Obelia is a colonial hydroid that belongs to the family of Hydrozoa. It is a small, tube-like structure that is found in both freshwater and marine environments. The Obelia colony is made up of numerous tiny polyps, which are interconnected to form a branching structure. Each polyp is responsible for carrying out specific functions within the colony.
Obelia colonies can be found in a variety of habitats, including coral reefs, rocky shores, and kelp forests. They are commonly found in shallow waters and are known to attach themselves to rocks, shells, and other hard surfaces. Obelia colonies can range in size from a few centimeters to several meters, depending on the species and the habitat in which it is found.
The Obelia colony is made up of both sexual and asexual polyps. Asexual polyps are responsible for reproducing and building the colony, while sexual polyps produce eggs and sperm. The eggs and sperm are released into the water, where they fuse to form a new Obelia colony.
Obelia colonies play a vital role in the marine ecosystem. They provide a habitat for a variety of small organisms, such as algae and small invertebrates. They also serve as a source of food for larger animals, including fish and birds.
Despite their importance in the ecosystem, Obelia colonies are facing numerous threats. Pollution, habitat destruction, and climate change are all factors that can negatively impact the survival of Obelia colonies.
In conclusion, the Obelia colony is a fascinating and important part of the marine ecosystem. It is made up of numerous interconnected polyps that carry out various functions within the colony. Obelia colonies provide a habitat for small organisms and serve as a source of food for larger animals. However, they are facing numerous threats, including pollution, habitat destruction, and climate change. It is important that we work to protect and preserve Obelia colonies for the benefit of the ecosystem and future generations.
Structure of Obelia (With Diagram)
The gonads mature after the medusae escape from the gonotheca. The ocelli consist of patches of pigment and photoreceptor cells organised either within a flat disc or a pit. They are diploblastic, with two true tissue layers—an epidermis ectodermis and a gastrodermis endodermis —with a jelly-like mesoglea filling the area between the two true tissue layers. Sense organs: The bell margin is richly supplied with sensory cells and also contains two types of true sense organs, viz. It has a cylindrical body attached to the axis of the hydrocaulus by its proximal end and free at its distal end.
A statocyst is a tiny, circular closed vesicle lined with ectoderm and filled with a fluid containing calcareous granules called otoliths which lie in a special cell called lithocyte. The cavity of the blastostyle pushes the coenosarc out to form a small protuberance or bud. However, the tentacles are solid they are hollow in hydra and each is filled with a cord of endodermal cells with secreted matrix material separating adjacent cells. Undigested food is then egested through the month. Therefore, a true alternation of generations is always between a diploid asexual and haploid sexual generations, as is exhibited by fern plant.
It has a ridge-like structure on the inner margin, called a velum. Biological Bulletin 147: 397-410. This larva uses the cilia to swim while developing. Hydroid or Polyp Phase 2. The immature hydranth, known as hydrula, resembles a basic polyp like hydra and undergoes recurrent asexual budding to produce a complicated Obelia structure. Cleavage holoblastic but unequal. The contraction of these processes shortens the body column and tentacles.
ADVERTISEMENTS: The free distal end is produced into a conical elevation, the hypostome or manubrium which is about one-third of the length of the hydranth. Hydro-theca is transparent and is formed by the modification of the perisarc. A cavity forms inside the endodermal mass, the cavity becoming the enteron gastrovascular cavity of the adult. This zooid and medusa are carnivorous, feeding upon small aquatic crustaceans, nematodes and other worms. The outer ends fuse and gives rise to a continuous cuticle along the entire length of the body. Genetics Classical To Modern.
European Obelia Cnidaria, Hydroida : systematics and identification. ADVERTISEMENTS: The mouth is situated at the terminal end of the manubrium. The planula is transformed into a hydra tuba, which produces new hydra tuba by budding. ADVERTISEMENTS: In this article we will discuss about Obelia Sea Fur :- 1. Through these canals food matters are conveyed to the different parts of the body. The medusa also possesses a similar double network, but also has two nerve rings, one either side of the radial canal - an outer nerve ring and an inner nerve ring.
Life history shows alternation of generations and development through planula larva. Zoological Journal of the Linnean Society. The gonads are round, four in number and externally both male and female gonads are similar. Instead of secreting a horny case, as in Hydra, the ectoderm becomes ciliated and a planula larva is formed, which freely swims about in water. Between the ectoderm and endoderm is thick mesogloea forming the bulk of the bell of the medusa, manubrium and tentacles. The gonads found in medusa are not formed in it but actually they are formed in the ectoderm of blastostyle which later on migrate into the medusa and become situated on its radial canals.
Medusa swims freely on the surface water. The muscle processes form a striated circular muscle and some radial muscles in the sub-umbrella, they bring about locomotory movements. The medusae are dioecious, they have either four testes or four ovaries in the sub-umbrella just below the radial canals. The colours have been added for clarity in distinguishing the parts. They are strictly homologous or typically similar structures. The perisarc around a blastostyle is a gonotheca, the blastostyle and gonotheca are together called a gonangium.
The flagella of the flagellated cells, bring about a constant movement of food particles in the coelenteron. Some of the epitheliomuscular cells of the velum have their contractile extensions oriented to form a powerful circular band of fibres which are striated. Fertilization internal, the union occurs inside the enteron of the female. They are specially designated to perform nutritive function and feed the whole colony. The presence of the four radial canals distinguishes the four principal radii or per-radii. Obelia shows polymorphism in which the polyps are for feeding the colony, blastostyles for budding and medusae for disseminating gametes. On the sub-umbrella, the gonads ovaries or testis appear as knobs beneath the radial canals.
The tentacles are longer than hypostome, tapering and filiform. The nematocysts are abundant on the tentacles and manubrium only. Later on a split appears in the middle of the endoderm which represents the coelenteron. Product of fertilisation is the free swimming planula larva, which subsequently settles down to form the fixed asexual colony. ADVERTISEMENTS: From the centre of the sub- umbrellar surface emerges a hanging tube called the manubrium bearing a square mouth at its terminal end Fig.
Obelia (Sea Fur): Structure, Movement and Respiration
Initially the medusa has 24 tentacles, but the number increases with age. Nutrition The tentacled feeding polyps are called hydranths and the perisarc enclosing them forms a supporting cup called a hydrotheca. Polyp is the nutritive zooid of the colony. Each of these 8 lithocyst, is a minute globular sac containing a calcareous body in contact with hair-like processes of sensory cells. The ectodermis at the base of the tentacles may contain pigment spots which may be photoreceptors. The planula has one broader end which attaches to the substrate and puts out a horizontal creeping branch or stolon which may form a branching and anastomosing horizontal network from which vertical stalks rise up.