Tag: animal diversity - i (inverterbrate phyla)

Tentacles are the organs which are used to catch the prey. These are present at the opening of the gastrovascular cavity. Colloblasts are a cell type found in ctenophores. They are widespread in the tentacles of these animals and are used to capture prey. These are found in all ctenophores except those of the order Beroida, as they lack tentacles. So, the correct answer is option B.

Jellyfish are the major non-polyp form of the individuals of the phylum Cnidaria. They are free-swimming marine animals consisting of a gelatinous umbrella-shaped bell and trailing tentacles. They do not possess a proper skeleton.
Therefore, the correct answer is option D.

Ctenophora is a phylum of animals that live in marine waters. The outer surface bears usually eight comb rows. This is called as comb plates or swimming-plates, which are used for swimming. Ctenophora lack stinging nematocysts. Lasso cells are kind of defensive and offensive stinging cells. These are found in great numbers in all coelentrates. 

Ctenophora is a phylum of animals that live in marine waters. The outer surface bears usually eight comb rows. This is called as comb plates or swimming-plates, which are used for swimming. Ctenophora lack stinging nematocysts. Lasso cells are kind of defensive and offensive stinging cells. These are found in great numbers in all coelentrates.  The Beroe or Melon jellyfish and flattened species like Cestum belongs to Ctenophora. Ctenoplana is a genus of comb jellies andPleurobrachia is a common genus of Ctenophora.Thus, the correct answer is option D.

• Ctenophora are also known as comb jellies. This is a phylum of animals that lives in marine waters. 
• Many species in this group have the body which is biradially symmetrical. The main axis is oral to aboral (from the mouth to the opposite end). This gives the bilateral form. 
• The tentacles are present around the mouth. These tentacles radiate outwards. This gives the radial form of symmetry. Thus, the type of symmetry is known as biradial symmetry. 
  
  

Ctenophora shows several affinities with Cnidaria, some of them are:

Ctenophores, commonly known as sea walnuts or comb jellies are exclusively marine, radially symmetrical, diploblastic organisms with tissue level of organization. The germs layers include ectoderm and endoderm. 

Hydra traps its prey by  tentacles which are present at the opening of the gastrovascular cavity. Scattered over the outer layer tentacles are a great many of these stinging cells called cnidoblasts. Each cnidoblast contains a capsule (nematocyst) from which projects a small trigger called a cnidocil. Inside each capsule is a tiny hollow thread. It is inverted like a finger of a glove which is pushed into the hand part. These threads are the food-catching apparatus.