Wize University Biology Textbook > Invertebrates (Part 2: Molting)
Nematodes (Roundworms)
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Phylum Nematoda (Roundworms)
These are simple ecdysozoans, the top picture here is of C. elegans which is a common model organism used to research neural development.
- Roundworms / Threadworms
- Compared to Annelids
- Lack segmentation
- Lack appendages
- Lack eyes
- One end is blunt, the other is pointed
- Undergo molting
- Simple body design
- Absorb nutrients
- Reproduce
- Pseudocoelomate
- Spiral cleavage
- Some hermaphroditic
- Direct developers
- Eutelic: organism grows when cells increase in size, not by adding new cells
- Born with set number of cells
- Removing a cell in embryo will permanently remove the cell
- Movement
- Longitudinal: side to side
- Free living
- In organic substrates
- Soil, freshwater, marine
- Some are parasitic, some are important in medicine
Top: C. elegans
Bottom: Soy Bean Cyst Nematode with Egg
Practice: Nematodes
Which of the following features of Nematodes differentiates them from Annelids? (select all that apply)