B
ackhaus
:
Phormidium ingrediens sp. nova
17
the cyanophycean thallus was then coated with
metal under vacuum, studied using SEM and de-
picted.
3
Results and discussion
The gravels and cobbles containing endolithic
layers of the cyanophyte in focus mostly showed
a smooth surface without overlaying parts of the
thallus. Biogenic deposits of calcium carbonates
were not observed. In sawed stones a peripheric
± 0.5 mm deep bluegreen band within the calcar-
eous matrix became evident (fig. 2). After mash-
ing of little pices from this zone, single filaments
or bundles of filaments could be made visible,
but without elucidating the construction of layers
within the rock matrix.
The filaments had diameters of 3,5-4,5 µm,
extremes reached 3-5 µm. They were remark-
ably straight and stiff, and only rarely bent. The
lyngbya-like sheaths were thin, firm and colour-
less, not lamellated and could not be stained with
chlorine-zink-iodide-solution.
The trichomes were bright blue-green, (2,2) 2,9-
3,7 (4,4)
µm wide, straight, neither attenuated at
the ends nor capitate. Apical cells were gently
rounded to obtuse conical, without calyptra. Over
the whole length of the trichome the cells were
uniformly isodiametric, only in zones of active cell
division somewhat shorter or longer than broad,
immediately after division 2,2-2,5 µm, later on
3-4,4 (5)
µm long, not constricted at the cross
walls and not, or very slightly, granulated. The
cross walls themselves were mostly hardly visible
(
figs 4-6). Within the cells the centroplasma was
quite noticeably separated by a pale colour from
the strong blue-green coloured peripheric chro-
matoplasma. This special feature is discussed by
K
ann
(1978)
to be a phenomenon of light condi-
tions within the rock matrix.
Following the nomenclature of A
nagnostidis
&
K
omárek
(1988),
K
omárek
&
A
nagnostidis
(2005),
H
indák
(2008),
species of filamentous
Cyanophyceae with a phormidian trichome mor-
phology have to be transferred to the genus
Phormidium, despite the presence of sheaths.
The taxon in focus is in line with that. In the fol-
lowing text for the present it will be denoted as
“
Phormidium spec.”.
Using the above mentioned Araldite- and SEM-
applications the boring behaviour of the filaments
and the framework of the endolithic thallus be-
came visible (figs 7-14). Fig. 7 shows an overall
view of the distribution of the bore-canals within
the rock matrix.The distances between the canals
are in a range of only some µm and do not follow
a preconceived pattern. It can be seen that the
filaments penetrate the substrate directly without
following micro-cracks or micro-channels reveal-
ing a clear euendolithic behaviour. The sheaths
obviously were withdrawn during the boring proc-
ess (fig. 8). Higher magnification shows that the
bored tunnels were perfectly circular and the
crystal lamellae immediately penetrated (figs 9,
10).
The smooth insides of the boreholes indicate
that the filaments filled the canals almost com-
pletely. The width of the boreholes of 3-4 µm in
the majority of cases corresponded with that of
the filaments. These results show “Phormidium
spec.” as an euendolithic life form.
The casting procedure left the canals filled with
Araldite. After etching the substrate the tunnels
remained in their original position, showing a
forest of micro-pillars. In this view the brush-like
form of the thallus appeared clearly (figs 11, 12).
It can be concluded that the filaments invade the
stones ± parallel perpendicular to the surface.
They reach a length of max. 300 µm. At the sur-
face of the stones the outside of the thalli seem
to be abrazed by gravel movings.
The front parts of columns appear slightly thick-
ened and club-shaped with a scaly surface (Figs
13, 14).
Here the cleavage planes of the calcite
crystals are apparent in the same manner as
they were depicted in a Hormonema-preparation
by G
olubi
ć
et al. (1975, fig.12.7 B). The club-
shaped swellings at the front could be a result of
continuing boring activities at the top of the fila-
ments, whereas a further penetration of the ma-
trix is no longer possible as light-compensating
borderline conditions had been reached.
3.1
Comparison with similar species
It remains to be clarified how “Phormidium spec.”,
specified through the mentioned features, is re-
lated to taxa which are already represented in
scientific literature. It is possible that the building
of endolithic thallus described above is only one
of several possible forms of life of a Phormidium
species, which otherwise is known as a epilithic
form from lotic waters.
Comparisons were done with species descrip-
tions and remarks from the following literature:
G
eitler
(1932),
E
lenkin
(1949),
D
esikachary
(1959),
P
resscott
(1962),
S
tarmach
(1966),
K
ann
(1978),
J
ohn
et al
.
(2002),
K
omárek
et A
n
-
agnostidis
(2005).
