Simple Marine Organisms PLANKTON

Simple Marine Organisms – Jellyfish

Jellyfish Basics

·  Jellyfish are not fish nor do they taste good with peanut butter . Rather, they are primitive (they have been around for >500 million years ), gelatinous animals with stinging tentacles and one body opening.

·  Jellyfish and their relatives- including coral polyps and sea anemones - are in the phylum Cnidaria . Cnidarians are characterized by their ability to sting their prey with structures called cnidocytes .

Cnidocyte Structure

Before firing After firing

·  Cnidocytes are tiny, one-use, automatic, barbed, harpoon-like structures designed for impaling prey. They generally contain venom for paralyzing and digesting their victims.

Anatomy of a Jellyfish

·  A generalized jellyfish consists of a bell or hood , with tentacles hanging down.

·  They are extremely simple organisms, 95 - 98% water, one body opening that acts as both their mouth and anus , and no central nervous system.

·  Most do have light sensing structures called eye spots, and a nerve net , for coordination and movement.

Life Cycle of Jellyfish

·  Jellyfish can reproduce both sexually and asexually. They reproduce sexually in the adult medusa form, and asexually, through budding in the juvenile polyp form.

·  Although they are short lived- usually 3 - 6 months- some jellyfish can release upwards of 40,000 eggs daily!

·  Their fast development, ability to reproduce both sexually and asexually , and massive egg production allows jellyfish to produce blooms- very large numbers of organisms in a short period of time .

Common types of Jellyfish

Cannonball Jelly

·  Common along the east coast of the North and South America, these jellies are not especially venomous, and average 8 inches in diameter.

Moon Jelly

·  Also found in the Atlantic along the eastern U.S., this slightly venomous jelly averages 8 – 10 inches across its bell. It can be identified by the four crescent moon shapes atop its bell.

Box Jelly

·  This extremely venomous jellyfish kills more- many more- people than sharks do. It is found worldwide, but predominates in waters of the Indo-Pacific region.

Portuguese Man o’ War

·  Not a true jellyfish, rather a relative that is a colony of organisms called zooids working together, this surface drifting jelly can have tentacles up to 165 feet long, deliver a painful, possibly deadly sting, and can occur in significant numbers in places around our Atlantic and Gulf coasts.