So...that's new!

SA Guide: Grand Tank

It's possible to get a bit jaded after spending quite a few hours and miles hiking in the same area. But now and then you find your way into something unusual - perhaps a new perspective on familiar terrain, or an unexpected and delightful botanical specimen, or it could be as simple as experiencing old haunts in different seasons and conditions. And sometimes, as happened to us the other day, you look down into an apparently stagnant and lifeless pool of water in middle of the desert, see some movement, and wonder out loud, "What the hell is that thing!?"

Laura and I love spending time in Joshua Tree National Park. So when her sister Mary decided to visit we took the opportunity to show her around a few (it is a huge park, after all) of what we consider some of the more interesting and beautiful spots. After walking to Arch Rock out of the White Tank campground, we opted to extend our hike and headed for a place called Grand Tank. (In the Joshua Tree desert the water holes, a few natural but most artifacts of old mining and homesteading operations, are known as "tanks.") The path fades quickly after you leave the main trail (so map and compass are a must) but following some fun and easy scrambling, we managed to find the location.

Normally, the flowering plants - which were numerous here due to the recent rains and accumulated water - would have captured all of Laura's attention, during which normally I'd hang out and play on the rocks. But in this case all three of us ended up on our knees next to the pool just behind the little dam, staring down into the water. Water which, in spots, roiled with what for all the world looked like tiny little horseshoe crabs.

Upon returning home a few minutes of research revealed that the odd critters were an "ancient" crustacean dubbed Triops longicaudatus, a species of tadpole shrimp. Considered a "living fossil" because of their external similarity to 70 million year old ancestors, they are related to fairy shrimp (brine shrimp) and live in temporal pools where they'll eat and lay eggs for a month to three months, depending on how long the pool lasts. Then the eggs lay dormant in the sediment until the pond refills.

We'd never seen tadpole shrimp before, and these active little guys were fascinating to watch as they filtered the water and sifted the mud (both for food), and swam around after each other (quite possibly also for food - they'll try to eat anything smaller than they are, and are not too proud to indulge in a little cannibalism). I thought at the time that the chasing may have been about sex, but it seems they mostly reproduce by parthenogenesis (born from non-fertilized eggs - essentially female clones).

Oh, and the "Triops" thing, that's a reference to the fact they have three eyes: two compound (like insects) and a more primitive one above and between the others. Cool, huh?

I can honestly say we've never spent a bad day at Joshua Tree, but when we left the park after showing Laura's sister around we not only brought with us our usual satisfied glow, but also the anticipation of learning about an unusual discovery.

And in the process of doing so gained (as if we needed it) yet another reason to return.