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Common name: Acorn worm

Geographical distribution: cosmopolitan or world –wide

Habitat: marine burrowing worm like


1. Body: soft and cylindrical having ciliated surface

2. Body Length: 10-50 cm long

3. Body division: short conical proboscis , collar and long trunk

4. Cavity of proboscis open exterior by a proboscis pore and proboscis has thick muscular walls

5. Short , muscular cylinder-like collar encloses cavity (collar coelom) which open on the dorsal surface by a pair of collar pores

6. Superficially ringed trunk (devoid of segmentation)

7. Trunk divided into anterior branchio-genital region, a middle hepatic region and a posterior abdominal region

8. In branchio-genital region present a pair of genital wings formed by internal gonads and a branchial groove having numerous paired gill-slits arrange in 2 rows

9. In hepatic region double rows of hepatic caeca are present

10. Straight alimentary canal

11. Anus is present on posterior end of body

12. Sexes separate

13. Fertilization external

14. Development includes free-swimming pelagic larva Tornaria


Geographical distribution: India, Pacific and the Atlantic oceans and from Malaya and West Indies

Habitat: solitary marine form

Food: microscopic plants and animals i.e. diatoms, algae and infusorians


1. Body: roughly oblong in outline

2. Body Length : 9.5 to 12 cm long

3. Body Colour : pink

4. Attachment of animal is at posterior ventral end by foot

5. Body free end is provided with two external openings of the branchial and the atrial apertures

6. Opening of mouth through branchial aperture or siphon,while anus by atrial aperture

7. Sac-like pharynx perforated by numerous stigmata

8. U-shaped alimentary canal

9. Respiration through branchial – sac. Test also act as an accessory respiratory organ

10. Open – type blood vascular system

11. Excretory organ is neural gland present above the nerve ganglion

12. Hermaphrodite


Geographical distribution: Western region

Habitat : solitary marine form attached to rocks


1. Body: cylindrical ,tubular ,transparent and longer than broad

2. Body Length : 3.5-5inches

3. Body covered with thin transparent test or mantle

4. Opening of mouth is in branchial siphon and anus into atrial-siphon

5. Branchial aperture =8 lobed while atrial aperture =6 lobed

6. Longitudinal folds absent in pharynx

7. U – shaped alimentary canal consist of pharynx, oesophagus, stomach and intestine

8. Rectangular stigmata

9. Horse-shoe shaped dorsal tubercle

10. Hermaphrodite and protogynous


Geographical distribution: Tropical and sub-subtropical waters

Habitat : free- swimming,pelagic form inhabiting the warm water


1. Body: barrel-shaped with the mouth and at opposite end lies anus

2. Test or tunic : thin,transparent and has no cells

3. Open ends of barrel are fringed with lobes

4. In volumnous pharynx oral funnel opens broadly

5. Pharynx: perforated by dorsal and rows of stigmata present ventrally

6. In the pharynx Endistyle and peripharyngeal ciliated bands are present

7. Absence of dorsal lamina and tentacles

8. Stomach small and intestine short and anus open posteriorly

9. Hermaphrodite

10. Near the anterior end dorsal ganglion and subneural glands are situated

11. Life cycle show an alteration of sexually mature adult , the gonozoid with the asexually reproducing phase,the oozoid


Geographical distribution: Tropical seas

Habitat : free swimming,solitary pelagic forms


1. Body: barrel-shaped with the mouth and atrial aperture present at opposite end

2. transparent test

3. Presence of Endostyle and pharyngeal bands

4. Dorsal lamina present and is known as gill

5. On dorsal surface a single tentacle is present

6. Digestive system and heart is present in a spot called nucleus

7. Eye is present near near the nerve ganglion

8. In front of the pharynx dorsal tubercle is present

9. Presence of subneural gland ventral to the ganglion

10. Salpa is found in 2 forms:

         a Asexual phase or oozoid

         b Sexual phase or blastozooid


Geographical distribution: World -wide in distribution ,found on the shores of all continents and many oceanic islands

Habitat : fish-like burrowing marine animal


1. Body: enlongated,laterally compressed and pointed at both the ends

2. Body length : 5 cm

3. Projection of anterior end forward called Rostum

4. Low and continous fins :

            a  dosal fin

            b  ventral fin

            c  caudal fin

5. Two metaneural folds

6. Myotomes are present on both sides and separated by v-shaped connective tissue ,the myosepta or myocommata

7. Mouth is ventral to rostum and guarded by oral hood bearing oral cirri

8. Atriopore is median and ventral and present at the junction of metaneural folds and ventral fin

9. On the left side a short distance in front of the posterior end anus is present 

10. 26 pairs of gonads are present and arranged metamerically arranged on both sidesof the pharynx

11. Sexes separate but can't be distinguish externally