. These include red starfish (Echinaster sepositus), Honduran star (Luidia ciliaris), Common spiny star (Marthasterias glacialis) and similar other species.
Contribution of Starfishes to Ecosystem
Starfishes are that species of animals that help keeping the environment clean. They play a pivotal role in cleansing the marine ecosystem.
Often the ocean is infested with harmful chemicals and toxins due to water pollution from human activities. Starfishes filter these toxic wastes and prevent it from entering the ocean and infecting it.
However, in the process, often starfishes end up getting killed. Though they are not endangered yet, the environment must be taken care of.
Starfishes are sometimes harmful to the environment too. They are responsible for diminishing of coral reefs. Studies confirm, coral reefs in Polynesia showed visible declination after migratory starfishes occupied the waters.
Dangers Associated with Starfishes
Starfishes emit acids that can cause nausea, infection and swollenness in human beings. The scuba divers and snorkelers who go deep into the sea usually risk the harms inflicted by starfishes while under water.
In most cases, the acid emitted by the starfish is injected back into it through one of its many tentacles. This in turn kills them.
Though this serves the purpose of self-defense, a huge number of starfishes are killed everyday and should be avoided until and unless the situation is dire.
However, there are a very few alternatives since, starfishes regenerate themselves, leaving poisoning them as the one of the most feasible options.
Starfishes are colorful creatures and attractive to the eyes but must be dealt with very carefully.