BIO 385 Invertebrate Zoology
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Invertebrate Diversity
Phylum Annelida

(Click on any image for larger version)

Annelid Characteristics

  • Well developed true coelom
  • Segmented (reduced or lost in some)
  • Complete digestive tract with regional specialization
  • Closed circulatory system with respiratory pigments
  • Well-developed nervous system
  • Usually with lateral chaetae (spines) on each segment
  • Marine, fresh water, and terrestrial environments

Class Polychaeta
Subclass Errantia Bristle Worms


  • Numerous chaetae (setae) on segments
  • Most have parapodia
  • Most have sensory tentacles and eyes on head
  • Most have chitinous jaws
  • Lack clitellum
  • Mostly marine
  • Mobile: crawl over substrates or swim
  • The monophyly of this group is not certain
Scale Worm
Scale Worm, Halosydna brevisetosa, CA
Calif Fireworm
California Fireworm, Pareurythoe californica; La Jolla, CA
Bristle worm
Orange Fireworm, Eurythoe complanata
Paddle Worm
Blood Worm, Glycera sp., La Jolla, CA
Glycinde Worm
Polychaete Worm, possibly Glycinde sp., CA; and tubes of Spiral tube worms Spirorbis sp.
Paddle Worm
Paddle Worm, possibly Phyllodoces sp., VA

Class Polychaeta
Subclass Sedentaria Tube and Fan-headed Worms


  • Parapodia and chaetae often reduced or lost
  • Most are sedentary, living in burrows or secreted tubes
  • Many with feathery tentacles for feeding
  • Mostly filter feeders or suspension feeders
  • This subclass may be paraphyletic
Xmas Tree Worms
Christmas Tree Worms Spirobranchus giganteus; two color variations
Sabellid Tube Worm
Feather-duster Worm, Eudistyla sp.
Feather-duster Worms
Red Tube Worm, Serpula sp.
Feather-duster Worms
Sabellid Tube Worms, possibly Sabella sp., on Mangrove Roots, Belize
Bispira Fan Worm
Fan Worm, Bispira sp.?
Spiral Tubeworms
Spiral Tubeworms, Pileolaria sp. (note also acoel flatworm in lower left)
Parchment Worm
Parchment Worm, Chaetopterus sp., preserved specimen (the phylogenetic position of parchment worms is uncertain)
Spaghetti Worm
Spaghetti Worm, Terebella californica?, tentacles. The numerous fine tentacles are used to locate small food particles.
Spionid Tube Worm
Spionid Tube Worm

Class Clitellata
Subclass Oligochaeta Earthworms


  • Few chaetae; lack parapodia
  • Little structural specialization of head
  • Presence of clitellum (forms muscus and egg cocoon)
  • Mostly in terrestrial or fresh water environments
Earthworm Dissection
Dissected Earthworm, Lumbricus sp.
See also labeled photo.
Earthworm, Lumbricus sp., CA
Fresh-water worm, Dero sp.
Earthworm, Lumbricus sp., stained cross-section slide, posterior to clitellum; 40x
See also labeled photo.
Tubifex Worms
Tubifex sp. Worms, a fresh-water species
Fresh-water worm, Stylaria sp.

Class Clitellata
Subclass Hirudinea Leeches


  • Segmenting less defined; body not divided by septa
  • Clitellum present
  • Lack setae or parapodia
  • Have a posterior sucker and usually also an anterior sucker
  • Mostly in fresh water, a few are marine and semi-terrestrial
  • May be scavengers, predators, or external parasites
Leech slide
Leech, wholemount slide
See also labeled photo.
2 Species of Leeches
Two species of freshwater leeches. Large individual on left is Erpobdella sp.; Two smaller species on right are glossiphid leeches, possibly Helobdella sp. Also unidentified egg capsules. Phoenix, AZ
Predatory leech, probably Nephelopsis obscura, showing ventral surface and suckers
Erpobdella Leeches
Scavenging leech, possibly Erpobdella sp., KY

Class Echiura Spoon Worms


  • Unsegmented (most likely secondarily lost)
  • Muscular, non-retractable proboscis with a groove (gutter)
  • Many have chaetae or warty skin
  • Long gut with with posterior anus
  • Marine sediments: deposit or suspension feeders
  • Formerly considered a separate phylum
Innkeeper Worm
Innkeeper Worm, Urechis caupo, preserved specimen

Class Sipuncula Peanut Worms


  • Unsegmented (secondarily lost?)
  • Anterior introvert can be fully withdrawn
  • Fluid-filled tentacles around mouth
  • Gut U-shaped; anus near introvert
  • Live in marine sediments
  • Formerly considered a separate phylum
Sipunculan Dissection
Dissected Peanut Worm, Sipuncula sp.
See also labeled photo.
Peanut Worm
Peanut Worm, Phascolosoma agassizzii, CA
Peanut Worm
Peanut Worm, Phascolosoma sp.
This page last updated 24 July 2015 by Udo M. Savalli ()
Images and text Udo M. Savalli. All rights reserved.