ZOO-ology column: No blood, no bones - no problem
By Judie Farnsworth
March 18, 2012 at 10:02 p.m.
Updated March 19, 2012 at 10:20 p.m.
What creature has no bones, no heart, no blood, no brain and resembles Darth Vader?
Did you guess Bathykorus Bouilloni? Way to go. This creature is only one of more than 200 species we call jellyfish and is an Arctic deepwater species.
Jellyfish have existed long before the age of dinosaurs, living at various depths and temperatures in oceans and some even in fresh water.
If you can detach yourself from the thoughts (and maybe memories) of stinging welts, super interesting and unique creatures await. Jellies are a photographer's dream - they look exactly the same from all sides. Bell-shaped and often referred to as medusas, jellies are 95 percent water.
They breathe through their entire surface, absorbing oxygen and releasing carbon dioxide. They're filled with a gelatinous material and have no skeletal form. The pressure of surrounding water is vital. Out of the water, a jellyfish will collapse and die.
Although not really a fish, the name fits with their gelatinous look and watery habitat. They're invertebrates and related to corals and sea anemones. Jellyfish are capable of vertical movement by pushing water in and out of their bell with a circular muscle.
Some may have an air bladder which deflates, helping them sink. Basically, they're like plankton - dependant on water currents, tides and wind for any horizontal movement - a moving vehicle minus steering and brakes. Contact with people is accidental.
Jellies are meat eaters (carnivores) with a simple digestive system. Their mouth is under the bell and surrounded by several oral arms. Long tentacles are covered with stinging cells (nematocysts) little venom-filled harpoons. They fire automatically on contact, stunning or killing the small sea life they eat. A cavity for digestion is attached to the mouth opening. Digestion is quick and the same mouth opening is used for expelling waste.
Jellies go through several life stages. Embryos form after sperm and eggs are released into the water. A larval stage (planula) is next. The planulae sink and attach to rocks or shells where they become polyps and begin a fascinating cloning or budding process.
This stage may last for months, or even years, depending on conditions like temperature and food supply. Polyp clusters are connected by feeding tubes and may grow and spread to enormous proportions. Deepening grooves form on the polyps, eventually separating them and releasing baby jellies.
A group of jellyfish is called a smack. Sometimes, two currents meet and many thousands of jellies drift into the same area creating what is called a bloom. If there is an onshore breeze, jellies can become beached. Don't touch even a beached or dead jellyfish. The nematocysts on the tentacles may still be potent and able to fire.
Jellies range in size from tiny Caribbean thimble jellyfish to the huge Arctic lion's mane with a bell eight feet in diameter and tentacles 200 feet long. Japanese fishermen once reported about one thousand jellyfish with "bodies the size of washing machines!" Jellyfish in all sizes and wonderful colors are amazingly interesting. I hope you'll want to learn more. • jellyfishfacts.net/jellyfish-baby.html#ixzz1o5eahbFt
Judie Farnsworth is a longtime volunteer at the Texas Zoo specializing in educational programs.