Classification:

• Phylum : Hemichordata
• Class : Enteropneusta
• Genus : Balanoglossus

Comments:

1. 1. Balanoglossus is commonly known as acorn worm.
2. 2. Body is soft and cylindrical having ciliated surface reaching a length of 10 -15 cm .
3. 3. The body is divisible into short conical proboscis, collar and a long trunk.
4. 4. Proboscis has thick muscular walls and its cavity -proboscis coelom opens to the exterior
5. by a proboscis pore.
6. 5. Collar is short, muscular , cylinder-like , enclosing a pair of coelomic cavities (collar
7. coelom) opening by a pair of collar pores on the dorsal surface.
8. 6. Trunk is superficially ringed (devoid od segmentation ). It is divisible into anterior
9. branchiogenital region, a middle hepatic region and a posterior abdominal region.
10. 7. In the branchio-genital region are present a pair of genital wings formed by internal
11. gonads and a branchial groove having numerous paired gill-slits arranged into two rows.
12. 8. In the hepatic region are present double rows of hepatic caeca.
13. 9. Alimentary canal is straight and anus is present on the posterior end of the body.
14. 10. Sexes are separate and fertilization is external.
15. 11. Development includes a free-swimming pelagic larva, the tornaria.
17. Habit and habitat: Balanoglossus is a burrowing and exclusively marine animal. It is found in
18. shallow waters between tide marks along the coasts of warm and temperate oceans.
20. Distribution: Balanoglossus is cosmopolitan or worldwide.

Source:

1. Practical Zoology Vertebrates by S.S.Lal . 2. A Manual of Practical Zoology Chordates by Dr. P.S. Verma.