ZOO 115 Invertebrate Zoology

1. ZOO 115 Invertebrate Zoology Phylum Sipuncula

2. http://www.ucmp.berkeley.edu/sipuncula/sipunculids_big.jpg 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. http://www.calacademy.org/research/izg/SFBay2K/peanutworm.htmhttp://www.calacademy.org/research/izg/SFBay2K/peanutworm.htm http://www.calacademy.org/research/izg/SFBay2K/peanutworm.htm http://www.gulfspecimen.org/PhylumSipuncula.html http://www.calacademy.org/research/izg/SFBay2K/peanutworm.htm Phylum Sipuncula - external anatomy • Two main body parts • Trunk • Introvert • Tentacles • Often have hooks

4. Introvert extended by squeezing body which forces fluid into it and extending it • Contraction of introvert retractors while relaxing circular muscles brings introvert back into trunk • Contraction of circular muscles around fluid filled compensation sac causes fluid to fill hollow tentacles and extend them Pressure from circular muscles http://bio.classes.ucsc.edu/bio136/sipuncula/sipuncula.html Phylum Sipuncula – Internal Anatomy • Spacious coelom

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 • mucus and cilia on tentacles

7. Mouth Dorsal Anus http://www.ucmp.berkeley.edu/sipuncula/sipunculids_big.jpg Phylum Sipuncula - Feeding and Digestion • Some take up nutrients directly through body wall • 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 • 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