Monday, February 25, 2013

Book Lungs?

Many people view Animal Care husbandry as simply a series of housekeeping/critter-feeding chores. And in fact, that is an essential part of our jobs. However, observation of animal behavior is critical to learning how to keep our creatures healthy and happy. Sometimes animal observations are too good to keep to one’s self.

Recently, Life Science Manager Sarah Moore experienced one such observation. Please note the addendum.

Today as I was removing a black widow spider that has passed on, and feeding the ones that were still alive, I noticed the scorpion moving around restlessly in the cage.

On its underside, I saw what looked for all the world like wings – two pale symmetrical structures with many fine plate-like subunits.

I was fairly sure this was the scorpions’ respiratory system, called “book lungs” because they act like lungs and are made of many thin pieces stuck together, like pages in a book. But they were so weird I had second thoughts. Often when something weird is sticking out of the underside of an animal, this means S-E-X. After all, reproductive organs come out to play, and then get stored away again. A lung that stayed out in plain view seems very vulnerable to the elements.

So I double-checked, and I was right the first time! Those things were its book lungs, and they were just as they should be.

Book lungs are a fascinating example of convergent evolution. They appear to have evolved separately in spiders and scorpions as each became terrestrial. Their common ancestor was aquatic, resembled a horseshoe crab, and had book gills, which were a very similar organ for gathering oxygen from water. And like our own lungs, both are a great way to maximize surface area for oxygen exchange in a fairly small body part.

Addendum: As it turned out, I was right to second guess my first guess. The book lungs are more internal. What we were looking at was the scorpion’s pectines. These are a sensory organ that seems to be used by the male to detect pheromones produced by the female. While it is not fully understood it’s pretty clear my second idea was much nearer the mark.

We did our best to snap photos of the scorpion displaying its book lungs pectines. An annotated view of scorpion anatomy can be found here:

The very next day, Animal Care Lead Lauren Bloomenthal caught our Chilean Rose Tarantula showing off her book lungs. Or is there something in the air or is this just another case of the power of observation - as when you buy a red car you suddenly see red cars everywhere?

The next time you visit Pacific Science Center check out the residents in our Insect Village. Let us know what interesting animal behavior you observe.

1 comment:

  1. just spider and scorpion?but my teacher said crab also have book lungs