09 November 2012

Miniature Mating Rituals

     Imagine a world where your everyday is fraught with danger.  Danger from predators hundreds of times your size.  Danger from your potential food which might try and eat you back, or if you're lucky, is only poisonous.  Imagine a world so dangerous, that even trying to ask a pretty girl out for a bite to eat could result in you being what was eaten.  If you can do all this, then you are starting to understand the world of a jumping spider male on the quest for a mate...

     Jumping spiders have some of the most elaborate and complex mating rituals in the arthropod world.  There are a some really good theories behind this complexity, and in today's post we will discuss a few of them.
     Many male spiders use vibration as a signal when courting an attractive female, and jumping spiders are no exception.  However, unlike many spiders, salticids also have very elaborate visual displays to accompany their vibratory signalling.  When you combine the visual display (signal) and the vibratory display (know as a seismic signal in the scientific community), you end up with what is called a multi-modal signal.  In other words, if you (the signaler) emit a signal over multiple sensory channels (seismic + visual in this case) you can potential provide more information in less time to the listener (receiver).  For instance, the seismic signal could say one thing (ex: I'm a male of your species), while the visual signal could say something else (ex: I'm really fit and attractive!).  However, the cost of sending signals this way include things like increased complexity of the transmission, which also increases the difficulty of sending this signal without making an error.  This idea of increased difficulty is one of the ideas behind a jumping spiders multi-modal courtship.  By using a more complex and difficult to produce signal, the male spider can potentially increase his attractiveness to the female by demonstrating how much more fit he is than his competitors.  To put it in more human terms, think of it as having to choose between a mate who can do push-ups while doing basic arithmatic (ex: 2+2=4) in his head versus a mate who can do as more pushups while also doing calculus (ex: d/dx tan x = sec2 x) in his head.  Pretty easy choice right?

     Another idea (the signal redundancy hypothesis) asserts that these multi-modal signals are not sending multiple pieces of information, but rather the same information two different ways.  The idea here is that if one signal is blocked or poorly received, for instance because the light is poor, then the second part of the signal can compensate for the deficiency. This theory makes a lot of sense when you consider the environments in which some of these spiders live.  Tropical forests, for example, have a patchy light distribution and so a spider may not always be able to signal in the lighting that makes him look best.  In this case, he would rely on the seismic signal to help him impress the ladies.  While he would probably give the best impression in bright light and a nice seismically conductive surface, the males have adapted to being able to signal even under less than ideal conditions.  After all, when the consequences of not impressing a female on the first try include death, you don't want to mess things up when you do find the elusive mate you've been hunting.

Enough with theory, how about some practice?  The video below is an excellent example of multi-modal courtship.  What you will be watching is a male spider courting a female spider.  The female is the one who is pinned in place with wax, while the male is the one moving around and making all of the buzzing and revving sounds.  It does take the male about 30 seconds to really get going, but once he does, he puts on quite the show!

For other examples of salticid courtship, I highly recommend searching youtube for "Jumping spider courtship," there is some amazing footage and even a few amusing remixes on the site.

Happy spidering!

26 September 2012

I am Arachnophobic

    Hello, my name is Jon and I am arachnophobic. When I mention that I work with spiders and am arachnophobic many people question how it works. I myself sometimes question how I manage it and why my arachnophobia excludes Salticids. It wasn't always that way; any and all spiders got swift “justice” underneath my foot or beneath a rolled up magazine or newspaper.

My slow transformation from complete arachnophobia to working with spiders began sophomore year of college in an Introduction to Zoology class.

   Matt was looking for a student volunteer to help him with his research, somehow I volunteered. My first trip into the field with Matt was an icy shock into the world of spiders. Matt had set up a grid system of marking flags with small vials turned upside down taped to them. The idea is that Salticids, which don't build webs but instead make nests, would use the vials as substrate for their nests and we would come along and coax the spiders out of them. So around dusk, Matt and I arrived at our first set of traps. Matt calmly showed me what we were doing and then let me at it. I will admit, I was deathly frightened that the salticids would jump out and attack me as soon as I turned the flags upside down to tease them out, but I slowly realized that this was mental overreaction. After enduring two months of this “torture” I was finally coming to appreciate the creatures I was collecting.

   Once winter had set in, I was then tasked with identifying what we had collected. Little did I know how much identification I would be doing over the next three years! The dichotomous key was difficult to understand at first as most of the terms were completely new to me (have no fear, we'll make ours easy to understand as you'll see below). Much of my time was spent looking up what the labium was and if it was wider then the sternum or not or trying to keep the names and order of the eyes straight.

Lateral view of Salticid eye locations

   But slowly I became familiar with the key and soon was able to locate multiple morphological features that I would need during my initial inspection of the specimen. From that point on, I rapidly learned the frustrations of working with specimens that were tiny, some only a few millimeters. Trying to tease the chelicerae and fangs open to see if and how many retromarginal teeth were present, is the PME closer to the ALE or PLE, is patella-tibia 3 longer or shorter then patella-tibia 4, how many macrosetae are on tibia 1?

