Hello, my name is Rickson and welcome to my blog. The blog talks about Papua New Guinea's untouched Natural environment and how best we utilize, without harming or endangering them.
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Sunday, March 7, 2010

CNIDARIANS - Hydrozoans and Sea Jellies

Mastigias papua - Papuan sea jelly (Photo: Selma P.)

The Phylum Cnidaria is a large group of over 10 000 species that includes hydroids, sea wasps, hard corals, soft corals, sea fans, corallimorphs, sea anemones, sea pens, black corals and zoanthids. All Cnidarians have tentacles with stinging cells in their tips which are used to capture and subdue prey. In fact, the phylum name "Cnidarian" literally means "stinging creature." The stinging cells are called cnidocytes and contain a structure called a nematocyst. The nematocyst is a coiled thread-like stinger. When the nematocyst is called upon to fire, the thread is uncoiled, and springs straight. The harpoon-like thread punctures through the cnidocyte wall and into the prey. Most Cnidarians also have a toxin in their stinger which helps to disable the prey. The nematocyst is fired either by the tentacle touching something, or in some cases by a nerve impulse from the animal telling it to fire.

Mastigias papua -Papuan sea jelly (Photo: Selma P.)

Hydrozoans include hydrocorals; hydroids, or sea ferns and floating sea jelly. Some are solitary, meaning that they live alone, but some are colonial, meaning that they live in groups, connected together with living tissue, and share food resources.

Hydrocorals have calcareous skeletons and look like hard corals.

Millepora sp.- Fire Coral (Photo: Simeon Daple)

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