The planula larva is produced by the polyp forms. The planula is formed from the prepared egg of a medusa, similar to the case in scyphozoans and a few hydrozoans, or a polyp, as on account of anthozoans. These larvae are found in cnidarians and ctenophores so we will also learn about these species in detail.

What does the planula develop into?

Following external or internal fertilization, a free-swimming planula larva develops, that soon attaches to a suitable substratum, and evolves into a hydra or a hydroid colony.

Do planula larvae eat?

Feeding and locomotion

The planulae of the subphylum Medusozoa have no mouth, and no digestive tract, and are unable to feed themselves, while those of Anthozoa can feed.

Do all cnidarians have planula?

Cnidarian morphology: Cnidarians have two distinct body plans, the medusa (a) and the polyp (b). All cnidarians have two membrane layers, with a jelly-like mesoglea between them. Some cnidarians are polymorphic, having two body plans during their life cycle. An example is the colonial hydroid called an Obelia.

What is a planula in biology?

planula, plural planulae, free-swimming or crawling larval type common in many species of the phylum Cnidaria (e.g., jellyfish, corals, and sea anemones). The planula body is more or less cylindrical or egg-shaped and bears numerous cilia (tiny hairlike projections), which are used for locomotion.

Do all invertebrates have planula larvae?

Many invertebrates (e.g., cnidarians) have a simple ciliated larva called a planula. Flukes have several larval stages, and annelids, mollusks, and crustaceans have various larval forms.

How do Aurelia reproduce?

The life cycle of Aurelia aurita include both sexual and asexual reproduction. Medusae are sexually mature jellyfish and can be seen floating in open waters. Adult females and males release eggs and sperm respectively into the open water after development in the gonads.

Is Aurelia a polyp or medusa?

Aurelia aurita, is of the Phylum Cnidaria, which are characterized by having a polyp and medusa stage, radial symmetry, planula larvae, cnidia, and tentacles around the mouth.

Are Scyphozoa medusae or polyps?

Jellyfish life cycle (Scyphozoa) Most scyphozoan jellyfishes—including most of the large jellyfish with which many people are familiar—have a two part life cycle: free-swimming medusa and bottom-dwelling polyp (although there are notable exceptions).

Do sponges have planula?

For example, phylum coelenterata have the larva called as planula, phylum platyhelminthes have the larva called as cysticercus and phylum mollusca have the larva called as glochidium. The common larval stages found in sponges are Amphiblastula (found in scypha) and parenchymula (found in leucosolenia).

What makes anthozoa unique?

Anthozoans have special glands that secrete digestive fluids. Some have been known to digest extremely large fish. Anthozoans are found around reefs and shallow waters. Since they help build coral reefs they have been valuable to scientists in learning about the past climates of certain regions.

What is the name of free swimming larva of Hydra?

The larva-like stage of Hydrozoan Cnidarians such as Hydra is known as a planula. These are open-water swims.

What does the Gastrodermis do?

Gastrodermis helps in extracellular digestion of food in the gastrovascular cavity.

How do cnidarians breathe?

Cnidarians lack organs. This means that they do not have respiratory or circulatory systems. Like the cells in sponges, the cells in cnidarians get oxygen directly from the water surrounding them.

Are Cubozoans polymorphs?

Cubozoans live as box-shaped medusae while Hydrozoans are true polymorphs and can be found as colonial or solitary organisms.

What is a jellyfish planula?

A planula is a tiny oval structure the outer layer of which is lined with minute hairs called cilia, which beat together to propel the larva through the water.

How do hydras feed?

Food. Hydras wave their tentacles slowly in the water. When food touches a tentacle, special stinging cells discharge to help subdue the prey. The tentacles draw the food into the hydra’s mouth.

What is the larva of ctenophora known as?

Most ctenophores, however, have a so-called cydippid larva, which is ovoid or spherical with two retractable tentacles.