Ryan Photographic - Scyphozoa - sea jellies, "jellyfish"


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Class Scyphozoa

The Class Scyphozoa are the true sea jellies (they used to be called "jellyfish" but purists point out they have nothing to do with fish so they were renamed). Like most other members of the Phylum Cnidaria they are characterized by the possession of extraordinary stinging cells - the cnidocytes - sometimes referred to as nematocysts. While few of the sea jellies have the toxicity of the box jellies, some species are still capable of packing quite a punch - enough to kill a fish quickly or seriously incapacitate a human. The cnidocyte is triggered when something touches a sensory trigger - the cnidocil. Once this occurs the cnidocyte discharges with stunning force. It contains an inside-out hollow barb, somewhat like the pushed in finger of a rubber glove. A release of calcium ions changes the osmosticity of the cell which causes an inrush of water and mind-boggling G forces. Forty thousand G is normal and one study reports an almost preposterous 5,000,000 G.

Sea jellies are found in all the world's oceans where they are important predators. Some marine ecologists feel that with the removal of many commercial fish species (from over-fishing), sea jellies are starting to increase in numbers. Certainly major blooms of sea jellies appear to be more common recently.

Most scyphozoans exhibit an alternation of generations. There is usually a polyp stage which asexually produces mini medusae (the adult free swimming form that we call a sea jelly). These bud off on a regular basis and take up a free-swimming life style. The medusa is the sexually reproductive stage which typically produces eggs and sperm. The fertilized egg develops into a planula larva which eventually settles on the bottom forming a polyp. Here is an incredibly cool video of a polyp strobilating (producing medusae asexually).

Some cultures eat dried sea jellies and recently there has been research into the mucus they produce for possible use as a dry eye treatment (amongst others).

Aurelia aurata Moon jelly

Aurelia aurata Moon jelly and young jack Belize

CNID 330 Aurelia aurata Moon jelly and young jack Belize.

Aequorea aequorea Crystal jelly

Aequorea aequorea, Crystal jelly

CNID 8671 Aequorea aequorea, Crystal jelly, captive.

Cassiopea andromeda upside down sea jelly

Upside down jelly, Glover's Reef,  Belize

CNID 3466 Cassiopea andromeda upside down sea jelly, Belize.

Upside down jelly, Glover's Reef,  Belize

CNID 3470 Cassiopea andromeda Upside down jelly, Glover's Reef, Belize.

Upside down jelly, Glover's Reef,  Belize

CNID 3471 Cassiopea andromeda Upside down jelly, Glover's Reef, Belize.

Chrysaora achlyos Black sea nettle

Chrysaora achlyos black sea nettle

CNID 0062 Chrysaora achlyos black sea nettle.

Chrysaora colorata Purplestriped sea jelly

Chrysaora colorata Purplestriped sea jelly

CNID 0040 Chrysaora colorata Purplestriped sea jelly Captive

Chrysaora colorata Purplestriped sea jelly Captive

CNID 0045 Chrysaora colorata Purplestriped sea jelly Captive.

Chrysaora melanaster North Pacific sea nettle

Chrysaora melanaster North Paciifc sea nettle

CNID 0052 Chrysaora melanaster North Pacific sea nettle captive.

Unidentified sea jelly

jellyfish

Unidentified sea jelly, Fiji.

sea jelly planet

Planet sea jelly, Fiji.

 
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