Diversity

1. ALLIZAAZHAR
22011514-006
Department of Zoology

2. Content:
 Introduction
 General characters
 Classes of hemichordates
 Class Enteropneusta
• Characters
• Structure
• Feeding and digestion
• Nervous system
• Gas Exchange
• Circulation

3. Content:
• Excretion
• Reproduction
 Class Pterobranchia
• Structure
• Maintenance and function
• Reproduction and development

4. Introduction:
Hemi means half, chorda means chord
Habitat: Live in marine environment
Deuterostomates (Anus develops first)

5. General characteristics
 Worm like body
Bilateral symmetry
Triploblastic organisms
Have true body cavity
Three major body parts:
1. Proboscis
2. Collar
3. Trunk
 Pharyngeal slits are ciliated

6. Cont….
Complete digestive system
Open circulatory system
Dorsal and tubular nerve chord present
Live alone or form colonies

7. Classes of Hemichordates:
Classes of
hemichordates include:
Enteropneusta
(Acorn worms)
Pterobranchia
(Pterobranchs)

8. Class Enteropneusta:
 Habitat: Marine environment
 Size: 10-40 cm long, some are 2 m longs
 Species: 70 species are described by zoologist

9. Characters:
 Commonly called acorn worms
 Three body parts; Proboscis, collar and trunk
 Mostly occupy U-shaped burrow in muddy and sandy
substrates
 Body remain in sand while mouth and anus remain
outside

10. Structure:
Proboscis:
• Projection at anterior end
• Short and conical projection
Collar:
• Ring like collar
• Present posterior to proboscis
Trunk:
• Third and posterior part of body
• Trunk is elongated

11. Cont….
 Acorn worm cover with ciliated epidermis and gland
cells
 Mouth present ventrally between collar and proboscis
 Pharyngeal slit present laterally on trunk
 Slits few to hundred
 Pharyngeal slits are opening between digestive tract
and outside of body

12. Feeding and digestion:
Feeding:
Cilia and mucus help the food to move toward mouth
Food particles attached with mucoid proboscis
Smaller particles are selected
Large particles rejected
Small particles enter the mouth
Digestive system:
Digestive tract is simple tube
Contain extended part called diverticula of gut
Release enzymes for digestion

13. Cont….
 Posterior part involve in defecation
 Fecal round material is called casting

14. Nervous system:
 Ectodermal in origin
 Present below ciliated epidermis
 Consist of dorsal tubular nerve chord
 Network of nerve cell; nerve plexus present
 Some contain giant fibers in dorsal nerve chord
 No major ganglia
 Sensory receptors are unspecialized

15. Gas Exchange:
No respiratory system
Gases exchange take place through
diffusion
Gases exchange occur through
pharyngeal slit when water move in
them

16. Circulation:
Two contractile blood vessels present
• Dorsal contractile blood vessel
• Ventral contractile blood vessel
Direction of blood flow:
Blood flow posterior to anterior in dorsal blood vessel
Blood from anterior to posterior in ventral blood vessel
Branches of blood vessels lead to sinuses of body
Flowing blood anteriorly enter in in to series of blood vessel in proboscis ;
Glomerulus

17. Excretion:
Excretory waste filtered from base of
glomerulus into coelom of proboscis
Release from pores of proboscis to
outside
Blood is colorless and lack respiratory
pigments
It just transport food and waste of body

18. Reproduction:
Dioecious
Two rows of
gonads in
front of trunk
Gonads open
outside to
body
External
fertilization
They release
spawning
pheromones
ciliated larvae
formed;
Tornaria
larvae
Float on
surface of
water and
transformed
to adult

19. Class Pterobranchia
Small class of
hemichordate
Habitat: Deep
oceanic water
20 Species
Asexually
produced
colonies

20. Diagram:

21. Structure:
Size: 0.1-5mm
Body consist of three regions
• Proboscis
• Collar
• Trunk
Proboscis is expanded and shield like
They secrete tubes and move in tubes
Collar contains 2-9 arm like ciliated tentacles
Trunk is U-shaped

23. Maintenance and function
Tentacles
present
There cilia
involve in
filter
feeding
and food
capturing
Cilia trap
and
transport
food
toward
mouth
Only one
genus
contains
single pair
of
pharyngeal
slits
Excretory
and
respiratory
structure
not present
Gases
exchange
and
excretion
take place
through
diffusion

24. Reproduction and development
• Budding is
common
• Make a
colony
Asexual
reproduction:

25. Cont….
• Most species are dioecious
• External fertilization
• Planula larvae is formed
• Lived in female secreted
tubes
• After metamorphosis
transformed in to adult
Sexual
reproduction:

26. Questions?