Lab 3 – Ecdysozoa (8 phyla)
The Ecdysozoa are the animals that have an external exoskeleton that must be shed in order to grow in body size. The Ecdysozoa contains the insects, crustaceans, and spiders (Arthropoda), so it contains the greatest richness of species of any invertebrate grade. In addition to the Arthropoda, the Ecdysozoa contains 7 other phyla the largest being the Nematoda (roundworms). The purpose of this lab is to introduce you and familiarize you with the non-arthropod Ecdysozoan phlya.
- Onychophora – The Onychophora are also known as the “velvet worms.” They are found in forested regions in the tropics. Approximately 90 species have been described. The Onychophora are predaceous and forage on the forest floor at night or during rainy periods.
External features of Onychophora Details of
anterior of Onychophora
Internal anatomy of Onychophora Cross-section of an Oynchophoran
Pictures courtesy of BIODIDAC
Classification: The Onychophora is divided into one order the Onychophorida and two families: Family Peripatidae and Family Peripatopsidae.
Morphology: Onychophorans are worm like with paired antennae on the head. They have paired, un-jointed limbs with claws along the body used for locomotion. The Onychophora produce a sticky adhesive substance from an adhesive gland that is used in prey capture.
Fossil Record: Cambrian (543 – 490 myr bp)
Read more on Onychophora on the UCMP website
The Onychophora Homepage
Onychophora on Palaeos
- Tardigrada – The Tardigrada small, microscopic animals also know as “water bears.” Approximately 800 species have been described. Tardigrades live in marine and freshwater environments and in limno-terrestrial environments such as in water droplets on mosses and lichens. Tardigrades feed on the fluid of plant and animal cells and fungi. Tardigrades are adapted to environmental fluctuation and can enter a crytobiotic state I which their metabolism is reduced to 0.01% of active metabolism, and their moisture content to 1% or normal. In such a state, Tardigrades can survive for many years and hence escape death due to desiccation.
External features Tardigrada Internal anatomy of Tardigrada
Pictures courtesy of BIODIDAC
Classification: The Tradigrada is divided in one subphylum Pentastomida, and three orders Eutardigrada, Heterotardigrada, and Mesotardigrada.
Morphology: Tardigrades are less than 1 mm in size and have segmented bodies with four pairs of un-jointed limbs like Onychophora. The limbs terminate in 4-8 claws or discs.
Fossil Record: Cambrian (543 490 myr bp)
More on Tardigrada including pictures and video clips
More on Tardigrada from the South African Museum
More on Tardigrada
Tardigrada on Palaeos
- Nematoda – The Nematoda is also known as “roundworms.” There are approximately 15,000 described species. Nematodes are parasites of vertebrates, including humans, and plants, and are also free living predators, detritivores, and fungivores that live in the soil.
Male and female fresh water Details of posterior ends of male and
female Nematoda
Nematoda
Pictures courtesy of BIODIDAC
Classification: The Nematoda is divided into two classes: Class Adenophorea and Class Secernentea
Morphology: The external morphology of Nematodes is very simple. They are cylindrical worms that taper at both the anterior and posterior ends. Nematodes have no appendages, but have a chitinous cuticle that must be shed for growth to occur.
Fossil Record: Since most species are microscopic, few fossils have been found. Definite fossils date from the Carboniferous (354 - 290 myr bp), but Nematoda is like to have originated in the Cambrian.
Read more on Nematoda at the UCMP web site
Nematoda on the Tree of Life web site
Nematoda on the AnimalDiversity Web
More on Nematoda
- Nematomorpha – The Nematomorpha are also known as the “horse-hair worms.” There are about 300 described species found in mostly in freshwater and a few in marine. All Nematomorpha are parasitic during part of their life cycle, but they are usually parasites of insects. The adults are free living in aquatic environments. Nematomorph worms are usually 15-25 cm in length, but some species reach a length of 2 meters.
External features of Nematomorpha Larval
Nematomorph worm
Nematomorph worm parasitizing a grasshopper
Pictures courtesy of BIODIDAC
Classification: The Nematomorpha is divided into two classes: Class Gordioida and Class Nectonematoida.
Morphology: Nematomorph are long thin un-segmented worms.
Fossil Record: Unknown.
Nematomorpha on the Tree of Life web site
More on Nematomorpha
The Nematomorpha Page
Nematomorpha on the Animal Diversity Web
- Kinorhyncha – The Kinorhyncha are also known as the “spiny-headed worms.” Kinorhyncha are found in marine mud and sand where they feed on bacteria. There are approximately 150 described species of Kinorhyncha.
External features of Kinorhyncha Cross-section of a
Kinorhyncha
Pictures courtesy of BIODIDAC
Classification: The Kinorhyncha are divided into two orders: Order Cyclorhagida and Order Homalorhagida.
Morphology: The Kinorhyncha are microscopic worms with an eversible, spiny proboscis that is extended from the anterior of the head.
Fossil Record: Unknown from fossils
Read more on Kinorhyncha on the UCMP web site
Kinorhyncha on the Tree of Life web site
Kinorhyncha on the AnimalDiversity Web
More on Kinorhyncha
- Loricifera – The Loricifera are a recently discovered group of diminutive animals. Only 10 species have been described so far. Loriciferans are microscopic and live adhered to marine sand and gravel.
Pictures courtesy of BIODIDAC
Classification: The Loricifera are divided into two genera: Nanaloricus and Pliciloricus.
Morphology: Microscopic animals with spiny heads and an un-segmented body. The anterior of the body is vase-shaped and can retract into the posterior or trunk of the animal.
Fossil Record: Unknown from fossils
Read more on Loricifera on the UCMP web site
Loricifera on the AnimalDiversity Web
Loricifera on the Tree of Life web site
- Priapulida – The Priapulida are marine worms that burrow in sediments. Some species reach several centimeters in length. Priapulids are predators often of polychaete worms. There are 16 described species of Priapulida.
External features of a Pripulid worm
Internal anatomy of a Priapulid worm
Pictures courtesy of BIODIDAC
Classification: The Priapulida are divided into three families: Maccabeidae, Priapulidae, and Tubiluchidae.
Morphology: Priapulids are un-segmented and worm-like. They have a spiny body and an eversible proboscis used in feeding and locomotion
Fossil Record: Cambrian (543-490 myr bp)
Read more on the Priapulida on the UCMP web site
Priapulida on the Tree of Life web site
Priapulida at the Smithsonian Institution
Priapulida on the Animal Diversity Web
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Lab 3 Exercise
You will need to use the web sites linked to this lab to complete the tasks outlined below.
- Prepare a dichotomous key to the 7 phyla covered in this lab. Try to use readily observable traits as a basis for the couplet questions (e.g., morphological traits, habitat distribution, and geographical distribution). Can you add a couplet that separates these phyla from all that we have discussed before?
- Choose any two of the drawings in this lab that show the internal anatomy of members of two phyla and try to label the organ/organ systems that are depicted.
- Choose any two drawings that depict the external anatomy of members of two phyla and try to label the external morphological features depicted in those drawings.
- Try to locate 3 more useful links that deal with any of these Edysozoan phyla.