Found on an immature Marpissa.  PS: There are only supposed to be eight macrosetae! (Photo by Jonathan Knudsen)

It was during the first year of identifying that I discovered the two steps that I hated the most: Step 33 and Step 58. These are two steps that require the specimen to be sexually mature, and both involve the shapes and structures of the embolus and epigynum.

   As we begin work on the key for our guide, one of our main goals is to make it easy to understand and use. Instead of using technical jargon and details about each spider, we plan on using easier to see morphological traits and terms to key each species out. In a true dichotomous key, each species keys out in only one place. However, because we plan on taking a broader view of each species, multiple species may key out the same. This may seem like a problem, but we think it will be easier to say, “It may be Spider A (pg. XX), Spider B (pg. XX), or Spider C (pg. XX)” and then comparing our photos to their specimens to make the final species identification. Many of the specimens we've collected are fairly unique looking, so any confusion during the keying process can be sorted out using our photos.

   I have enjoyed being a contributor to this guide and now to this blog. I look forward to continuing our work on this project and keeping you updated as we progress. It has been a fun challenge so far and it will continue to be. Keep you AME's peeled for my next posting!

24 September 2012

Spotlight on the genus Phidippus

   Our spotlight genus this go round is the loveable and charismatic Phidippus.  This genus is one of the more commonly photographed jumping spiders due to their large size (1cm or larger is not uncommon), often ornate coloration, and generally curious disposition.  

 The Phidippus genus encompasses at least 60 different species, including several that are often used in behavioral studies.  For example, my research primarily focuses on the foraging and learning behaviors of Phidippus audax.  

Phidippus audax from Bugguide.net

 Other commonly studied species include P. clarus, P. johnsoni, and P. princeps.  While most of the work on this genus consists of natural history descriptions out of Dr. Robert Jackson's lab,  much of the more recent work has been conducted by Dr. Beth Jakob’s lab where the focus is on vision and visual processing. 

File:Phidippus clarus female 01.jpg
Phidippus clarus from Wikipedia.org
File:Kaldari Phidippus johnsoni female 03.jpg
Phidippus johnsoni  from Wikipedia.org

Phidippus princeps from Bugguide.net

Phidippus are unusually bulky for salticids, giving them the appearance of being rather short-legged.  Unlike some of their more slender cousins, Phidippus often remind me of tiny tanks when they are cruising around in search of a prey item.  While they are still quite capable of pouncing on potential prey items, they tend to do so from a distance of only 1-2 body lengths, rather than the 4+ body lengths a Habronattus or Lysomannes might jump.  

black and white jumping spider - Habronattus agilis - male
Habronattus agilis from Bugguide.net

One of the defining features of Phidippus are their iridescent chelicerae.  This unique character makes field identification of this genus considerably easier than some of their more cryptic cousins.  In addition to aiding in id, they are also very colorful and can be red, orange, green, blue, and even purple!

Phidippus audax chelicerae by Thomas Shahan

Like virtually all salticids, they are cursorial (wandering hunters) and do not spin webs for prey capture.  As such, you may catch a glimpse of these tiny predators on the hunt.  As Robert Jackson says, the often look like “tiny eight-legged cats” when on the prowl.
Finally, if you see one of these spiders, I highly recommend you take a minute or two and watch their behaviors; they could even be watching you!

Happy watching!

10 September 2012

Salticids... in Space?!?

While that may sound like the title to yet another cheesy spider horror movie, it is in fact a real thing.  Thanks to NASA's "You Tube Space Lab" program, a very curious young man by the name of Amr Mohamed was given the opportunity to send Salticus scenicus into space.  The video to below was his entry into the contest and briefly outlines his experiment.

As you can see, he does pose quite an interesting problem.  While I have my own ideas on how they will adapt, I am curious about your thoughts, dear reader.  Do you think the spider will be able to hunt successfully in a Zero-G environment?  Why or why not?  I would absolutely love to hear your comments and thoughts in the comment box below.  Finally, if you want to find out what happens, a live stream of the experiment will be broadcast this Thursday September 12 at 0950 (ECT).

For a full write up on this project and the other winning entries, please go to http://www.nasa.gov/mission_pages/station/research/news/livestream.html

07 September 2012

And the spider marches on...

Dear readers,

In spite of the lack of regular (or otherwise) updates lately, we here at Yours for 8 Eyes are not in fact dead.  What we are though, is incredibly busy.  Two weeks ago I (Matt) and a soon to be new contributor (Jon) went to Cedar Point Biological Station in Ogallala, NE for a little collecting trip.  What we ended up with instead was Matt and Jon's Wild Spidery Ride.  Instead of bring back between 100-150 salticids as we had hope, we picked up nearly that many on our second day!  We even had some days where we were only able to collect for part of the day due to the weather, but still collected more than 100 specimens that day.  Long story short, we ended up returning with ~400 live salticids and several more preserved specimens.

