Overview of:

Rotifers

Nematodes

Annelids

READINGS FOR LABS:

Plus, please be sure to read the following two articles on rotifers and nematodes before lab:

http://web.archive.org/web/20011101134452/http://www.animalnetwork.com/fish/library/articleview2.asp?Section=Aquarium+Frontiers+--+Without+A+Backbone&RecordNo=3212

http://web.archive.org/web/20010420231930/http://www.animalnetwork.com/fish/library/articleview2.asp?Section=&RecordNo=283

Additional reading on the annelid worms (a very nice overview of the polychetes in particular):

http://web.archive.org/web/20001201172800/http://www.animalnetwork.com/fish2/aqfm/1998/june/wb/default.asp

(the above article was written to follow an additional article that is not required reading, but that you might find interesting: http://web.archive.org/web/20010410004514/http://www.animalnetwork.com/fish2/aqfm/1998/may/wb/default.asp )

1. Phylum Rotifera - the rotifers

http://www.animalnetwork.com/fish/library/simage.asp?Src=aqfm_art/2001/sep/rotifers.jpg

2. Phylum Nemata: the nematodes (roundworms)

"If all the matter in the universe except the nematodes were swept away, our world would still be dimly recognizable...we would find its mountains, hills, valleys, rivers, lakes and oceans represented by a film of nematodes."

Nathan Augustus Cobb, 1914

3. Phylum Annelida - the annelid worms

See internal structure of an earthworm:

http://www.biologyjunction.com/images/earthw4.jpg

Movement in an earthworm (left) and leech (right):

• Oligochaeta - e.g. earthworms and related worms
  mostly land and freshwater
  earthworms feed on dead leaves, decomposing vegetation
  aquatic forms fed on variety of organic materials

  Tubificid worms (e.g. Tubifex species) are common oligochetes in polluted streams

• Polychaeta- polychaetes
  mostly marine

  Errant polychaetes -free living.

  These are the most important animals in marine sediments

  A few examples:

  fireworms

Parapodia on errant polychete:

• lugworms - live in burrows

• Terebellid worms (medusa worms and spaghetti worms):

Go to this link for photos of Terebellids: http://scilib.ucsd.edu/sio/nsf/fguide/annelida3.html

• Go to http://scilib.ucsd.edu/sio/nsf/fguide/annelida.html for photos of more polychetes

• Sessile polychaetes - a few examples
  Spionid worms: http://www.pmel.noaa.gov/vents/nemo/explorer/bio_gallery/biogallery-Info.00059.html
  Spirorbid worms - Photo of Spirorbid worms on Turtlegrass leaf
  Christmas tree worms - live in tubes burrowed into corals

http://www.sanctuaries.nos.noaa.gov/pgallery/pgflower/living/living_26.html

http://www.subaqua.ch/p014e.htm

"Feather duster" worms (Sabellid and Serpulid worms):

 

 

See photos at:

 

http://www.kasson.com/Solomons94/feadust1.htm

 

http://www.divegallery.com/tubeworm.htm

 

http://www.lawrence.edu/dept/biology/BIOL_81A/invert/invert31.jpg

 

Cross-section of a feather-duster worm feeding appendage:

• Hirundinoidea -leeches

Leech mouth (with teeth):

 

 

Leeches:

• live in freshwater (and on land in some moist climates)
• have "suckers" at front and back to hold on to things
• many feed on blood
  blood-feeders use anticoagulants to aid in feeding
  useful medicinally (even in current medicine)
• some are scavengers

Earthworms:

• hermaphrodites
• produce eggs in "cocoons"
• young look like small versions of adults

Polychaetes:

• most species release eggs and sperm into water

Photo of fireworms spawning in an aquarium (photo shows sperm release):

 

• Most species have planktonic larvae that don't look like adults

Diagram of trochophore larva of a polychete worm:

• Some polychetes have tail end with gonads break loose and swim away (this is called an epitoke) to release gametes higher in the water!

Epitoke of a polychete worm:

 

See http://web.augsburg.edu/~capman/photoofmonth/polychetesswimming.html for a short movie of swimming, spawning polychete worms on one of our aquaria.