Cnidaria - The Stingers!
Defining Characteristics
- has true tissue - diploblastic (ectoderm & endoderm)
- radial symmetry
- has a nerve net nervous system (statocysts - balance & ocelli - eyes)
- incomplete digestive system (mouth=anus)
- Alternation of Generation - polyp and medusa
- contains cnidocytes which contains nematocytes
- predators
- asexual reproduction through budding
- sexual reproduction by motile gametes
- live in fresh and salt water
- Three classes: Hydrozoa - polyp dominant, Anthrozoa - only polyp (generally), Scyphozoa - medusa dominant
Lab results
ANALYSIS
- Alternation of Generations. Polyp stage: stationary, reproduces asexually via budding, develops into medusa. Medusa stage: motile, reproduces sexually via gametes.
- The cnidocytes are cells that are lining the tentacles of jellies. Within the cnidocyte, there is a nematocysts which is fired out the cnidocyte into its prey.
- When something hits the tentacles of a jelly, it hits the triggers on the cnidocytes. This causes the operculum to open, and the nematocyst inside the cnidocyte fires out. The nematocysts is connected to the cnidocyte by the nematocyst tube. Venom is passed through the tube into the prey. The tentacles pull the victim into its digestive system.
- Feeding polyp: captures food (nutrients) on the tentacles which pulls the food into the digestive system through the mouth/anus. Reproducing polyp: produces medusa. Medusa: moves around and reproduces sexually with gametes
- Similar: medusa and polyp stages, diploblastic, predators, alternation of generation, cnidarians, asexual reproduction. Scyphozoa: medusa dominant. Hydrozoa: polyp dominant, medusa is used for species dispersal