Communication and Perception
There have been many studies done about the visual senses of Panulirus cygnus. These lobsters have eyes on eyestalks on their heads. They use them to see, but tests have been done that prove that they do not necessarily need their eyes to know where to go. Scientists believe that, like birds, lobsters may be using the Earth's magnetic field to find their way around.
It is also known that Western rock lobsters have special sound producing structures to produce acoustic signals. Panulirus cygnus produce a very unpleasant noise in a fascinatingly individual way. Similar to a violinist, they slide a bow across a vibrating surface. The bow is called the plectrum which is at the base of each antenna, and the vibrating surface is the file, a lump on both sides of a lobster's head. The lobsters simply wave their antennae and the sound produced is a loud, scratchy buzz. The technique is known as the stick-and-slip motion and the key to sound production is friction. The friction comes from microscopic shingles on the files of the lobsters. Hence, the longer the file, the longer time the lobsters can produce their sound.
Scientists believe that lobsters make these noises to startle predators enough to scare them away. This tactic is especially useful during the time right after molting. It appears that this feature of being able to produce the sound even when soft-bodied is an evolutionary response to predation. Protecting themselves in their most vulnerable time is very important.
However, not much is known about their sensitivity to vibration. It is hypothesized that the way lobsters interpret the acoustic signals they receive is by tiny structures in their inner ear called stereocilia. When the sound reaches the ears of the lobsters it shakes the eardrum which displaces the endolymphatic fluid in the inner, and deflects the stereocilia. The stereocilia then convert the sound into nerve impulses. However, scientists believe that lobsters cannot hear unless at very close range, so they have come to the conclusion that their sound production is not intended to help them communicate with their own species, but instead to talk to other species. As a matter of fact, it is believed that the lobsters can't even hear the sounds they produce.
Additionally, Panulirus cygnus also communicate by the use of chemical signals or pheromones. They release these in their urine through little holes found at the base of their antennae. These pheromones are carried by currents to nearby lobsters who use their chemoreceptors (on their antennules) to detect the signals. Scientists suppose that males and females have different pheromones in their urine, which allow rock lobsters to distinguish between male and female in other rock lobsters. Other uses for the chemical signals are not yet known.
Communication Channels: visual ; acoustic ; chemical
Other Communication Modes: pheromones
Perception Channels: visual ; acoustic ; chemical