Cnidarians Jellyfish, Corals Anemones and Hydroids

Cnidarians eat by stinging their prey so it becomes paralyzed, and then they bring the food into their stomach. Cnidarians eat mussels, fish, plankton, and worms.

Phylum Cnidaria 1. Soft bodied animals with stinging tentacles arranged in circles around the mouth 2. Radial Symmetry 3. Specialized cells and tissues, including nervous sys 4. Lifecycles often include two different stages: polyp and medusa 5. 3 Body layers: Ectoderm, Mesoderm, Endoderm 6. Nematocysts – stingers 7. Only one internal cavity, the digestive cavity, with a mouth, but no anus.

Life Cycle & Polymorphism Two basic types of individuals: polyps and medusae. Dominance of Medusa or Polyp lifecycle varies species to species.

Polyp = adapted for sedentary or sessile life. Tubular body w/ mouth at one end surrounded by tentacles. May live singly or in colonies. Polyp Stage of Life Cycle

Colonial polyps

Medusa Medusa = jellyfish form, free swimming and sexually mature form, bell-shaped or umbrella-shaped bodies, radial symmetry mouth centered on concave side, tentacles and one or more types of sense organs borne on rim of umbrella. Medusa provides dispersal mechanism so don't compete with parents. Mesoglea much thicker than in polyp - constitutes bulk of animal - makes it buoyant = "jelly" of jellyfish.

Medusa

CNIDARIANS have no bones, are hollow with 3 layers of cells. They live in salt or fresh water. When a cnidarian reproduces, the young hatch into the mother stomach, then, She spits them out.

Classification of Cnidarians Classes: Scyphozoa, Cubozoa and Anthozoa 1. Jellyfishes (Classes Scyphozoa and Cubozoa) are predominantly medusae w/ polyp stage very reduced or completely absent. 2. Corals and anemones (Class Anthozoa) are entirely polyps, no medusa.

The Portuguese Man o War wasn’t just a Ship

Physalia from Jamaica

Portugues e Man O War A tenacious hunter with a taste for fish and the poison to render most prey helpless Yikes!

Portuguese Man 'O War Physalia physalia Size: to 1 ft (float) and 50 ft (tentacles) Habitat: floats at the surface Notes: dangerous Fortunately, this creature, with its powerful battery of stinging tentacles, is more common in bays and protected waters than in the open ocean. The sting of the Man'O'War can vary from extremely painful to incapacitating to fatal, depending on the severity and the victim's reaction.

When a cnidarian reproduces, the young hatch into the mother’s stomach, then, she spits them out Jellyfish sting to defend themselves. The Man of War is poisonous to humans.

Other Dangerous Jellyfish Moon Jellyfish / Red Jellyfish ( Lion's Mane ) Aurelia aurita / Cyanea capillata Size: to 10" ( Moon Jellyfish ) to 36" ( Red Jellyfish ) Habitat: anywhere Notes: Jellyfishes are free-swimming relatives of corals, anemones, and hydroids. In fact, in many cases they are the same animal, just in a different stage of life ! Not all medusas ( as jellyfishes are called ) have a corresponding polyp stage, and likewise not all polyps have a corresponding medusa stage, but most conform to this life cycle. Small jellies ( up to 1" across ) are most likely the medusa stage of some hydroid, while large jellies are usually the dominant stage of a species in which the polyp stage is almost absent.hydroid Translucent Moon Jellies are harmless and quite common. Red Jellies have a painful wasp-like sting, but are usually much less common. And try as you might to avoid it, sooner or later every northern diver will get a stray tentacle draped across the face and lips - the only places exposed to attack.

Moon Jellyfish

Beached Moon Jellies: the surf has stripped away all the tentacles, leaving just a harmless dying blob of goo.

Red or Lion's Mane Jelly Avoid these. Swim away – swim away NOW! !

Nematocysts 1.Hold prey 2.Sticky -- aid in locomotion by attaching tentacles 3.Penetrate and anchor in prey and poison it.

Nematocysts can be Pretty

Nematocyst poison Most dangerous to man is Cubozoan jellyfish, the sea wasp (Chironex fleckeri). Caused more human suffering and death off Australian coasts than Physalia (Portuguese man-of-war) has in any of its home waters. Symptoms range from: 1. burning pain at site of contact 2. lesions and eruptions of various sorts, often severe enough to leave scars, 3. great pain, fever, and respiratory interference. 4. severe reactions due to shock & allergies 5. "Sting" of most is imperceptible to humans. Problems usually occur only when repeatedly stung.

Clown fish live in anemones, and coral and they’re immune to stings!

Fire Coral and Tube Anemone

Reproductive Characteristics Asexual reproduction by budding (in polyps) Sexual reproduction by gametes (in all medusae and some polyps). Sexual forms monoecious or dioecious; primitive gonads; ciliated free-swimming larva in life cycle of most