Bush Blitz Day 3: Wednesday 17th February

Today I helped Dr Rob Raven collect spiders

At the first site we went to, at Trumpeter Bay, Dr Rob found evidence of a spider that has not previously been found on Bruny Island before. It is calledamaurobioidesand even though there is evidence in the records that this spider exists on the Tasmanian mainland, no-one has found it on this island before! Can you imagine how excited Rob was? Even though we didn't find the actual spider, Rob was absolutely certain that the silk tube we found belonged to this spider because it was the right shape and in exactly the right place for this spider to live. And the amazing part is that the spider makes its home in really small cracks between large rocks on beaches in the 'splash zone'. It builds a slender silk tube in the cracks and that is where it spends its 'down time'. Other wise it is out looking for food I guess. Rob let me feel the silk. It is so strong and water proof, but also fine and soft. I think if there was a bit more funding for research into spider silk uses we would find that humans could apply this natural material to many purposes.

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Yesterday Dr Rob also found a marine earthworm at Coal Bay that has not been found on the island before and yesterday Kevin, our snail expert found four previously unmapped snails on Mount Mangana. This is pretty amazing considering some of the snails he finds are 2mm small!

There is so much that I learned from Dr Rob today that I probably won’t remember it all to record here but I will give it a try. First of all I want to share that SPIDERS ARE OUR FRIENDS, they are certainly not the fiends they are made out to be in the media or in movies. Spider bites that actually kill people are actually very, very small in number and Dr Rob believes that these cases are often associated with other underlying health factors. In fact White Tail spider bites do not cause horrible skin decay. There is a long story that will explain why this myth persists but Dr Rob explained how White Tail spider fangs operate and I am absolutely convinced by him that this spider doesn’t even bite humans!

Another thing I learned is that there is a species of spider that lives on marine kelp. It actually lives most of its life in the sea, often under the water. The really cool this is that scientists don’t even know how they live out there yet – how they breathe under water and how they eat under water. There is still so much to find out.

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As far as spider anatomy is concerned, I now have some strategies for accurately identifying two types of spiders and for how to tell whether a spider is male or female. One way of sorting spiders is to look at what is on the ends of their legs. One type has hooks on the ends of their legs for grabbing on to bark and uneven surfaces and the other type has hairy pads that help it walk on smooth surfaces and stay connected even when they are upside down, like the Huntsman, for example. If you catch a live spider it is actually quite easy to tell if it is one or the other by placing it in a smooth plastic container and seeing if it can walk up the wall quite easily. If it can it probably has the hairy pad feet.

Everybody knows that spiders have four pairs of legs but did you know that spiders also have up to four pairs of eyes and up to four pairs of spinnerets. Dr Rob explained that in the development of living things, there was something in spider DNA that must have been replicated four times whereas in insects this happened three times, thus insects have only three pairs of legs. Spiders’ lungs are just below the head, on the abdomen on their underside. They appear to the eye as two light coloured patches, one on either side. If the spider is female, a small dark patch can be seen between these lungs. This is where the eggs are produced. Males have no such dark spot. Male spiders do, however, have bulbous pedipalps. Those shorter ‘leg like’ appendages towards the front of the spider’s head are present in both males and females but the female ones remain slim, like the other legs, while the males have little enlarged ends. If the ends are pear shaped then the male is probably a juvenile. The adult male pedipalps are more circular and have spiky things growing out of them. These pedipalps are a necessary part of spider reproduction.

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Yesterday Dr Rob also found two Trapdoor spiders. This find has raised more interesting questions for research because one spider was found on Mount Mangana, the other was found at Coal Point. These places are at least 20 minutes drive apart and Mt Mangana is about 500 metres higher than Coal Point. It is reasonable to believe that the first colony of Trapdoors on Bruny would have been the Mount Mangana one since this high point would have been above sea level even when the seas rose before the last ice age. Finding the second Trapdoor at Coal Bay then raises the questions: Are there other colonies between Mount Mangana and Coal Point? At what point did the Coal Point colony arrive? Why did they head to Coal Point? As far as we know no human actually speaks ‘spider’ so we can’t ask them, but the answers to these questions might be found in studying spider DNA. In order to do that, one of the spider’s legs would have to be removed but luckily Trapdoors are a species that can grow their legs back if they are removed since they live for so long and they molt every year. Molting is the only time when a spider grows. In effect, it grows a new covering every year and in the 30-40 minutes after the old covering has been shed and the new one hardens around the spider, the growing happens. Trapdoors are categorised as ‘ancient’ or ‘primitive’ spiders. They live for up to 20 years. I guess that makes them really ancient since most spiders live for about one life-cycle or one year.

Today I learned at least five techniques for finding and collecting spiders. The first is simply removing a section of bark from a tree and shaking it over a collection tray to see what falls out. We found a number of flat spiders this way. The second is taking handfuls of leaf litter, placing them on the tray, disturbing the litter and seeing what moves. I was successful in finding a couple of smaller spiders in leaf litter. The third was by waving a butterfly net across the tops of small shrubs and trees. After removing the vegetation from the net one may be lucky enough to find spiders inside. This method didn’t yield much for us today. Another method that was suggested but that we couldn’t really use today was to look into the sun to see the silk in areas where spiders would be expected to be – which is anywhere in the wild really. Today was a REALLY windy day here so there was no silk to be seen in the air.

The final method shown to us today was one that I found really interesting. Dr Rob told us that the vibrations though the earth of a mechanical engine would draw the spiders out of their hiding places. Today we used the 4WD diesel vehicle that we were driving, placed in neutral on a flat area to create vibration. We think that the ground may have been too damp for the vibration to travel too far because this method was not very successful today. Dr Rob says that this method works really well on dry earth, especially on sandy ground and when it is hot. He also said that scientists are not exactly sure why this vibration attracts the spiders – this is another question for further research.

I wonder if you have any possible answers to this question.

I also wonder what you would like to ask Dr Rob Raven – Australian Spider Expert…