1. ZOO 115 Invertebrate Zoology
Phylum Sipuncula

2. Phylum Sipuncula - General Characteristics
“Peanut worms”
~ 250 species
Similar to Annelids but NO segmentation
All marine – mostly shallow water
Usually burrow in mud or sand but some crawlers

3. Phylum Sipuncula - external anatomy
Two main body parts
Trunk
Introvert
Tentacles
Often have hooks

4. Phylum Sipuncula – Internal Anatomy
Contraction of circular muscles around fluid filled compensation sac causes fluid to fill hollow tentacles and extend them
Contraction of introvert retractors while relaxing circular muscles brings introvert back into trunk
Spacious coelom
Pressure from circular muscles
Introvert extended by squeezing body which forces fluid into it and extending it

5. Phylum Sipuncula - Locomotion
Hydrostatic skeleton (coelom)
Burrowing – sediment
Peristalsis
circular contract and longitudinal relax
Also use introvert
Burrowing – hard substrate
use secretions from epidermal glands
spines

6. Phylum Sipuncula - Feeding and Digestion
Most detritivores
mucus and cilia on tentacles
Direct Deposit feeders
use introvert and shortened tentacles
Suspension feeders

7. Phylum Sipuncula - Feeding and Digestion
Mouth
Some take up nutrients directly through body wall
Dorsal Anus
Mouth at end of introvert with muscular pharynx
U-shaped digestive tract – esophagus and intestine

8. Phylum Sipuncula – Excretion/Osmogregulation
Anus – solid waste
Metanephridia
one pair
Fairly resistant to osmotic stress

9. Phylum Sipuncula – Nervous system
Paired cerebral ganglia
Ventral nerve cord
Sense organs
Tactile throughout body but concentrated on tentacles
Many have nuchal organs (chemosensory) on introvert

10. Phylum Sipuncula - Respiration
Rock borers and burrowers in low-oxygen sediments
Use tentacles
Burrowers in oxygen-rich sediments
Use whole body surface
Tentacles and introvert
Some have special coelomic channels for gas transport

11. Phylum Sipuncula – Reproduction
Reasonable regenerative powers
Some use fission and regeneration to reproduce asexually.
Sexual
Dioecious
Gametes released and mature in coelom
Gametes transferred and stored in nephridia until released.
Male spawn triggered by environmental. Female spawn triggered by sperm in water

12. Phylum Sipuncula –Development
Cleavage – Spiral and holoblastic
have some cleavage patterns in common with molluscs.
Some direct developers
Some indirect developers
trochophore larvae
Some with pelagosphera larvae