|BIO190: The Class: Pseudocoelomates: Lesson 16|
Characteristics of pseudocoelomate phyla (p. 303)
Visit these web sites for more information on Rotifera:
Rotifer Systematics Database
Rotifera derive their name from the characteristic ciliated crown, or corona, that, when bearing, often gives the impression of rotating wheels.
Gastrotricha includes small, ventrally flattened animals about 65 to 500 um long, somewhat like rotifers, but lacking the corona and mastaz. They have a characteristically bristly or scaly body.
Kinorhyncha are marine worms a little larger than rotifers and gastrotrichs, but usually not more than 1mm long.
Phylum Loricifera (fig. 16-8)
The Loricifera are tiny animals (0.25 mm long)that live in the space between the grains of marine gravel.
Phylum Priapulida (fig. 16-9)
The Priapulida are a small group (only 15 species of marine worms found chiefly in the colder waters of both hemispheres).
Phylum Nematoda (fig. 16-10 & 16-17; tab. 16-1)
Known as roundworms. Nematoda live in the sea, in freshwater, and in the soil, from polar regions to the tropics.
most numerous of all pseudocoelomates
female adult worm in human intestines lays
eggs pass with feces -->
eggs injested by human -->
eggs hatch in to larva -->
larva burrow through intestinal wall and enter blood stream -->
larva go through several molts -->
travel to lungs and exit through the aveloi -->
these are coughed up and swallowed -->
pass into intestines and mature into adults
View this site on Ascaris lumbricoides:
Review LC hookworms (p. 311); trichina (p.312); pinworm (p. 312); filarial worms (p. 319)
The popular name for the Nematomorpha is "horsehair worms" based on an old superstition that the worms arise from horsehairs that happened to fall into the water, and they look something like hairs from a horse's tail.
Phylum Acanthocephala (fig. 16-19 --> 16-20)
The members of the phylum Acanthocephala are commonly known as spiny-headed worms.
Phylum Entoprocta (fig. 16-21)
Entoprocta is a small phylum of about 150 species of tiny, sessile animals.
See phylogeny/Adaptive Radiation (pg. 317)
Once you have completed the lesson, you should go to Assignment 16-1.
E-mail Sylvester Allred at
Northern Arizona University
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