Why Obelia colony is a trimorphic colony?
Each ultimate branch terminates in nutritive zooids called hydranth and axils of the older polyps consists of reproductive zooids called blastostyles or gonangia, thus obelia colony is dimorphic and when gonangia produces saucer shaped buds as a result of asexual reproduction and develops into sexual zooids called …
What body form is the Obelia colony?
Structure. Through its life cycle, Obelia take two forms: polyp and medusa. 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. They carry a nerve net with no brain or ganglia.
What are the parts of Obelia colony?
The Obelia is a trimorphic colony, that is, having three kinds of zooids which are as follows:
- Polyps or hydranths (nutritive zooids);
- Gonangia or blastostyles (budding zooids);
- Medusae, (sexual zooids).
What are the two types of polyps in Obelia?
The colonial sessile form of Obelia geniculata has two types of polyps: gastrozooids, which are adapted for capturing prey, and gonozooids, which asexually bud to produce medusae.
What is the function of polyp of Obelia?
Polyp or hydranth (nutritive zooids): This nutritive zooid of the colony is also known as gastrozooids or trophozooid. It is yellow in color, radial symmetrical and cylindrical in shape. They are specialized for capture, ingestion and digestion of food.
Is Ocelli present in Obelia?
There are eight spherical statocysts spaced evenly around the margin of the bell. Each is at the base of a tentacle. The statocysts are hollow, thin-walled, epidermal vesicles containing a calcareous statolith and a ciliated sensory epithelium. There are no ocelli in Obelia or other Leptothecatae.
Which is correct about polyp stage of Obelia?
Obelia is a genus in the class Hydrozoa, which consists of mainly marine and some freshwater animal species and has both the polyp and medusa stages in their life cycle and shows metagenesis.
How many points are correct about Obelia?
| Question | (i) Radial symmetrical (ii) Diploblastic (iii) The cellular level of organization (iv) Digestion is intracellular only (v) Exhibit two basic body forms called polyp and medusa. How many points are correct about Obelia? |
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| Question Video Duration | 3m33s |
How does Obelia eat?
Contrary to other Hydromedusae that are macrophagous, Obelia is a microphagous and filter-feeding medusa, at least at the onset of its medusan life. As Cnidaria evolved before their current metazoan prey, their ancestral diet was probably microphagous.
What is the function of polyp in Obelia?
What are the functions of Coenosarcal cavity in Obelia?
A narrow canal, called coenosarcal canal runs through whole colony of Obelia which is continuous with the gastrovascular cavity of the zooids. The continuity of the canal system helps to transport the digested food throughout the colony.
What is the function of Gastrozooids in polyp?
The role of gastrozooids, which have mouths surrounded by tentacles tipped with stinging cells, is to capture and consume food. The reproductive duties, however, belong to the gonzooids, which create the successive generation, small jellyfish known as medusae, via budding.
