ZOO 115 Invertebrate Zoology Phylum Sipuncula

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

Phylum Sipuncula - external anatomy http://www.gulfspecimen.org/PhylumSipuncula.html http://www.calacademy.org/research/izg/SFBay2K/peanutworm.htm http://www.calacademy.org/research/izg/SFBay2K/peanutworm.htm Two main body parts Trunk Introvert Tentacles Often have hooks http://www.calacademy.org/research/izg/SFBay2K/peanutworm.htm

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 http://bio.classes.ucsc.edu/bio136/sipuncula/sipuncula.html Pressure from circular muscles Introvert extended by squeezing body which forces fluid into it and extending it

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

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

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

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

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

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

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

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