Hot Gift Hint: the splendid "La Salamandre" nature magazine from Switzerland just at the moment is preparing a  Special Salamandre Issue exclusively dedicated to tardigrades.

You will be able to follow the events in French language via the Salamandre Blog. Even though you should possibly not be able to read in French language we would like to draw your attention to those many high-res tardigrade photomicrographs and, in addition, beautiful tardigrade graphics which are to be expected in the special issue.

Christmas is not that far away, so you might consider to directly order the Salamandre Special Issue via the  La Salamandre Website . It might be the appriopriate gift for some of your really choosy friends.

Maritime tardigrades (I) - a long-lasting search

Felix Dujardin (1801-1860), since 1840 zoology and botany professor at the University of Rennes (France) detected the first maritime tardigrade in 1851. He called it Microlyda. His French colleague Lucien Cuénot (1866-1951) has provided the sober story of this important discovery: according to Cuénot Dujardin appears to have seen just a single individuum of Microlyda which was found in a sea water bottle brought along by one of Dujardin's students. Imagine a situation like the one depicted in the following illustration:

Zoology lecture by means of the micro aquarium. 18th entury engraving.

Dujardin published three drawings of his Microlyda and thus cemented his reputation as the first discoverer of a sea water tardigrade. Later on scientists commented in deep respect: "Dujardin was the first man on earth to know a marine tardigrade". Microlyda has never reappeared since then.

14 years later, in 1865 Max Schultze from Ostende, Germany, announced the discovery of a further marine species which he called  Echiniscoides. Echiniscoides lives on green algae at the seashore. As a consequence this species was among the first losers in the hide-an-seek between tardigrade and man.

One might assume that the worldwide introduction of apochromatic microscope optics (since 1872) might have helped to find those many more marine tardigrade species as known today. Strange enough the highly-motivated scientists didn't find anything else, even with the new costly apo optics. In the end of the 19th century it was Lucien Cuénot who safeguarded the honour of the scientific community by his discovery of the tardigrade   Tetrakentron synaptae   on the whiskers of the sea cucumber.

Also Prof. Ferdinand Richters, discoverer of many terrestrian tardigrade species, encountered difficulties with those marine species. He explains the situation as follows: "in August 1908 I was invited to take part in an excursion by the zoological institute of the Kiel University organized by Prof. Apstein und Dr. Reibisch on a little steamship called "Frieda". We fished at the "Stoller Grund" landmark (close to buoy 2), at a depth of about 20 m and recovered some stones covered by Fucus vesiculosus und serratus. ... When screening the respective sediment in October I found three individuums of a new, really bizarre tardigrade which I would like to introduce to the scientific community under the name of  Batillipes mirus . End of November Prof. Apstein re-checked the same location and took additional samples. After three weeks of searching I was able to find just two more individuums in those new samples. Other samples from the Small Belt, from Fakkebjerg and Oderbank didn't contain a single further tardigrade." [translated from German].

Nota bene: after a three weeks' search ... two tardigrades!

It took a long time, decades in fact, to find further marine species. Today many more species are known and even more are suspected to wait for future discovery.

The resume for us is fairly simple: searching and finding marine tardigrades cannot be easy. Also a quick web image research reveals that the number of marine tardigrade photomicrographs in the internet is rather modest.

Though reknowned as to be among the most abundant articulate animals it is difficult to get hold of the marine and maritime tardigrades. One reason is that they are the dwarfs among the tardigrades, slim, transparent, with a body length of 0.1 - 0.2 mm. As we have learnt that the ordinary terrestrian tardigrades are already marvels of ultra-miniaturization it is really surprising to find further tardigrades which are even smaller.

Starting from the next issue we will inform you about our own experiences in marine tardigrade search. But, please be warned: you will have to invest much more time and energy in order to study those evasive beings and you might even be unable to re-find them on you slide. Sometimes you will be happy to get a view of their backside before they will vanish behind the next sand grain - but this is of course still better than to find nothing at all:

Batillipes tardigrade, rear side of body. Overall body length ca. 0.2 mm.

Searching in the sand reminds of those nerve stressing childrens' books like "Where's Wally?". In contrast to Wally the maritime tardigrades don't wear a conspicuous shirt. You will have to look out for a more or less transparent micro-animal in the true sense of the word - between and behind a layer of sand grain as depicted below:

Typical sea sand sample with Batillipes tardigrades as seen under a good dissecting microscope. Image width ca. 5 mm. The waterbear shown above was found in this sample. The typical sand grain diameter in the image (0.1 - 0.2 mm) is about the same as the Batillipes body length. So please don't expect any 'elephants' when screening your Petri dish under the dissecting microscope.

In the next issue we will explain how to improve your chances to find those evasive maritime tardigrades. Just come in again in December!

© 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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