Phylum Cnidaria: Jellies, anemones, corals and hydroids Cnidarians Phylum Cnidaria: Jellies, anemones, corals and hydroids Mrs. Covington: Marine Biology

Basic Facts Simple:slightly more complex than sponges Radial Symmetry: no head, front or back; looks the same from every side Abundant: Nearly 10,000 species (mostly found in warm, marine habitats)

Body Layers Body wall consists of 2 layers separated by jelly Layer 1: ECTODERM- muscle, nerve, or thread cells called nematocysts NEMATOCYST: contains stinging cells (cnidoblasts)with neurotoxic poison, used for defense and food capture.

Body Layers cont… Layer 1 and 2 are separated by the Mesoglea, a non-cellular, gel colloid Layer 2: ENDODERM- Digestion and absorption of food

Body Parts (sides) Oral Aboral Part 1: Oral- Digestive cavity, sac-like, the open end is the mouth Part 2: Aboral- Tentacles located around mouth, used to catch food and assist in movement

Diagram: Showing oral and aboral parts BOTTOM VIEW OF BODY Oral (mouth area) Aboral (tentacle area)

2 Body Forms (Stages) POLYP- mouth & tentacles face up, most are sessile MEDUSA- mouth & tentacles face down, free swimming

Jelly Reproduction Jellies are either male or female and reproduce sexually by releasing sperm into the water. Corals (& hydroids) may reproduce sexually by releasing egg and sperm or asexually by budding or fragmentation Jellies are either male or female and reproduce sexually by releasing egg & sperm into the water. Repro

Coral (& Hydroid) Reproduction                                   Asexually by budding or fragmentation Sexually by releasing egg and sperm

Practice Body Parts (Sides) Practice Body Forms (Stages)

CORAL REEFS: The most densely populated ecosystem on earth!

Types of Reefs 1. Fringing Reef- Grows close & parallel to shore as a narrow band (inner reef is flat, outer reef is sloped) *Barrier Reef- Farther off shore than fringing & separated by a lagoon. Parallel to shore, may be exposed at low tide

Andros Barrier Reef: 140 miles long! (3rd longest in the world ) Visible from east shore of Andros on the horizon…look for waves breaking.

Reef types cont… Atolls- Ring of reef with steep outer slopes enclosing a shallow lagoon *Patch Reef- Small, isolated growths of reef that usually form between fringing or barrier reef and the shore.

Illustration of Reef Types Fringing Reef Barrier Reef Atolls Patch Reef

Conditions for Reef Growth Hard Surface Shallow Water (165 ft. or less) Warm Water (about 68° F) Clear Water *Coral can grow ½ in. per year in good conditions! *Which side of Andros will have coral?

Importance of Algae to Coral Coral exhibits mutualistic symbiosis with Zooxanthellae Algae (dinoflagellates) Photosynthetic Dinoflagellates nourish corals with sugars which help them produce limestone corallite Corals feed mainly on zooplankton, with the help of zooxanthellae                                 

Competition, Predation, & Disease Corals may be overgrown by a different creature competing for space & light Some creatures attack coral, destroying it Some creatures eat coral but don’t destroy it, others graze heavily

Coral Aggression Corals will send out filaments to attack and digest another coral in its way! This would be an example of competition for space (light).                                                

Competition, Predation, & Disease cont… Coral bleaching: If stressed, corals expel algae causing loss of color. If algae are regained, it may recover Black-Band Disease caused by Cyanobacteria, kills coral as it grows Pollution Natural death by unknown causes

Man using dynamite to either blow up coral to sell or to kill reef fish…very, very bad!

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