The Spectacular Glow Worm

If one were to walk around any dark cave in either Australia New Zealand, or Tasmania and look up at the ceiling they would find a spectacular display. This display would seem like stars, however; they are not stars. In fact, they are actually glow-worms. Glow-worms are an incredibly interesting invertebrate. In order for one to fully appreciate them it is necessary to understand what the glow-worms are, what the structures is that makes them so unique and how these structures aid in their survival and what in the past made these structures so advantageous.

There are only a few of the glow-worm species in the world. These species include the Arachnocampa flava, Arachnocampa richardsae, Arachnocampa tasmaniensis, and Arachnocampa luminosa (Pyper, 2009). The A. flava are found in Queensland, Australia, A. richardsae can be located in New South Wales, Australia, A. tasmaniensis are found in Tasmania, and the A luminosa are found in New Zealand (Pyper, 2009). These glow-worms are most likely to be found in dark, damp areas like caves, old mining shafts, and in rainforests (Pyper, 2009). In addition, depending on where they are located they are also particular to temperature change (Pyper, 2009). What exactly is a glow-worm in Australia and the surrounding area? They are the larva of a fly that is similar to a mosquito (Pyper, 2009). As Gatenby (2008) stated, "This insect belongs to the group of fungus flies, Mycetophilidae, sometimes called shade-flies because they like damp shaded situations" (p.86). Glow-worms in Australia have not only captured the imaginations of visitors but also have captured the attention of scientists that have found the glow-worms intriguing. Therefore, there have been scientists that have studied the particular structures that make these glow-worms unique.

One of the first structures that had captured the minds of people is the malpighian tubules that allow the glow-worm to be bioluminescent (Gatenby, 1960, p. 86). These malpighian tubules are more or less like trashcans (Gatenby, 1960, p. 86). These tubules are where bi-products are placed and it is attached to the abdomen area where the mesenteron, which is the stomach, and the intestine are linked (Gatenby, 1960, p.86). It is within the region of the bi-product dispensers where all the magic happens. This is where, Pyper (2009) said, "The blue-green light is produced by a chemical reaction between luciferin - a waste product produced by the glow-worm - and the enzyme luciferase, in the presence of oxygen and a form of energy known as ATP (adenosine triphosphate)." This light is used to act like those insect traps that are lit up. These lights are used to lure pray into the glow-worms other structure, which is also intriguing to the scientists that study them, and is used to trap their prey. Therefore, the next structures that are used to aid in the glow-worms survival is the silk and mucus producing glands.

The glands that produce the silken strands within the glow-worms are relatively huge (Gatenby, 1960, p.88). The glow-worms produce silk strands, hang them on the ceiling of a cave or somewhere that is dark, and damp (Gatenby, 1960, p. 87). These lines of silken string are actually made up of a mucus tube (Pyper, 2009). Each of these mucus tubes have a droplets of mucus on them that is placed in a specific distance from each other and have a specific size (Gatenby, 1960, p.87). Then these strands are then places in the perfect place next to the other finished strands (Gatenby, 1960, p. 87). By the time the glow-worm finishes the task of making his beaded strands it has more than likely have made up to "forty vertical lines" (Gatenby, 1960, p. 87). Each of these strands can reach about "twenty-four inches long" (Gatenby, 1960, p. 87). These strands create what seems like a beaded curtain that one would put in front of a passageway, however; it is more like a curtain of death because the mucus on each strand when comes in contact with a flying insect become entangled around their victim (Gatenby, 1960, p. 87). With the vibrations that the struggling insects make it sends signals up the strands to the glow-worm where it is registered through sense organs (Gatenby, 1960, p. 88). When the glow-worms realize it has caught something it springs into action by pulling up the strands that had trapped its prey or climbing down to use its next structure that also helps them to survive (Gatenby, 1960, p. 88). When the ability to produce a curtain of death is used in conjunction with its bioluminescent light it makes the glow-worm even more like likely to capture its food. Although, the glow-worm is not the only invertebrate that uses a jaw to eat with they do use it for their survival, this structure is a necessary part of the glow-worms survival.

The glow-worm uses its jaw to kill and consume its captured prey. If the conditions are right, the glow-worm just "sucks out the blood of its prey..." (Gatenby, 1960, p. 88). In addition, if there is plenty of food then the glow-worm will consume only the softer parts and discard the harder parts of its victim (Gatenby, 1960, p. 88). If there is little food then the glow-worm uses its jaw to break up the body and legs of its victim so that it is easier to swallow (Gatenby, 1960, p. 88). This particular structure gives the glow-worm the ability to adapt to the conditions of its environment. After all, if the glow-worm did not have its jaw then they could not survive in places where food was limited. Throughout time, the structures that makes these glow-worms unique and very successful hunters there were many different possible events that could have lead up to these adaptations.

There could have been many reasons for the glow-worms ability to be bioluminescence, make silk strands that makes a curtain of death, and the ability to choose whether to just suck the blood of its victims or to be able to consume its victim's entire body. Maybe, the insect's preference for the dark and damp habitat made them to adapt to using light to lure their prey. When the worms found out that it took more than just luring their prey with light they began creating beaded strings made from its mucus to be able to trap their pray. As time went on they could have adapted to using more than one string and maybe learned that the longer the string the better chances they had. The fact that there was probably little prey the glow-worm probably found that if they had a powerful jaw they could consume its entire prey instead of just sucking its blood. So as time went on the longer the string got, the brighter the lights had gotten, and the stronger its jaw had gotten could have lead to these particular structures to being so advantageous. There are many other possibilities of why this invertebrate obtained the type of structures and why they are so advantageous. However, there is very little knowledge of these invertebrates and are still being studied by many kinds of scientists.

Glow-worms are very interesting invertebrates that are able to put on an amazing show inside of a cave. If one was to truly know, what they are fully capable of and why they put on these displays, would people think of them the same way? The ability to capture their prey like a fisherman using his fishing lines, the use the light to attract its prey like the bait on a hook, and their strong jaws capable to break down the hardest shells of insects together makes this invertebrate a formidable fisherman. These are all structures that have made these glow-worms to be able to survive in conditions that had little food sources and in complete darkness. These structures are very advantageous for the glow-worm and have been for possibly longer than what scientists may hypothesize.

Sources:

Gatenby, J. B. (May, 1960). The New Zealand Glow-Worm. Tuatara: Journal of the Biological Society 8(2), 86-91. Retrieved Apr. 3, 2009, from http://www.nzetc.org/tm/scholarly/tei-Bio08Tuat02-t1-body-d4.html.

Pyper, W.. (2009). In The Lure of glow Worms. Retrieved Apr. 4, 2009, from http://www.abc.net.au/science/slab/glowworm/default.htm