Each row of vials represents a "new" species found at CPBS.

I can hear you thinking, dear reader, "what does this have to do with you and why haven't you been posting more anyways?"  Well, what this has to do with you is that our booklet (mentioned in earlier posts) will now contain more than 40 species of salticid from Nebraska and should be rife with beautiful color pictures of all of the specimens.  As for the lack of posting, lets just say 400 salticids is more than double the amount we've ever had alive in the lab and is turning out to be a ton of work.  Thankfully, we enjoy the work!

Salticus scenicus, an incredibly common species we encountered  at CPBS.

So what's to come then?  Well, the short term plan is to keep posting, hopefully on a weekly basis.  The longer term plan includes getting that booklet done and published, continuing to pursue arachnological outreach through this blog and in person, and even graduating!  It's going to be a busy little while, but stick with us and some exciting things should appear here shortly.

19 June 2012

Teaching and Specimen Collecting

I apologize for the delay in posting.  The month long hiatus is due to poor internet availability, poor timing and a generally exhausted researcher.  For the last two and a half weeks, I have been in Ogallala, NE teaching a course on Field Animal Behavior.  Conveniently enough, the area I have been teaching in is also one that is rife with species of salticid that I have yet to find around Lincoln.  So far I have not been able to put too much effort into collecting.  However, in the brief time that I have spent collecting, I've managed to find at least seven species not found in my previous collection attempts.  Unfortunately, I have not had time to identify them to species yet, nor even to photograph the majority of them.  However, the picture below is a nice preview of some of the amazing new species that will now make an appearance in the book.

One of several iridescent salticids found while sweep netting.

I have one more week of teaching to go, and then the posts should resume their "normal" weekly schedule.  Also, be on the look out for more book photos in the near future!

18 May 2012

Photo batch round 1!

As promised, here are a few photos of some amazing salticids that will be featured in the upcoming book. While not all of these will necessarily make the cut, the species will all be present.  All photos were taken by Jonathan Knudsen.

Female, unidentified.
Female ant mimic, unidentified.
Male ant mimic, unidentified but different species from the one above.
Male Phidippus audax.
As always, we welcome your feedback!

15 May 2012

Spiders have Teeth?!

Sort of...

If you take a very close look at some spiders, including several species of salticid, you will see on their chelicerae (fangs) a few small bumps.

Male,  Salticus sp. arrows indicate cheliceral teeth.  Photo Credit: Shawn Custer

These bumps (red arrows) are known as cheliceral teeth and are used to masticate (chew) prey in much the same way as our teeth.  The major difference being that while our teeth come in a variety of shapes and sizes so that they can be used for different purposes, the cheliceral teeth on a spider are only used to break down prey items into smaller bits.  The particular specimen shown above is a male from the genus Salticus.  In this case it is very easy to determine the sex of the spider as only males have the very enlarged chelicerae, and only when they are sexually mature.  Normally, however, the cheliceral teeth and fangs are not so exposed.  The picture below presents a much more normal view of this same specimen, very much how we would find one in nature.

Male, Salticus sp. Top down view with scale bar.  Photo Credit: Shawn Custer

As you can see from this photo, the chelicera are normally folded up and are frequently covered by the pedipalps (the two small appendages on top of the chelicera in this photo).  As a result, virtually the only people to have ever seen a spider's cheliceral teeth are arachnologists who are trying to identify the specimen, as the presence and shape of the teeth are a diagnostic character used in many dichotomous keys

You may have noticed that both of these photos are not only of the same specimen but are also by the same person.  That is because these photos, and the few that follow, are all preliminary photos for the book mentioned in last week's post.  From now until the book is released, we will strive to release at least one new photo a week so that you, dear reader, will have an idea of what is to come.  We hope you enjoy the photos and would love to hear your feedback on them!

Male, Salticus sp. front view.  Photo Credit: Shawn Custer

Platycryptus undulatus, Top down view.  Photo Credit: Matt Adams

Face on view of an unidentified salticid.  Photo Credit: Jonathan Knudsen

07 May 2012

Exciting things to come!

I am very pleased to announce that one of my collaborators and I have just recieved funding to make a small book on local jumping spiders!  The book (which will be published in pdf form on this blog for free) will feature full color close ups (macro photography), a dichotomous key to species and a few hands-on activities aimed at teaching kids about jumping spiders.  While we have only just started work on the project, we are hoping to have the bulk of the photos taken by the end of the summer and will definitely be posting some of our favorites as we progress.

If there is anything that you, my dear readers, would like to see in the book, please tell us in the comments!  We will make every effort to address all of your reasonable requests.  In the mean time, stay tuned for more Salticid-tastic updates and sneak previews of the book.

18 April 2012

More on vision

I came across this interesting tidbit of a video about jumping spider color vision and how they hunt.  The link will take you straight to the video, and from there you can find out more information about the study by clicking on the link to the right labeled "read the article."

Happy Watching!