ZOO 115 Invertebrate Zoology Phylum Sipuncula Phylum Sipuncula

ZOO 115 Invertebrate Zoology Phylum Sipuncula

Phylum Sipuncula - General Characteristics n n “Peanut worms” ~ 250 species Similar to Annelids but NO segmentation All marine – mostly shallow water n Usually burrow in mud or sand but some crawlers http: //www. ucmp. berkeley. edu/sipuncula/sipunculids_big. jpg

Phylum Sipuncula - external anatomy n Two main body parts n n http: //www. calacademy. org/research/izg/SFBay 2 K/peanutworm. htm Trunk Introvert Tentacles n Often have hooks n http: //www. calacademy. org/research/izg/SFBay 2 K/peanutworm. htm nhttp: //www. gulfspecimen. org/Phylum. Sipuncula. html

Phylum Sipuncula – Internal Anatomy n Spacious coelom n n Introvert extended by Contraction of circular introvert squeezing body which retractorsaround muscles while fluid forces fluid into it and relaxing filled compensation circular sac extending it to fill musclesfluid causes brings introverttentacles hollow back intoand trunk extend them http: //bio. classes. ucsc. edu/bio 136/sipuncula. html Pressure from circular muscles

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

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

Phylum Sipuncula - Feeding and Digestion n Mouth Some take up nutrients directly through body Dorsal Anus wall Mouth at end of introvert with muscular pharynx U-shaped digestive tract – esophagus and intestine http: //www. ucmp. berkeley. edu/sipuncula/sipunculids_big. jpg

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

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

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

Phylum Sipuncula – Reproduction n Reasonable regenerative powers n n Some use fission and regeneration to reproduce asexually. Sexual n n 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

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