Question

Give classification and characteristics of urichordata​

Answer 1

These animals are known as ‘sea squirt’. The life-history of urochordates passes through a dramatic change. Their chordate characters are more pronounced during larval period. While in adults they are more like invertebrates than chordates. Therefore, the characters are described in two heads

Larval characters of Urochordates:

1. Elongated larva of Urochordata is known as ascidian tadpole larva. Adult emerges from the larva by the process of meta­morphosis.

2. Notochord restricted at the caudal end, hence name Urochordata.

3. Dorsal hollow nerve chord spreads end to end.

4. Pharyngeal gill slits are present.

5. Highly active post anal tail is prominent.

Adult characters of Urochordata:

1. The body of the adult is covered by a tunic (hence named Tunicata). The tunic is composed of a protein tunicin and a polysaccharide similar to plant cellulose

Answer 2

Urochordates are small marine animals with larvae that swim freely and adults that attach themselves to the ocean floor. The 1,300 species of urochordates, like all members of the phylum Chordata, possess four characteristic anatomical structures as embryos: a flexible body-length rod (the notochord ) that provides resistance against muscular contractions and allows for more efficient movement; a dorsal , hollow, nerve cord that forms the central nervous system; slits in the beginning of the digestive tract (the pharynx) that allow filter feeding and gas exchange; and a postanal tail. Urochordates, commonly known as tunicates, differ from other chordate subphyla (Cephalochordata and Vertebrata) in that the adult form has no notochord, nerve cord, or tail. In fact, an adult tunicate is an immobile, filter-feeding marine animal that in some ways looks more like a sponge or a mollusk than a chordate.