Lab Topic 22
Protostomes II: Ecdysozoa and Great Diversity
Clade Ecdysozoa
Phylum Nematoda
(refer to latter portion of Lab Topic 20 for nematode study)
NOTE: Recent genetic information and futher study of nematodes have shown them to be closely related to arthropods. Their DNA similarity and the shared feature of ecdysis, shedding of exoskeleton during growth, placed them in the clade Ecdysozoa..

Ascaris

External Anatomy
Ascaris are intestinal parasites commonly found in animals.
Female Ascaris
Female Ascaris have a slight curve to thier posterior end unlike the hook on the posterior end of a male seen below.
Male Ascaris
   
Internal Anatomy whole opened ascaris coming soon!
     
 
In both male and female Ascaris, the pharynx and the thrashing movement of the nematode pumps food into the intestinal tract.
 
Male reproductive parts coming!
 
Close-up view of the female reproductive organs.
Close-up view of the male reproductive organs
     
Microscopic Anatomy
The imgage to the left is a cross section of a female Ascaris. The labels show the uterus(1), the oviduct(2), the intestine(3), and the pseudocoelom(4).
Review Questions for study of this phylum:
Why are nematodes considered to have pseudocoeloms and not true coeloms?
What kind of organs and or structures are involved in the following:
 

Feeding

  
  Circulation  
  Gas Exchange  
  Movement or support  
  Nervous/sensory response  
  Excretion  
  Reproduction  

Parasitic nematodes

Enterobius vermicularis

(commonly knows as pinworm)

 
Enterobius vermicularis is a common parasite which lives in the intestinal tract of humans.
 
 
Anterior end of parasite, 10X
Posterior end of parasite, 4X
 
Trichinella spiralis
  Uncooked pork infected with this parasite can be transferred to humans and infect muscle tissue. In some cases, it can be fatal. The pointer shows an infected specimen of encased larva in muscle tissue. Trichinosis is the common name for this infection.

 

 
Clade Ecdysozoa
Phylum Arthropoda
Subphylum Trilobitamorpha
Now extinct, trilobites occasionally can be found in the fossil record. This specimen was discovered in a stream bed in New Zealand.

Subphylum Chelicerata

(horseshoe crab, spiders, mites, scorpions, and ticks)
Horseshoe Crab
 
Dorsal view of horseshoe crab
 
 
 
The ventral side of this horseshoe crab shows the telson(1), carapace(2), chelate legs(3), and collapsed book lungs(4)
Close-up view of book lungs(1) and chelicera(2)
 
What unique features are found in animals of this subphylum?
     
Spiders
 
Dorsal view of spider showing the cephalothorax, abdomen, 8 legs, and 2 pedipalps
Close-up ventral view of spider abdomen. Note spinnerets at base of abdomen for making silk for webs.
 
 
Spider ocelli (4 pairs of simple eyes)
Spider pedipalps
     
Clade Ecdysozoa
Phylum Crustacea
Barnacles
 
 
Inside the calcified exoskeleton or carapace of this acorn barnacle(Balanus balanoides) lives a unique animal protected by hinged structures called opercular plates. Barnacles are sessile creatures that attach to most anything found in the water.
 
A gooseneck barnacle with 4 opercular plates comprising the operculum. They have opened slightly to show the cirri partially extended.
   
  Opening the carapace of a gooseneck barancle, one can see how the animal stores away the cirri used to gather good and protects other vital reproductive and digestive organs. .
A close up of cirri show the intricate almost feather like detail of this structure. How would this help in gathering food?
     
Daphnia
 
Commonly known as a water flea, this is an image from a prepared slide of the microcrustacean
Captured image of live Daphnia feeding.
     
     
     

Crayfish dissection

Subphylum Uniramia under construction

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Credits:
  
Photos by Allison Hall, and Linda Westgate  
Text and layout by Linda Westgate
Last update March 2008