A great many hydrozoans are also colonial. These forms are dependent upon nutritional content of the living environment. In some species, these two stages alternate between each other, such as in Hydrozoa. c. Look at the photo of the hydra (a small freshwater cnidarian, bottom left photo). A polyp is fixed and cylindrical structure which represents the asexual stage and Medusae is a free moving, umbrella-like structure which represents the sexual stage. Is it exhibiting the polyp or medusa stage? Obelia is a form of hydrozoans that have branched stalks. If you think about the shape of a pumpkin, there's a top and a bottom, but no left, right, back, or front. In the phylum Cnidaria, which includes jellyfish and sea anemones, polyp and medusa are two different stages of the life cycle. Hlavní rozdíl - Polyp vs Medusa. Fixed, rarely free, found near water mark attached to rocks. • Unlike Obelia, Hydra has great regenerative powers. Which of the following is not characteristic of... How do cnidarians defend themselves and catch... Look at the photo f the hydra (a small freshwater... What is the major characteristic of cnidarians? answer! Like the difference between a pumpkin and a human head. Fylum: Cnidaria se skládá ze čtyř tříd: Hydrozoa (Hydra, siphonophores), Scyphozoa (medúza), Cubozoa (krabicové želé) a Anthozoa (sasanky, korály, mořská pera).Anthozoa je přisedlý. Main Difference. The implication is that polyp is transformed into medusa with the development of gonad: either ovary or testis. Obelia’s sexual stage is medusa. Images Courtesy: Hydra via Wikicommons (Public Domain) Obelia by Doc. It also has a vast and greater majority of species in both the ecosystems. The polyp is a sessile, or nonmotile, organism; well-known solitary polyps are the sea anemone and the freshwater hydra. - examples of cnidarians exhibiting the polyp body form include freshwater hydra, as well as anemones, corals, and others - in many species, the polyps live in interconnected colonies (e.g., see discussion of stony coral structure below) the medusa body form - this … Some animals of this group are always polyps, some are always medusae, and some exhibit both a polyp and a medusa stage in their life cycle. These forms are dependent upon nutritional content of the living environment. The upper, or free, end of the body, which is hollow and cylindrical, typically Examine the live specimens of Hydra fuscus (brown hydra) and Hydra viridens (green hydra has symbiotic algae). That's radi… The mouth is surrounded by tentacles, which are used to capture food and convey it to the mouth; these tentacles are armed with stinging cells which paralyze the prey. Body saucer shaped, umbrella like with a reduced stalk (Jellyfish). Polyp and medusa body shapes Next. Free swimming, found in open waters. The middle bits are all the same. - Solitary and Colonial. 8 years ago. • Hydra live in freshwater habitats, whereas Obelia is exclusively marine. Coelenterata is a Greek word named for a group of animals that possess a single large central cavity coelenteron (comes from the Greek "koilos"- hollow; "enteron" - intestine or gastrovascular cavity with a single opening that serves both as a mouth and as anus. Hydras are sessile animals, but the polyps are able to move and change their location. Where only the medusa occurs, as in many jellyfish, the larva never settles, and grows directly into a medusa. In the class Anthozoa, comprising the sea anemones and corals, the individual is always a polyp; in the class Hydrozoa, however, the individual may be either a polyp or a medusa, with most species undergoing a life cycle with both a polyp stage and a medusa stage. Other creatures start life as fee-swimming medusa, then settle and become polyps. Like porifera, the hydra has two layers of cells separated by a jelly-like layer. Some animals of this group are always polyps, some are always medusae, and some exhibit both a polyp and a medusa stage in their life cycle. Other characteristics: 3. d. What part of the hydra contains the stinging cells? In hydra, the medusa stage is absent and polyps reproduce both sexually and asexually. 1. The medusa is a means for dispersal. Most questions answered within 4 hours. Now these eggs develop and thrive as polyp and reproduce asexually as polyp in favorable climate. However, Hydra is not typical of the Hydrozoa as a whole. Shortened forms of this life cycle are common, for example some oceanic scyphozoans omit the polyp stage completely, and cubozoan polyps produce only one medusa. So it catches food from prey that swim past them. Class Hydrozoa. Sea anemones are solitary polyps that reproduce sexually to form new polyps. Hauptunterschied - Polyp gegen Medusa. Hydrozoan colonies (Obelia) are composed of smany specialized polyps called "zooids". 