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