Lab 5 - Deuterostomia

The Deuterostomia contains three phyla the Echinodermata, the Hemichordata, and the Chordata. The Echinodermata includes the sea stars, basket stars, sea urchins, sand dollars, sea biscuits, and sea cucumbers. The Chordata includes the Urochordata, Cephalochordata, and the Vertebrata.

1. Echinodermata - Phylum Echinodermata have a pentamerous radial symmetry with rays or arms in multiples of five. They are entirely marine in distribution and mostly live in benthic habitats (ocean bottom).

	Starfish (Asteroidea)							Sea Urchin (Echinoidea)
	Sea Lily (Crinoidea)						Sea Cucumber (Holothuroidea)
				Basket Star (Ophiuroidea)
			Pictures courtesy of BIODIDAC

Classification - The Echinodermata are divided into five classes: Class Crinoidea (sea lilies), Class Asteroidea (Starfish), Class Ophiuroidea (brittle stars and basket stars), Echinoidea (sand dollars, sea urchins, and sea biscuits), Holothroidea (Sea cucumbers). Several other classes of Echinodermata are known only from fossils.

Morphology - The Echinoderms have an endoskeleton made of interlocking calcareous plates and spines. Echinoderms have a water vascular-system, an internal set of fluid filled canals, that lead to podia or tube feet that are hydraulically powered and used in location and in grasping substrates.

Fossil record - The earliest fossil echinoderms are from the Vendian to early Cambrian (600 - 525 myr bp).

Read more about the Echinodermata on the UCMP web site

Echinodermata on the Tree of Life web site

Echinodermata on the CAS web site

Echinodermata on the AnimalDiversity Web

Echinoderm Images Gallery Swedish Museum of Natural History

2. Hemichordata - Phylum Hemichordata have some chordate characteristics, but are not considered true chordates. There are approximately 300 described species found in marine habitats.

	Acorn worm (Balanoglossus) Hemichordata
	Pictures courtesy of BIODIDAC

Classification - The Hemichordata are divided into three classes: Class Enteropneusta (acorn worms), Class Pterobranchia, and Class Graptolithina. The Graptolithina are an extinct group that resembled the Pterobranchia.

Morphology - The Enteropneusta are worm like and have three body regions. The Pterobranchia are small and individual zooids are connected by stolons, making them colonial. Zooids are often less than 1 mm in length. The Pterobranchia live within tubes made of collagen secreted by special glands.

Fossil Record - The Graptolithina are common as fossils in rocks from the Ordovician (490 - 443 myr bp).

Read more about Hemichordata on the UCMP web site

Hemichordata on the Tree of Life web site

3. Chordata - Phylum Chordata includes the Urochordata, Cephalochordata, and Vertebrata. Five major characteristics distinguish chordates from other animals: the presence of pharyngeal slits, a dorsal nerve chord, a notochord (a cartilaginous rod supporting the nerve chord), and a post-anal tail (an extension of the body beyond the anus.

a. Urochordata - Subphylum Urochordata are also known as Tunicates or sea squirts. The body of an adult tunicate consists of two siphons (incurrent and excurrent), and a sac. Food is filtered from the water brought into the sac-like body. Adult tunicates often lose traits that distinguish them as chordates, but larval tunicates have the requisite traits to be classified as chordates. At least one Precambrian fossil has been assigned to the Urochordata.

	Sea Squirt or Tunicate (Urochordata)
	Pictures courtesy of BIODIDAC

b. Cephalochordata - Subphylum Cephalochordata are known as lancelets. Lancelets are small and found in sandy bottom marine habitats. Approximately 25 described species are found inhabit shallow water in tropical and subtropical regions. Their fossil record is sparse, but the earliest fossils date from the Mid ? Cambrian (myr bp).

	Lancelet (Amphioxus sp.; Cephalochordata)
		Pictures courtesy of BIODIDAC

c. Vertebrata - Subphylum Vertebrata are covered in Labs 6-10.

Read more about the Deuterostomia on the UCMP web site

Read more about the Chordata on the UCMP website

Chordata on the AnimalDiversity Web

Chordata on the Tree of Life web site

Lab 5 Exercise

1. Create a dichotomous key using three phyla from each of Labs 1, 2, 3, and 5 (total 12 phyla).
   
   
2. Some of us were able to see several members of the phylum Echinodermata and one species of the subphylum Urochordata at Pigeon Point. List three echinoderm species of at least 2 different classes and one urochordate species that are found in central California intertidal areas. Indicate what and how each eats. Fully cite the task using the CBE name year style or a comparable method.
   
   
3. Write a short research paper on the taxon that will be emailed to you.
   

Due Monday , March 20 .