Classification: Animalia Eumetazoa Bilateria Protostomia Ecdysozoa Nematoda Adenophorea Secernentea
Animalia: Animals, multicellular eukaryotic organisms, who are also heterotrophs.
Eumetazoa: Metazoans, another name for the animalia kingdom.
Bilateria: All bilaterally symmetrical animals, a front, back, upside, and downside. These animals also have three germ layers, which form during embryogenesis.
Protostomia: Protostomes are bilaterally symmetric with a triploblastic, three germ layers, and are classified by their presence of a coelom, body cavity.
Ecdysozoa: A group within the protostomia, whose mouths are the first to develop in the embryo.
Nematoda: Roundworms, bilaterally symmetrical, worm-like organisms that are surrounded by a strong and flexible non-cellular outer layer, called a cuticle.
Adenophorea: A nematode who does not have deirids or phasmids. A non-tubular excretory system and hypo dermal glands
Secernentea: Classified by numerous caudal papillae and an excretory system with lateral canals.
Eumetazoa: Metazoans, another name for the animalia kingdom.
Bilateria: All bilaterally symmetrical animals, a front, back, upside, and downside. These animals also have three germ layers, which form during embryogenesis.
Protostomia: Protostomes are bilaterally symmetric with a triploblastic, three germ layers, and are classified by their presence of a coelom, body cavity.
Ecdysozoa: A group within the protostomia, whose mouths are the first to develop in the embryo.
Nematoda: Roundworms, bilaterally symmetrical, worm-like organisms that are surrounded by a strong and flexible non-cellular outer layer, called a cuticle.
Adenophorea: A nematode who does not have deirids or phasmids. A non-tubular excretory system and hypo dermal glands
Secernentea: Classified by numerous caudal papillae and an excretory system with lateral canals.
- Nematode fossils are very hard to find because of their microscopic size and lack of hard structure.
- Some fossils have been found dating back to the Cambrian period, proving that nematodes have been around since over 500 million years ago.
- Since nematodes have a very simplistic body plan, their evolutionary developments have not been jurassic.
Some of the most defining characteristics which distinguish nematodes are:
- The nematodes lack of a vertebrae.
- They are bilaterally symmetrical, but are not segmented.
- The presence of an internal body cavity, or coelom. They are the first organisms found to have an internal body cavity, which contributes to more efficient mobility.
- Very few specific species of nematodes have been classified, because there are so many.
- Nematodes are very uniform in structure, so a classification has to be very specific to the individual body plan.
- Researchers believe that the shared ancestor of present day nematodes had the same basic characteristics and simple body plan as all roundworms.
- This would prove that the change and developments between a nematode ancestor and a present day nematode would be very small and unnoticeable.
- The common characteristic between round worms is the body cavity.
- Phylum nematoda is divided into two classes: the Secernentea and the Adenophorea.
- The Secernentea, also know as Phasmidia because of its sensitivity to the chemical on the tail of some nematodes, are usually land animals.
- Adenophorea, or Aphasmidia because of its lack of phasmids, are usually found in water.
- This is the closest breakup of nematodes that scientists have found so far. Since their is no definitive classification or common ancestor, scientists have not been able to fully agree on a phylogenetic tree.
When a study was done by the same scientist who found the genetic structure of C. elegans, she was able to find some relationships between a fly, a mouse, and a C. elegan:
- In figure A, the mouse and fly are more related than than either was to C. elegans.
- In figure B, the fly and the worm are more closely related than either is to the mouse.
- In figure C, the worm and the mouse are more closely related than either is to the fly.
- Additional data and more representations are needed to make this experiment more accurate, but increased data may prove an answer as to what the common ancestor of the nematode is, in the near future.