Question

Read the article and watch the short video at the link below, and then answer the following questions.

LINK: http://www.sciencemag.org/news/2017/10/spider-genes-put-new-spin-arachnids-potent-venoms-stunning-silks-and-surprising-history

Question 1. Why do researchers think the web-building abilities of many spiders may have evolved more than once? (2 points)

Question 2. What are the three main groups (suborders) of spiders? What makes each one distinct?

Question 3. Are all three main groups found in New England? Use iNaturalist to identify one spider (genus and species) from each of the main groups that are found in New England. Note that not all groups may occur in New England!

Question 4. What did spider biologists (arachnologists) use to classify different types of spiders prior to the now widespread use of DNA?

Question 5. What is so unique about Stegodyphus mimosarum?

Question 6. Why have spider genomes been difficult to sequence?

Question 7 . Provide a hypothesis for why black widow possess toxins that attack vertebrate nerve cells, but related house spiders do not.

Answer 1

Answer 1- The genetic analysis of 100s of genes of nearly 40 spider species showed that several web-building spiders have similar genetic makeup as those of various nonweb-building spiders. This makes the researchers to believe that either the behaviors, body structures, and materials used in weaving webs evolved twice, or web capabilities evolved much earlier in a common ancestor of both branches and were lost in many species.

Answer 2 – The three main groups of spiders are 1) Mygalomorphae: these are ground-dwelling creatures characterized by fangs that point straight dow. 2) Liphistiidae: these are the ones that build trap-doors to capture prey, 3) Araneomorphae: these include the ones suchas jumping spiders, dwarf spiders, wolf spiders, and thousands of web spinners.

Answer 3 - The three main groups of spiders found in New England are

1) Water spiders - Six Spotted Fishing Spider (Dolomedes Triton)

2) Garden spiders - Black and Yellow Garden Spider (Argiope Aurantia)

3) Poisonous spiders - Black widow (Latrodectus Mactans)

Answer 4 – Prior to widespread use of DNA, biologists used the direction of their fangs, the shape of their sexual parts, and other aspects of their appearance or behavior to classify different types of spiders.

Answer 5 - Stegodyphus mimosarum.: are homebodies and therefore tend to breed only within their colony. Due to this inbreeding the colonies of these spiders frequently die off because they lack genetic variation that could shield them against die-offs.

Answer6 - Spider genomes are big and full of repetitive DNA. Moreover, spiders are not closely related to most of the other animals whose genomes have already been sequenced, which makes it difficult to use those references to piece together and analyze spider genomes. For all the above mentioned reasons, spider genomes have been difficult to sequence.

Answer 7 - The possible hypothesis could be that due to the large size of black widow spider, they were required to neutralize larger preys such as lizards that have backbones. Hence the ?-latrotoxin, which specifically attacks vertebrate nerve cells was evolved in black widow as a result of some genetic mutation.

Thanks!