(ˈpɛrɪˌsɑːk) n. (Zoology) the outer chitinous layer secreted by colonial hydrozoan coelenterates, such as species of Obelia.

What is a perisarc?

: the outer usually chitinous integument of a hydroid.

What is Hydrotheca?

: a cup-shaped extension of the perisarc in hydroids of the group Leptomedusae that surrounds and protects the hydranths when they are contracted.

What is a Hydranth?

: one of the feeding zooids of a hydroid colony.

What is the function of the Hydranth?

A hydranth, is encased and protected in a transparent vase-like hydro-theca. It captures minute prey by using its tentacles which contain batteries of nematocysts. The coelenteron of the hydranth communicates with the cavity of the hydrocaulus and thus the absorbed food is distributed to the entire colony.

What is Zoology?

What is obelia Medusa?

The obelia medusa is a zooid in the shape of an umbrella. It is radially symmetrical and measures around 6 to 7 mm in diameter. It is a free-swimming reproductive zooid of the obelia colony.

What is Perisarc in obelia?

The entire colony is covered by a tough, yellow chitin secreted by the ectoderm, this covering is known as perisarc. The perisarc constitutes the exoskeleton and it covers the hydrorhiza, hydrocauli and their branches, and at the base of each polyp, it forms a clear, wine glass-shaped hydro theca.

In what form does obelia exist?

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.

What is polyp and medusa?

There are two basic cnidarian body shapes: a polyp form, which is attached to a surface; and an upside-down free-floating form called a medusa. Some cnidarians change form at different phases of their life cycle, while others remain in one form for their entire life.

Why Obelia is an animal?

Obelia, genus of invertebrate marine animals of the class Hydrozoa (phylum Cnidaria). ... Obelia medusae release sperm or eggs into the surrounding water, and the resulting ciliated larva eventually metamorphoses to produce a branching colony of polyps.

How can we identify Obelia?

[Obelia-medusa] Umbrella flat, with velum minute or lacking (authorities differ). Stomach short, with quadrangular base, without peduncle; mouth with four short simple lips. Radial canals four, straight; they and ring canal narrow, the latter hard to discern.

What is the function of Perisarc?

The perisarc of hydroids is a sheath of chitin, proteins and inorganics that protect the main stalk and soft tissues.

What is coenosarc and Perisarc?

As nouns the difference between perisarc and coenosarc

is that perisarc is (zoology) the outer hardened integument that covers most hydroids while coenosarc is (zoology) living body held in common by many organisms included in a composite zoophyte, by which they are in connection with each‐other.

Why is obelia Trimorphic?

It is called trimorphic because it has 3 stages in its life and these are polyp medusa and blastostyle.

What is Aurelia in biology?

Aurelia is a genus of scyphozoan jellyfish, commonly called moon jellies. ... Aurelia undergoes alternation of generations, whereby the sexually-reproducing pelagic medusa stage is either male or female, and the benthic polyp stage reproduces asexually.

Is obelia medusa colonial or solitary?

Colonial hydrozoans include siphonophore colonies, Hydractinia, Obelia, and many others. In hydrozoan species with both polyp and medusa generations, the medusa stage is the sexually reproductive phase. Medusae of these species of Hydrozoa are known as "hydromedusae".

What is the function of medusa?

The medusa form is generally small and short-lived. Its primary function is to carry out sexual reproduction and to allow the species to disperse to different locations. Hydrozoa are classified based on the presence of a membrane called the velum that lines the inside edge of the bell in the medusa forms.

What is the meaning of Corallite?

: the skeleton of a single coral polyp consisting of a septate investing wall or theca and an underlying basal plate and being imbedded in the general structure of the corallum.

Why is the coenosarc important?

The coenosarc connects the entire coral colony and covers the underlying coral skeleton. Reproduction through an asexual budding process results in development of duplicate daughter polyps and allows for growth of the colony.

How does Obelia eat?

Previous observations reported that Obelia medusae might eat phytoplankton, driven to the mouth by movements of both the bell and the tentacles. ... Contrary to other Hydromedusae that are macrophagous, Obelia is a microphagous and filter-feeding medusa, at least at the onset of its medusan life.

How does Obelia reproduce?

At this stage, the Obelia medusa swim freely and reproduce sexually by releasing either eggs or sperm into the water. Upon fertilization, the resultant zygote develops into a free-swimming larva (plural: larvae) covered in cilia, or tiny hairs. This larva uses the cilia to swim while developing.

Is Obelia a sponge?

Stereogastrula also known as Parenchymula larva belongs to organisms of the phylum Porifera composed of sponges. Obelia belongs to the phylum Cnidaria.