1. ZOO115 Invertebrate Zoology
Phylum Onychophora

2. Onychophora (Talon bearer)- General Characteristics
Common name: Velvet worms
Intermediate between annelids and arthropods
~110 species
Fossil records from Early Cambrian period (~530 MYA)
Terrestrial
Dark humid tropical regions

3. Onychophora - General Characteristics
Soft-bodied
Wormlike 5mm-15cm in length
Segmented with serial repetition of organs

4. Onychophora – Support Body is covered by thin chitinous cuticle
Similar to arthropods
Highly permeable
Flexible
Accordion-like
Longitudinal, circular, diagonal and surface oblique muscles
Body wall, other than cuticle, similar to Annelids
Circular/Diagonal muscle
Longitudinal muscle
Hemocoel
Slime gland
Oblique muscle
Attached to surface

5. Onychophora - Locomotion
Trunk bears pairs of appendages
with claws
Like parapodia of polychaetes
Operated as part of the hemocoel

6. Onychophora - Nutrition
Carnivores - eat small arthropods
Secrete jets of slime up to 30 cm to entangle prey
Lacerate prey with mandibles (jaws)
Secrete saliva with hydrolytic enzymes
Pharynx pumps liquid food into stomach

7. Onychophora - Digestion
Chitin-lined foregut (pharynx and esophagus
midgut (intestine – digestion and absorption
Slime gland

8. Onychophora - Excretion
Anus for solid waste
Nephridia - like arthropods

9. Onychophora – Circulation
Open system similar to arthropods
tubular heart with pericardial sinus
large hemocoel
Gas exchange
small openings in each segment– Spiracles
lead to tracheal tubes
Heart
From Brusca and Brusca (2003)
Hemocoel
Nephridia

10. Onychophora - Nervous system
Ladderlike nervous system - like both annelids and arthropods
Paired ventral nerve cord
Sensory
Antennae
Eyes at base of antennae
Sensilla on sensory papillae

11. Onychophora - Reproduction
Separate sexes
Sexually dimorphic
Males smaller
Sperm transferred by spermatophore
In Peripatopsis, spermataphores placed anywhere on female, her cuticle temporarily dissolves and takes up the sperm.
Most bear live young