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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.
- How does a cnidarian move?
- How do polyps move?
- How does adult hydra attach to feed?
- What do planula larvae turn into?
- Are Cnidaria motile?
- What does the Gastrodermis do?
- How do cnidarian polyps move?
- What is the function of the polyp?
- What is polip?
- How does a hydra move?
- How does hydra use the Nematocyst?
- How do hydras digest food?
- What does a planula become?
- Which stage is the planula?
- Do all invertebrates have planula larva?
How does a cnidarian move?
How do cnidarians move? Since Cnidarians do not have a mesoderm, they do not have any true muscle. They move by epithelial muscular cells (cells in the epidermis that can contract and are made up myosin and actin. ... Cnidarians respire by diffusion and all cells are near the digestion cavity.
How do polyps move?
However, most do so weakly and are carried passively by currents over long distances. Polyps are generally sedentary. Pennatulacean colonies move slowly across soft substrata by action of their inflatable peduncle (a stalk that attaches to the strata in the lower end and to the polyp body on the higher end).
How does adult hydra attach to feed?
Feeding. Hydra mainly feed on aquatic invertebrates such as Daphnia and Cyclops. While feeding, Hydra extend their body to maximum length and then slowly extend their tentacles. ... Upon contact, nematocysts on the tentacle fire into the prey, and the tentacle itself coils around the prey.
What do planula larvae turn 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.
Are Cnidaria motile?
Medusa forms are motile, with the mouth and tentacles hanging down from an umbrella-shaped bell. Cnidarian morphology: Cnidarians have two distinct body plans, the medusa (a) and the polyp (b). ... Some cnidarians are polymorphic, having two body plans during their life cycle.
What does the Gastrodermis do?
Gastrodermis helps in extracellular digestion of food in the gastrovascular cavity.
How do cnidarian polyps move?
Some polyp forms reproduce asexually by budding, while some medusa can split down the middle. Despite not having bones, these animals do move. Jellyfish mostly drift, but they can move on purpose if they need to. Our muscles pull on our bones to make us move.
What is the function of the polyp?
Polyps extend their tentacles, particularly at night, containing coiled stinging nettle-like cells or nematocysts which pierce and poison and firmly hold living prey paralysing or killing them.
What is polip?
A polyp is a projecting growth of tissue from a surface in the body, usually a mucous membrane. Polyps can develop in the: colon and rectum. ear canal. cervix.
How does a hydra move?
The hydras usually move by looping and somersaulting, by attaching the tentacle ends and pulling themselves along. When there is an insufficient supply of oxygen, hydras move to regions of higher oxygen content.
How does hydra use the Nematocyst?
Nematocysts are produced by nematoblasts, or cnidoblasts, and are used for capturing and paralyzing prey or for defense. ... Each nematocyst contains a coiled, hollow thread that can have barbs or spines and often contains poison.
How do hydras digest food?
The food is put into the mouth and digestion begins. The gut of Hydra is simply the hollow cavity within the body and has only one opening, the mouth. Enzymes are produced by special cells in the endodermis and released into the gut cavity. These enzymes begin to break down the food into smaller particles.
What does a planula become?
The planula metamorphoses into a sessile (i.e. fixed-position), usually benthic (i.e. bottom dwelling) polyp called a 'scyphistoma' and it is the scyphistoma, still attached to the surface on which the planula settled, that produces a new free-swimming medusa.
Which stage is the planula?
The planula is the first larval stage of Aurelia, and is formed soon after the egg and sperm combine to form a zygote. The planula is lined with cilia and eventually settles, forming a scyphistoma.
Do all invertebrates have planula larva?
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.
