Sponges and Cnidarians Overview

Study Notes

Sponges are the most primitive animals.
They lack distinct tissues, organs and a nervous system.
Sponges can regenerate from fragments.
They are filter feeders.
Choanocytes (collar cells) pump water through the sponge using flagella.
Flagella in the choanocytes capture food.
Choanocytes line inner chambers.
The fluorescent dye in the video highlights the water flow through the sponge's canals.

Cnidarians are predatory animals with stinging cells.
Cnidarians contain specialized cells called cnidocytes, which are used to paralyze their prey.
Cnidocytes contain nematocysts, a capsule with a coiled thread that can be ejected.
One anemone uses tentacles to fight off a rival.
Stomphia detach itself from the sea bed to escape a predator.
Preya represents two classic cnidarian forms: polyps and medusa.
Some jellyfish use a bell to propel themselves away from danger.

Sponges lack:
- Tissues
- Organs
- Nervous system
If you break a sponge apart with a sieve, each piece will regenerate into a new sponge.
Fluorescent dye demonstrates the movement of water through the sponge canals.
Collar cells (choanocytes) look like tiny cells with a collar and a flagellum.
When a particle runs into a collar cell, the flagellum whips around, creating a current that pulls the particle into the cell for digestion.

Cnidarians use stinging cells (nematocysts) to paralyze or capture their prey.
The battle between two anemones involves them stinging and fighting each other for territory.
When attacked by a sea star, Stomphia detaches itself from the ground and swims away.
The two classic forms brought together in Preya are polyps (stationary, like anemones) and medusas (free-swimming, like jellyfish).
When startled by a predator, a jellyfish can pulse its bell and swim quickly away.