Jellyfish

During the Theyyam photography, I visited nearby Chithari river. Chithari were the Theyyam was held is a coastal village at Kasaragod district, is located 5 KM away from Kanhangad City and 5 KM away from famous tourist spot of Bekal fort. The Chithari river covers three part of Chithari. The name Chithari mean “River rounded place” is derived from Chuttum Arru (Arru = river).

There was a temporary bamboo bridge across the river and inside the river I could spot plenty of white blobs floating. On close observation they turned out to be jelly fishes. Sine the river was far way down from the bridge and since I did not have the water proofing equipment for my camera, I resorted to take pictures of the jellyfish from the bamboo bridge. I used Canon EF 300mm f/4.0 L IS USM lens on Canon EOS 7D with 77mm Circular Polarizing filter. This filter allowed me to avoid much of the reflection of the muddy water.

I had to post process these picture using Adobe Photoshop CS4 to get rid of the murkiness of the water. What you need to do in such a murky shot is to reduce both the white point as well as black point in the Levels adjustment. For the picture above the when you change white point of the histogram to 200 and black point to 60 as you see the the accompanying screen shot the image transforms to the one you see. This same technique can be used in any washed out photo like one on a foggy day, when you want to clear the fog in the picture.

It tuned out that this jellyfish is Acromitus flagellatus which belongs to Order Rhizostomeae, Family Catostylidae.

Few marine creatures are as mysterious as the jellyfish which is often misunderstood by bathers and beach goers, who react with fear upon encountering this creature. When a human is stung, the victim may experience skin rashes, muscle cramps, or even death.

Commonly known members of Cnidaria, neither of which is considered a true jellyfish are the Portuguese Man-of-War (Physalia physalis) and the Sea Wasp (Chiropsalmus quadrumanus). Although a member of the phylum Cnidaria, the Portuguese man-of-war is not a true jellyfish. These animals consist of a complex colony of individual members, including a float, modified feeding polyps and reproductive medusae. Though pain from its sting may be accompanied by headaches, shock, collapse, faintness, hysteria, chills, fever, nausea and vomiting, this cnidarian is not the most harmful to humans.

The Sea Wasp known as the Box Jelly because of its cube-shaped bell, is one of the most venomous of the pseudo-jellyfish. Their potent sting can cause severe dermatitis and may even require hospitalization for humans. Sea wasps are strong, graceful swimmers reaching 150 mm in diameter and in height. Several long tentacles hang from the four corners of the cube. A similar species, the four-tentacled Tamoya haplonema, occurs along the east coast of the United States. Chironex fleckeri is a small tropical Cubomedusea and has been responsible for over 50 fatalities along the Australian coast. The toxins are so potent to humans that death can occur in three to twenty minutes after the sting.

Jellyfish inhabit every major oceanic region of the world and are capable of withstanding a wide range of salinity and temperature. Most jellyfish live in shallow coastal waters, but a few species inhabit depths of 4600 meters. In northern waters, large groups of jellyfish several kilometers long sometimes hamper fishing by clogging nets. Jellyfish range in size from a mere twelve millimeters to more than two meters across, the largest is Cyanea arctica, which may have tentacles over 40 meters long. Despite their often enormous size, jellyfish have no head, no skeleton, and no special organs for respiration or excretion.

Instead of a brain, true jellyfish possess an elementary nervous system, which consists of receptors capable of detecting light, odor and other stimuli and coordinating appropriate responses. Scyphozoans have very efficient sensory receptors. They have a balance organ called a statocyst, simple light detectors called ocelli and some species have touch receptors called sensory lappets. These simple organs are distributed around the margins in club-shaped structures called rhopalia. The rhopalia hang freely around the bell at the margin. Each of the rhopalia is next to sensory cilia. If the animal tilts in a particular direction, the statocysts press against the cilia, causing the nerve cells to generate their action potentials. This system provides a mechanism through which the animal can become informed of its orientation and can alter its posture by stronger contractions on one side of the bell .

Life Cycle
The jellyfish’s life cycle is what truly distinguishes it. True jellyfish have two distinct body forms, medusae and polyp, reproduce both sexually and asexually, and go through five life stages: egg, planula, polyp, ephyra and medusae. Parental care in the class Scyphozoa is not known to occur. Jellyfish normally live three to six months.

Locomotion
The adult medusa jellyfish drifts in the water with limited control over its movements. When the animal contracts its circular and radial muscles, the volume of water enclosed under the bell decreases propelling the animal. The net forward movement of the animal occurs primarily because the speed with which the bell contracts exceeds that speed with which the bell recoils to its resting state. This pulsating rhythm allows for some regulation of vertical movement. Because scyphomedusae are sensitive to light, this vertical movement can be important. Some jellyfish, like the (Aurellia), descend to deeper waters during the bright sun of the midday and surface during early morning, late afternoon and evenings. Despite this ability to move vertically, jellyfish depend upon ocean currents, tides and wind for horizontal movement. It is the world wide ocean currents that are responsible for the successful distribution of scyphozoans.

Jellyfish have evolved to produce a very unique and efficient means of capturing various types of prey. They also have a short life span and an amazing life cycle that can produce many offspring that are able to drift with the currants to be dispersed almost anywhere. Jellyfish are known to inhabit all levels of ocean, in all latitudes worldwide, which speaks of their adaptive abilities.

Jellyfish may appear to have no apparent value, but they are, in fact, a very important part of the marine food web. One species, the Mushroom Jelly, is even considered a delicacy by humans. Both fresh and pickled mushroom jellyfish are consumed in large quantities in China and Japan.