FEATURE ARTICLE

Jellyfish, jellyfish, jellyfish. Is there a word that beach goers dread more than clouds and rain (other than the "S" word)? If so, this could be the one. Then why the great attraction to the numerous jellyfish exhibits at aquariums worldwide? Down deep people want to know what makes an organism tick and why does it look so graceful yet in some cases be so dangerous? This is evident in the young beachcomber during the summer who is not just interested in the jellyfish that are washing up, but starts a collection in the family sand buckets or even the cooler! Here is some information to get you started on a group of organisms that is nearly all water.

Classified information (jellyfish and their relatives) . . .

Architecture . . .

Cnidarians are said to be the simplest organisms at the tissue level of organization since their cells are the first to be organized into true tissues among the animal kingdom. Cnidarians are essentially bags made of two tissue layers. The outer ectoderm, or epidermis, contains the cnidocysts, the stinging cells that are characteristic of the phylum. The inner endoderm, or gastrodermis, lines the gut, which in some Cnidarians may be divided up by septa (as in the Anthozoa) or elaborated into branching canals (as in many Scyphozoa). In between epidermis and gastrodermis is the mesoglea, a layer of jellylike substance which contains scattered cells and collagen fibers. The mouth is often, but not always, surrounded by a ring of tentacles. The simplicity is not a reflection of the beauty and elegance that are represented by the group from large moon jellies to the long tentacled lions mane jellyfish, or the docile comb jellies of the Ctenophora.

Getting Defensive . . .

Cnidarians have the ability to sting as many of us can attest. The function of the sting is to paralyze prey since most Cnidarians are slow moving and in some cases nearly sessile. However, there are some which are efficient predators like the box jellyfish capable of moving a few meters per second. The stinging cells embedded in their tissue (cnidoblasts) are equipped with miniature barbed harpoons that contain a variety of venom depending upon the species. Some jellyfish and their relatives like the box jellyfish, the lions mane, and the colonial Portuguese Man-O-War can cause painful or fatal stings. Other Cnidarians like the anemone are for the most part harmless to humans and use their stings for paralyzing small prey. Not all organisms are effected by Cnidarian stings. Some predatory sea slugs will actually incorporate the stinging cells from Cnidaria into their bodies and use them as "borrowed" defense mechanisms.

Jellies in the Chesapeake . . .

The most familiar jellyfish in MD is most likely the sea nettle (Chtysaora quinquecirrha). This jellyfish is well known by it's name, shape, and sting by most MD natives. The encounters with these jellies have been enough reason in the past for some watermen to change occupation. While sea nettles occur from Cape Cod south along the U.S. East Coast, Caribbean and Gulf of Mexico they inhabit the Bay in numbers unequaled elsewhere. They are found most abundantly in the tributaries of the middle Bay where salinities are between 10 and 20 parts per thousand. At those salinities, they are white in color. In the southern Bay, where salinities are higher, they often have red/maroon markings on the long central tentacles and on the swimming bell, or medusa.

Web References . . .

Some great references on jellyfish and other marine invertebrates:

• Neither Jelly nor Fish, Maryland Marine Notes, July-August 1994, Volume 12, Number 5
  http://www.mdsg.umd.edu/MarineNotes/Jul-Aug94/side1.html An article from Maryland Sea Grant on the sea nettle and other interesting jellyfish information.
  
  
  
• Mapping Sea Nettles in Chesapeake Bay
  http://orbit-net.nesdis.noaa.gov/orad2/doc/seanettlemain.html
  A NOAA site that allows the user to map data, report sitings, identify jellyfish and gain an extensive background on these unique creatures.
  
  
• University of California, Berkeley, Museum of Paleontology, systematics of cnidaria
  http://www.ucmp.berkeley.edu/cnidaria/cnidariasy.html
  Developed by UCMP, this website is an excellent starting point if you are trying to find information on organisms in any Kingdom. The site features an easy navigation system that links you directly to information on systematics, ecology, fossil record, and morphology.
  
  
• Aquascope 2000 web page is an excellent reference for jellyfish and other invertebrates
  http://www.vattenkikaren.gu.se/fakta/arter/cnidaria/overcnid/nass07e.html
  Developed by the Tjärnö Marine Biological Laboratory, Strömstad, Sweden, this page gives a wealth of information on systematics, morphology, classification, and ecology of a multitude of marine invertebrates. The page also contains real photos and excellent color artwork of the invertebrates.
  
  
• E medicine article on sting remedies
  http://www.emedicine.com/emerg/topic104.htm
  
  
• Digital resource for teaching biology
  http://biodidac.bio.uottawa.ca/

http://www.mdsg.umd.edu/Extension/msgsnn/msgsnn04_1/jellyfish.html