Simply collecting, fishing or hunting? (Marine sampling techniques II)

As announced you will find a description of a dedicated tardigrade fishing device here, actually and successfully used by us during our holiday time in Croatia.

The basic idea can be easily understood: a mssive iron tube with the sampling vial in it is thrown down from above the water level, into the sampling area. When sinking down the tube is being stabilized by a hind fin (blue triangle in the diagram) and in addition by a laminar flow of water running through its interior. During the sinking time the fin is pointing upwards. Due to its high weight the iron tube will be able to penetrate a few centimeters into sandy ocean grounds. Seconds later it will topple over because of its unstable, highly positioned center of gravity. As a rule the sand in the vial will behave inertly: so some part of it will not sink back to ocean grounds, instead remain trapped in the vial tube when being turned upside down. The tardgrade fisherman now will be able to recover the fishing device with the sandy prey. That's it.

We are going to illustrate the procedure on the basis of a schematic sketch and some photographs of the real thing.

Simple device for sampling sandy ocean grounds
- schematic sketch -

Fin, pointing backwards (1), for direction stabilization when sinking down to the ground.






Massive cast iron cylindrical tube (2), ca. 10 cm in length. Intended to favour some laminar water-flow passing through it.






Crucial anchoring point (3) for wire and thread,
used to trap and recover your sandy prey.




Collecting vial (4), here made out of copper, but it might be some plastics as well. The vial should have a markedly lower diameter than the tube, so that some flow of water can still pass between vial and inner side of tube (direction stabilization)

The fishing result: some sand (5) hopefully inhabited by tardigrades.

The following photographs might serve as an incentive for you to design your own tardigrade fishing equipment based on arbitrary, perfectly useless junk material which might be available everywhere on earth. But please keep in mind that the sea water will "rust-feed" on almost any metallic item in your perfectly ingenious plan.

Simple device for sampling sandy ocean grounds (I)

Simple device for sampling sandy ocean grounds (II)

Simple device for sampling sandy ocean grounds (III)

The described method doesn't make use of sophisticed mechanics nor electronics. Nevertheless it renders reliable results, helping poor swimmers and poor divers to reach out for greater water depths without getting their feet wet. The procedure might require some repetitions but it will work on most sandy grounds. Moreover, the chances to find tardigrades are high: you know, our tardigrades are everywhere :-). Please find a first photo example based on successful dry feet tardigrade fishing below:

Hind leg of a tardigrade fished from sandy ocean grounds by means of the device described above. Genus Batillipes. Use of highest magnification and extreme raking light in order to reveal detail in an extremely low-contrast scenario. Oil immersion objective 90x/N.A. 1.30. Image width ca. 30 µm (0.03 mm).

© Text, images and video clips by  Martin Mach  (webmaster@baertierchen.de).
Water Bear web base is a licensed and revised version of the German language monthly magazine  Bärtierchen-Journal . Style and grammar amendments by native speakers are warmly welcomed.

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