1. All cnidarians only have one opening with functions for both ingestion and excretion. Hydra (genus) remains a polyp at all stages, but other hydrozoa do show both polyp and medusa stages in their life cycles. Corals, sea anemones and jellyfish belong to a group of animals called cnidarians. The upper, or free, end of the body, which is hollow and cylindrical, typically A jelly-like substance called mesoglea lies between the outer and inner layers of the body. The latter reproduce sexually giving rise to new polyps. Most species of hydra are less than 15 mm long (not including the tentacles). So it catches food from prey that swim past them. Long, movable tentacles, which the hydra uses to catch food, surround the mouth. • Hydra is a solitary species and lives attached to substrates, whereas Obelia is a colonial species and lives as polyps in an interconnected branching network. Create your account. Hydra can exist in both forms namely a polyp and a medusa throughout their life cycle. This is the beginning of the rest of the animal kingdom, the eumetazoa, or "true animals" (we eumetazoans are a little biased). answered • 07/26/16. Many other members of the class Hydrozoa, however, change from a polyp … The polyp (hydra) body plan is different from medusa and colonial because it’s sessile, which means it remains in one place their entire life. 2. Hydra can exist in both forms namely a polyp and a medusa throughout their life cycle. Life cycle: Cnidarians alternate between the polyp and medusa life forms. Simply, the modes of living are different between a medusa and a polyp. Body cylindrical with a long stalk (Hydra). Also, the dominant phase of the life cycle of Obelia is the polyp. The outer structure is made up of a disk-like structure which is slightly convex on the outer side, whereas the inner side remains concave in shape. Polyp. Der Stamm: Cnidaria besteht aus vier Klassen: Hydrozoa (Hydra, Siphonophores), Scyphozoa (Quallen), Cubozoa (Kastengelees) und Anthozoa (Seeanemonen, Korallen, Seekugelschreiber).Anthozoa ist sessile. The polyp produces buds in a regular and orderly manner and the result is a moss-like colony of Obelia bearing the two kinds of hydroid zooids: hydranths and blastostyles. Hydra exists in both forms: Polyp and Medusa. Hydras are sessile animals, but the polyps are able to move and change their location. The body wall is composed of three layers of tissue. Hydra can exist in both forms namely a polyp and a medusa throughout their life cycle. Medusae. All rights reserved. Most hydrozoans alternate between a polyp and a medusa stage — they spend part of their lives as "jellyfish" which are hard to distinguish from scyphozoan jellyfish. The hydra can exist in its adult and sexual form which is... Our experts can answer your tough homework and study questions. Two distinct body plans are found in Cnidarians: the polyp or tuliplike “stalk” form and the medusa or “bell” form. Hydra does not have a medusa form and reproduces sexually by the formation of gametes. Body attached below so that manubrium is … Smith. Genus Hydra. Obelia’s sexual stage is medusa. Hydra exists in both forms: Polyp and Medusa. Some polyps (e.g. Start here or give us a call: (312) 646-6365. Most hydras have a polyp and medusa stage. Simply, the modes of living are different between a medusa and a polyp. Hydras are up to 30 mm long solitary polyp animal, while Obelia is up to 25 cm long colony of interconnected polyps. Polyp phase is also one of the structural differences between Obelia and jellyfish. • Hydra live in freshwater habitats, whereas Obelia is exclusively marine. Hydra polyp form is a hollow tube with a single opening (or mouth). The stinging animals are more complex than the . Genus Hydra. It is present in both the freshwater and marine water habitat. Hydras are sessile organisms, but sometimes move when hunting. • Hydra does not have medusa form in their life cycle, whereas Obelia has both forms; polyp and medusa. Eumetazoans have tissues that develop from the germ layers of the embryo, and there are two basic body styles that are defined by our symmetry, either radial or bilateral. Get a free answer to a quick problem. Hydra never goes through a medusoid stage and spends its entire life as a polyp. Phylum Cnidaria, which include about 9000 species is also commonly called Coelenterata. in the tentacles Services, Working Scholars® Bringing Tuition-Free College to the Community. Under harsh living conditions and starvation, hydra reproduces sexually. Medusa is the adult and sexual form whereas Polyp is juvenile and asexual form. Explain Polyp and Medusa bodyforms give examples to support the answer. Two distinct body plans are found in Cnidarians: the polyp or tuliplike “stalk” form and the medusa or “bell” form. Medusa is a type of body form found in cnidarians. Jellyfish, on the other hand, exhibit only the medusa stage, while members of the genus Hydra exhibit the polyp form. Hydrozoa have a variety of life cycles. A medusa is a specific condition of an organism where body is shaped like that of an umbrella. Polyp Phase. The polyp phase of Obelia produces branched stalks while the medusa phase of jellyfish produces unbranched stalks. Polyps and Medusae are the names of two body forms. In the class Hydrozoa, Hydra is considered as a polyp. They have a simple body consisting of a central gut cavity surrounded by tentacles. • Hydra does not have medusa form in their life cycle, whereas Obelia has both forms; polyp and medusa. Examine the live specimens of Hydra fuscus (brown hydra) and Hydra viridens (green hydra has symbiotic algae). Sciences, Culinary Arts and Personal Hydra does not have a medusa form and reproduces sexually by the formation of gametes. They develop into medusa again when food sources are scarce and temperature in unfavorable for asexual reproduction. Scyphozoans consist of a larval planula metamorphose as a polyp. There can be variations in the structure but the similarity in shape is the presence of tentacular structure and the outer structure. The polyp may be solitary, as in the sea anemone, or colonial, as in coral, and is sessile (attached to a surface). 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