CLASSIFICATION OF ECHIURIS
Phylum :- Echiuroidea (Traces of segmentation, coelomate, bilaterally symmetrical.)
Genus :- Echiuris
GEOGRAPHICAL DISTRIBUTION
It is found in Atlantic and Pacific coasts, Europe, Italy, Mediterranean Sea and California.
HABIT AND HABITAT
Echiuris is a marine worm living in the sand and mud or between stones usually near the shore.
GENERAL CHARACTERSTICS OF ECHIURIS
- Body is thick and cylindrical without or indistinct segmentation. Parapodia and cephalic appendages are also absent.
- Formation of the head is peculiar. It is elongated, cylindrical, spoon shaped in front of the mouth. It is called as proboscis.
- Proboscis is homologous with prostomium of annelids. Ventral surface of the proboscis is grooved and ciliated for traping micro-organisms for feeding.
- Body surface is covered by minute papillae arranged in regular transverse rings.
- A pair of hooked setae is found near the anterior and posterior ends.
- Mouth is found at the base of the proboscis.
- Anus has 2 rings of setae.
- Nephridiopores of the anterior nephridia open ventrally close behind the anterior setae. Nephridia act as gonoducts.
- Body wall is highly muscular and coelom is spacious.
- Sexes are separate. Development is indirect and larva is trochophore.
IDENTIFICATION
It has spatulate proboscis and all above features, hence it is Echiuris.
Characterstics of Minor Phyla
On the basis of presence or absence of a true coelom minor phyla are divided into two groups.
(A) Minor Acoelomate Groups 1. Mesozoa, 2. Ctenophora, 3. Endoprocta, 4. Nemertinea (Rynchocoela), 5. Acanthocephala, 6. Nematomorpha, 7. Rotifera, 8. Gastrotricha, 9. Kinorhyncha, 10. Nematoda
(B) Minor Coelomate Groups 1. Ectoprocta, 2. Brachiopoda, 3. Phoronida, 4. Chaelognatha, 5. Priapulida, 6. Sipunculida, 7. Echiuroidea, 8. Brachiata. Some of the representatives of the above phyla are discussed below.