So today we went to see the glowworms located in the caves in Te Anau. The caves here are relatively young compared to other caves being only 12,000 years old. The cave is still growing to this day due to the slightly acidic river that runs through. The water is acidic because of the carbon dioxide produced by us humans above the cave. The highest point in the cave is about 20 meters.
The glowworms are mostly condensed to a small open space at the end of the cave called the glowworm grotto. We had to climb into a boat in order to see the glowworms up close. All the lights were turned off and we were asked to be silent so that we would not scare them. When we entered the grotto we were surrounded by thousands of glowing specks covering the walls of the cave. It was an amazing site.
The lights that we were seeing are produced by the glowworm in their larva stage. This is actually the only stage the glowworm eats and it lasts for most of its life. The larva stage lasts for about 9 months. During this time the glowworm is eating and growing. To capture its food the glowworm sends down fishing lines that are made of sticky mucus. An insect that flies into this trap is stuck, sucked up, and eaten by the glowworm. They can even become cannibalistic when it comes to issues of territory. We saw a video of an older glowworm devouring a younger glowworm that got too close. The glowing is used as a tactic to attract the insects to the fishing lines. The hungrier the worm is the brighter the glow. It was really interesting to see how an animal will adapt to dark cave environments.
The next stage in a glowworms life is the pupa stage. This begins after the larva reaches about 30-40mm and covers itself with a protective skin. This will only last for 12-13 days where the larva is developing into an adult fly. The adult fly is released from the protective layer. The fly’s life is very short because they are born without mouthparts. Their only purpose is to breed in their 1-5 day life. If successful, the female will lay up to 130 eggs. Then the stages begin again.
Jessica
Hey Jess, your blog was very interesting to read as you mentioned human production of carbon dioxide that keeps eroding the limstone in the caves. I think thats gonna create habbitat destruction for those beautiful glowworms that everyone loves to watch. You also mentioned the ability of the worms to adapt to such a dark environment. That was impressive! I enjoyed reading your blog...
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