Medusa

Definition

A medusa is a free-swimming, gelatinous form of certain cnidarians, such as jellyfish. It typically has a bell-shaped body with tentacles hanging down.

5 Must Know Facts For Your Next Test

1. Medusas are one of the two main life stages of cnidarians, the other being the polyp.
2. They move by contracting their bell and expelling water, a process known as jet propulsion.
3. Medusas reproduce sexually, releasing eggs and sperm into the water where fertilization occurs.
4. Their tentacles are equipped with specialized cells called cnidocytes that contain nematocysts for capturing prey and defense.
5. Medusas can vary greatly in size, from a few millimeters to several meters in diameter.

Review Questions

• What are the main characteristics that distinguish a medusa from other life stages of cnidarians?
• How do medusas move through the water?
• What role do nematocysts play in the life of a medusa?

Related terms

Polyp:

A sessile, tubular form of certain cnidarians that attaches to surfaces and reproduces asexually.

Cnidocyte: A specialized cell found in cnidarians used for capturing prey and defense, containing stinging structures known as nematocysts.

Nematocyst: A stinging structure within cnidocytes used by cnidarians to inject toxins into prey or predators.