CNIDARIANS

What makes Cnidarians Unique? Cnidarians are group of animals that are very diverse from stony coral to jellyfish. What common thread keeps this phyla of animals together?

Common Thread Cniadarians are DIPLOBLASTIC (2 Layers – epidermis and gastrodermis) TRUE TISSUES(muscular, nervous, gastric) CNIDAE (stinging tentacles)

Diploblastic Body The two tissue layers are the epidermis and the gastrodermis Mesoglea- Jelly like portion between that separates the two layers.

True Tissues True tissues: muscular, nervous, gastric

Cnidae Cnidocytes used in defense, feeding, and attachment Some Cnidocytes can produce Nematocysts or stinging cells

Nematocysts Food gathering and defense. Long tube with spines that penetrates prey delivering toxin

Nematocysts

Two Body Forms Polyp: tentacle up (anenomes, coral, hydra) Medusa: tentacle down (jellyfish)

Polyp Stage Sessile, Asexual Reproduction, usually attached to substrate, some “walk”

Polyp Stage Budding Fission

Polyp Stage Polymorphism in polyps

Medusa Stage Dioecious, free swimming, sexual reproduction Develop reproductive organs (testis and ovaries)

Reproduction Sexual and Asexual reproduction Alternation of generations

Reproduction (sexual) Egg and Sperm released from GVC Once combined egg + sperm will form a planula (free swimming larva) Once GVC devolops forms a Polyp

Reproduction (asexual) Budding Fission

Alteration of Generations 2 Stages: Polyp & Medusa (dimorphic) Polyp Stage – some species asexual reproduction by budding, usually sessile

Nutrition Gastrovascular Cavity: Functions in digestion, the exchange of respiratory gases, metabolic waste, and release of gametes

Nutrition Feeding: Prey mostly small crustaceans (copepods) Nematocysts paralyze prey, contractile cells move prey to mouth, GVC releases enzymes

Skeletal System Hydrostatic – fluid filled body (mesoglea) Epitheliomuscular cells (longitudinal and circular)

Nervous System Nerve Net – Nervous system is spread throughout entire body Most primitive nervous system Some sensory structures – ocelli sense light

Circulation, excretion, respiration No special structures or tissues, these life functions are carried out directly with the environment

Hydrozoa Alteration of generation Mostly Marine (although a few freshwater) Hydra Obelia Physalia

Scyphozoa True Jellyfish Mostly found in Medusa stage Some harmful some not to humans Ocelli (rhodopalia) allow for Phototaxis (move toward light)

Cubozoa Box Jelly Fish Some possess dangerous nematocysts Active swimmers and feeders Tentacles on corners of medussa

Anthozoa Corals & Anemones Lack medusa stage

Anemones Can move slowly over some surfaces Live as individuals but in colonies Feed on fish and crustaceans or organic debris

Corals Secrete a calcium skeleton Stony coral, large polyped stony corals, and soft corals May use symbiotic algae called zooxanthelle for autotrophism. Can live individually or in groups.

Zooxanthelle Symbiotic Algae that provides food for the coral Found in reef- building coral

Soft Coral No hard calcium skeleton (although may contain fragments inside them)

Large Polyped Stony Coral (Octocoral) Have both soft tissue as well as produces a hard calcium skeleton

Stony Corals Little soft tissue mainly hard calcium skeleton

Reef building Corals can grow on one another to create entire reef systems

Issues Affecting Reefs Many Reef Ecosystems are in peril from being destroyed. There are many culprits aiding in destruction of the reefs.