Thursday, September 13, 2012

Face to Face with a Brown Recluse

Biologist have something interesting happen to them all the time - people bring them organisms out of the blue.  I cannot tell you how many times I have been presented with or pointed toward some sort of creature.  Snake in the building - get the biology teacher.  Dead bird on the sidewalk - get the biology teacher.  Find a dessicated gecko under a carpet tile? Balance its stiff body on the door handle of the lab - you just know he wants to see it. 

It sounds like I am complaining, but I have gotten some really cool stuff this way.  Just last week one of my colleagues here at Eastfield walked into my lab with a rather large Brown Recluse  spider (Loxosceles reclusa) in a jelly jar.  He knows I like spiders and, being the true biology nerd that I am, it was pretty cool.

Not only was this particular spider a Brown Recluse, but it was a honking big, mature male.

 Dorsal Portrait
The characteristic "violin" marking on the cephalothorax is very obvious. 
Note also the two large pedipalps in front of the chelicerae.

 In this close up you can see that the "violin" marking is due to a dense patch of hairs. 
Notice also that this is a 6-eyed spider. 

Ventral view with a focus on the pedipalps - the male sex organs. 
That long spike, or embolus, fits specifically into the genital opening of the female.

Hi there!  Face to face with a spider that you should be afraid of.
This image shows two main characteristics for identification - three pairs (dyads) of eyes in a backwards facing curve (strongly recurved) and fused chelicerae.

This image is less magnified and more dorsal.
Recurved eye dyads

A close up of the eye dyads.
I didn't intend it to be, but this is kind of a creepy picture.

Ventral view showing mouth parts (labium and endites), chelicerae, cheliceral fangs, and pedipalps with bulbs and embloli.

Left pedipalp with bulb and embolus

Right pedipalp with bulb and embolus

Close up of bulb




I mounted the spider on its back to get a clear view of the cheliceral fangs.
In the image above the openings through which the spider injects its venom are clearly visible.

A close up of one of the fangs.

I will admit that I am very pleased with this image.  This extreme close up of the cheliceral fang not only shows the opening for injecting venom but also the serrated edge of the fang.

This spider turned out to be fairly hard to work with - not because it is a poisonous spider, but because it has unusually long legs.  Positioning him for images was difficult and resulted in me accidentally piercing his abdomen.  Drat!  No worries though, I am sure someone will bring me one of his relatives any day now.

If you would like to begin to make your own discoveries please remember that Eastfield College supports student and faculty research at all levels - in fact I am talking to some 3rd, 4th, and 5th graders next week.
You are invited to come to Eastfield to use our scopes.  If you are not in the area, I would be delighted to Skype with classes.

Hope to hear from you soon!

Murry Gans
Scanning Electron Microscope Lab Coordinator
Eastfield College
Mesquite, TX

Rosemary's Spider

Eastfield College has some beautiful courtyards with lots of shade and benches.  Even in our extremely hot Texas summers I can always find a place to sit and relax for a few minutes.

The other day I was sitting on one of my favorite benches when I noticed that the rosemary in the planter next to me was covered in spider webs.  I am a good enough arachnologist to realize that where there are spider webs there are spiders.  I took a quick look but couldn't find the little creatures so I clipped off a sprig of rosemary and took it back to my scopes in the SEM Lab.

Once I got the sprig of rosemary back to the lab I put it on the dissecting scope and began my search.  Within a few minutes I found the little guy.

Another very small Theriidian spider.  (You can see another species of this same family of spiders in a previous blog.)  These spiders are commonly referred to as cobweb spiders. Black widow spiders belong to the same family.

By this time you can imagine that my lab and hands are smelling very strongly of rosemary.  All of that aromatic oil must be stored in glands on the leaf.

A look at the top surface of the leaf shows the expected oil glands.  If you look carefully at the image above you can see there are two different sizes of glands.  Do they contain different oils? Sounds like a good question for someone with a gas chromatograph.

As observant as I try to be I am a bit embarrassed to admit that I had never looked closely at the leaf on the rosemary bush - and I have one in my own backyard. 

What I didn't realize is that the top surface of the leaf curls around to the bottom of the leaf.

 This image shows the curled edges of the top surface of the leaf out of focus at the top and bottom.  The brighter out of focus structure in the middle is the midrib of the leave.  Even at this magnification you can clearly see the densely packed oil glands.

 A closer look at the oil glands on the lower surface of the rosemary leaf.

The images above illustrates a problem - a limited depth of field.  How to solve that problem - don't use light - use electrons in the SEM.

 Top surface of rosemary leaf. [60x]
The image above shows the epidermal cells of the leaf as well as the two different sizes of oil glands.

 Lower surface of the rosemary leaf [24x]
Note how all levels of the leaf are now in focus.

 Lower surface of rosemary leaf [70x]
This image shows the midrib with smaller oil glands.  You can also see some spider web stretching diagonally across the upper half of the picture.

 Spider web [99x]

 Stomata and oil glands [1,000x)

 Stoma portrait [2,490x]
The high vacuum and electron beam of the SEM dry out specimens.  This stoma was open when I first saw it, but quickly closed as the guard cells lost their turgor.

As I use the instruments in the SEM Lab at Eastfield College I am discovering that even the most common organisms have some pretty fantastic morphology under high magnification.

The imaging instruments at Eastfield College are available for research to students and faculty everywhere.  Want to get a better look at your world - give us a call.

Murry Gans
Scanning Electron Microscope Lab Coordinator
Eastfield College
Mesquite, TX