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Echiniscoides sigismundi - more in-depth

Echiniscoides sigismundi  is among those few marine tardigrade species which were known already in the 19th century. A quick glance at the respective scientific literature reveals that most of the other marine tardigrades remained hidden well throughout the first half of the 20th century - not to speak of those many assumed marine species which are unknown until to the present day.
Walter Maucci, a reknowned tardiologist who has written a splendid book on italian tardigrades (see literature) lists a series of italian species which are widespreadedly found if not ubiquitous at the italian beaches. Nevertheless all of them have been been found rather late in the history of natural science:

Halechiniscus perfectus SCHULZ (1955), in sand at Naples
Halechiniscus remanei SCHULZ (1955), Naples as well, other localities in Italy
Batillipes similis SCHULZ (1955), Naples
Batillipes adriaticus GRIMALDI DE ZIO (1979), Brindisi
Stygarctus bradypus SCHULZ (1951), Lecce

Why did all this happen so late? We think that it is simply a kind of bizarre game of hide-and-seek. As a rule it is not appropriate to quickly screen a nutshell of sand unter the dissection microscopes. Sometimes you will have to seek for more than 30 minutes in oder to find a first individual even though several more might be present, well hidden between the sand grains.
The professional tardiologists have been working hard when searching for new species. Just think about this understatement hint: Walter Maucci indicates that Halechiniscus perfectus lives in sand "up to a depth of 170 cm (!)".
Once you have been trying to dig down into sand 170 cm you will finally accept support by professional digging tools and machinery.
Furthermore the typical marine tardigrade closely adheres to its substrate. When we are moving the petri dish in order to find it under the microscope the tardigrade has a marked tendency to avoid any movement for a few seconds. And, as a rule of thumb, more than 50% of the tardigrades are hiding at the backsides of the grains of sand when you are screening a sample ;-)

With Echiniscoides sigismundi things are slightly easier to manage as it clinges not so much to grains of sand but moreover lives in green Enteromorpha algae which can be easily collected at the beach. Remember the habitat scenario as shown in the  previous issue  of our magazine.

E. sigismundi is really a tough animal. It can tolerate oscillating salt contents (osmobiosis). Scientist Gisela Grohé has shown that E. sigismundi, when transferred to pure freshwater, will survive up to three days and will return to normal live when salt water is added again. Just think about the variable conditions on sun-lit black algae at the beach in order to understand that these must be really tough guys. On the other hand all those findings sum up to good news for us: E. sigismundi will survive also in a modest sea water aquarium, at least for several months, with some care possibly for years.

How about an Echiniscoides sigismundi video clip? Just have a look here !

The number of claws is unique in the tardigrade world. It varies, probably mainly depending on the age of an individuum, between 5 and 11. Keep in mind that those animals have to survive amidst the grinding power of waves at sandy beaches.

[ Echiniscoides sigismundi ]

Many, many claws ...

The body appears colourless. Only the contents of the intestine (green, brown, or black) reveal that there is somebody living. Most E. sigismundi have no or very rudimentary filaments, though they are members of the tardigrade class of "Heterotardigrada" normally characterised by armour plates and filaments. But, during movement it becomes clear that they must be relatives of the Echiniscus genus, individuals of which are shown here in our magazine quite extensively (also in the header of each issue). According to the literature is appears that there is a high variety of filaments in this species, some authors tend to classify those varieties into separate species.
The long, straight stylets remind of those of terrestrial Echiniscus tardigrades:

[ Echiniscoides sigismundi ]

Thin straight stylets, heart shaped pharynx.

[ Echiniscoides sigismundi ]

Folded skin between the hind legs.
The red arrow indicates newly formed claws. Strongly dentate intestine.

The eye pigment is black and has a concave shape with the hollow side turned to the outside. The Cirri mediales externi und interni in the head region are very small and look like beard stubbles at most.

[ Echiniscoides sigismundi ]

Minute cirri
in the head region, black eyes.

The eggs (spheroid, smooth without ornamentation) are deposited freely or glued to small aggregates. This is a quotation from literature as we were not able to find any eggs ourselves :-(


Grohé, Gisela: Das marine Bärtierchen Echiniscoides sigismundi. Verhalten bei extremen Umwelteinflüssen. Mikrokosmos 65 (1976) p. 129 - 132.

Maucci, Walter: Fauna d'Italia - Vol. XXIV - Tardigrada. Bologna 1986 [ very good review of italian Mediterranean Sea tardigrades. ]

© 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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