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.