Ebay tardigrades (III)
You will remember our previous reports that those exotic mosses that we had received
by yellow mail - thanks to Ebay and thanks to classical, true material transporting yellow mail -
turned out to be heavily loaded with a sound mixture of different tardigrades,
well preserved, in the dry state.
But the numbers of individuals representing the various tardigrade genera
were markedly different from what we are used to encounter in Europe. The red,
armoured Echiniscus species
were few in species number and low in individual count. And only rarely we did
come across individuals to be recognised as the carnivore Milnesium tardigradum .
Instead, Macrobiotus and Hypsibius
were present in large numbers of species and individuals, with a high degree of species variation.
Most impressive were a few giant Macrobiotus tardigrades. They measured
more than 700 µm and even 800 µm in length and were strongly
pigmented so that our photomicrographs look a little bit like Hamilton style
But please note that this is a purely technical effect due to the tremendous
image contrast that simply needed some softening:
from the Canary Islands. Body length ca. 700 µm.
The so-called macroplacoids (calcified structures with a stick-like
geometry used for chewing) and microplacoids within the pharynx of the
giant tardigrades were structured and arranged as follows:
the giant tardigrades. Arrangement of micro- and macroplacoids.
left to right are visible: a pair of microplacoids (small grains),
a pair of short macroplacoids and a pair of longer macroplacoids with
a slight median throttling.
Image width ca. 70 µm.
As in this case everything is a little bit supersized in
comparison to other, smaller tardigrade species, we are able to present
more anatomic detail in higher resolution. When focusing into the depth of
the pharynx we will see a third pair of macroplacoids coming out more clearly.
This is one of the rare cases where we can actually imagine that the tardigrade
pharynx consists of a tri-radiate volume which has a rather mean tendency
to be always partially out of focus. Please remember that it just pretends
to be a simple, paired, symmetrical 2D structure but that it is instead a system
in urgent need for appropriate 3D representation:
a giant tardigrade from the Canary Islands, other focus position.
The red numbering refers to the different placoid pairs.
The schematic cross section represents the true geometry of the pharynx which we
would see when standing face-to-face with the tardigrade.
Image width ca. 70 µm.
Even very fine structures like the mouth lamellae, normally falling
into the reign of scanning electron microscopy can be seen, as well
as the central mouth tube supporting bar, which is characteristic
for the Macrobiotus genus:
Mouth region of
a giant tardigrade from the Canary Islands. The mouth tube bears fine
rectangular lamellae. Between the stylets, directly under the mouth tube,
the ventral mouth tube supporting bar becomes visible.
The black eye-spots of the giant tardigrade are relatively small.
Very nice and only rarely to be seen in this clarity are the muscle
strains fixed to an equatorial position at the pharynx, linking to the
stylet bases and working in counter-action against the stylet springs:
Head region of
a giant tardigrade from the Canary Islands.
A: eye-spot. M: muscles working against the stylet springs.
The claws are typical for the Macrobiotus genus as well:
claw pairs at the rear legs of the giant tardigrade.
Very rare is the attractive red banding on the rear part of the body
which probably has to be interpreted as an indicator of considerable age:
of a giant tardigrade from the Canary Islands (I).
of a giant tardigrade from the Canary Islands (II).
So, overall, we felt quite confident to attribute our giant tardigrades to the
Macrobiotus hufelandi species. But, sad enough, we were not able to find any
of those highly characteristic eggs with cup-shaped egg-protrusions in order
to further support our species judgment. So we try to remain appropriately modest
and conclude that this giant tardigrade probably belongs to the Macrobiotus genus
and that it is at least a close relative to our common Macrobiotus hufelandi species.
Remember: tardigrade taxonomy will remain a hopeless endeavour for us amateurs.
© Text, images and video clips by
Martin Mach (firstname.lastname@example.org).
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.