Granulated Sea Star

 Taxonomic Classification:

Domain: Eukarya

Kingdom: Animalia

Phylum: Echinodermata

Class: Asteroidea

Order: Valvatida

Family: Oreasteridae

Genus: Choriaster

Species: Choriaster granulatus [87]

Figure 45: Sea Star Parts

Figure 46: Granulated Sea Star

Figure 47: Choriaster granulatus close up

Why does the organism belong to this kingdom?

            The organism Choriaster granulatus is a multicellular eukaryotic organism. One way to justify is this is that this organism is complex consisting of sexual reproduction and is capable of regeneration. Another thing that demonstrates the organism’s complexity is that the organism contains a nervous system. [88] Since the organism is eukaryotic and multicellular the organism is only able to be classified in the Domain Eukarya. Domains Archaea and Bacteria only include unicellular prokaryotes. The Choriaster granulatus is able to reproduce sexually or asexually. The fertilization happens outside the organism in the environment. Both sexes release their gametes and embryos are produced from a part of a zooplankton. Starfish are very interesting because of their capability for regeneration. If an arm is chopped off, the arm will slowly grow back. Through the years the starfish will grow bigger as a whole using the process of mitosis. [88] Sexual or asexual reproduction are the two different methods used for organisms in the kingdom Animalia. In sexual reproduction the process meiosis is used, and when asexual reproduction is used, the processes of budding fragmentation, or parthenogenesis are done. [11] This is not the only kingdom that does these two methods of reproduction. In fact, all the organisms in all the different kingdoms are able to reproduce sexually or asexually. When the Choriaster granulatus wants to receive its food and nutrients, the organism eats different algae, detritus, and small invertebrates. This means the organism is a heterotroph, receiving nutrients from organic matter. [88] In the kingdom Animalia, there is one type of organism for their mode of nutrition which is heterotrophs. These heterotrophs ingest organic matter and then break it down to be used to help make energy. [10] The only kingdom that does not include any heterotrophs is the kingdom Fungi. [5] The movement for the Choriaster granulatus is helped by the water vascular system. Through the madreporite, water enters, and then circulates from the stone canal to the ring canal to finally the radial canal. From this location water is brought to the ampulla. Here suction is able to be used in the tube feet. The tube feet move in waves, attach itself to solid surfaces. The movement of the starfish is slow and adhesion is used to make sure the organism can stick and break away from the surface. [89] There are two kingdoms where motility is present, one of these kingdoms is the kingdom Animalia. However, the other kingdom is Protista. The only kingdom in all the kingdoms that has a nervous system is the kingdom Animalia. Furthermore, the Choriaster granulatus contains a nervous system. In the nervous system there is a nerve plexus but yet no brain because this is a simple nervous system. It could be found right under the skin. Some of the nervous signals will indicate the movement with the branches of the water vascular system. This system coordinates the balance of the organism but also the directional system. [89] The Choriaster granulatus is classified in the kingdom Animalia because of all these reasons, and is not classified in other kingdoms because no other organism in other kingdoms contain a nervous system.

Why does the organism belong in this Phylum?

            The Choriaster granulatus belongs to the Phylum Echinoderms. In this phylum the organisms are simple with not many defined characteristics. The Echinoderms have the hemal system for their circulatory system that happens to be simple. This system is connected to the excretory system too. One of the jobs of this system is to transport nutrients around the body. Another characteristic the echinoderms have is their water vascular system that is used for movement. The water enters the madreporite and circulate around until they reach the feet or arms to provide a suction to move. The organism would attach one part of the body and release everything else to be able to move from one location to another. The characteristic that separates the phylum from the other phyla is that these organisms have several arms. The arms usually come from the center of the body. Also the organisms would have a spiny back. [86] The Choriaster granulatus has all these characteristics. In has 4-6 arms at all time, it uses the hemal system for transport of substances and uses the water vascular system to provide motility to the organism. [89] Since the organism has these characteristics the Choriaster granulatus is classified in the Phylum Echinodermata.

The Granulated Sea Star is put of the phylum Echinodermata. This phylum is circled in  green.  This phylum is closely related to the phylum Chordata. It is said that Chordata organisms evolved from the Echinoderms. These two phyla are not closely related to any other phylum besides each other. They are distantly related to the Porifera which consists of all the sponges. The Arthropoda is the phylum the Echinoderms evolved from. The Echinoderms and the Chordates have a characteristics that evolved from the other phyla and makes these two phyla separated from the others.  The Chordata phylum has evolved from the Echinodermata.

General Description:

            The Choriaster granulatus has multiple names. The most common name is the Granulated Sea Star. Other names include Cushion Sea Star, and Doughboy star. In the genus Choriaster it is the only organism. [88] Granulated Sea Star is one of the largest sea stars of all the sea stars. It has five large, short arms. It is pale pink with brown papillae in small clusters that is on the central area of the sea star. The growth is maximized at the radius of around 27 cm. It is found by itself or in small groups that are over reefs, where there is an abundance of rubble and detritus. It is found on the rubble slopes and coral reefs. It is widespread in the Indo-West Pacific. Also found in parts of the Indian Ocean. Other areas include the Red Sea, Fiji, and Great Barrier Reef. In the water the Choriaster granulatus likes to live in the shallow water. It is found on the rubble slopes and coral reefs. The organism has an endoskeleton that is very closely related to the endoskeleton of the chordates. The mouth is under the water vascular system on the ventral surface. The anus is located on the top of the Choriaster granulatus. This organism has two separate stomachs. The cardiac stomach engulfs and digests food. The digested food is moved from the cardiac stomach to the pyloric stomach where further digestion occurs. Then the waste is excreted through the anus. [88]

            Granulated Sea Star have regeneration. When a predator comes and attacks and damages the organism, it is able to grow new arms. They usually have all five arms but in a time of regeneration there could be less. However, when small parasites are found on the underside of arms, it can deform the arms. In order to regenerate, the central body has to be complete. [89]      

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