Balanoglossus- A Hemichordate

It discusses basic information regarding a hemichordate animal called Balanoglossus or Acorn worm, which is also a good connecting link between the non-chordates and chordates.

1. Balanoglossus : A hemichordate -By Pranjal Gupta(0047), Bsc (H) Zoology Ramjas College 1

2. CLASSIFICATION Phylum: Chordata (Deuterostome,presence of notochord, nerve cord & pharyngeal gill slits) Subphylum: Hemichordata (Small soft bodied,marine,notochord confined to head region, sexes separate) Class: Enteropneusta (Solitary form; straight alimentary canal, mouth and anus at opposite ends, two rows of caecae,numerous gill slits) Genus: Balanoglossus Common name: Acorn worm 2

3. Habitat and Habit Geographical distribution: Worldwide or cosmopolitan. Habitat: Marine, live in shallow waters generally but few go deeper upto 15000 feet, lives inside U-tubes( tubicolous ). Habit: Adapted for burrowing life in sandy bottoms. It burrow slowly by soft proboscis. Worm casting 3

4. 4 B.gigas is The largest Species, found in B razil. Measures to 2.5m. Balanoglossus secretes iodoform like foul smelling compound as a defense mechanism Balanoglossus is used as fish-bait by local fishermen. It is also called Tongue worm due to the resemblance of the proboscis & genital wings to Ox tongue.

5. Feeding Habit and Respiration. Since Balanoglossus is a tubicolous animal, it feeds by filter-feeding mechanism. As the water enters the tube from the anterior opening. It opens its mouth situated in the collar and takes up the food particles, and filters out the unwanted. The same water gushes through the gill pores to provide necessary oxygen for respiration. 5

6. External Morphology proboscis collarette collar Branchial region Gill pores Genital wings Mid dorsal ridge hepatic caeca Hepatic reg. Anus Post hepatic reg. 6

7. Balanoglossus:Distinct Features It measures 10cm to 2.5metres, depending on species. Worm-like body divisible into three regions. > Anterior proboscis which is conical. > Middle collar which is funnel like > Posterior trunk which is cylindrical and further divided into: Branchiogenital region , hepatic region & abdominal region . Notochord represented by small buccal diverticulum . Development includes tornoria larva 7

8. Localization of Internal Organs 8

9. Internal Morphology 9

10. Reproduction Fertilization is external and development includes tornoria larva. Reproduction in Balanoglossus Tornoria Larva resembles echinoderm larva 10

11. Embryo development and Neurulation. 11

12. Affinities of Hemichordates 12

13. Thank You 13