Phylum: Onychophora, Example: Peripatus Topic for II Semester B.Sc. Zoology Students

3. PHYLUM: ONYCHOPHORA
Eg.: PERIPATUS

4. Onychophora
Includes small group of Primitive Worm like and
Bilaterally symmetrical animals
Commonly known as Velvet Worms or Walking Worms
They exhibits several important Annelidan characters
and Arthropodan characters.
They act as the connecting link between annelids and
arthropods.
They exhibit discontinuous distribution: ie they are seen
in widely separated, geographically discontinuous &
relatively restricted areas.
This group is very ancient & its members have not
undergone significant evolutionary changes since the
Cambrian period & hence they are also called as living
fossils

5.  PERIPATUS
 Peripatus is a soft
bodied wormlike,
& bilaterally smetrical
 It looks like a
caterpillar
 It is nocturnal & feeds
on small insects
 Male and Female sexes are separate (gonochoric)
 Development is direct without larval stages
 Peripatus is seen in neotropical regions like West
Indies, America, Congo, Australia, Tasmania, New-
Zealand, Malaya etc.
 It exhibits discontinuous'distribution".

6. Peripatus is a unique organism.
It forms a connecting link between Annelids are
Arthropods.
It exhibits several important Annelidan
characters and Arthropodan characters.
In addition to these, Peripatus exhibits some
peculiar characters not shown by either
Annelids or Arthropods.

7. Annelidan Characters:
1) Presence of worm like body with bilateral
symmetry.
2) Absence of distinct head region.
3) Presence of thin & flexible cuticle.
4) Presence of dermomuscular body wall with circular
and longitudinal muscles.
5) Presence of a pair of simple eyes, similar to
polychaetes, on the dorsal side of head.

8. 6) Presence of hollow, un jointed parapodia like
appendages
7) Presence of paired Nephridia in every segment.
8) Presence of cilia in the reproductive ducts
9) Alimentary canal is straight with terminal
mouth and anus
Annelidan Characters contd..

9. Arthropodan Characters:
1) Presence of a chitinous cuticle.
2) Presence of antennae
3) Presence of claws in the appendages
4) Presence of jaws in the mouth which are
modified appendages.
5) Presence of haemocoel

10. 6) Presence of tracheal system for respiration
7) Presence of Salivary glands.
8) Development is mainly arthropodan type
9) Presence of long, tubular and dorsal heart with
a pair of opening in each segment (ostia).
Arthropodan Characters contd..

11. Primitive characters of Peripatus:
1) Presence of superficial segmentation of the body.
2) Three segmented head: condition in b/w that of
annelids& arthropods
3) Antennae are not homologous with arthropod
antennae
4) Presence of velvety skin.
5) Presence of only one pair of jaws in the mouth cavity.
6) Legs are un jointed, short, hollow & clawed
7) Distribution of spiracles are irregular
8) Ventral nerve cords are widely separated, True ganglia
are absent

12. Thank You