Animal Life, 10:00 MWF
Researchers like Martin Jones, director of the great Barrier Reef Aquarium in Townsville, Queensland, and Peggy Hamner joined Robert Hartwick and Masashi Yamaguchi from James Cook University of North Queensland to capture Chironex. Martin Jones and Peggy Hamner wanted to do research relating the Chironex’s ability to see with its four eye groups, even though it does not have a brain.
Robert Hartwick and Masashi Yamaguchi, on the other hand, wanted to document the life stages of Chironex. This proved to be a difficult task since neither Chironex planulae (ball of cells) or polyps (tiny organisms with a crown of tentacles) had been documented before their research. Therefore, they did not know what to look for; however, they theorized that if they mixed water from a bucket containing sperm with one containing eggs, they would get fertilized Chironex eggs. Therefore, they set out one night and captured buckets of Chironex eggs. However, this attempt was not successful since the planulae had died after transforming into microscopic polyps that had settled on the bottom of the buckets. Hartwick and Yamaguchi were persistent and continued their research. They collected thousands of rocks from 14 rivers, to examine for polyps under a microscope. After six years they were finally successful in finding a Chironex polyp on a rock collected at Alligator Creek in Australia. This particular polyp matured into the medusae of box jellies. With this discovery, we are able to describe the entire life cycle of the box jelly: (1) adults aggregate in river mouths in late summer to spawn and then die, (2) the ova and sperm unite, (3) a planula develops into a polyp that attaches to the underside of rock, (4) reproducing asexually, creeping polyps shed new polyps, (5) metamorphosis occurs and polyps become young medusa, from which an adult emerges.
In addition, Martin Jones and Peggy Hamner did a series of experiments in which they presented the jellies with various targets, painted black to contrast with the white wall of the tank. Each time they displayed the targets, the jellyfish turned away in the opposite direction. Their findings concluded that box jellies are capable of seeing by sensing foreign objects and preys. Even today, there remains no precise scientific explanation on how box jellies can see without a brain. What do you suppose gives them the ability to see?
Hamner, W. (1994, August). A killer down under: Australia's Box Jellyfish.
Geographic, pp. 116-130.