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Sipuncula (Peanut Worms)
Transcript of Sipuncula (Peanut Worms)
Fluid-filled coelom that acts as a hydrostatic skeleton
U-shaped gut with mouth and anus
Live in marine environments
Unsegmented with body divided into trunk and retractable introvert
Mouth surrounded by ciliated tentacles
Two nephridia present
possess various introvert hooks
Diet and Feeding Habits
Most are filter feeders who use their tentacles to push in algae and sediment.
Some use their introvert hooks to scrape sediment and organisms in from the surrounding surface.
Most are dioceious
Gametes collect in nephridia, excretory organs that are modified gamete storage organs. Then released into water from nephridiopores. Fertilization external.
Spiral cleavage of the zygote creates a trochophore (free-swimming) larva, which will undergo metamorphosis to its characteristic shape.
No circulatory system
Introvert tentacles probably function as gills
Brain with single branching ventral nerve cord
Main nerve cord runs down the center of the ventral side.
Simple photoreceptors, surface covered with sensory cells.
Nephasoma minutum are the only known hermaphroditic worm from the phylum
It is called a peanut worm because of the shape of its anterior end resembling a peanut kernel
Capable of regeneration
Phylum Sipuncula (Peanut Worms)
Model Organism, Fish Bait
Inhabit Mollusc Shells
Sydney Harter & Alana Einspahr