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.
What are the three body forms of cnidarians?
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. Animals in this phylum display two distinct morphological body plans: polyp or “stalk” and medusa or “bell” (Figure 2).
How many body forms do cnidarians have?
Cnidarians have
two body forms
—polyp and medusa—which often occur within the life cycle of a single cnidarian. Sea nettle (Chrysaora fuscescens). The body of a medusa, commonly called a jellyfish, usually has the shape of a bell or an umbrella, with tentacles hanging downward at the margin.
What body form do cnidarians move?
The
Medusas Stage
allows for the cnidarians to actively move using their long tentacles to pull the water into themselves to gain nutrients.
What are the body parts of cnidarians?
The body of a cnidarian consists of
two cell layers, ectoderm and endoderm
. The cellssurround a digestive cavity called the coelenteron (see Figure below). Cnidarians have a simple digestive system. The single opening is surrounded by tentacles, which are used to capture prey.
What are the two body layers of cnidarians?
Cnidarians have two tissue layers. The outer layer is the epidermis. It is formed from ectoderm.
The inner layer, the gastrodermis
, secretes digestive juices into the inner space called the gastrovascular cavity.
Do cnidarians have a muscular system?
Muscles in cnidarians are
extensions of the bases of ectodermal and endodermal cells
. … Most cnidarian muscles, however, are thin sheets at the base of ectodermal and endodermal layers. muscle: Cnidarians. The phylum Cnidaria includes the hydras, jellyfishes, and sea anemones.
Are jellyfish polyps or Medusa?
A polyp is the form that attaches to a surface, while
a medusa is the form that is free-floating
; a species of cnidarian may take each form in a different phase of its life. The medusa form predominates in the classes Scyphozoa (the common, colourful, large jellyfish) and Cubozoa.
Why is a jellyfish called a Medusa?
A jellyfish is called a Medusa
The shape of this bell is called a medusa
because it looks like the evil Medusa in Greek mythology
– a woman who had offended the goddess Athena who then changed her hair into snakes and made her face so hideous it turned people into stone.
Is obelia a plant or an animal?
Obelia is a genus of hydrozoans, a class of mainly marine and some
freshwater animal
species that have both polyp and medusa stages in their life cycle. Hydrozoa belongs to the phylum Cnidaria, which are aquatic (mainly marine) organisms that are relatively simple in structure. Obelia is also called sea fur.
What are 5 characteristics of cnidarians?
- Radially Symmetrical.
- Body multicellular, few tissues, some organelles.
- Body contains an internal cavity and a mouth.
- Two different forms exist, medusa and polyp.
- Reproduction is asexual or sexual.
- Has a simple net like nervous system.
- Has a distinct larval stage which is planktonic.
Why Coelenterates are called cnidarians?
Coelenterates are called Cnidarians
because they contain specialized cells called cnidoblasts
. They possess stinging structures called nematocysts.
What are 4 functions of nematocysts?
Nematocysts are the means by which coelenterates capture prey and defend against predation. The 25 or more known types of nematocysts can be divided into to four functional categories:
those that pierce, ensnare, or adhere to prey, and those that adhere to the substrate
.
What are the 3 steps for the life cycle of most cnidarians?
Cnidarians often have a life cycle consisting of
planula larva, polyp, and medusa stages
. A neuropeptide, pGlu–Gln–Pro–Gly–Leu–Trp–NH
2
, induces metamorphosis of the marine hydroid from a hydroid planula larva to a polyp.
What is the primary body form of Scyphozoans?
Scyphozoa is a class of marine organisms under phylum Cnidaria. They have blind sac body plan, while
umbrella like free swimming medusa form
is dominant phase of life.
Do cnidarians have a body cavity?
Cnidarians have an
incomplete digestive system
with only one opening; the gastrovascular cavity serves as both a mouth and an anus.
