Fishing for Water Bears

Picture a desert, dotted with only a few small bushes, cactuses, and the occassional Joshua tree. A green van is parked at the edge of a straight highway bisecting this flat and seemingly featureless plain. Traffic is sparse; the sounds of the desert - cactus wrens, locusts, a distant red-tailed hawk - rarely interrupted.

About 70 meters from the van, two biologists stand ankle-deep in a temporary rain pool. One carries a turkey baster and a glass jar, the other a long bamboo fishing pole dangling a short line and a small plankton ne ..This was the setting for our „discovery of an outstanding example of the group known as „water bears. Of course, standing there in the pool we did not yet know what was in our collections, and we were about to finish and return to the van for our microscope, when suddenly a voice called to us, loud and clear:

"Do you fellas have a license for that fishing?"

We looked around - no one there, not a single person in sight. Nothing on the road but our van. Was this a divine proclamation? Was the plankton getting back at us? Were we loosing our minds? (Given the setting and our activities, most people would argue that we had already lost our minds) The answer to this mystery below ***.

Back at the van, we set up the microscope and scanned the collections. Temporary desert rain pools hold water for only a few days and are subject to extreme temperatures. It's an ideal setting for a blossoming of living things that have lain dormant on the desert sand. And this fine pool was no exception. Our samples were loaded with a variety of micro-organisms. The dominant producer - tiny cyanobacteria that formed a thick coating on the bottom of the pool.

Scanning through the photosynthetic bacteria we discovered an abundance of Hypsibius, a member of phylum Tardigrada, feeding on the cynobacteria cells. Tardigrades, or water bears, as they are aptly called, form a cryptic and mysterious Phylum that has been associated with everything from rotifers to arthropods. Tardigrades can slip into abiosis, a dormant state that can last for years, and then rehydrate and revive after a few minutes of wetting.

Hypsibius is one of the most widespread tardigrade genera, often common in temporary or „vernal pools, but also found in many other aquatic habitats.If you would like to study living tardigrades we suggest rinsing tree moss in a petri dish. Moss, like our desert rain pool, experiences cycles of dry and wet, making it an ideal habitat for water bears.

*** Mystery answered. From a distance, the pilot of a Highway Patrol spotter plane caught sight of us standing out on the desert. He cut his engine perhaps a mile away from our pool and glided silently until he was directly over our heads at a hundred meters in altitude or less. We were so caught up in the joys of „plankton fishing in our fine desert pool, we had no inkling of his approach. To say that we were startled by the voice out of no where demanding our fishing license is truly an understatement. Even after he started up the engine and flew off, we could still hear him laughing.