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
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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
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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
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4. 4
B.gigas is
The largest
Species, found
in Brazil.
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.
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6. EXTERNAL MORPHOLOGY
proboscis
collarette
collar
Branchial region
Gill pores
Genital wings
Mid dorsal ridge
hepatic caeca
Hepatic
reg.
Anus
Post
hepatic reg.
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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
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8. LOCALIZATION OF INTERNAL ORGANS
Proboscis
• It contains heart vesicle, central sinus and buccal
diverticulum.
• coelom opens to exterior by proboscis pore
Collar
• It contains the mouth and collar coelom, which
open to dorsal surface through collar pore.
Trunk
• It contains-pharynx, gonads or hepatic region.
• Branchio-genital region contains: genital wings
with gonad, branchial region with paired gills,
hepatic caecae.
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9. INTERNAL MORPHOLOGY
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10. REPRODUCTION
 Fertilization is external and development includes
tornoria larva.
Reproduction in
Balanoglossus
Tornoria Larva
resembles
echinoderm larva 10

11. EMBRYO DEVELOPMENT AND NEURULATION.
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12. AFFINITIES OF HEMICHORDATES
• Worm-like and segmented body.With Annelids
• Blastopore, enterocoelus coelom
and ciliated bands in the respective
larvae.
With
Echinoderms
• Presence of pharyngeal gill slits,
nerve cord and so-called
notochord.
With Chordates
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13. THANK YOU
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