Zoology 250 Lecture 19
PHYLUM SIPUNCULA (peanut worms)
- 1) Widespread phylum of approx. 300 species; marine deposit feeders
- 2) The bizarre body plan includes:
- a) two coeloms (small- tentacles, large- trunk)
- b) completely invertable head end! (introvert)
- c) crown of tentacles surrounding mouth
- d) unusual gut (terminal mouth, mid-dorsal anus)
- 3) Related to molluscs by several distinctive characteristics:
- a) molluscan cross (apparent at the 64 stage embryo)
- b) eversible scraping buccal organ in larva; some think it may be related to the radula in gastropods
- c) creeping muscular lip; some think it may be related to the creeping foot in benthic molluscs
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(revised Jan. 14, 1999)