Main Difference – Porifera vs Coelenterata
Both Porifera and Coeleterata are two phyla in the kingdom of Animalia. The animals in the phylum: Porifera are usually called sponges. The animals belonging to the phylum: Coelenterata is identified as Cnidaria. Sponges are sessile metazoans, which lack body symmetry. Some Cnidarians are sessile whereas others are free-swimming. Cnidarians consist of radial symmetry. The key difference between Porifera and Coelenterata is that Porifera consist of numerous pores throughout the body, working as water intake and outlet openings whereas Coelenterata consist of a single opening on the body working as mouth/anus.
This article explores,
1. What is Porifera
– Characteristics, Structure
2. What is Coelenterata
– Characteristics, Structure
3. What is the difference between Porifera and Coelenterata
What is Porifera
Porifera contains pore bearing animals, who are usually called sponges. They are non-motile, multicellular organisms whose body is full of pores and channels. The pores and channels allow the circulation of water. Porifera contains two cell layers; a jelly-like mesohyl exist in between these two layers. Sponges contain unspecialized cells which can transform into other types. These cells migrate between the two cell layers and become the mesohyl, allowing the sponges to remold their body. Thus, the body shape of the sponges is maintained by the mesohyl.
Sponges lack nervous, digestive or circulatory systems. Instead, they maintain a constant water flow throughout the body which allows them to obtain food and oxygen and remove the wastes. The water intake and outlet openings are connected by chambers which are lined with choanocytes. Choanocytes form the choanoderm, a cell layer in the inner surface of the sponges, consisting of a central flagellum surrounded by a collar of microvilli. The wipe-like flagella drives the water flow by its wave-like motion. There are some other types of cells moving in the mesohyl such as lophocytes, collencytes, rhabdiferous, oocytes, spermatocytes etc.
Four classes of sponges can be identified depending on the composition of their skeleton: Calcarea, Hexactinellida, Demospongiae and Homoscleromorpha. Though sponges are considered as sessile, they exhibit amoeba-like movements across the sea bed in a speed of 1-4 mm per day.
Asexual reproduction of sponges occurs in three methods: after fragmentation, budding and producing gemmules. Sponges do not possess gonads, but the sperms are produced by choanocytes and eggs are produced by the transformation of archeocytes during the sexual reproduction.
Figure 1: Orange tree sponge
What is Coelenterata
Coelenterata is a phylum found in kingdom: Animalia. These animals are predominantly found in marine habitats. The most characteristic feature in Coelenterata is Cnidocytes, specialized groups of cells used for capturing prey. Coelenterata is also recognized as Cnidaria due to the presence of cnidocytes. Mesoglea is found in between the two cell layers. The epithelium is one cell thick in Cnidarians. The phylum Cnidaria forms two body forms: medusa and polyp. Both medusa and polyp exhibit radial symmetry.
Polyp
Polyp is one of the two body forms found in Cnidarians. They are approximately cylindrical-shaped animals. Solitary polyps are attached to the substrate by their adoral end. The attachment is occurred through the pedal disc which is a disk-like holdfast. Some polyps form colonies. Each polyp is connected to the other polyps in the colony either directly or indirectly. The mouth of the polyp is found in the oral end. It is surrounded by a circlet of tentacles. Polyps reproduce asexually by budding.
Medusa
Medusa is the other body form found in Cnidarians. Medusae are aquatic animals which are considered as free-swimming softbodies. They contain a gelatinous, umbrella-shaped bell along with the trailing tentacles. The mouth/anus of medusa is located at the base of the bell. Adults consist of gonads which release ova and sperm into the water in the sexual reproduction. A white-spotted jelly fish is shown in figure 2.
Figure 2: White-spotted jellyfish
Both polyps and medusa use the body cavity for respiration and digestion. In between the two cell layers, Cnidaria consist of a nerve-net. Most of the sexually reproducing Cnidarians are composed of a polyp stage which is asexual and a medusa stage, which is sexual.
Difference Between Porifera and Coelenterata
Pores/ Body Cavity
Porifera: These organisms contain numerous pores or holes in the body.
Coelenterata: These organisms contain a body cavity, referred to as coelenteron, which is composed of a single opening.
Cell Layers in the Body
Porifera: Mesuhyl is found in between the two cell layers.
Coelenterata: Mesoglea is found in between the two cell layers.
Exoskeleton
Porifera: They possess an exoskeleton.
Coelenterata: They do not possess an exoskeleton.
Organization
Porifera: They exhibit a cellular level organization.
Coelenterata: They exhibit a tissue level organization.
Circulation in the Body
Porifera: The characteristic canal system circulate water, food and oxygen throughout the body.
Coelenterata: The circulation of water, food and oxygen is occurred through the coelenteron.
Location
Porifera: They are non-motile, mostly marine and found attached to rocks.
Coelenterata: They are either live in colonies (Corals) or have a solitary life span (Hydra). They exhibit some sort of locomotion.
Asexual Reproduction
Porifera: Asexual reproduction of sponges occurs through after fragmentation, budding or producing gemmules methods.
Coelenterata: Asexual reproduction takes place by budding in the polyps.
Sexual Reproduction
Porefera: They do not have gonads. Sperms are produced by choanocytes and eggs are produced by the transformation of archeocytes.
Coelenterata: Adults consist of gonads which release ova and sperm into the water.
Body Symmetry
Porifera: Bodies have no symmetry.
Coelenterata: They consist of radially symmetric bodies.
Nervous System
Porifera: Porifera do not posses a nervous system.
Coelenterata: Coelenterata consist of a nerve-net in between the two cell layers.
Cells in Each Layer
Porifera: Cells of the each layer are not bound together.
Coelenterata: Coelenterata consist of inter-cell connections and the basement membrane.
Remolding
Porifera: Cells in Porifera can move inwards and change their function.
Coelenterata: Remolding does not occurr.
Conclusion
Both Porifera and Coelenterata are primitive phyla found in the kingdom of Animalia. Porifera are multicellular immobile animals. Coelenterate is commonly named as Cnidaria due to the presence of cnidocytes. They can be either mobile medusae or immobile polyps. Cnidarian also consist of a simple nervous system. Porifera are composed of special openings throughout the body for the circulation of water, food and for the respiration. The key difference between Porifera and Coelenterata is that Coelenterata consist of a single opening working as mouth/anus as opposed to Porifera.
Reference:
1. “Sponge”. Wikipedia, the free encyclopedia, 2017. Accessed 24 Feb 2017
2. “Cnidaria”. Wikipedia, the free encyclopedia, 2017. Accessed 24 Feb 2017
Image Courtesy:
1. “Orange tree sponge with crab at dreadlocks Reef P1308277″By User: (WT-shared) Pbsouthwood at wts wikivoyage (CC BY-SA 3.0) via Commons Wikimedia
2. “Phyllorhiza punctata (White-spotted jellyfish) edit”By Papa Lima Whiskey at English Wikipedia (CC BY-SA 3.0) via Commons Wikimedia
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